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Car Forum / BMW Cars / March 2007I don't like electric assist stearing.
I have had my Z4 since November and normally drive it on weekends. My everyday vehicle is a 4Runner. I can see where if one drove the Z every day one could get used to the understeer of the electrical assist. But it feels sluggish to me and I think could contribute to accidents. That almost happened to me. I came into a corner a little hot, I turned the wheel and then had to quickly compensate for the understeer. I hate to say it but the 4Runner is more responsive. I don't know why they had to mess with something that worked. Maybe adding tower braces will help. >I have had my Z4 since November and normally drive it on weekends. My >everyday vehicle is a 4Runner. [quoted text clipped - 8 lines] > I don't know why they had to mess with something that worked. Maybe > adding tower braces will help. Did you try increasing the front tire pressures as I suggested to you last week? For the 3.0 stock cold pressures are 33F, 36R and for the 2.5 they are 30F, 33R. IIRC, there haven't been any understeer complaints on the Roadfly Z4 board. Tom K. >Did you try increasing the front tire pressures as I suggested to you last >week? >For the 3.0 stock cold pressures are 33F, 36R and for the 2.5 they are 30F, >33R. >IIRC, there haven't been any understeer complaints on the Roadfly Z4 board. That was my fix as well. I've also heard of people increasing the negative camber or adding a strut brace. epbrown -- How can you know where I'm at if you haven't been where I been? Can you see where I'm coming from? "How I Could Just Kill A Man" Cypress Hill >>I have had my Z4 since November and normally drive it on weekends. My >>everyday vehicle is a 4Runner. [quoted text clipped - 17 lines] > > Tom K. I did and it helped a little. I am thinking the tower brace as well getting rid of the ride flat tires may help. But I am not going to swap tires just yet. And I would not expect too many complaints on this board. > I have had my Z4 since November and normally drive it on weekends. My > everyday vehicle is a 4Runner. [quoted text clipped - 8 lines] > I don't know why they had to mess with something that worked. Maybe adding > tower braces will help. I don't see how adding braces would change anything. Sell the car and buy one you like to drive. Oh, and test drive the next one.  Signature-Fred W >> I have had my Z4 since November and normally drive it on weekends. My >> everyday vehicle is a 4Runner. [quoted text clipped - 11 lines] > I don't see how adding braces would change anything. Sell the car and buy > one you like to drive. Oh, and test drive the next one. Thanks for the help homer. Oh, I did. But it is difficult to get a real good feel for a car in just a 15 minute ride and other features were comparable to the competition. >> I have had my Z4 since November and normally drive it on weekends. My >> everyday vehicle is a 4Runner. [quoted text clipped - 11 lines] > I don't see how adding braces would change anything. Sell the car and buy > one you like to drive. Oh, and test drive the next one. Braces will reduce flex on hard corners thereby keeping more tire on the road and improving cornering performance. >>>I have had my Z4 since November and normally drive it on weekends. My >>>everyday vehicle is a 4Runner. [quoted text clipped - 14 lines] > Braces will reduce flex on hard corners thereby keeping more tire on the > road and improving cornering performance. Undoubtedly true. But that was not your initial complaint. You said you did not care for the feel of the electric assist. Reducing or eliminating chassis flex will help reduce understeer, but not really change the feeling of the electric assist. Signature-Fred W >>>>I have had my Z4 since November and normally drive it on weekends. My >>>>everyday vehicle is a 4Runner. [quoted text clipped - 19 lines] > chassis flex will help reduce understeer, but not really change the > feeling of the electric assist. I guess I should have been more explicity. The "feeling" I was describing was understeer. Another description might be sluggish (not unresponsive but not quick). I realize it is better than found on a SLK but is not as good as a Boxster or Miata. >>>>>I have had my Z4 since November and normally drive it on weekends. My >>>>>everyday vehicle is a 4Runner. [quoted text clipped - 24 lines] > but not quick). I realize it is better than found on a SLK but is not as > good as a Boxster or Miata. I have a feeling that you are misunderstanding and misusing the term "understeer", which may be leading to a lot of the confusing answers that you are getting. Understeer is the condition that occurs during cornering where the car wants to "push out" the front end, pointing the car toward the outside of the corner. In essence you are "under steering" the corner. Oversteer is exactly the opposite, where the rear end kicks out and points the car toward the inside of the corner. These have mostly to do with chassis balance, weight distribution and dynamic weight transfer during cornering. It has very little to do with the amount of steering "power assist" or the steering ratio. Signature-Fred W >>>>>>I have had my Z4 since November and normally drive it on weekends. >>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 38 lines] > dynamic weight transfer during cornering. It has very little to do with > the amount of steering "power assist" or the steering ratio. From a review: "In fact, if there's a fault to be found with the Z4's handling, it's the opposite: The rear sticks longer than necessary (read "understeer")." >>>>>>>I have had my Z4 since November and normally drive it on weekends. >>>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 43 lines] > "In fact, if there's a fault to be found with the Z4's handling, it's the > opposite: The rear sticks longer than necessary (read "understeer")." Correct, just as I said above. And this has zero to do with the electric steering assist. Signature-Fred W >>>>>>>>I have had my Z4 since November and normally drive it on weekends. >>>>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 46 lines] > Correct, just as I said above. And this has zero to do with the electric > steering assist. You're right - I was wrong. Unfortunately unlike many members in this group I recognized a flaw in the Z4's handling and attributed it to the electrical assist steering. I should have attributed to the design of the suspension. In any case. The understeer is still present regardless of the source. >>>>>>I have had my Z4 since November and normally drive it on weekends. >>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 38 lines] > dynamic weight transfer during cornering. It has very little to do with > the amount of steering "power assist" or the steering ratio. From another review (this happened to me): Out on the fabulous Jerez circuit, the dull steering doesn't really dent your progress, but the Z4 M's