cb@hlwpc.UUCP (Carl Blesch) (07/08/85)
I just bought new Michelin XH tires for my not-very-sporty 1980 Chevrolet Malibu, and the guy who installed them told me to keep the pressure at 34-35 pounds cold. That's the pressure listed on the sidewall as maximum. I've always kept my tires inflated to the manufacturer's recommendation printed in the manual and the door sticker (which for my Malibu is 26 pounds in front and 29 pounds in the rear) When I questioned the tire installer about his, he said in no uncertain terms to ignore the mfgrs. recommendation and keep them filled to the tire maker's maximum. Seems to me the installer should know his tires, but I'm reluctant to believe him without further comments. Can anyone confirm or deny this recommendation? Carl Blesch
mr@isrnix.UUCP (Are we) (07/09/85)
]:[ > From: cb@hlwpc.UUCP (Carl Blesch) > When I questioned the tire installer about this, he said > in no uncertain terms to ignore the mfgrs. recommendation > and keep them filled to the tire maker's maximum. i too have learned the same. i've had two sets of b.f. goodrich t/a radials installed in the past six years (52,000 miles on the first set!). both installers (one in virginia beach, the other here in bloomington) recommended keeping the tires inflated to the max. this i have done, and am probably no worse off. it would seem to me that with maximum tire pressure, so too would come maximum stability and ride. > Seems to me the installer should know his tires... i agree. who am i to question a man who has installed tens of thousands of b.f. goodrich tires? -- .:. / \ '|_|` michael regoli ...ihnp4!inuxc!iuvax!isrnix!mr <mr%isrnix.UUCP> letterman: worth the lack of sleep and lowered job performance?
9234dwz@houxf.UUCP (The Rev. Peak) (07/09/85)
->it would seem to me that with maximum tire pressure, so too would
->come maximum stability and ride.
->
With maximum pressure you'll get an increase in stability
and a harsher,firmer ride (better for performance not so good for
your behind or ears[increased road noise]).
In autosport competition tyres are usually at max. pressure but
bear in mind in most competition tyres are expendable as long as they
give MAXIMUM performance(longevity is not a prime consideration).
As you are buying a performance tyre max pressure might be the way
to go, HOWEVER if you notice the centre of the tyre wearing more
rapidly than the outer edges drop the pressure a bit.
->> Seems to me the installer should know his tires...
->
->i agree. who am i to question a man who has installed tens of
->thousands of b.f. goodrich tires?
->
-> michael regoli
->
Both points are valid , but is this installer the owner of the
shop ? Would he prefer to see you buy new tyres every year instead
of every year and a half ?
Dave Peak
@ ihnp4!hotel!dxp
"My buddy..................Buddy Bear !" - Jimmy Buffetnzm10@amdahl.UUCP (Neal Macklin) (07/10/85)
> I just bought new Michelin XH tires for my not-very-sporty > 1980 Chevrolet Malibu, and the guy who installed them told > me to keep the pressure at 34-35 pounds cold. That's the > pressure listed on the sidewall as maximum. I've always > kept my tires inflated to the manufacturer's recommendation > printed in the manual and the door sticker (which for my > Malibu is 26 pounds in front and 29 pounds in the rear) > When I questioned the tire installer about his, he said > in no uncertain terms to ignore the mfgrs. recommendation > and keep them filled to the tire maker's maximum. > > Seems to me the installer should know his tires, but I'm > reluctant to believe him without further comments. > Can anyone confirm or deny this recommendation? > > Carl Blesch Carl, I have a 77 Trans Am and have always kept the tires at the tire manufactures maximum (checked cold). Mileage is better, and the tires are wearing fine (over 55K so far). The Trans Am has a stiff ride anyway, but I'm sure that my high inflation isn't helping. It definitely corners better at the high pressure. You should watch your tires for center wear if you do this, but I doubt you'll see any. In fact, you'll probably see edge wear if you don't do this (and leave the tires at glove compartment spec. (low)). Car manufacturers seem to be more concerned with getting a softer ride than with tire wear and possibly reduced cornering. Though I thought they were supposed to be concerned with mileage.... You'll know your tires are too high if things are shaking loose from the car when you go over bumps! Good Luck. -- Neal Macklin (408) 737-5214 ...{hplabs,ihnp4}!amdahl!nzm10 [There are no opinions expressed in this article].
