Re Tyring 164

["Doug Gould" <dgould@domain.elided>]

Michael Smith's tyre problems are almost certainly due to worn lower control
arm bushes. What happens is that braking forces create toe - out as the
tyres try and pull back and they pivot around the front lower control arm
bush. The toe out under the increased braking load causes rapid tyre wear.
You probably also feel that the car "darts" a little under brakes and when
following ridges along the road (such as pavement joins and tramlines). On
the other hand, camber needs to be outrageously excessive before it creates
tyre wear and it is usually felt as 'pulling" on the steering wheel. A quick
visual inspection, sighting the front tyres by eye with the rear should give
you a good enough indication of whether camber is the culprit.

The bushes that seem to wear most are the rear ones, which tend to wear so
that the inside "hole" goes oval. The front ones can also deteriorate and
that usually looks obvious as rubber deterioration. The rear ones are easy
to replace and the front ones much less so. Alfa Bill is the resident expert
on lower control arm bushes and the easiest source for "superflex"
polyurethane bushes - which will be the cheapest and arguably best solution.
If I remember correctly, a lot of his postings on this subject are in the
164 home page FAQ's. I agree with previous authors who suggest that the rear
bushes should be considered as consumable items on the 164 and replaced
regularly.

One you have the front end "tied down" properly, wheel alignment is the next
priority. Handling and torque steer are sensitive to correct wheel alignment
on the 164. Fred Delacerda recommends 0mm toe in front and rear. I prefer
1mm toe out at the front and 1-2 mm toe in at the rear. The objective of
front end alignment is to achieve the best compromise between having the
tyre point straight ahead at speed and optimising bump steer. Driveline
torque at cruising speed creates a toe in moment on front wheel drive cars,
so you need some static toe out to compensate for this. Rear toe in improves
straight line stability. Once again the objective is close to straight
ahead, but tyre drag at speed creates a toe out moment on undriven wheels,
so some toe in is advisable to compensate. Too much toe in and the car
starts to feel "dead" and like it doesn't want to "turn in" (Try driving a
current model 5 series BMW - who are using lots of rear toe in at the
moment). Conversely, too little toe in (or toe out) and the car starts to
feel "skittish".

Doug Gould
Melbourne, Australia
91 164L

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