quite pronounced understeer does. If you misjudge your entry speed it's not easy to rein it in and exit the corner cleanly. Through the slower corners particularly you have to work hard to keep it neat and tidy. > >>>>>>I have had my Z4 since November and normally drive it on weekends. > >>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 57 lines] > > - Show quoted text - Yes but you say the problem is the wheels don't turn as quickly as you want them to, not that the front end was losing traction. >> >>>>>>I have had my Z4 since November and normally drive it on weekends. >> >>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 73 lines] > Yes but you say the problem is the wheels don't turn as quickly as you > want them to, not that the front end was losing traction. I never said the front end was losing traction. I described understeer ("That almost happened to me. I came into a corner a little hot, I turned the wheel and then had to quickly compensate for the understeer.") . Now I think the electric assist steering is not the problem. The problem is the way the car is set up. From another review: "Basically, it is tuned to be an inherent understeerer. Always understeer, understeer and understeer. Whenever you push it harder and faster, understeer will get into the picture. The harder it corners, the more understeer it shows. Now we don't know why BMW needs rear-wheel-drive and an engine locating behind the front axle to create an understeerer. " Frankly I am surprised this has not been discussed in the forum before. Maybe people don't recognize it for what it is or maybe they don't drive the car hard enough to realize the problem. > "adder1969" <adder1969@yahoo.co.uk> wrote >> Yes but you say the problem is the wheels don't turn as quickly as you [quoted text clipped - 17 lines] > Maybe people don't recognize it for what it is or maybe they don't drive > the car hard enough to realize the problem. It's been very well discussed that BMW sets up their cars (indeed, *EVERY* car manufacturer does this) for understeer as the primary response, because it's *generally* safer for most drivers. Even cars whose basic design (rear or mid-engined) would be expected to exhibit oversteer have tuned their cars to exhibit understeer. You just haven't looked for articles discussing this. FloydR >> "Basically, it is tuned to be an inherent understeerer. Always >> understeer, understeer and understeer. Whenever you push it harder and [quoted text clipped - 14 lines] > or mid-engined) would be expected to exhibit oversteer have tuned their > cars to exhibit understeer. My rear engined '65 Corvair could be set up to oversteer by changing the stock 15F, 27R tire pressures to about 30F, 30R. Of course, a 10 mph side wind would then blow the car off the road at any speed over 35 mph, but when you're young and adventurous... > You just haven't looked for articles discussing this. You're right - Grinder needs to get out more. Just about every Road & Track BMW test indicates "mild" as opposed to "moderate" or "heavy" understeer and usually describes BMW steering as excellent. Tom K. >>> "Basically, it is tuned to be an inherent understeerer. Always >>> understeer, understeer and understeer. Whenever you push it harder and [quoted text clipped - 29 lines] > > Tom K. The problem is you are looking at ALL BMWs. I am concentrating on the Z4. It's unfortunate Homers are unable to recognize understeer much less too afraid to put a car into that type of situation. Try google - 18000 hits on Z4 and understeer. Took me less than 2 minutes to find (by the way, nobody referred to as the understeer as an excellent attribute). "This sensory satellite delay does little to bring you in phase with the Z4's responses, and combined with the numb electrically-assisted (a first for a BMW), non-linear steering and the chassis' tendency towards steady-state understeer, it's no wonder things can feel slightly out of kilter when you're pressing on." "Sadly, when we pitched it against the Porsche Cayman S (097), it revealed a propensity for understeer and a confidence-denting sense of disunity between the front and rear ends. " "Out on the fabulous Jerez circuit, the dull steering doesn't really dent your progress, but the Z4 M's quite pronounced understeer does. " "Basically, it is tuned to be an inherent understeerer. Always understeer, understeer and understeer. Whenever you push it harder and faster, understeer will get into the picture. The harder it corners, the more understeer it shows. Now we don't know why BMW needs rear-wheel-drive and an engine locating behind the front axle to create an understeerer. " >> "adder1969" <adder1969@yahoo.co.uk> wrote >>> Yes but you say the problem is the wheels don't turn as quickly as you [quoted text clipped - 30 lines] > > FloydR It's a matter of degree. I have not found any articles referring to understeer in Boxsters or the Toyota 2000 but have countless on the topic for Z4s. And you are wrong. I have looked for Articles on this. Truth of the matter is you are grouping "most cars" when the topic at hand is a handful of sports cars. > "Floyd Rogers" <fbloogyuds@hotmail.com> wrote > ... [quoted text clipped - 20 lines] > matter is you are grouping "most cars" when the topic at hand is a handful > of sports cars. I may have been confusing rec.autos.driving postings with postings here - I've certainly seen many postings on this matter. However, you are wrong if you think that a Boxster (my wife has one) does not understeer - at least for initial and middling responses. My NSX understeered. Modern Porsche 911's are tuned for understeer - although if you go to the limit it oversteers. My statement stands that all cars (including BMWs) understeer. FloydR > My statement stands that all cars (including BMWs) understeer. Modern ones yes - and rightly so for safety in extremis. But it's not so long ago the semi trailing arm equipped ones like the E28 etc could oversteer pretty easily and bite the unwary. The very first BMW I drove was a 525 auto - the one before the E28 - and lost it at a pretty low speed on a wet roundabout. No harm was done and I caught it before it spun, but it surprised me - my car was a considerably more powerful auto and would have taken the same treatment easily. But then it had a De Dion rear axle. Signature*Hard work pays off in the future. Laziness pays off now * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > Floyd Rogers <fbloogyuds@hotmail.com> wrote: >> My statement stands that all cars (including BMWs) understeer. [quoted text clipped - 8 lines] > more powerful auto and would have taken the same treatment easily. But > then it had a De Dion rear axle. Indeed. I had an E12 530i and it was that way. We also had an E21 320i that we lost in a ditch spinning just like that. FloydR >It's a matter of degree. I have not found any articles referring to >understeer in Boxsters or the Toyota 2000 but have countless on the topic >for Z4s. Well that's peculiar. My Google