bhs@siemens.UUCP (07/10/85)
peoplethinkthatthislineiseatenbutitisnot,isit?youcanseeitafterall,canyounot? There is no cardinal rule on tire pressure It is a good idea to consider the manufacturers max. pressure as the upper permissible cold limit. However, it is not a must to obey that pressure setting. Car manufacturers will post a pressure recommendation which will give what they consider to be an appropriate ride/handling balance for the given car. So, for example, it seems that Chevrolet is trying to tell you to run lower tire pressures in order to give you a softer ride over small bumps, expansion joints, etc. Instead of blindly obeying either the tire merchant's recommendation or Chevrolet's recommendation, you should really find a setting that you like for your personal driving. For example, you could experiment with various settings between the manuf. max. and Chevrolet's setting. Set the tire pressure to maximum pressure, and drive around like that for two days. Then, try out Chevrolet's setting. Notice how the car got smoother, but flabbier in the corners? Then, after a few days, try out a pressure setting in between- say 31 front, 29 rear. What I am trying to say is : juggle the figures around until you like the ride. On my car, I run 32 front, 35 rear (cold). By the by: the correct procedure for checking tire pressure: before you leave the driveway in the morning, right after breakfast, you should check the tire pressure. Then, note how much each tire is off by. Later on at the gas station, check the pressure again, and then start adding the missing amount into the tires. For example, tommorrow morning your front right tire might show 27 psi instead of 29, which means that you are 2 psi short. Later on, at the gas station, your tire may show 30 psi, because of tire heating. Now you could say that the tire is over 29 psi, and you could leave it. However, you should still add more air into it until you have added in the missing 2 psi, thus making it 32 psi. Bernard H. Schwab Siemens RTL, Princeton, NJ
ugdomino@sunybcs.UUCP (Michael Domino) (07/10/85)
> I just bought new Michelin XH tires for my not-very-sporty > 1980 Chevrolet Malibu, and the guy who installed them told > me to keep the pressure at 34-35 pounds cold. That's the > pressure listed on the sidewall as maximum. I've always > kept my tires inflated to the manufacturer's recommendation > printed in the manual and the door sticker (which for my > Malibu is 26 pounds in front and 29 pounds in the rear) > When I questioned the tire installer about his, he said > in no uncertain terms to ignore the mfgrs. recommendation > and keep them filled to the tire maker's maximum. > > Seems to me the installer should know his tires, but I'm > reluctant to believe him without further comments. > Can anyone confirm or deny this recommendation? > > Carl Blesch In my experience the higher pressure causes the tires to wear more evenly, the car handles better and gas mileage improves somewhat. I have an old Karmann Ghia and the manufacturer recommends only 19 psi in the front tires. I increased that to 29 and the rears to 32 (my tire man agrees). Michael Domino -- ------------------------------------------------------------------------------- Michael A. Domino uucp:[bbncca,decvax,dual,rocksanne,watmath]!sunybcs!ugdomino SUNY/Buffalo Computer Science csnet:ugdomino@buffalo arpanet:ugdomino.buffalo@csnet-relay voice:(716)881-6420 -------------------------------------------------------------------------------
don@umd5.UUCP (07/11/85)
