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Car Forum / Mazda / Mazda Miata / May 2005bouncing ride
My '97 Miata with 80K miles has an annoying ride. Even on smooth roads, if I hit a normal street manhole cover, the car bounces around. I know it is supposed to have a firm ride, but this seems dangerous... going around a curve and hitting a small bump results in a little side skid. I checked the shocks by pushing down on each corner of the car - no bouncing on the rebound, but it is very firm. Is it possible that the shocks are worn out, yet still do the job of eliminating rebound? Will replacing with a softer set help? Pushing down on the car to check the shocks on a Miata will not work ! Your shocks were all done at about 30K. Time to change. Buy some GOOD ones that will last and you will be happy. :-) Bruce RED '91 Thanks Bruce - Can you recommend a particular brand that will give a good ride? I think that you should go to, "Miata.net" and look on Marketplace. The price and kind of ride is so open that you should look at all makes. "KYB AGX"or "KYB AGN" are good. "Koni" has an adjustable height setting. "Tokico" is another one. The adjustable kind will let you pick the right feel that you want and are about the same price as the "stock" shocks. I have "Koni Yellow" on my '91 and when set on a low setting, the ride is about like "stock". I crank mine tighter when I Autocross. (Never run them "full soft" on the settings! The valves do not work properly. 1/4 turn off full soft works well.) Hope this helps :-) Bruce RED '91 >I think that you should go to, "Miata.net" and look on Marketplace. The >price and kind of ride is so open that you should look at all makes. [quoted text clipped - 7 lines] >run them "full soft" on the settings! The valves do not work properly. >1/4 turn off full soft works well.) New to me. I think mine are on full soft. In what sense do the valves not work correctly? Leon >Hope this helps :-) > > Bruce RED '91  SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) Hi Leon, The Koni rep. I got that from said that I should not run them at full hard or full soft. The valving at the very end of the settings "may not" work properly and not to "bottom" the settings out, (hard or soft) Bruce RED '91 >Hi Leon, >The Koni rep. I got that from said that I should not run them at full >hard or full soft. The valving at the very end of the settings "may not" >work properly and not to "bottom" the settings out, (hard or soft) Thanks. I'll try changing them a bit and see whether I notice a difference. Leon SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) >My '97 Miata with 80K miles has an annoying ride. Even on smooth >roads, if I hit a normal street manhole cover, the car bounces around. [quoted text clipped - 7 lines] >Is it possible that the shocks are worn out, yet still do the job of >eliminating rebound? Will replacing with a softer set help? Just a thought - have you checked your tire pressure? When I bought my Miata, the tires were exactly 38 psi. Changing them to a more realistic 30 psi did wonders for the ride. > >My '97 Miata with 80K miles has an annoying ride. Even on smooth > >roads, if I hit a normal street manhole cover, the car bounces around. [quoted text clipped - 10 lines] > Miata, the tires were exactly 38 psi. Changing them to a more > realistic 30 psi did wonders for the ride. Even so, if he hasn't changed his shocks at 80k, he should. Adjusting tire pressure now would be putting a bandaid on the problem. My '91 has 77k miles and shocks are on the to-do list for the summer. I'm going with KYB AGX from Ebay. A set of four runs you just under $300 that way, and many other members report getting good shocks this way. They are new, just way cheaper than if bought anywhere else. Sorry Guys, but I have to rant about this one. I think unless you are going to offer good advice, then do not offer any advice. To say that the shocks are knackered after 30k is absolute rubbish. First of all mileage has nothing at all to do with shock wear, 80k on good roads will affect the shocks far less than 80k on bad roads, Mileage is an extremely rough gauge and only a gauge, a car with 80k may well have worn shocks, but I have had Miatas coming into the shop that have done 100k+ and drive better than they did new, my 94 only had its shocks changed last year, after over 130k and 10 years. Secondly a visual check of the shock will give you far more information than looking at the milometer, granted access is very tricky, but you need to carefully peel back the shock boot and check if any of the shocks are leaking. Correct tire pressure a Band-Aid!!!!! Your tire pressures are not a band aid mate they are a SAFTY ISSUE, and the cheapest ever handling fix you will ever get. If you are running a Miata at 38psi its going to handle like a Hippo on ice, only with less grace. If there are any suspicions about handling 9 out of 10 times its down to tires, if you put 10 people in a car with worn shocks, then replace them and give them another drive 9 out of the 10 won't even notice!!!! We once had a guy come to us for a service, we did the full service including adjusting his tire pressures, after he picked it up he came back in total amazement, he asked if we had fitted new suspension!!! This is the order I would tackle any handling problems. 