Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / October 2007
Tire pressure vs ride
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news - 25 Oct 2007 03:33 GMT Here's one I'm having a hard time figuring out:
My truck is a 90 Chev 1/2 Ton 4x4 reg cab longbox. Stock tires were a LT225/75R16, door sticker recommends 45psi. Current tires are LT 265/75R16's (IIRC load range D) They're Canadian Tire M&S tires. (Thought I wanted the ground clearance for winter - they're the largest stock size you could get on that truck, but now I'm wishing I hadn't bothered.)
Normally I was running them around 40-45psi, and the truck drove fine, but like a 17 year old truck. When I was towing my race car this summer, I bumped them up to max pressure (65 psi) because we're fully loaded with gear, car, and trailer.
I forgot to lower the pressure after - and the truck rides SMOOTHER. Enough smoother that my wife was wondering if I changed the shocks or something and hadn't told her. This is completely the opposite of what I was expecting - I was expecting the back tires to be just about bouncing off the pavement over bumps.
Can anybody explain how adding 20 psi to the tires would smoothen the ride out on an old truck?
(The shocks aren't new, only had the truck 2 years, so I'd guess they're probably 5 years old and this thing was a farm truck for the first 15 years of existence...)
Ray
Built_Well - 25 Oct 2007 22:55 GMT news wrote:
> Here's one I'm having a hard time figuring out: > [quoted text clipped - 24 lines] > > Ray ========
That's a good question. The recommended tire pressure in my manual for an '06 Camry LE is 29 psi. 29 psi also appears on the sticker in the door jam.
29 psi produces a nice, smooth ride. When I pumped up the stock P205/65R15 tires by 5 psi to 34 psi, I definitely experienced a rougher ride--could easily feel the bumps. Didn't like it much at all. But my gas mileage seemed to improve from 20 mpg city driving to 24 mpg city driving, a 20 percent improvement. 20 percent seems like a lot. Is that even possible? I was expecting 5 percent at most.
Anyway, I next pumped up the tires to 38 psi, 9 psi over the recommended 29 psi. The stock Goodyear Integrity tires have a maximum cold tire inflation pressure of 44 psi, according to the sidewall, so I'm within the safety margin. Well, I don't know if it's just in my mind, but 38 psi feels smoother to me than 34 psi--I don't feel the bumps as much, and I like the ride as much as at the recommended 29 psi.
mjc13<REMOVETHIS> - 26 Oct 2007 04:47 GMT > news wrote: > [quoted text clipped - 49 lines] > than 34 psi--I don't feel the bumps as much, and I like the ride > as much as at the recommended 29 psi. I generally run our cars at about 5 psi (cold) below the maximum - the figure posted on the car is almost always too low for both fuel economy and a good safety margin. I get similar improvements in economy. As for ride, different vehicles seem to be affected differently. I suspect it may have something to do with shock/strut damping rates interacting with sidewall damping rates at various pressures, but that's only a guess. One other thing I've noticed: the increased wear I regularly get warned about never happens - we always take our tires off because of extreme age, with plenty of even tread left on them...
Built_Well - 26 Oct 2007 05:01 GMT > I generally run our cars at about 5 psi (cold) below the maximum - > the figure posted on the car is almost always too low for both fuel [quoted text clipped - 5 lines] > regularly get warned about never happens - we always take our tires off > because of extreme age, with plenty of even tread left on them... ========
Yeah, I guess there's suppose to be balding that occurs with over-pumped tires (loss of tread in the middle of the tire). Nice to hear that's not necessarily so.
I was thinking of going back to 34 psi from 38 (29 being recommended by the manual), but now that I hear you're not experiencing problems, I might just leave'm at 38 psi.