> I just bought new Michelin XH tires for my not-very-sporty > 1980 Chevrolet Malibu, and the guy who installed them told > me to keep the pressure at 34-35 pounds cold. That's the > pressure listed on the sidewall as maximum. I've always > kept my tires inflated to the manufacturer's recommendation > printed in the manual and the door sticker (which for my > Malibu is 26 pounds in front and 29 pounds in the rear) > When I questioned the tire installer about his, he said > in no uncertain terms to ignore the mfgrs. recommendation > and keep them filled to the tire maker's maximum. > > Seems to me the installer should know his tires, but I'm > reluctant to believe him without further comments. > Can anyone confirm or deny this recommendation? > > Carl Blesch *** REPLACE THe worn-out tires WITH new ones *** I've done what they recommend (tire people) and the tires wear out in half the time -- all worn smooth in the middle. Then I go by the car manufacturer's advice, and they last a long, long time. Don't believe him!! He wants to sell you tires .... -- --==---==---==-- ___________ _____ ---- _____ \ //---- IDIC ----- _\______//_ ---- ---------- ARPA: don@umd5.ARPA BITNET: don%umd5@umd2 SPOKEN: Chris Sylvain UUCP: {seismo,rlgvax,allegra,brl-bmd,nrl-css}!umcp-cs!cvl!umd5!don
dove@fortune.UUCP (Michael Dove) (07/11/85)
> Carl, > > I have a 77 Trans Am and have always kept the tires at the tire > manufactures maximum (checked cold). Mileage is better, and the tires > are wearing fine (over 55K so far). > > Car manufacturers seem to be more concerned with getting a softer ride > than with tire wear and possibly reduced cornering. Though I thought > they were supposed to be concerned with mileage.... For most passenger car tires, following the tire manufacturers maximum pressure is fine. But you run into problems. Usually associated with those maximum pressures is maximum load, which also must be taken into account. Most off road tires, you can not follow this rule. Since the weights of off road cars differ so much with respect to the tires people are putting on them. There are Toy Mini's which could almost blow over in the wind, with 42 inch tires on them, and big heavy Bronco's with 30 inch tires. I have 31.5-10.50x15 BF Goodrich Radial All-Terrain, TA's on my Landcruiser, and I am 20 lbs below manufacturers maximum. BF Goodrich has a maximum rating on these tire of 50-55 psi (I do not have the exact number), and over a ton (around 2200 as I recall), per tire. That means 50-55 psi is fine if you have a 4 ton car, but who has one of those. I run mine at 32 average psi and have very good wear all across the tire. Since off road tires cost considerably more, people who purchase off road tires usally will do all they can do to get the most mileage out of their tires. One of the things I do is have my car weighed at all 4 corners, then base the pressure to that. All cars have different weights on each tire. Left-right weight changes are usually not much ( basically you are the delta ), but front to rear can sometime be dramatic. Then if you make the pressure slightly higher on the heavier end, your tires will wear better all around. Plus handling, braking, traction are improved. -- /*****************************************\ * *| |* Michael Dove *| |* Forutne Systems Corporation *| |* {ihnp4, ucbvax!dual}!fortune!dove *| |* *| \*****************************************/
uggoodjm@sunybcs.UUCP (a Model I) (07/13/85)
> I just bought new Michelin XH tires for my not-very-sporty > 1980 Chevrolet Malibu, and the guy who installed them told > me to keep the pressure at 34-35 pounds cold. That's the > pressure listed on the sidewall as maximum. I've always > kept my tires inflated to the manufacturer's recommendation > printed in the manual and the door sticker (which for my > Malibu is 26 pounds in front and 29 pounds in the rear) > When I questioned the tire installer about his, he said > in no uncertain terms to ignore the mfgrs. recommendation > and keep them filled to the tire maker's maximum. > > Seems to me the installer should know his tires, but I'm > reluctant to believe him without further comments. > Can anyone confirm or deny this recommendation? > > Carl Blesch Due to problems with the return address at seismo, I am posting this for all of the net to see. To: harpo!whuxlm!whuxl!houxm!ihnp4! Subject: tire pressures\ Did your Malibu originally have METRIC radials. If not, this is the reason