Re: [bmw] Torque wrench/'89 535i

[mkohlbrenner@xxxxxxxxxxx]

"Gerry Phillips" <gphill03@domain.elided> wrote:

> ... Is is okay to keep the stock 15" as my spare or should I go
> ahead and purchase another 17" wheel and tire?  I know having
> the same size is best, but can I do any damage by riding on a
> 15" spare with 17" tires?

If you have a limited slip differential, then it is important 
that the outside diameters of the TIRES on the rear axle are
close.  Otherwise, the limited slip will be working (and
wearing) even while you are driving straight.  The size of
the WHEEL doesn't matter in this context.

If you don't have a limited slip, then outside diameter doesn't
even matter that much for temporary use of a spare.  That's why
so many cars use those "space saver" spares.

Tire Rack should have sold you 17" tires that are close to the
same outside diameter as stock, otherwise they would suck and
I know that they usually don't suck at those things.  You can
always look up your specific tire on the Tire Rack web site to
see if the diameter is close to the just-under-26" diameter of
the stock tires.

> Also, the car seems to be tracking perfectly straight but I
> was wondering if I should look into getting my alignment
> checked with the new wheels and tires.

A car that tracks straight may still have alignment settings
that will chew up expensive 17" rubber in a hurry.

How did the tires you removed look in terms of even wear?  If
they looked fine, then you are probably safe, but then again,
it might be money well spent to just to ensure that your toe
and camber settings are correct.

Regards,
Mike Kohlbrenner
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