search for "boxster understeer" turned up 14,800 articles. Many mention how *all* cars these days are set up to understeer. For Z4 understeer, the most common fix I've seen is adding an extra degree of negative camber, iirc. I think there's a DIY for this on www.z4um.com. epbrown -- How can you know where I'm at if you haven't been where I been? Can you see where I'm coming from? "How I Could Just Kill A Man" Cypress Hill Seems like grinder now justs want to complain. As someone else wrote you're not stuck with the set-up you have - you can change it. Contrary to popular opinion BMW do NOT always produce car with everything being at the best it can be. What's best for BMW isn't always what's best for the driver. I can a bit tired when people say "BMW know what they're doing leave things alone". > Seems like grinder now justs want to complain. As someone else wrote > you're not stuck with the set-up you have - you can change it. > Contrary to popular opinion BMW do NOT always produce car with > everything being at the best it can be. What's best for BMW isn't > always what's best for the driver. I can a bit tired when people say > "BMW know what they're doing leave things alone". What annoys me is when 'they' take a car on a track and criticise the outright handling. The design of a track car has little to do with a road one - especially if that road one is more of a fast tourer than out and out sports car. Signature*Why is 'abbreviation' such a long word? Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> Seems like grinder now justs want to complain. As someone else wrote >> you're not stuck with the set-up you have - you can change it. [quoted text clipped - 7 lines] > one - especially if that road one is more of a fast tourer than out and > out sports car. I experienced serious understeer on an off ramp from 280 merging on 92 in Half Moon Bay. It was not on a track. >>It's a matter of degree. I have not found any articles referring to >>understeer in Boxsters or the Toyota 2000 but have countless on the topic >>for Z4s. >> > Well that's peculiar. My Google search for "boxster understeer" > turned up 14,800 articles. I can't do anything better than that. Mine turned up over 18,000. Many mention how *all* cars these days are > set up to understeer. That is like saying all tires provide traction. Your statement is true but there is a matter of degree. "It is common practice among automobile manufacturers to configure production cars deliberately to have a slight linear range understeer by default. If a car understeers slightly, it tends to be more stable (within the realms of a driver of average ability) if a violent change of direction occurs, improving safety." I own a Mini S and a Z4. There are situations where the Mini is glued where the Z4 slips. http://www.goupstate.com/apps/pbcs.dll/section?category=NEWS&template=wiki&text= understeer Understeer values How much a car understeers can be measured in the number of degrees more the steering wheel have to be turned per G of lateral acceleration. Here are the measured linear range values for some cars. The higher the number the more the car understeers. Nissan 350Z 19 Mazda MX-5 21 Nissan 350Z Roadster 21 Ford Mustang GT 22 Renault Megane Sport 22 Maserati Gran Sport 23 Mini Cooper S 23 BMW 330i 25 Alfa Romeo 147 GTA 27 Corvette C6 27 Corvette Z06 28 Lotus Elise 111R 28 Porsche 997 Carrera S 28 Saab 9-3 Aero combi 28 Å koda Octavia RS 28 Porsche 997 Carrera 29 Porsche Cayman S 29 VW Golf GTI 29 Porsche 987 Boxter S 31 BMW M6 32 Range Rover Sport Supertech 32 Ford Focus ST 33 Mitsubishi Lancer EVO8 34 Porsche 968CS 34 Audi RS4 35 BMW M5 35 BMW Z4 Roadster M 35 BMW M3 Comp Package 36 Opel Astra OPC 36 BMW Z4 3.0i 37 Subaru Impreza WRX STi 37 Subaru Legacy 3.0 aut 38 Volvo V70 T5 39 Audi A4 2.0 T Q 41 Mercedes E55 AMG 42 Audi A4 V6 3.2 Q Avant 43 Porsche Cayenne Turbo 45 Smart ForFour Brabus 45 Mercedes SLK 350 47 TVR Tuscan 49 Alfa Romeo 159 2.2 JTS 51 Morgan Roadster V6 71 >>>It's a matter of degree. I have not found any articles referring to >>>understeer in Boxsters or the Toyota 2000 but have countless on the topic [quoted text clipped - 4 lines] > >I can't do anything better than that. Mine turned up over 18,000. As *opposed* to your original position there were no articles to be found? What happened there? >Many mention how *all* cars these days are >> set up to understeer. > >That is like saying all tires provide traction. Your statement is true but >there is a matter of degree. Point conceded. However, your original post didn't claim to be unhappy with the *degree* of understeer; you were in a state of high dudgeon that understeer existed at all, claiming the Boxster had none. As you continue to research this, I think you'll find that the Z4 steering tells you as you're about to lose it. What I've read about the Boxster is that you're in complete control until, suddenly, things are hopeless. Weird how high the 3-series placed on that list you posted. Less understeer than a Lotus Elise? epbrown -- How can you know where I'm at if you haven't been where I been? Can you see where I'm coming from? "How I Could Just Kill A Man" Cypress Hill > I never said the front end was losing traction. I described understeer > ("That almost happened to me. I came into a corner a little hot, I turned > the wheel and then had to quickly compensate for the understeer.") . Now I > think the electric assist steering is not the problem. The problem is the > way the car is set up. Well the understeer is the front end losing (some) traction. The process of hard cornering doesn't change the steering geometry so much that it doesn't steer enough. Almost all cars will have that characteristic if you barrel into a corner, it's simply physics. You can reduce the effect by tweaking the suspension, springs, dampers, anti-roll/sway bars, different tyres etc etc. >>>>>>>>>I have had my Z4 since November and normally drive it on weekends. >>>>>>>>>My everyday vehicle is a 4Runner. [quoted text clipped - 91 lines] > Maybe people don't recognize it for what it is or maybe they don't drive the > car hard enough to realize the problem. Yes. The car understeers. But your complaint was the electric assist. Know how I know this to be true? Read the subject line (above) that you entered. Signature-Fred W >>>>>>>>>>I have had my Z4 since November and normally drive it on >>>>>>>>>>weekends. [quoted text clipped - 100 lines] > Know how I know this to be true? Read the subject line (above) that you > entered. You're right. I was wrong to attribute it to electrical assist steering. That should make you feel better. Unfortunately the understeer is still there regardless of the source. >>>>>>>>>>>I have had my Z4 since November and normally drive it on >>>>>>>>>>>weekends. [quoted text clipped - 106 lines] > > Unfortunately the understeer is still there regardless of the source. OK, sorry to be redundant. So... now we get to the crux of the matter. The car exhibits more understeer