for the change in preessure. Metrics have different load capacities than the Alphanumeric series they replace. Another thing to consider, at higher pressure (harder) the tire has a greater load capacity, runs cooler, and often gets the same tread wear or better. The reason is that Detroit (especially GM) has been putting smaller and smaller tires on the same weight car. I have personally seen this as on my 68 Chevy (3800#) the label says 8.85x14 (J78-14). My 72 Chevy (4200#) says G78-15. The tire capacity is determined by the letter, the "higher" the letter, the higher the capacity. The J78 has almost 400# more capacity, yet the 400# more car has the smaller tires. When I bought the '72 I immediately changed to L78-15 on the 72, and run them 2-5# higher than the label pressure. This gives a little harsher ride, but the safety and handling have improved immensely, as has the tire life. All in all, I would stick with the higher pressure, and maybe next time, go one or two sizes larger. Usually one or two sizes won't adversely effect the speedometer, but if it should, your dealer has different size gears for in the transmission case. These are a one bolt job which anyone can do on ramps in their driveway. The dealer can help get the right gear. J. Matthew Good
jlw@ariel.UUCP (J.WOOD) (07/13/85)
> Did your Malibu originally have METRIC radials. If not, this is the reason > for the change in preessure. Metrics have different load capacities than > the Alphanumeric series they replace. Wrongo. The reason `metric' tires have higher numbers on them is because the DOT does not allow a non-`metric' tire to have more than 32psi max stamped on its side. The `metrics' are allowed 35psi, therefore, they can claim a higher rating. I run the Goodyear European 205/60HR13 s on my RX-7 at 32psi cold all around and the Goodrich Comp T/As 195/60VR15 s on my wife's Volvo Wagon at 30 front and either 30 or 34 rear unloaded or loaded. Joseph L. Wood, III AT&T Information Systems Laboratories, Holmdel (201) 834-3759 <ariel!>titania!jlw
smh@rduxb.UUCP (henning) (07/14/85)
**** **** From the keys of Steve Henning, AT&T Bell Labs, Reading, PA rduxb!smh > It is a good idea to consider the manufacturers max. pressure as the upper > permissible cold limit. However, it is not a must to obey that pressure > setting. > On steel belted radials you can use any pressure from the car manufactures rating to the tire manufacture's rating since the steel belt will keep the tire flat and make it wear evenly if the cast and camber are correct. On other tires all bets are off. You have to adjust the pressure for tire wear or your good handling will get very expensive. Remember to adjust the pressure for heavy loads to at least the car manufacturer's rating for that load or you risk tire failure.
geoff@denelvx.UUCP (Geoff Baum) (07/15/85)
> I just bought new Michelin XH tires for my not-very-sporty > 1980 Chevrolet Malibu, and the guy who installed them told > me to keep the pressure at 34-35 pounds cold... > Can anyone confirm or deny this recommendation? > > Carl Blesch I recently bought Pirelli P77s for one of my Honda Civics and Michelin XZXs for the other Honda Civic. The tire dealer insisted that I keep the Pirellis at 32 psi and the Michelins at 28 psi (same car). He stated that the mfgr's recommended tire pressure was designed to give the most comfortable ride and did not take into account increased tire wear or decreased gas mileage. I now keep my tires at the tire installer's recommended pressure. I have not noticed any decrease in cornering power, although the ride is marginally less soft and steering effort has decreased.
jkl@husky.uucp (Jonn Lau) (07/15/85)
I'm no expert at automotive technique but I recall talking to some tire and wheel engineers who say that inflating tires over the recommended inflation gives better dry traction and better gas mileage but worse wet traction, and less smooth ride. It also makes the tire heat up faster so decreases tire life.