EdV - 26 Oct 2007 14:48 GMT > > I generally run our cars at about 5 psi (cold) below the maximum - > > the figure posted on the car is almost always too low for both fuel [quoted text clipped - 17 lines] > that I hear you're not experiencing problems, I might > just leave'm at 38 psi. I am using 31-32 psi. I never tried going more than that. Maybe I should try it too. However, many recommend lowering pressure in snow or wet roads, and its been raining in NJ for sometime now.
Mike Romain - 26 Oct 2007 17:54 GMT >>> I generally run our cars at about 5 psi (cold) below the maximum - >>> the figure posted on the car is almost always too low for both fuel [quoted text clipped - 20 lines] > should try it too. However, many recommend lowering pressure in snow > or wet roads, and its been raining in NJ for sometime now. Wow....
Unlike some I seem to be reading the right 'books' and running tires fully loaded with air when the vehicle weight doesn't need that is not only wrong, it is dangerous.
When I overinflate my tires by as little as 8 psi, I only end up with 3 1/2" of tread in the center of the tire touching ground. They will then spin really easy and slide out easy. The U shape this causes also lets water under the edges of the tire so it hydroplanes like mad. Very Very unsafe!
When I run proper pressure for the load, in my case 28-29 psi around town and 32 loaded for highway trips, I then get a nice 7" of the available 7.5" of tread touching the ground and no issues in the rain. My tires will take 44 psi 'if' I put that kind of load on it to 'need' that much air.
I 'also' 'use' my tires, I don't change them from age, so I actually 'see' the wear patterns.
Proper inflation allows my $225.00 each, tires to wear all the way down evenly.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile...
clifto - 26 Oct 2007 18:23 GMT > Proper inflation allows my $225.00 each, tires to wear all the way down > evenly. The more I think about this issue, the more it occurs to me that the automotive engineer who specified the tire pressure for my make and model of car and my tire size probably knows more about proper inflation than the wrench down the street who says to inflate to the maximum allowable pressure shown on the sidewall. So I look at the sticker behind the car door and inflate accordingly.
 Signature One meter, to within 0.0125% accuracy (off by just under .005 inches): Three feet Three inches Three eights of an inch
EdV - 26 Oct 2007 19:14 GMT > > Proper inflation allows my $225.00 each, tires to wear all the way down > > evenly. [quoted text clipped - 11 lines] > Three inches > Three eights of an inch Very well said, I never thought of it that way. I tend to over inflate a few psi more because I imagine tire gauges have some reading inconsistencies and the fact that my tires still *looks* like it still needs some air. I'm thinking over inflation would have the lesser evil compared to a under inflated tire.
ChrisCoaster - 27 Oct 2007 00:21 GMT > > > Proper inflation allows my $225.00 each, tires to wear all the way down > > > evenly. [quoted text clipped - 19 lines] > > - Show quoted text - _____________________ Me too. Only I overinflate the door pressure by 1-2lbs depending on the season and the handling of the car I'm driving. Just a tip on your tires *looking* like they need more air: Radials tend to look a little "flatter" than equivalent sized bias plies set to the same pressure.
-CC
dbu. - 27 Oct 2007 00:42 GMT > > > > Proper inflation allows my $225.00 each, tires to wear all the way down > > > > evenly. [quoted text clipped - 27 lines] > > -CC Five lbs makes quite a difference in ride. I keep mine at five under max too, at around 30 lbs
clifto - 27 Oct 2007 22:00 GMT >> The more I think about this issue, the more it occurs to me that the >> automotive engineer who specified the tire pressure for my make and model [quoted text clipped - 8 lines] > needs some air. I'm thinking over inflation would have the lesser evil > compared to a under inflated tire. Rather than compensate for an inaccurate gauge, I decided to slog around until I got a gauge I trust. I have a friend who's almost anal about tire pressure (yet who ignores the manufacturer's recommendations), and my gauge reads the same as his three favorite gauges.
Bought a cool new compressor from Costco a while back and just got around to trying it. The compressor is great, but the gauge on it is off by a lot; it read about 27 when I got the tire to 32PSI by my aforementioned tested gauge.
