Rear suspension wheel toe in/out

[johnney]

Interesting solution john to the problem of rear wheel steering, I would assume they heated the lower link tube in the area opposite to the radius arm mounting point. If you don't quench it after heating then it wouldn't fully return to its original position when cooled, leaving you with toe in as you describe. Heating the same area and quenching would give toe out or reduce existing toe in. In your case it looks like the three degrees of toe in reduces to zero on the outer loaded wheel when cornering so effectively no rear wheel steering, but at the expense of increased tyre wear when driving in straight line.

[rfs1957]

Been trawling through searches for IRS AND shims, IRS AND alignment etc without much luck regarding how you go about refitting an IRS when you're not confident that the shimming of the rubbers was done correctly.

Can someone point me to an erudite source of first principles so I don't just perpetuate someone else's guess-work please ?

[PeterCrespin]

AFAIK the IRS mount shimming has got little to do with alignment. The only effect is on lateral IRS position and the maximum displacement from one extreme (all four mounts shimmed fully left or fully right) is a matter of a few millimeters. I.e. insignificant in the context of that sort of wheelbase on a road car.

The shims are mostly there in my inexpert view to accommodate production tolerances. I don't think I've ever read a manual instruction about the shimming, which supports my assumption. That, or I wasn't paying attention and have two pages stuck together :-)

Pete

[rfs1957]

I wondered whether you could "crab" the back end either inadvertently or deliberately, by - for example - shimming on the LHS outside/rear/left and inside/front/left etc which over the barely 20cm that separates the rubbers might make quite a difference to the rear axle alignment, at least in the context of the debate regarding toe.

Perhaps I should reverse the question : what's the procedure when you've got a new IRS cage going into an unknown shell ?

Remember Peter that shims are close to a Borgo Panigale heart.

[Dicko4]

after my rear overhaul fitting new axle and brakes I lost track (no pun intended) of the shims and found a slight pull to the left. Could this be misalignment which as has been said there is little scope for? Adjustment of tyre pressure made the tendency disappear. Any other explanation?