than you'd like. How to reduce understeer (or induce oversteer if taken far enough): Increase front tire pressure Decrease Rear tire pressure Shave Front tires (decrease tread depth) Wider Front Tires Narrower Rear Tires Make Front Camber more Negative Make Front Caster more Positive Reduce Front Toe-in Softer front swap bar Stiffer rear sway Bar Soften front springs Stiffen rear springs Softer front shocks Stiffer rear shocks So you see... you aren't exactly stuck with the handling you have right now. Many BMWs come with staggered tires. Get rid of that as a first step. Put the same size tire and wheel on both axles and you may find things are much more "balanced" right there. Of course it won't look like a dragster anymore... C'est la vie. Signature-Fred W >>>>>>>>>>>>I have had my Z4 since November and normally drive it on >>>>>>>>>>>>weekends. [quoted text clipped - 140 lines] > much more "balanced" right there. Of course it won't look like a dragster > anymore... C'est la vie. Actually my first step will be to change tires away from run flats. The softer sidewall will provide better traction. The second choice will be to put a STIFFER roll bar (25mm) on the front AND a softer (22mm) on the rear. http://www.dinancars.com/Series.asp?Series=30&Chassis=32&Model=74&Class=Chassis% 20Tuning#1665 >Actually my first step will be to change tires away from run flats. The >softer sidewall will provide better traction. The second choice will be to >put a STIFFER roll bar (25mm) on the front AND a softer (22mm) on the rear. I'd love to hear how this works out for you. Please post again once you've done this. epbrown -- How can you know where I'm at if you haven't been where I been? Can you see where I'm coming from? "How I Could Just Kill A Man" Cypress Hill >>Actually my first step will be to change tires away from run flats. The >>softer sidewall will provide better traction. The second choice will be [quoted text clipped - 9 lines] > Can you see where I'm coming from? "How I Could Just Kill A Man" Cypress > Hill It will be a while. I will change tires first to see how that works. If the understeer is still more pronounced than I would like, I will put on the roll bars. BTW, I will purchase the M5 mobility kit and stick it into the trunk after the tires are changed. I spoke with the DINAN engineers and the wanted to upgrade to the Stage 2 suspension which I cannot afford right now. Their second choice was to add roll bars which "adds larger and adjustable front and rear anti-roll bars to reduce body roll for superior handling. The adjustable anti-roll bars provide the ability to fine-tune the system for closer to neutral balance reducing understeer. " CLOSER to neutral balance is what I want. The tire changes should also improve traction. >The tire changes should also improve traction. They will. Since switching to my Goodyears, it takes a lot of silliness for my little triangle to start flashing. On the run-flats, hitting the on-ramp aggressively did it every time. epbrown -- How can you know where I'm at if you haven't been where I been? Can you see where I'm coming from? "How I Could Just Kill A Man" Cypress Hill > Actually my first step will be to change tires away from run flats. The > softer sidewall will provide better traction. The second choice will be to > put a STIFFER roll bar (25mm) on the front AND a softer (22mm) on the rear. > > http://www.dinancars.com/Series.asp?Series=30&Chassis=32&Model=74&Class=Chassis% 20Tuning#1665 If you do, it will increase the understeer. Signature-Fred W >> Actually my first step will be to change tires away from run flats. The >> softer sidewall will provide better traction. The second choice will be [quoted text clipped - 4 lines] > > If you do, it will increase the understeer. Not if selected and adjusted correctly. >>>Actually my first step will be to change tires away from run flats. The >>>softer sidewall will provide better traction. The second choice will be [quoted text clipped - 6 lines] > > Not if selected and adjusted correctly. If the result of the selection and adjustment is a stiffer front bar and a softer rear bar than the ones you have now, the car will understeer more. JRE >>>Actually my first step will be to change tires away from run flats. The >>>softer sidewall will provide better traction. The second choice will be [quoted text clipped - 6 lines] > > Not if selected and adjusted correctly. No, I'm sorry you are just wrong. Regardless of how you "select" them, if you increase the stiffness of the front sway bar you will increase the amount of understeer. If you decrease the stiffness of the rear sway bar you will increase the understeer. If you do both you will *really* increase the understeer. You have it exactly backwards to what you want to do. For what you want (decrease understeer or introduce oversteer) you need to stiffen the rear and/or soften the front. Signature-Fred W >>>>Actually my first step will be to change tires away from run flats. The >>>>softer sidewall will provide better traction. The second choice will be [quoted text clipped - 16 lines] > (decrease understeer or introduce oversteer) you need to stiffen the rear > and/or soften the front. Whatever. I will turn it over to the engineers/technicians and tell them what I want to do. > Whatever. I will turn it over to the engineers/technicians and tell > them what I want to do. You'd be best to tell them what you *want* rather than what to do otherwise you'll end up with even more understeer and a ride like a truck. Signature*I wonder how much deeper the ocean would be without sponges* Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> Whatever. I will turn it over to the engineers/technicians and tell >> them what I want to do. > > You'd be best to tell them what you *want* rather than what to do > otherwise you'll end up with even more understeer and a ride like a truck. Not to worry. I will tell them "I know Dave!!!!" and my problems will be solved (or they will be bored to death). ;>) > > Many BMWs come with staggered tires. Get rid of that as a first step. > > Put the same size tire and wheel on both axles and you may find > > things are much more "balanced" right there. Of course it won't look > > like a dragster anymore... C'est la vie. > > > > -- -Fred W > Actually my first step will be to change tires away from run flats. The > softer sidewall will provide better traction. Maybe, but won't change the handling *balance* > The second choice will be to put a STIFFER roll bar (25mm) on the > front AND a softer (22mm) on the rear. Both of which will increase understeer. ;-) Signature*The first rule of holes: If you are in one, stop digging! Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> > Many BMWs come with staggered tires. Get rid of that as a first step. >> > Put the same size tire and wheel on both axles and you may find [quoted text clipped - 7 lines] > > Maybe, but won't change the handling *balance* I wasn't talking about balance. The added traction of soft sidewall tires will help reduce slip. >> The second choice will be to put a STIFFER roll bar (25mm) on the >> front AND a softer (22mm) on the rear. > > Both of which will increase understeer. ;-) Only correct if incorrect sized roll bars are selected. http://www.turnfast.com/tech_handling/handling_antiroll.shtml As we mentioned, the anti-roll bar helps increase the mechanical downforce of the outside tire during cornering. This increases the traction of that tire, and that end of the car (front or rear). An increase in traction at that end, may leave the opposite end with too little traction. An imbalance of traction occurs, and one end of the car will lose traction before the other end. If the front tires lose traction before the rear tires, the car will understeer. If the rear tires lose traction before the front tires, the car will oversteer. Changing the anti-roll bar stiffness can adjust this out. According to Dinan engineering: "adds larger and adjustable front and rear anti-roll bars to reduce body roll for superior handling. The adjustable anti-roll bars provide the ability to fine-tune the system for closer to neutral balance reducing understeer. " <snip> > According to Dinan engineering: > > "adds larger and adjustable front and rear anti-roll bars to reduce body > roll for superior handling. The adjustable anti-roll bars provide the > ability to fine-tune the system for closer to neutral balance reducing > understeer. " Yes. Stiffer front *and* rear bars will increase lateral transfer and reduce body roll. The adjustability can be used to change the balance of the car by making the front bar *relatively* less stiff than the rear one to decrease understeer. JRE > <snip> > [quoted text clipped - 11 lines] > > JRE I do not think that last statement is correct. An adjustable bar allows you to tweak the tension from side to side on the same axle. It does not allow you to change the tension from front to rear because a) the bars are not tied together and b) nor are they fixed in position like a torsion bar (spring). The sway bar pivots in its bushings if the 2 wheels on that axle travel up and down together. It only applies cross force when one wheel moves up or down compared to the other wheel on that axle. Signature-Fred W >> <snip> >> [quoted text clipped - 20 lines] > force when one wheel moves up or down compared to the other wheel on > that axle. Think about the end effect. If you reduce the roll stiffness at the front through either replacement or adjustment of the front bar, you will decrease understeer. If you increase the roll stiffness at the rear you will also decrease understeer. But if you increase or decrease them both in proportion it will not change the balance of the car. It's the proportioning between the front and rear roll stiffness you're trying to manage, right? So if one installs stiffer bars front and rear and wants to decrease understeer, one must stiffen the rear one more than the front one...in other words the front has to be relatively softer than the rear at the end of the change. JRE >>> <snip> >>> [quoted text clipped - 33 lines] > > JRE I agree with you 100%. You simply restated my case. None of which has anything to do with "adjustable roll bars". You cannot increase (or decrease) an adjustable bar's stiffness. You can only adjust how much gets applied left to right. Signature-Fred W > >> Actually my first step will be to change tires away from run flats. > >> The softer sidewall will provide better traction. > > > > Maybe, but won't change the handling *balance* > I wasn't talking about balance. The added traction of soft sidewall > tires will help reduce slip. At both ends. Resulting in the same understeer. It might improve the steering response, though. > >> The second choice will be to put a STIFFER roll bar (25mm) on the > >> front AND a softer (22mm) on the rear. > > > > Both of which will increase understeer. ;-) > Only correct if incorrect sized roll bars are selected. I'm only commenting on what you've written. Increasing roll stiffness at the front increases understeer. As does reducing it at the back. > http://www.turnfast.com/tech_handling/handling_antiroll.shtml As we > mentioned, the anti-roll bar helps increase the mechanical downforce of [quoted text clipped - 6 lines] > the front tires, the car will oversteer. Changing the anti-roll bar > stiffness can adjust this out. It's not for me you need to quote this. You need to read and try and understand it. ;-) > According to Dinan engineering: > "adds larger and adjustable front and rear anti-roll bars to reduce body > roll for superior handling. The adjustable anti-roll bars provide the > ability to fine-tune the system for closer to neutral balance reducing > understeer. " Actually just adding larger anti-roll bars is a bodge which will spoil the ride. Camber changes are a better way to set about it. Signature*Always remember you're unique, just like everyone else. Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> >> Actually my first step will be to change tires away from run flats. >> >> The softer sidewall will provide better traction. [quoted text clipped - 6 lines] >At both ends. Resulting in the same understeer. It might improve the >steering response, though. Maybe, but it depends on the car. The OEM tyre sidewalls for the NSX are stiff to the point of being damned near solid, but they have a soft compound tread rubber set in a bias pattern. With non-OEM tires (ObUS) on this car, there is a 'slingshot' delay effect in the handling which is really nasty. It's completely absent with the correct tyres. Obscure trivia, but I'm in an obscure mood tonight. SignatureDan. > >> >> Actually my first step will be to change tires away from run > >> >> flats. The softer sidewall will provide better traction. [quoted text clipped - 6 lines] > >At both ends. Resulting in the same understeer. It might improve the > >steering response, though. > Maybe, but it depends on the car. The OEM tyre sidewalls for the NSX > are stiff to the point of being damned near solid, but they have a > soft compound tread rubber set in a bias pattern. With non-OEM tires > (ObUS) on this car, there is a 'slingshot' delay effect in the > handling which is really nasty. It's completely absent with the > correct tyres. Obscure trivia, but I'm in an obscure mood tonight. Could be. Most of the reports I've read when changing from OEM run flats to 'conventional' suggest comfort is the main gain. Signature*Never put off until tomorrow what you can avoid altogether * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> >> >> Actually my first step will be to change tires away from run >> >> >> flats. The softer sidewall will provide better traction. [quoted text clipped - 16 lines] > Could be. Most of the reports I've read when changing from OEM run flats > to 'conventional' suggest comfort is the main gain. Read the post from E Brown. Also when I went to conventional over ride flats on my Mini S the handling improved dramatically AND the noise difference was huge. It was like going from a go-cart to a limo. > > Could be. Most of the reports I've read when changing from OEM run > > flats to 'conventional' suggest comfort is the main gain. > Read the post from E Brown. Also when I went to conventional over ride > flats on my Mini S the handling improved dramatically AND the noise > difference was huge. It was like going from a go-cart to a limo. So the handling went from excellent to dreadful? Signature*I yell because I care Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> > Could be. Most of the reports I've read when changing from OEM run >> > flats to 'conventional' suggest comfort is the main gain. [quoted text clipped - 4 lines] > > So the handling went from excellent to dreadful? I will make this as simple as I possibly can: 1. I replaced ride flat tires with conventional tires on my Mini S. 2. The handling improved dramatically. This includes a smoother ride that handled rough stretches better and cornering. 