 Signature One meter, to within 0.0125% accuracy (off by just under .005 inches): Three feet Three inches Three eights of an inch
Ray - 26 Oct 2007 19:20 GMT >> Proper inflation allows my $225.00 each, tires to wear all the way down >> evenly. [quoted text clipped - 5 lines] > pressure shown on the sidewall. So I look at the sticker behind the car > door and inflate accordingly. Except these people all have a say in the tire pressure: Marketing. "Dubs" for everyone! The people who mandate that the OEM tires last through the warranty period. The company lawyers who don't want a Ford/Firestone repeat. The fuel economy guys. The handling department. The NVH department.
No, I'm not smarter than the car company, but I'm also not bound by the same rules they are.
I like to use the cold air intake (intake lid) on my Trans Am. Aftermarket ones are worth 10hp. How can GM do such a lousy job? In this case, it's induction noise - the GM piece has a big honkin' resonator on it and the aftermarket ones don't. More air coming in = more noise. Also, the GM one probably cost them $15 or less, mine was $100. (FWIW, I also didn't want to cut up a factory piece when installing nitrous, and I can confirm the intake lid is worth a tenth at the strip.)
It's all a tradeoff.
Ray
z - 30 Oct 2007 21:15 GMT On Oct 26, 2:20 pm, Ray <ray@!rollingviolation.example.com.invalid> wrote:
> >> Proper inflation allows my $225.00 each, tires to wear all the way down > >> evenly. [quoted text clipped - 13 lines] > The handling department. > The NVH department. Indeed; the "story" on the FordFirestoneFiasco was that lower than optimal pressure was specified specifically to reduce tire grip, in order to prevent getting enough side Gs to tip the beast over. Unfortunately, when that came up against a run of tires on the low side of the safety margin for abuse, due to management problems at the factory, they blew.
"For example, the documents show that Ford lowered its recommended tire pressure on the 15-inch Firestone P235 ATX tires to improve the Explorer's stability after engineering simulations showed it failing J-turn emergency-avoidance maneuvers in 1989. The lower tire pressure was considered a critical component of the Explorer's safe handling, enough so that Ford weighed adding a warning sticker inside the vehicle alerting occupants that a tire inflation level of 26 pounds per square inch was "required" to help prevent "loss of control, rollover and serious injury." The warning labels were never added, however. A Ford spokesman said Tuesday that the company made design and suspension modifications in the final months before the Explorer's February 1990 launch that obviated the need. Ford considered and rejected several major design changes, including widening the Explorer by 2 inches to lower its center of gravity. Instead, Ford lowered the vehicle by one-half inch and stiffened its front suspension springs. "The engineering team felt they had achieved their goal of becoming a safety leader, so there was not the need for that warning label," said Ford spokesman Jon Harmon. Nevertheless, Ford's decision to lower the recommended tire pressure on its Explorer tires to 26 pounds per square inch, from 30 pounds per square inch recommended by Firestone, is expected to figure prominently when a fourth congressional hearing over the Firestone tire crisis begins tomorrow in Washington. -Role of Ford Explorer Design Is Studied In Connection With Firestone Tire Suits THE WALL STREET JOURNAL September 20, 2000
johngdole@hotmail.com - 27 Oct 2007 05:31 GMT > > Proper inflation allows my $225.00 each, tires to wear all the way down > > evenly. [quoted text clipped - 11 lines] > Three inches > Three eights of an inch johngdole@hotmail.com - 27 Oct 2007 05:34 GMT I'd use the recommended pressure. No less. No more. Yeah, Fords/ Firestones were just too bad, unfortunately.
Michelin on tire life and air pressure: http://www.michelinman.com/tire-care/tire-saving-tips/ http://www.michelinman.com/tire-care/tire-basics/
> > Proper inflation allows my $225.00 each, tires to wear all the way down > > evenly. [quoted text clipped - 11 lines] > Three inches > Three eights of an inch johngdole@hotmail.com - 27 Oct 2007 05:40 GMT I'd use specified pressure. No more, no less.
