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From: steve@mtu.UUCP (Steve Seidel)
Newsgroups: net.auto
Subject: Re: Tire Questions (info request)
Message-ID: <205@mtu.UUCP>
Date: Mon, 29-Jul-85 09:38:35 EDT
Article-I.D.: mtu.205
Posted: Mon Jul 29 09:38:35 1985
Date-Received: Tue, 30-Jul-85 01:53:44 EDT
References: <1839@amdahl.UUCP>
Reply-To: steve@mtu.UUCP (Steve Seidel)
Distribution: na
Organization: Michigan Tech, Houghton, MI
Lines: 39
Summary: 175/70 13's are OK

In article <1839@amdahl.UUCP> dss00@amdahl.UUCP (dss00) writes:
>
>I just bought 4 new tires for my Accord. As usually happens with
>most of my purchases, I have a few questions about what I bought
>after the fact.
>
>The tires are Michelin MX, Size P175/70R13. I have the following
>questions, and would appreciate answers from any one in the know.
>
>1. The original tires were size 155SR13. The tire dealer said that
>   P175/70R13 are acceptable size replacement for 155SR13. As far as
>   I know, the main difference is the 175 mm width of the new tires
>   as against 155 mm width of the old ones.
>   What I am not sure about, is the overall size (outer diameter)
>   of the new tires compared to the old ones ?
>   It may affect the speedometer/odometer.
    
A booklet I got from Euro-Tire, Inc. (an aftermarket mail order tire
outlet that advertises every month in C/D) lists the approximate overall
diameters of 155SR13 and 175/70R13 tires as 578 mm and 580 mm,
respectively.  These figures surely vary from one brand to the next
and precise numbers depend on other variables like inflation pressure and
temperature.  But that was as true for the old tires as it is for the new.
Your speedometer/odometer should not be affected.

Can't answer your other question, but I do have an aside to add to the
controversy about tire inflation pressures.  I and lots of other people
regularly inflate their street legal tires to pressures in the neighbor-
hood of 50 psi for autocrossing.  Heat buildup is not an issue since
speeds seldom exceed 40 mph during a run, and then only for a few seconds.
I have never seen a street tire rated above 36 psi maximum inflation
pressure; the implication I draw is that street tires won't blow up if
you overinflate them a bit.  Nobody would want 50 psi for the street, but
I sometimes run 36 - 38 psi with no immediate ill effects.
-- 
Steve Seidel
Michigan Technological University
uucp: {lanl, ihnp4, glacier}!mtu!steve
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