3. There was a huge reduction in noise. The noise reduction was comparable to going from a go-cart to a limo. Hope this clears everything up for you and hopefully you can figure it out without pictures. >> >> Actually my first step will be to change tires away from run flats. >> >> The softer sidewall will provide better traction. [quoted text clipped - 40 lines] > Actually just adding larger anti-roll bars is a bodge which will spoil the > ride. Camber changes are a better way to set about it. Read the post from E Brown. > > How to reduce understeer (or induce oversteer if taken far enough): > [quoted text clipped - 16 lines] > softer sidewall will provide better traction. The second choice will be to > put a STIFFER roll bar (25mm) on the front AND a softer (22mm) on the rear. Reread what Fred wrote because he's absolutely correct. *Your* proposed antiroll bar changes on the car will simply aggravate your problem. Hopefully, the sheer number of those of us pointing this out will convince you. If, OTOH, you are a sworn Disciple of the Denizens of Dinan, give them the list of suggested changes above and ask them about it. I've met (actually, 'had dinner with') Steve and he's not an idiot. Although he'd love for you to buy a whole suspension package from him, I don't think he'd lie to you about the effect of those simple changes on understeer/oversteer. If you want a more tailored approach, you might contact my old pal, T.C. Kline, since he's done a lot with the Z4 in the past few years. You can tell him I sent you. -- C.R. Krieger (Knows they all understeer) >> > How to reduce understeer (or induce oversteer if taken far enough): >> [quoted text clipped - 35 lines] > C.R. Krieger > (Knows they all understeer) Next time you have dinner with Steve ask him to clear up his web site which states: "adds larger and adjustable front and rear anti-roll bars to reduce body roll for superior handling. The adjustable anti-roll bars provide the ability to fine-tune the system for closer to neutral balance reducing understeer. " You may also ask him to tell his engineers not to suggest roll bars to help reduce understeer. > Next time you have dinner with Steve ask him to clear up his web site which > states: [quoted text clipped - 5 lines] > You may also ask him to tell his engineers not to suggest roll bars to help > reduce understeer. Dinan's website is doubtless correct. It's your interpretation that's wrong. Relatively stiffer front bars will increase understeer. Relatively less stiff front bars will decrease it. Since nothing comes for free, decreasing the stiffness of the front bar by itself will also increase body roll. JRE >> Next time you have dinner with Steve ask him to clear up his web site which >> states: [quoted text clipped - 14 lines] > >JRE Missed the start of this but I have just test driven a 2006 E65 7 Series. The steering is very light but positive. At low speeds it's a kin to Jaguar XJ but at higher speeds it does stiffen up slightly and is nice but going from my E38 to the E65 takes getting used to and moving back to the large (by comparison) steering wheel of the E38 and heavier steering makes me want to go back to the dealer and say "I'll take it". However, there is a little matter of "where do I get the £40K from.................. Sir Hugh of Bognor The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it! Hugh Gundersen hsg@h-gee.co.uk Bognor Regis, W.Sussex, England, UK > Missed the start of this but I have just test driven a 2006 E65 7 > Series. The steering is very light but positive. At low speeds it's a > kin to Jaguar XJ but at higher speeds it does stiffen up slightly and is > nice but going from my E38 to the E65 takes getting used to and moving > back to the large (by comparison) steering wheel of the E38 and heavier > steering makes me want to go back to the dealer and say "I'll take it". BMW of course stuck with steering boxes on their larger cars long after the rest of the world went to R&P. Something to do with our US cousins not liking too positive steering on this sort of vehicle, IIRC. > However, there is a little matter of "where do I get the £40K > from.................. Tell me about it. ;-) Signature*He's not dead - he's electroencephalographically challenged Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> Missed the start of this but I have just test driven a 2006 E65 7 >> Series. The steering is very light but positive. At low speeds it's a [quoted text clipped - 6 lines] >the rest of the world went to R&P. Something to do with our US cousins not >liking too positive steering on this sort of vehicle, IIRC. Correct me if I'm wrong, but I recall that Mercedes held out even longer. > BMW of course stuck with steering boxes on their larger cars long after > the rest of the world went to R&P. Something to do with our US cousins not > liking too positive steering on this sort of vehicle, IIRC. More like; They wanted to jam a big V8 lump in the engine compartment and couldn't manage to fit a steering rack in there too. A RB steering box is tiny by comparison and the tie rods, arms and links can be made to go all over the place to clear the engine. Signature-Fred W >> BMW of course stuck with steering boxes on their larger cars long after >> the rest of the world went to R&P. Something to do with our US cousins [quoted text clipped - 5 lines] > tiny by comparison and the tie rods, arms and links can be made to go all > over the place to clear the engine. An surprisingly, the RB in my 540 works quite well. Very crisp steering, handles like a dream. Not as crisp or nimble as my M3, but you wouldn't expect it to be. > > BMW of course stuck with steering boxes on their larger cars long > > after the rest of the world went to R&P. Something to do with our US > > cousins not liking too positive steering on this sort of vehicle, > > IIRC. > More like; They wanted to jam a big V8 lump in the engine compartment > and couldn't manage to fit a steering