Michelin tire life and air pressure: http://www.michelinman.com/tire-care/tire-saving-tips/
> > Proper inflation allows my $225.00 each, tires to wear all the way down > > evenly. [quoted text clipped - 11 lines] > Three inches > Three eights of an inch Mark A - 27 Oct 2007 06:45 GMT > I'd use specified pressure. No more, no less. > > Michelin tire life and air pressure: > http://www.michelinman.com/tire-care/tire-saving-tips/ They say that to protect themselves against lawsuits, since changing the air pressure can have an adverse affect on rollover tendency of a vehicle, especially SUV's and trucks. Trust me, there are many rollover accidents and deaths each year, and some of those are with Michelin tires. If Michelin started recommending tire pressures different from the vehicle manufacturer, they would be sued for hundreds of millions of dollars each year as a result of the accidents and deaths.
With regard to their rotation diagram, it is clearly wrong since you never want to cross tire from one side to the other. It causes a horribly harsh ride when you do that.
E Meyer - 27 Oct 2007 18:14 GMT On 10/27/07 12:45 AM, in article WfAUi.46758$c9.4410@bignews8.bellsouth.net,
>> I'd use specified pressure. No more, no less. >> [quoted text clipped - 12 lines] > want to cross tire from one side to the other. It causes a horribly harsh > ride when you do that. Huh? Total BS.
mjc13<REMOVETHIS> - 28 Oct 2007 11:13 GMT >>Proper inflation allows my $225.00 each, tires to wear all the way down >>evenly. [quoted text clipped - 5 lines] > pressure shown on the sidewall. So I look at the sticker behind the car > door and inflate accordingly. Has anyone at all said to inflate to the maximum? Was the tire you're using now on the market when your car was designed? Do you think that all makes and models of tire were tested by this hypothetical engineer...?
Bruce L. Bergman - 28 Oct 2007 20:15 GMT >>>Proper inflation allows my $225.00 each, tires to wear all the way down >>>evenly. [quoted text clipped - 10 lines] >that all makes and models of tire were tested by this hypothetical >engineer...? Well, some people do say to blindly "Inflate to the tire sidewall maximum", but thankfully it's getting rarer as knowledge is diffused. That maximum pressure is very rarely going to get you the optimum ride, traction and tread life, usually it will make things much worse.
If the car still has the exact OEM size and type tires on it, then the car maker recommendations on the door sticker are still valid. But people often switch to different size, speed rating or load rating tires and sometimes rim size is also changed, and then you need to (metaphorically) throw the car sticker out the window and go with the tire maker's Load & Pressure Chart as the primary reference.
The one thing that is important about the manufacturer label is any front/rear pressure biases, usually related to weight distribution in the vehicle - the tires at the heavier end of the car are usually kept higher. If you are figuring pressure for new tires place the same ratio of bias between the axles, even if the overall pressures are higher or lower because of the different tire type.
--<< Bruce >>--
Retired VIP - 28 Oct 2007 22:21 GMT >>>>Proper inflation allows my $225.00 each, tires to wear all the way down >>>>evenly. [quoted text clipped - 31 lines] > > --<< Bruce >>-- The sticker the car manufacturer puts on the door regarding tire pressure is only for the tires that originally came on the car. When those tires are replaced, you should go with the tire manufacturer's recommendation on tire pressure. The weight-bias tire pressures between front and back might be different also. You can ball-park the pressure based on the max pressure on the sidewall or you can take the car to a grain elevator/truck scale and weigh the front and back axles. Then look up the recommended tire pressure for that weight. The tire dealer should have the pressure chart.
