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Path: utzoo!watmath!clyde!burl!ulysses!allegra!princeton!rocksvax!sunybcs!uggoodjm
From: uggoodjm@sunybcs.UUCP (a Model I)
Newsgroups: net.auto
Subject: Re: tire inflation pressures
Message-ID: <1916@sunybcs.UUCP>
Date: Fri, 12-Jul-85 20:59:34 EDT
Article-I.D.: sunybcs.1916
Posted: Fri Jul 12 20:59:34 1985
Date-Received: Sat, 13-Jul-85 16:39:34 EDT
References: <572@hlwpc.UUCP>
Distribution: net
Organization: WNY TRS80 Users Group
Lines: 53

> 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