1/ Tire pressure and wear, and doubts about wear change the tires, you will only ever usually have 1 high speed blow out in your life. 2/ Check the shocks for wear, leaking fluid on the stanchions is a big give away, also bouncing the car can give a very rough gauge, you need to bounce the car up and down about 3 times, when you are as far down as you can go, then let go, what you are looking for is the car to settle within the return bounce, if the car keeps bouncing up and down then it means you really need to have the shocks checked. 3/ go round you suspension with a torque wrench, check all the nuts and bolts are at the required torque settings, we have seen many rear sway bar bolts come off, giving the symptom you mentioned. 4/ If all above are ok then get your alignment checked, make sure you get a good shop though, as getting it set incorrectly is going to mess up everything. And come on guys lets not jump to conclusions that can end up costing people loads of money, think about what you are writing before you press send, making such sweeping statements doesn't help anyone. Cheers Mark. >> >My '97 Miata with 80K miles has an annoying ride. Even on smooth >> >roads, if I hit a normal street manhole cover, the car bounces [quoted text clipped - 21 lines] > that way, and many other members report getting good shocks this way. > They are new, just way cheaper than if bought anywhere else. > my 94 only had its shocks > changed last year, after over 130k and 10 years. That doesn't mean they weren't worn out at 30k (or 50k, or whatever). It just means you waited far too long to replace them. If Greek roads are as poor as you've described them, I'd think you'd be lucky to get 20k from OEM shocks. > Secondly a visual check of the shock will give you far more information than > looking at the milometer, granted access is very tricky, but you need to > carefully peel back the shock boot and check if any of the shocks are > leaking. A visual check will tell you nothing about internal wear. Leaking is only one mode of shock failure, and far from the most common. Bouncing on the bumper of a Miata is pointless. The first sign of failing shocks on a Miata is usually bottoming in the rear when going through dips. Of course, a Miata with defunct shocks can still be driven sedately for years, with only a ride penalty, as long as hard cornering or braking aren't required. Poise under stress will be absent, though. --- Lanny Chambers '94C, St. Louis http://www.hummingbirds.net/alignment.html Hi Lanny, You are right you could drive for many miles with defective suspension, if the car is driven as you say sedately, then most people would not even notice the suspension is defective. My shocks were knackered the rear right in particular was leaking badly, after I replaced my shocks I gave the old ones a good check over, 3 were still operating very well. As for wear and tear, as far as car components go the shock absorbers have a relatively easy life of it. The Basic but most widely used type of shock the Twin Tube design, works on the principle of fluid displacement and heat convection. By forcing a piston through oil or gas or oil and gas, shocks develop the hydraulic friction necessary to oppose the unwanted bouncing in your suspension. The hydraulic fluid located in the damper body, is forced through tiny holes (Orifices) in the piston head as it travels (compresses or rebounds). However, the orifices let only a small amount of fluid/gas through the piston, which in turn slows down spring and suspension movement. So the basic make up of a shock absorber are Piston, Valves, shock body, plus various seals washers nuts etc, Shock bodies are very sturdy usually only damaged in impacts, Piston failures are extremely rare, more often but still rarely dirt can cause internal wear and/or blocked/worn valves, as nearly all shock are very well sealed this is fairly rare, The 2 main reasons for shock failure are Contamination of the oil/gas, by various factors like excessive heat, or external interference like moisture But still the main failures as far as my experience goes are seals bursting/leaking, Internal wear as you say, only occurs if a seal is either leaking or burst, which will then cause wear, do to less lubricant being inside the body, as near on