Jack
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clifto - 29 Oct 2007 00:49 GMT > <blnospambergman@earthlink.invalid> wrote: >>>> [quoted text clipped - 38 lines] > those tires are replaced, you should go with the tire manufacturer's > recommendation on tire pressure. I can't find any. Tire dealer had no recommendation other than "30 pounds each", which they recommend for all cars to all people (great, huh?). If you can find a recommendation for TripleTreds on an '89 Grand Marquis I'm all ears.
> The weight-bias tire pressures > between front and back might be different also. You can ball-park the > pressure based on the max pressure on the sidewall or you can take the > car to a grain elevator/truck scale and weigh the front and back > axles. Then look up the recommended tire pressure for that weight. > The tire dealer should have the pressure chart. The weight on my rear axle is definitely less than the weight on my front, I'm pretty sure even with the trunk and passenger compartment loaded to capacity. The manufacturer specified a bias of 4 PSI rear for all loads.
 Signature One meter, to within 0.0125% accuracy (off by just under .005 inches): Three feet Three inches Three eights of an inch
Retired VIP - 30 Oct 2007 01:08 GMT >> <blnospambergman@earthlink.invalid> wrote: >>>>> [quoted text clipped - 43 lines] >If you can find a recommendation for TripleTreds on an '89 Grand Marquis >I'm all ears. Do you know who manufactured the tires? If so, contact the manufacturer and ask for a chart.
>> The weight-bias tire pressures >> between front and back might be different also. You can ball-park the [quoted text clipped - 6 lines] >I'm pretty sure even with the trunk and passenger compartment loaded to >capacity. The manufacturer specified a bias of 4 PSI rear for all loads. I keep 40 front and 35 rear on my 2000 Grand Marquis. That seems to give the best tire wear but the ride is a bit rougher. The tire sidewall list 45 psi at max load.
Jack
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cuhulin@webtv.net - 30 Oct 2007 04:31 GMT TP whatever (Tire Pressure) was indebially painted on our Army vehicles.So was, Official only.One time I ''borrowed'' a Jeep to go to down town Saigon to viisit my Vietnamese girl friend for a few minutes.Al, in Mesquite,Texas said it was a good caper. cuhulin
z - 30 Oct 2007 20:30 GMT > The weight on my rear axle is definitely less than the weight on my front, > I'm pretty sure even with the trunk and passenger compartment loaded to > capacity. The manufacturer specified a bias of 4 PSI rear for all loads. Might be a handling thing; more pressure in the rear = more grip in the rear = more understeer than oversteer = safety on the road; and, no offense, but I would guess the Grand Marquis doesn't get inherently excellent handling from chassis design, so tire pressure tuning is probably in order.
ChrisCoaster - 30 Oct 2007 01:03 GMT > On Sun, 28 Oct 2007 12:15:27 -0700, Bruce L. Bergman > [quoted text clipped - 48 lines] > Jack > - Show quoted text - Understood. But just because one plus-sizes their tires, or, keeps the same size tire but goes up a speed rating or two - IE from S to T or V-rated, does not mean all common-sense goes out the window and the new tires are automatically set to the max. pressure placard on the tire. I just had an alignment done and the car was riding smooth - too smooth, in fact the tires were barely gripping the road! (sure enough, the alignment shop had inflated them to 35psi - I checked - they were 38-39psi hot). So basically NOBODY in this country knows how to set tire pressure!
I know my "new" Malibu(Saab-based) has a pretty hard suspension and actually rode better with the original S-rated tires. But I went ahead and got H-rated tires of the same spec. With the S-rated tires, I could inflate them up to 3psi over the door sticker(30psi), improve my rolling, and still have a smooth supple ride; with the H-rated Yokohamas - 31psi. Anything higher and the whole damn car rattles like Arlen Specter's jaw!
-CC
ChrisCoaster - 01 Nov 2007 00:41 GMT > On Sun, 28 Oct 2007 12:15:27 -0700, Bruce L. Bergman > [quoted text clipped - 47 lines] > > Jack _____________________
*Posted two days ago but disappeared into cyberspace* <sigh> here we go again...
