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Re: Quattro & spare tyre

If the Opel had a problem with the difference between new and old tires of
the same size, I don't think it's safe to go on this type of calculation.
This may be fine for a non-Torsen center diff when it's not locked.

>Hairy green toads from Mars made Benjawan Kuecharoenwong say:
>>       I read in Complete Car4  Mag. that one Opel 4X4 owner
>> just change the
>> rear tyres (with the same size with the fronts) ,after that the
>> transmission gone (because of slightly differrence in radius between
>> front tyres and rear tyres.
>>       My car's tyres are 235/45-17 ,but the spare is 215/60-15 .
>>  Is it safe to use this spare tyre (for emergency only)  ?
>>  or I have to buy one set of 17" wheel to be a spare.
>According to Mark Sirota's tire_size program:
>Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
>235/45-17         4.2in  12.7in    25.3in         79.6in        796        0.0%
>215/60-15         5.1in  12.6in    25.2in         79.0in        802       -0.7%
>So, the spare has just about the same rolling circumference as the
>regular tire; it should be OK.
>If the 15" wheel physically fits on the car (clears brakes, struts, etc.),
>then you are fine.
>Andrew L. Duane (JOT-7)                 duane@zk3.dec.com
>Digital Equipment Corporation           (603)-881-1294
>110 Spit Brook Road                     http://www.zk3.dec.com/~duane
>M/S ZKO3-3/U14
>Nashua, NH    03062-2698
>Only my cat shares my opinions, and she's too heavy to care.

Richard Funnell,
San Jose, California
'83 urQ
'87 560 SL