rack in there too. A RB steering > box is tiny by comparison and the tie rods, arms and links can be made > to go all over the place to clear the engine. All over the place describes the steering response, too. Strangely I've got another make not dissimilar in size to a 5 Series which was also available with 4, 6 and eight cylinder engines. Diesel too. But with R&P steering and designed in the '70s. I'm not quite sure what there is about a small V-8 that would make fitting R&P steering any more difficult than with a six. Signature*Some people are alive only because it's illegal to kill them * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >>>BMW of course stuck with steering boxes on their larger cars long >>>after the rest of the world went to R&P. Something to do with our US [quoted text clipped - 7 lines] > > All over the place describes the steering response, too. Yes. My experience with my '94 E34 was it was pretty loosie goosie compared to my '95 E36. Of course in addition to RB vs R&P I'm comparing 3's and 5's. Probably not a fair comparison. The one E39 6 cylinder (R&P) that I drove seemed to have nice tight steering. But it was almost new. > Strangely I've got another make not dissimilar in size to a 5 Series which > was also available with 4, 6 and eight cylinder engines. Diesel too. But > with R&P steering and designed in the '70s. I'm not quite sure what there > is about a small V-8 that would make fitting R&P steering any more > difficult than with a six. Me either, but thats the story I heard. Hey, I read it on the internet, so it must be true... ;-) Signature-Fred W > > In article <t5SdnT3jPdzAVmDYnZ2dnUVZ_oLin...@comcast.com>, > [quoted text clipped - 15 lines] > cylinder (R&P) that I drove seemed to have nice tight steering. But it > was almost new. I have an E46 M3 (euro) and my 130k mile E38 V8 doesn't steer *all* that much worse to the point that I enter into a corner and think "woah!" Sure it won't do the high speed rough stuff with quite as much confidence but it's certainly not comedy cornering like a volvo. > > Yes. My experience with my '94 E34 was it was pretty loosie goosie > > compared to my '95 E36. Of course in addition to RB vs R&P I'm > > comparing 3's and 5's. Probably not a fair comparison. The one E39 6 > > cylinder (R&P) that I drove seemed to have nice tight steering. But it > > was almost new. > I have an E46 M3 (euro) and my 130k mile E38 V8 doesn't steer *all* > that much worse to the point that I enter into a corner and think > "woah!" Sure it won't do the high speed rough stuff with quite as > much confidence but it's certainly not comedy cornering like a volvo. But the type of steering should have little to do with the cornering ability - that's down to the suspension geometry. It's the steering 'feel' that changes. Generally, R&P lets you feel the road surface better - and some simply don't like this. It's much more noticeable on small cars with unassisted steering, though. Signature*Welcome to sh.t Creek - sorry, we're out of paddles* Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > > All over the place describes the steering response, too. > Yes. My experience with my '94 E34 was it was pretty loosie goosie > compared to my '95 E36. Of course in addition to RB vs R&P I'm > comparing 3's and 5's. Probably not a fair comparison. The one E39 6 > cylinder (R&P) that I drove seemed to have nice tight steering. But it > was almost new. And should stay like that unlike RB steering where the box can wear as can all those extra ball joints, etc. The E39 makes perhaps the best comparison - especially early US iron block sixes where the weight is close to the V-8 > > Strangely I've got another make not dissimilar in size to a 5 Series > > which was also available with 4, 6 and eight cylinder engines. Diesel > > too. But with R&P steering and designed in the '70s. I'm not quite > > sure what there is about a small V-8 that would make fitting R&P > > steering any more difficult than with a six. > Me either, but thats the story I heard. Hey, I read it on the internet, > so it must be true... ;-) On most vehicles the rack runs under the engine and there's no intrinsic reason for the crank throws of one to be greater than the other so it's down to sump design. I'd certainly like an explanation of why the E39 used different systems apart from the one I gave earlier. SignatureDave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> Next time you have dinner with Steve ask him to clear up his web site >> which states: [quoted text clipped - 14 lines] > > JRE Exactly. So the premium option (after first ditching the bling-bling staggered tire setup) is to increase the rear stabilizer bar. That way you can dcrease understeer *and* reduce body roll at the same time!! Signature-Fred W > >> Next time you have dinner with Steve ask him to clear up his web site > >> which states: [quoted text clipped - 18 lines] > staggered tire setup) is to increase the rear stabilizer bar. That way > you can dcrease understeer *and* reduce body roll at the same time!! Albeit on a non-BMW, I added a larger front anti-roll bar and it reduced the understeer. The body roll had been causing the front end's geometry to become less than optimum and the new bar kept more tyre in contact with the road. Whether that would work with the Z4 I dunno but the "bigger fronts always cause more understeer" folk should probably add an "in general" in there somewhere. If I were the OP I'd be putting on some Eibachs and new dampers. BMW suspension isn't always great from the factory for ride or handling. I did that on my E36 and coupled with decent tyres would out corner pretty much anything out there including my M3 and certainly any Mini. >>>>How to reduce understeer (or induce oversteer if taken far enough): >>> [quoted text clipped - 45 lines] > You may also ask him to tell his engineers not to suggest roll bars to help > reduce understeer. Considering what he says: Yes, increasing the size of both the front and rear roll bars (aka stabilizer bars, sway bars, etc.) will reduce body lean. However it will not improve understeer unless the rear sway bar is increased more than the front. Signature-Fred W > Next time you have dinner with Steve ask him to clear up his web site which > states: > "adds larger and adjustable front and rear anti-roll bars to reduce body > roll for superior handling. The adjustable anti-roll bars provide the > ability to fine-tune the system for closer to neutral balance reducing > understeer. " ADJUSTABLE antiroll bars. Not all bars *are* adjustable. In fact, most AREN'T. You simply stated that you were putting on a much larger one in front and a somewhat larger one in the rear. The net effect of doing this with NONADJUSTABLE bars is to enhance understeer. You MAY be able to adjust the relative balance of this with adjustable bars - and that's what Dinan is selling. Are you comfortable with crawling under your car to make those adjustments while testing or are you