Just because one plus-sizes their tires or goes up a speed rating(IE from S to H or V rated) doesn't mean to throw common sense out the window and fill the tires to their maximum pressure as listed on the tire.
My 2005 Malibu(Saab based) came with S rated tires. The door placard said 30psi. I could go as high as 33 and still be comfortable with them and get better gas mileage. I recently upgraded to the same size tire, a Yokohama, but H-rated. Now I can go up only a pound or two over the door placard pressure. The Malibu has a hard suspension already, and going significantly above GM's recommendations is like riding the Coney Island Cyclone. Fun, but not as fun. 31psi is where they'll stay.
-CC
Daniel Who Wants to Know - 29 Oct 2007 05:46 GMT >>>>Proper inflation allows my $225.00 each, tires to wear all the way down >>>>evenly. [quoted text clipped - 32 lines] > > --<< Bruce >>-- I know of one vehicle for sure where the factory recommended pressures aren't the best to choose even for the OE tires and that car is the '01-'03 Prius. The factory recommends 35 front 33 rear but many owners have noticed underinflation wear patterns such as edges wearing faster than the center at the factory pressures and have used higher pressures instead such as 40/38 or 42/40. Some have even foolishly exceeded the sidewall max cold ratings but I have not yet heard of anyone showing overinflation patterns such as center wearing faster. A side bonus to this seems to be increased fuel mileage
ChrisCoaster - 29 Oct 2007 18:00 GMT On Oct 28, 3:15 pm, Bruce L. Bergman <blnospamberg...@earthlink.invalid> wrote:
> On Sun, 28 Oct 2007 10:13:27 GMT, "mjc13<REMOVETHIS>"
> The one thing that is important about the manufacturer label is any > front/rear pressure biases, usually related to weight distribution in [quoted text clipped - 6 lines] > > - Show quoted text - __________________ Not if you owned a 1996 Ford Contour GL as I once did, size P205-60R15. Front: 31psi Rear: 34.
Try ta figger that one out!
-CC
z - 30 Oct 2007 20:20 GMT > > Proper inflation allows my $225.00 each, tires to wear all the way down > > evenly. [quoted text clipped - 11 lines] > Three inches > Three eights of an inch Back in the days when dinosaurs which came from Detroit ruled the Earth, it was pretty much a given that the recommended pressure was way low for reasons of ride comfort, and "serious" drivers would pump another five or so pounds in. The advent of compacts and Japanese cars has made this wisdom unreliable, but by the same token, you still can't rely on the recommended pressure to be the best performance (excluding comfort) wise. A little trial and error may be in order.
Elsewhere, I saw a rule of thumb **for an approximate starting place** for trial and error: Pressure in PSI= Total weight of car/100 + 2 lbs extra on the heavier end of the car + 2 lbs if car has stock suspension
(Notice that trial **and error** should take care that the error part isn't too bad.)
That said, my experience is that with pressures at recommended or a few lbs higher, I've never seen excess wear on the centers, indicative of overinflation.
Ray - 26 Oct 2007 19:13 GMT > Wow.... > [quoted text clipped - 23 lines] > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > 88 Cherokee 235 BFG AT's - Gone to the rust pile... That's the thing on my truck - I feel my tires are WAY overinflated, but the ride and traction say otherwise. unfortunately, it's going to snow here soon, so I'll see how the grip compares vs normal pressures.
I've been meaning to do that in the winter anyway - run my tires at 5 pound increments from 20 to 50 and see if I can determine any difference in handling or traction. I know on my Trans Am, I can feel the difference between 30 and 35. The tradeoff is 35 gives a sharper turnin but there's more traction at 30 - the back tires spin easier at 35.