cat@tommif.UUCP (Catherine Mikkelsen) (07/16/85)
In article <1916@sunybcs.UUCP>, uggoodjm@sunybcs.UUCP (a Model I) writes: > > I just bought new Michelin XH tires for my not-very-sporty > > 1980 Chevrolet Malibu, and the guy who installed them told > > me to keep the pressure at 34-35 pounds cold. That's the > > pressure listed on the sidewall as maximum.... > > When I questioned the tire installer about his, he said > > in no uncertain terms to ignore the mfgrs. recommendation > > and keep them filled to the tire maker's maximum. > > > > Seems to me the installer should know his tires, but I'm > > reluctant to believe him without further comments. > > Can anyone confirm or deny this recommendation? > > > > Carl Blesch Dear Carl: I'm sitting here and couldn't resist the following sage advice from Hunter Thompson himself [no permission for the following excerpt but too bad]: *At first I thought it was only because the tires were soft, so I took it into the Texaco station ... and had the tires pumped up to fifty pounds each -- which alarmed the attendant, until I explained that these were *experimental* tires. But fifty pounds each didn't help the cornering, so I went back a few hours later and told him I wanted to try seventy-five. He shook his head nervously. *Not me.* he said, handing me the air hose. *Here, they're your tires. You do it... You won't even get to the corner.* *We'll see,* I said, moving around to the rear with the airhose. In truth, I was nervous. The two front ones were tighter than snare drums; they felt like teak wood when I tapped on them with the rod. But what the hell? I thought. If they explode, so what? It isn't often that a man gets a chance to run terminal experiments on a virgin Cadillac and four brand-new $80 tires. For all I know the thing might start cornering like a Lotus Elan...* Fear and Loathing from the Silicon Valley Catherine *Whatever gets you through the night*
cramer@kontron.UUCP (Clayton Cramer) (07/18/85)
> I just bought new Michelin XH tires for my not-very-sporty > 1980 Chevrolet Malibu, and the guy who installed them told > me to keep the pressure at 34-35 pounds cold. That's the > pressure listed on the sidewall as maximum. I've always > kept my tires inflated to the manufacturer's recommendation > printed in the manual and the door sticker (which for my > Malibu is 26 pounds in front and 29 pounds in the rear) > When I questioned the tire installer about his, he said > in no uncertain terms to ignore the mfgrs. recommendation > and keep them filled to the tire maker's maximum. > > Seems to me the installer should know his tires, but I'm > reluctant to believe him without further comments. > Can anyone confirm or deny this recommendation? > > Carl Blesch Within certain limits, tire pressures are a trade-off. Higher tire pressures increase cornering and dry traction; they also make the ride rougher, and increase the danger of sharp objects penetrating the tire. Most important, high pressures reduce sidewall flex, which reduces heat buildup, which reduces the risk of catastrophic tire failure. For a long time, GM (and most of the other US car makers), have recommended pressures around 24 to 28; in the last several years they have started recommending higher pressures in order to improve gas mileage. Differential tire pressures front to rear can produce differing levels of oversteer and understeer --- although I have yet to get a nice simple relationship to describe the effect that isn't dependent on the car. When in doubt, increase pressures to the maximum specified on the sidewall.
ksg@houxj.UUCP (K.GRANT) (07/18/85)
When I bought tires from a tire distributor, they also recommended an inflation pressure which was greater than the car manufacturer's. In their brochure, they said that the car manufacturer was more concerned with a smooth ride so their recommended pressure was low. The tire manufacturer is more concerned with the tire life so their recommendation is higher. The way I see it, the tire manufacturer should know what's best for his tire. -Kevin S. Grant
carlson@ssc-vax.UUCP (Lee R Carlson) (07/18/85)
*** INFLATE THIS LINE TO 35 PSI *** My '85 STE seems to have solved the problem ... The door sticker specifies 35 pounds all around which is the max Eagle GT pressure. Lee R. Carlson - Boeing Aerospace, Seattle -- Lee R. Carlson - Boeing Aerospace - Seattle - ..fluke!microsof!ssc-vax!carlson
augustc@zeus.UUCP (Augustine T. Chan) (07/19/85)
A young gas station attendant was killed in Seattle a few years ago when the truck tire he was inflating exploded. Augustine C.
