"Dave Plowman (News)" wrote in message
...
In article
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Tim+ wrote:
Good luck running different sized tyres on the driven axle. The
differential will over-heat and fail.


Sounds improbable. Maybe a limited slip diff wouldn't like it but I
can't see a regular diff being seriously stressed by a small difference
in rolling radius. Many space savers *are* smaller in terms of overall
diameter/rolling radius.

I'm talking about normal use over a period of time. Which only an idiot
would do with a space saver. The gears and bearings in the differential
part ain't rated for continuous use. If you've actually ever stripped one
down, many have plain bearings for the planet wheels. While everything
else has ball bearings.

Does it matter whether or not the space-saver tyre is on a driven axle with
a differential, for the handling of the car?

If you put a smaller tyre on the same "virtual axle" as one with the normal
size wheel, won't mean that the car will be lopsided and the car will try to
go round in circles instead of going straight ahead with no steering input?
How much does the suspension of a car adjust to different sized tyres to
keep the car level and hence the same load on both of the driving wheels -
assuming it's not clever suspension like Citroen's hydropneumatic.

By "virtual axle" I mean two tyres that are side by side (two front or two
rear), whether they are connected by axles and a differential or are
completely independent (in the latter case, the front wheels of a RWD car or
the rear wheels of a FWD car).