Ray
z - 30 Oct 2007 20:23 GMT > >>> I generally run our cars at about 5 psi (cold) below the maximum - > >>> the figure posted on the car is almost always too low for both fuel [quoted text clipped - 48 lines] > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > 88 Cherokee 235 BFG AT's - Gone to the rust pile Interesting; normal recommendation is more inflation to prevent hydroplaning; might be a difference in tread pattern. I assume your tread pattern is pretty "aggressive" and therefore probably doesn't need help channeling the water out, compared to the close-treaded allseason car tires?
Mike Romain - 31 Oct 2007 00:22 GMT >>>>> I generally run our cars at about 5 psi (cold) below the maximum - >>>>> the figure posted on the car is almost always too low for both fuel [quoted text clipped - 50 lines] > need help channeling the water out, compared to the close-treaded > allseason car tires? I can see too low also allowing water to get under the center of the tread and causing trouble.
I do have large tread lugs which channel water although some folks cuss these tires in the wet. They behave for me. Most seem to be running them too hard though. They seem think larger tire means larger pressure.
We use a 'chalk' test to see. That is running some chalk marks across the tread and drive a short bit straight, then seeing how much chalk is left. On my style of tire, the best footprint for traction and handling leaves about 1/4" on each edge not touching.
Running either too low or too hard is pretty bad on large tires in particular and in certain conditions can cause big trouble.
I even remember the Volvo 240 GLT I used to own also didn't like hard tires either, they would hydroplane bad. They were 60 series, so 'wide' tires.
Mike
z - 31 Oct 2007 15:45 GMT > We use a 'chalk' test to see. That is running some chalk marks across > the tread and drive a short bit straight, then seeing how much chalk is > left. On my style of tire, the best footprint for traction and handling > leaves about 1/4" on each edge not touching. Oh yeah, good idea; I'd forgotten about that. A while back I got enamored of trying to take the tire temps across the tread like the pros do and wasted a lot of time and effort trying to get usable readings with the crappy equipment I can afford on no budget; should have remembered the simple old techniques.
mjc13<REMOVETHIS> - 28 Oct 2007 11:11 GMT >>> I generally run our cars at about 5 psi (cold) below the maximum - >>>the figure posted on the car is almost always too low for both fuel [quoted text clipped - 21 lines] > should try it too. However, many recommend lowering pressure in snow > or wet roads, and its been raining in NJ for sometime now. I sometimes drop the pressure in Winter, to maybe 34, but I think the tire itself matters more than the pressure.
mjc13<REMOVETHIS> - 28 Oct 2007 11:10 GMT >> I generally run our cars at about 5 psi (cold) below the maximum - >> the figure posted on the car is almost always too low for both fuel [quoted text clipped - 18 lines] > that I hear you're not experiencing problems, I might > just leave'm at 38 psi. 35 is fine if you aren't sure your readings are accurate. 38 is probably best of you can get it.
John S. - 26 Oct 2007 15:03 GMT > Here's one I'm having a hard time figuring out: > [quoted text clipped - 24 lines] > > Ray I had a similar experience with a Ford F250 with a heavy duty suspension. If the tires were run at 40 psi the ride was kinda jiggly. Run at 65 psi the ride was stiff but smooth if that makes any sense. The only reason I can give is that at low pressure those big tires flex a lot more than the shocks move. By upping the pressure the rate of flex or movement of tire and shock was brought closer together. Whether that is true or not is at least open to question. Seems to make sense to me though.
The downside of running those big tires at high pressure when the truck was empty was that the centers wore a bit faster than the outside.
Ray - 26 Oct 2007 19:07 GMT >> Here's one I'm having a hard time figuring out: >> [quoted text clipped - 37 lines] > truck was empty was that the centers wore a bit faster than the > outside. that was kind of my guess too. I'm going to see what happens when winter comes as far as traction goes - I'm worried that there won't be any grip because the tires will be overinflated, but it can't be any worse than the grip I had with the old tires (none) in the snow.
Ray
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