Re: Uneven tyre wear?

[Jerry Brown <jerbrown@xxxxxxxxxxx>]

John,

Well, I'm no tire expert, but...

I wouldn't expect this type of wear from toe, but camber. I would expect
excessive toe to diagonally "scrub" the tire surface, "feathering" the
tread blocks. You can feel this by running your hand across the tire
surface.

Many cars will wear the outside edges of the front tires more quickly
than the inside because of suspension geometry, body roll, etc.: our
turbo Volvos do this, but my 635 CSi does not. Stock camber settings on
the Volvos are slightly positive (!), while the BMW's are slightly
negative, and the Volvos - even with fat anti-sway bars - roll
substantially more than the 6er.

For DIY alignment, when I used to mess with stock car racing, we used a
piece of 2X4 lumber with a nail driven through it and a tape measure.
Jack up the car, support it via the suspension, place the 2X4 such that
the nail point just touches the tire near the outside shoulder, and give
the tire a spin to produce a nice, straight line. Repeat on the other
side. Now take your trusty tape measure and compare the distances
between the lines at the front and back of the tires. Resulting
difference is the toe.

HTH,

- -jerry


John G.Burns wrote:
> 
> My '85 635 CSi has uneven tyre wear at the front, the inner edge
> is wearing quicker. The car is lowered but not much, the
> problem existed before the new suspension anyway.
> 
> Would too much toe in or toe out do this or must it be
> camber related? Could I tie it down to too little toe in,
> too little toe out or could it be either?
> 
> Wrong tyre pressure would affect only the middle or BOTH
> edges right? I use 2.4 bar at the front.
> 
> How do shade tree mechanics like me check toe in? Point the
> wheels straight ahead and try to measure the distance from
> front-front vs rear-rear? Sounds too primitive.
> 
> --
> Who needs a life when you've got Unix? :-)
> Email: john@domain.elided, John G.Burns B.Eng, Aberdeen, Bonny Scotland
> Web  : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!

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