all the moving components within a shock body are immersed in some form of lubrication during both cycles, internal wear in a non leaking shock is extremely little. Because the Miata and most sport orientated cars have a firm ride with very limited suspension travel compared to a standard family car, it is often very difficult for the average driver driving sedately to tell if his cars shock absorbers are worn, for you to make such a sweeping statement that "The first sign of failing shocks on a Miata is usually bottoming in the rear when going through dips" again is complete rubbish, This is such a generalisation that it makes it a completely useless statement, there are not any accurate or consistent methods of measurement in that statement, there are so many variables, like ride height, spring strength, weight inside of the car, the speed at which you took the dip, not to mention the fact that 1 mans dip is another mans crater. Lastly I would bet a month salary, that if you took the average driver, put him in a standard Miata, with standard non trimmed bump stops, and got him to drive through a dip of your choice, he would not even tell the difference if he even hit the bumpstops, the transition is that smooth. I am not saying shocks do not wear before 30k, of course some faulty units will wear straight after fitment, what I am saying is that there is in no way shape or form, enough evidence to go around telling people in such confidence that their shocks are worn, the poster said the car had done 80k, the author of the reply did not even know if the shocks were changed in that time, advice is greatly appreciated, everyone here has been extremely helpful when I needed advice, I just think we have a responsibility to think about what advice we give. Cheers Mark. >> my 94 only had its shocks >> changed last year, after over 130k and 10 years. [quoted text clipped - 23 lines] > '94C, St. Louis > http://www.hummingbirds.net/alignment.html I appreciate all the discussion in response to my original posting! Nice to have such passionate people responding. For your information, I do not notice any bottoming out. I tried going over speed bumps at low speed and can feel very good travel in the shocks with no bottoming. However, with minor bumps at speed the shocks don't seem to respond quickly enough to travel up & down. The whole car shakes a bit when hitting a bump, with a little side-to-side motion involved. I've only had the car 1000 miles, no idea what previous owners did in replacing shocks, but the last owner was proud that he changed the oil every 2 months. He also replied to my question about when the timing belt was last changed with 'what's a timing belt?' ( I took care of that myself - fun job ) So I doubt shocks have been replaced. Pennsylvania roads are pretty bad, so the shocks have not had an easy life. I'll take the advice of the one person in this thread who said to check for leaks. But there is no lack of resistance in the shocks... more like no resilience is there. Tire pressure is 28 lbs, tires are cheapies with about 20% tread life left. I did notice that when my 220 lb friend rides with me, the car rides much better. Is this a good clue? Just 'too stiff' shocks? Glen > like no resilience is there. Tire pressure is 28 lbs, tires are > cheapies with about 20% tread life left. I did notice that when my 220 > lb friend rides with me, the car rides much better. Is this a good > clue? Just 'too stiff' shocks? The tires affect the ride as well. Since they are fairly worn I'd change them before the shocks (and NOT with cheapies). You may just be more sensitive to the feel of a very light car--220 lbs brings it up to more typical car weight. -John I have to agree with John, If you've only had the car a short while then it is going to feel strange. Don't want to offend you but have you driven many rear wheel drive light sports cars before your purchase? Before you do anything it may be best to find a Miata club in your area and go and meet those guys, if they are really nice a few may let you drive their cars as a comparison, if not I would ask a couple of the other members with the same sort of setup to drive your car. As I mentioned before it is difficult to notice a worn or defective shock during a sedate drive, but it does give you a comparison. It is well worth joining the local club and getting friendly with the members, if you buy them a beer they may even let you swap wheels, again for a comparison, I think you will be stunned by how different the car can feel with just new tires. Most have their favourites, I have found that Toyo T1-S work very well for my setup, style of driving and roads here, some complain of a sloppy feel and/or slow turn in, as the sidewalls are relatively soft, but on the road this is usually not a bad thing (within reason). Cheers Mark. >> like no resilience is there. Tire pressure is 28 lbs, tires are >> cheapies with about 20% tread life left. I did notice that when my 220 [quoted text clipped - 8 lines] > > -John > with minor bumps at speed the shocks don't seem to > respond quickly enough to travel up & down. The whole car shakes a bit > when hitting a bump, with a little side-to-side motion involved. This is the way shocks work. They resist fast movements, that's exactly how a damper works. Frankly it's not a very good design for automobiles but it's standard fare anyway. Progressive Suspension has been implementing some interesting technology for shocks that would probably work much better in sports cars but so far has only been implemented for offroad vehicles (for example, I have a shock like this on my mountain bike). Mountain bikers call it a "platform damper" but the idea is that in any position of the piston, the shock resists very slow movements (like in a car would be body roll), but allows small/fast movements (such as bumps). I think mostly most sports car drivers would not know what to think if they got in a car that felt like it rode smooth over bumps but had no body roll. But the idea of a regular car shock is this... fast movements are dampened because the fluid cannot be quickly pushed through the valve orifice. So high-speed small bumps will NOT cause the suspension to move, the shocks will resist that movement, so the car will just ride rough. Slow bumps or gradual bumps, anything that causes a slower movement of the shock (such as body roll) will not be damped by the shock. The harder the shock damping is, the less it will allow the suspension to be compliant over slower bumps/movements. So when you set your adjustable shocks on rock-hard, they will dampen even some body roll and transitional movement of the suspension in a corner or whatever, which are very slow movements by suspension standards. They will of course dampen all normal bumps and the car will feel like it has no springs. If you feel like the car rides too rough, then IF it has worn shocks, then new shocks will likely only make it worse. It's unfortunate that auto shock folks refer to "soft" and "firm" for damping settings. More accurate would be "fast" and "slow". More damping is "slow". Less damping is "fast". Mark's description of shock absorber wear is pretty much on, except that depending on how the damper works, sometimes there is a "shim stack" or "spring stack" kind of thing where the fluid is passed through orifices in the piston and then also has to go past a stack of shims (deflecting or bending them) in order to move from one side of the piston to the other, and the positioning/tension of these shims is how many adjustable dampers are adjusted. The number and thickness of shims would be how some shocks are tuned while apart on the bench. Anyway, the point is, if the shock uses shims then they eventually fatigue and bend so they reduce the damping of the shock and the car rides smoother over bumps but handling is compromised. Also as the inside of the shock tube wears and the piston sealing ring or whatever wears, then some fluid may be able to bypass the piston orifices and sneak around the seal which reduces damping, sometimes very significantly. If this o-ring/seal tears or comes off, then the shock is useless. Lastly, the size of the orifices themselves can wear and become enlarged, or at least worn so that where there was once a "corner" it's rounded off (I guess you'd call this a chamfer or a bevel from machining of the orifice in the piston). I would think this would be rare on a street car damper but on mountain bikes where every gram counts, an aluminum piston will wear like this just from fluid friction. So yes, shocks can wear, but when they do, at least until there is total failure and leaking of gas or fluid, the result is a more compliant ride. When they fail to prevent the car from bouncing or resonating when you compress the suspension, then they are in complete failure and have leaked fluid or gas or both, or have lost the o-ring on the piston so the fluid freely runs past the edge of the piston. Point is, though, if you think the car rides rough, then the shocks are probably not the cause, or at least worn out shocks are not the cause. "rides rough" is not a wear-related failure mode of an automobile shock. "rides rough" is usually a shock tuning/selection thing, or more likely, springs & sway bars. > Point is, though, if you think the car rides rough, then the shocks are > probably not the cause, or at least worn out shocks are not the cause. > "rides rough" is not a wear-related failure mode of an automobile shock. It is when worn shocks allow the car to hit the bumpstops too hard and too often. That's the typical first symptom