gvcormack@watdaisy.UUCP (Gordon V. Cormack) (07/20/85)
> I'm no expert at automotive technique but I recall talking to some > tire and wheel engineers who say that inflating tires over the recommended > inflation gives better dry traction and better gas mileage but worse > wet traction, and less smooth ride. It also makes the tire heat up faster > so decreases tire life. There are two popular misconceptions here. First, HARDER tires work better on wet pavement. The force per square inch between the tire and the pavement is almost exactly equal to the pressure in the tire. It is obvious that the higher pressure is better in overcoming the lubrication film strength of the water. Second, hard tires run cooler than soft, as there is less flexing of the sidewall and tread. It has been mentioned earlier, but the only time that increased pressure hurts tire life is with unbelted tires, where the centre of the tread may wear more quickly. The last (and only) set of steel radials that I wore out were on a '76 Mazda 808. I kept them at 32 psi and got 85,000 miles out of them. I regularly drove at 80+ miles/hour. -- Gordon V. Cormack CS Department, University of Waterloo gvcormack@watdaisy.uucp gvcormack%watdaisy@waterloo.csnet
fowler@uw-beaver (Rob Fowler) (07/20/85)
About the guy that got killed inflating a truck tire: Truck wheels and tires are different from what you get on light vehicles. The tires are so heavy and stiff that you cannot mount them by putting part of the bead in the center well of the wheel and pulling the rest over the rim. In fact, large truck wheels do not have center wells at all. This is to improve the strength/weight ratio. Heavy truck wheels have detachable rims. To mount a tire you remove one rim put the tire on, and put the rim back on. Some rims are held on with lots of bolts and "dogs" while others fit together like a puzzle under a shorter rim that the tire can fit over. The air pressure in the tire serves to lock the pieces together and to the wheel. When you inflate a truck tire for the first time there is a danger that the latter type of rim will not lock properly and and will be blown off. This throws several pounds of steel pieces outward at several hundred feet per second. This can occur with just normal inflation pressures (75 lbs/in^2 and more). Because of this danger it is standard procedure in truck shops to put the wheel and tire in a cage that will contain the shrapnel if the rim blows when the tire is first inflated. The guy that got killed in Seattle was taking a shortcut and was not using a cage. Safety first! -- Rob Fowler (uw-beaver!fowler or fowler@washington.arpa)
joel@peora.UUCP (Joel Upchurch) (07/22/85)
>back on. Some rims are held on with lots of bolts and "dogs" while others >fit together like a puzzle under a shorter rim that the tire can fit over. >The air pressure in the tire serves to lock the pieces together and to the >wheel. When you inflate a truck tire for the first time there is a danger >that the latter type of rim will not lock properly and and will be blown >off. This throws several pounds of steel pieces outward at several hundred >feet per second. This can occur with just normal inflation pressures (75 >lbs/in^2 and more). Because of this danger it is standard procedure in >truck shops to put the wheel and tire in a cage that will contain the >shrapnel if the rim blows when the tire is first inflated. The guy that got >killed in Seattle was taking a shortcut and was not using a cage. Also if there is metal fatigue in the rim it may explode just sitting there. There was a segment on 20/20 or 60 mintues a while back about these locking rims and there we some people killed when the rim in a truck near them exploded and came in through their window.
rouil@ada-uts.UUCP (07/22/85)
>***** ada-uts:net.auto / zeus!augustc / 1:06 pm Jul 19, 1985 >A young gas station attendant was killed in Seattle >a few years ago when the truck tire he was inflating exploded. > Augustine C. ---------- Hold it, different animals. As someone who used to have fun ?? putting air in truck tires (thank God for 18 wheelers :-)), You can't compare inflating truck tires with inflating car tires. Car tires have ONE piece hubs (rims). The hub is the metal ring thing in the middle of the tire. Truck tires, or at least the ones I worked with, had TWO piece hubs. Inflating the tires to normal pressure could make them shoot apart. To fill the two piece hubs we dismounted the tires from the trucks, placed them in a large steel cage hooked up the line and stood back. Stood way back. The case I believe you are talking about was discussed on 60 Minutes. Personally I would not worry about inflating the tires to max or possibly 5% over the max (I don't avocate this overinflation) but in any case you would be more likely to have a blowout while driving and not have the tire blow up in your face. Those two piece hubs should be banned from the road in my opinion. John Rouillard Phone:(617) 661-1840 Intermetrics Inc. 733 Concord Ave Net: {harpo, bellcore, ihnp4}! Cambridge, Ma. 02138 inmet!ada-uts!rouil "Caution the Surgeon General has determined that these thoughts can be dangerous to your health. Read at your own risk."