going to have to haul it back to a tech to do it every time? You still haven't presented the engineers with that list, have you? Why not? Afraid to discover we aren't all idiots here? > You may also ask him to tell his engineers not to suggest roll bars to help > reduce understeer. In the right circumstances, the right bars can help. But simply slapping on a set without the slightest clue of how they work or what effect they will have is a foolish waste of money. You will ultimately end up with an ill-handling pig and a lot lighter wallet. If you're going to buy Dinan's stuff, you'd better plan on buying ALL OF IT. You aren't yet educated enough to get a satisfactory result doing it piecemeal. You would do well to avail yourself of your local BMW CCA chapter's experts to fill in your knowledge gaps. -- C.R. Krieger >> Next time you have dinner with Steve ask him to clear up his web site >> which [quoted text clipped - 10 lines] > be able to adjust the relative balance of this with adjustable bars - > and that's what Dinan is selling. Must be why I included the Dinan link. Are you comfortable with crawling > under your car to make those adjustments while testing or are you > going to have to haul it back to a tech to do it every time? Done it before. Will do it again. > You still haven't presented the engineers with that list, have you? Yep. They agree with me. <rest snipped because of lack of relevence or worth> >>You still haven't presented the engineers with that list, have you? > > Yep. They agree with me. You have to be kidding. You asked the engineers at Dinan if putting a larger (and yes larger is stiffer) roll bar on the front and a smaller (yes softer) roll bar on the back would reduce understeer and they said YES? Are you perhaps confusing a salesperson for an engineer? That is total nonsense. Signature-Fred W >>>You still haven't presented the engineers with that list, have you? >> [quoted text clipped - 8 lines] > > That is total nonsense. They said the bigger sway bar goes on the front (maybe the bigger sway bar is softer). As for adjustments they said each has three holes, based on experience they said they set the initial adjustment in the center hole and have not had any problems in the past or cars being returned for additional adjustments. They also recommended change tires, camber plates, sway bars as the most economical sequence to correct the understeer. Now I would like you to NOT worry about it any further. It's o.k. Everything is o.k. It's over. Find somebody else's car to obsess over. > Now I would like you to NOT worry about it any further. It's o.k. > Everything is o.k. It's over. Find somebody else's car to obsess over. What a strange fellow. You start a thread, talk rubbish, then feel got at. Next time try talking to the mirror. Signature* I like you. You remind me of when I was young and stupid Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > What a strange fellow. You start a thread, talk rubbish, then feel got at. > > Next time try talking to the mirror. I think he's new. He should soon learn that there's lot of people on here keen just to keep arguments going when really people should have better things to do. Me included ;-) >>What a strange fellow. You start a thread, talk rubbish, then feel got at. >> [quoted text clipped - 3 lines] > here keen just to keep arguments going when really people should have > better things to do. Me included ;-) No there's not! ;-) Signature-Fred W >> What a strange fellow. You start a thread, talk rubbish, then feel got >> at. [quoted text clipped - 4 lines] > here keen just to keep arguments going when really people should have > better things to do. Me included ;-) I am sure Dave hasn't got that message. > > What a strange fellow. You start a thread, talk rubbish, then feel got at. > > > > Next time try talking to the mirror. > I think he's new. He should soon learn that there's lot of people on > here keen just to keep arguments going when really people should have > better things to do. Me included ;-) Of course. Little point otherwise. ;-) Signature*Virtual reality is its own reward* Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > They said the bigger sway bar goes on the front (maybe the bigger sway bar > is softer). FWIW the front is always the bigger of the two. > As for adjustments they said each has three holes, based on > experience they said they set the initial adjustment in the center hole and > have not had any problems in the past or cars being returned for additional > adjustments. OK, I retract my earlier statement. The "adjustable" sway bars I was talking about are the ones where the links on each end are variable in length. By using different holes drilled in the bar you *would* be changing the effective bar spring rate, albeit in very course and limited adjustments. > They also recommended change tires, camber plates, sway bars as the most > economical sequence to correct the understeer. > > Now I would like you to NOT worry about it any further. It's o.k. > Everything is o.k. It's over. Find somebody else's car to obsess over. Here's a free tip. If you want to stop a conversation, quit answering the replies. ;-) PS - Good luck with your suspension tuning. Seriously, I hope you can get the results you seek. Signature-Fred W >> They said the bigger sway bar goes on the front (maybe the bigger sway >> bar is softer). [quoted text clipped - 23 lines] > PS - Good luck with your suspension tuning. Seriously, I hope you can get > the results you seek. Thanks. I think this experience has confirmed my desire not to join any BMW clubs. >>>They said the bigger sway bar goes on the front (maybe the bigger sway >>>bar is softer). [quoted text clipped - 26 lines] > Thanks. I think this experience has confirmed my desire not to join any BMW > clubs. “I would never join a club that would have the likes of me as a member.” - Groucho Marx Signature-Fred W > >>>You still haven't presented the engineers with that list, have you? > [quoted text clipped - 11 lines] > They said the bigger sway bar goes on the front (maybe the bigger sway bar > is softer). No; the bigger bar is stiffer. That you even needed to speculate about that tells us that you are clueless. You are also a liar. You did not present them with that list of adjustments nor did they agree with *you* about anything - unless you misinterpreted their *a.s- kissing of the clueless customer* as 'agreement'. > As for adjustments they said each has three holes, based on > experience they said they set the initial adjustment in the center hole and > have not had any problems in the past or cars being returned for additional > adjustments. Mostly because overfunded ignorant dweebs like you think the car is better because you spent a lot of money on it, but have no idea how to tell. > They also recommended change tires, camber plates, sway bars as the most > economical sequence to correct the understeer. |
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