in a car with less than two inches of suspension travel. --- Lanny Chambers '94C, St. Louis http://www.hummingbirds.net/alignment.html >>Point is, though, if you think the car rides rough, then the shocks are >>probably not the cause, or at least worn out shocks are not the cause. [quoted text clipped - 3 lines] > too often. That's the typical first symptom in a car with less than two > inches of suspension travel. I believe that. I would imagine hitting the bump stops feels very "rough". As I mentioned before the transition to the bump stop is actually very smooth If you look at http://www.virkki.com/jyri/miata/bumps.html There is more than enough information about Miata bumpstops, Apparently the first inch of bump stop travel is 150 lb/in against the standard spring rate of 100 lb/in, although this looks a lot in actual fact when you also include the compression characteristics of the damper, you would be very hard pressed to notice the say inch of bumpstop travel. I have found the you can ride on the bump stops and it not make too much difference, I checked my mates Miata with new standard shocks, all the travel was being used with only mild road driving, likewise on my AGX's with stock springs, on the lower settings. Also if you have lowered you car any more than 1" and you do not have the recessed Shock Mounts I will guarantee you are spending near on all your cornering time on the bump stops. In theory the shock does not control the amount of travel when you hit a bump, this should be held in check by the spring, but as Josh rightly pointed out it is not just the force of a bump that affects the shock, it is also the speed, so in practice the shock does play a part in limiting the travel, still I think some of you guys are being overly sensitive on the worn shock front, it would be nice to get a supposedly worn shock on a rig and measure it against a new one. Cheers Mark. >>>Point is, though, if you think the car rides rough, then the shocks are >>>probably not the cause, or at least worn out shocks are not the cause. [quoted text clipped - 6 lines] > I believe that. I would imagine hitting the bump stops feels very > "rough". Hi Josh, The little bit of knowledge I have on suspension is mainly from Motorbikes and MTB's, I still cannot understand why even mid priced shocks KYB, Koni, Spax do not have the same amounts of adjustment that has been available on sports bikes for years, as standard spec!!!! Rebound damping is something I miss having available to tune independently not together with compression damping, it would also be nice to have a choice of oil viscosity, or even the ability for the user to change the oil, like on Front forks. But then again thank god we do not have elastomers in our shocks!!!! To be honest Josh I had never heard of shim stack being used on car suspension. I think it is so easy to fall into the trap of thinking changing shocks will dramatically change the behaviour of the car, when in fact it is tire and alignment faults that cause near on all handling problems. Hi Pat, I am currently running a stage 3 FM suspension kit with KYB AGX shocks, For track and spirited road driving on smooth roads the AGX's better than stock, but I still feel that the standard shocks are still best for road use, throw some bumpy corners into the equation and the standard shocks prove to be even better. I have no technical data, or measurements to back this up, I am going purely on my seat'o'pants meter and feel, but I would swear that the rebound on the AGX's is no where near as fast as on the stock shocks, I am consistantly slower on bumpy corners, and consistantly do not have the confidence to enter known bumpy corners as fast on the AGX's, as tires, alignment, springs and sways were all set exactly the same I have to deduce its the shocks, I have tried variation on all 8 settings on the AGX's but still the same outcome. It's a difficult balance, on the track the FM Sways, firmer springs and availability to dial higher damping rates, means the car really suits my style of driving to me it feels and functions near on perfectly the only limiting factor is now only my driving ability, yet on the roads here I feel it is just to much. What's the answer? swap the sways shocks and springs every time I visit the track, errrrrr no thanks, I must have had the suspension in and out of my car at least 10 times in the last year, no more pleaseeeeeeee!!! As for shocks failing at the 20k mark, yikes!!!!! I did just over 60k in my Eunos last year, if they failed every 20k that means I should have changed my shocks 3 times in the last year!!!!!!! Forget about working out MPG I should be working out miles per shock!! And if my shock did fail within 20k I would be at the dealer the next morning extremely pissed, and demanding a replacement. Cheers Mark. >> with minor bumps at speed the shocks don't seem to >> respond quickly enough to travel up & down. The whole car shakes a bit [quoted text clipped - 67 lines] > "rides rough" is usually a shock tuning/selection thing, or more likely, > springs & sway bars. > As for shocks failing at the 20k mark, yikes!!!!! I did just over 60k in my > Eunos last year, if they failed every 20k that means I should have changed [quoted text clipped - 4 lines] > > Cheers Mark. Hi Mark, the shocks did not fail at 22K miles, I replaced them voluntarily because I had the money at the time and had heard the raves about the Koni adjustables. I had already installed larger sway bars and I fully understand about the negatives and positives depending on the road surface, but I felt that the Konis on near-soft setting offered a better ride on the street than the stock shocks did. This was with stock springs. This may have just been my personal perception and a need to justify spending $400.00 plus the time, blood and sweat spent installing them. :-) I currently have the coilover system with Eibach springs and KYB AGX shocks. It is not as street-friendly as the Koni/stock spring setup, but I find it to be acceptable for street use. I still think that the best option for a street-driven car is the Konis with stock springs. Pat I am running the same set up then mate, FM Sways, FM Tower Brace, FM Shock mounts, FM GC kit and AGX's. I did not try the Koni's as I had major problems with Koni's on an old Cossy I had, put me off for life. At the end of the day though mate, its your money, you worked hard for it, what ever you spend it on is up to you, I just get pissed when I see people spending other peoples money, without even asking basic questions. I am a bit touchy on this subject because I have spent over a year and god knows how much money getting a balanced setup that works on the road but can be tuned for the track. Yours definitely older, and just a little wiser Mark. >> As for shocks failing at the 20k mark, yikes!!!!! I did just over 60k in >> my Eunos last year, if they failed every 20k that means I should have [quoted text clipped - 21 lines] > > Pat > I appreciate all the discussion in response to my original posting! > Nice to have such passionate people responding. For your information, [quoted text clipped - 17 lines] > lb friend rides with me, the car rides much better. Is this a good > clue? Just 'too stiff' shocks? Depending on *where* you are in PA, the roads are pretty freakin' bad! If you're anywhere near the eastern end of the state, you might be interested in checking out the Lehigh Valley Miata Owners Club - we do lots of tech days and installs and might be able to help you out. The website is at www.lvmoc.net if you're interested and/or anywhere near us. </commercial> <grin> Iva & Belle.) '90B Classic Red.) #3 winkin' Miata >> >My '97 Miata with 80K miles has an annoying ride. Even on smooth >> >roads, if I hit a normal street manhole cover, the car bounces [quoted text clipped - 21 lines] >that way, and many other members report getting good shocks this way. >They are new, just way cheaper than if bought anywhere else. First the symptoms described (rides too firm) fit too high tire pressure better than worn shocks. Second, if the tire pressures are too high, spending hundreds of $ on new shocks won't fix it. Calling it a "bandaid" is just wrong. If the pressures are too high the ONLY way to fix it is to lower them. Third, while it is certainly possible, maybe even likely that his shocks are worn out, it is hardly the 100% certainty you make it out to be. > My '97 Miata with 80K miles has an annoying ride. Even on smooth > roads, if I hit a normal street manhole cover, the car bounces around. [quoted text clipped - 7 lines] > Is it possible that the shocks are worn out, yet still do the job of > eliminating rebound? Will replacing with a softer set help? One thing is that the factory shocks on the miata are not that great to begin with. I replaced the shocks on my previous 1996 model at 22K miles with Konis and noticed a big improvement the way that the car handled. I agree that to say that all miata shocks are gone at 30K is an exaggeration, but your's have definitely suffered a large amount of wear by now and I would bet my Miata versus a Del Sol that you will see a big improvement in ride quality if you replace the shocks, and an even bigger improvement if you go with Konis or KYB AGX shocks and leave them on a softer setting for street use. On the other hand, I have driven a miata with worn out shocks in a manner that was far from "sedate", and it still handled and hugged the road far better and with more safety than most of the sedans and any of the SUV's or trucks that I have driven. Pat |
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