4 replies to this topic

[Spitz]

Last year I had an opportunity to drive behind my PUP for the first time.

It was quite obvious it was dog tracking ( aka, crabbing in the UK )

I had installed new tie rod ends the year before, and done a home "alignment" after I noticed some tyre wear due to a too much toe out situation.......

.....is this crabbing fixable with a proper front alignmnet ( at a shop ) or is crabbing strictly caused by a problem at the rear. I'm thinking this is so, but wanted to check.

If....my rear alignment is indeed off....how is it fixed if original rear brackets are in place, and not adjustables?
Thanks

[Dan]

Most of the time when people see this, it is actually an optical illusion. The back end of a Mini is a few inches narrower than the front, the rear track being 2" narrower. This means when you see it from the rear, given that you will be seeing it from off centre due to being a driver or passenger behind, makes it look like the car is crabbing quite badly. If you can follow it again, but from the other seat of the chasing car, you will more than likely see it appear to be crabbing the other way.

[Spitz]

I know what you mean Dan and am aware of this.

I did check from both sides...... and being a PUP it's a little straighter down the sides than a saloon .....it's very obviously not driving straight

[tiger99]

The crabbing problem is always at the rear, and is caused by misaligned or rusty heelboard, bent subframe or radius arms, worn radius arm bearings, etc.

The rear toe in needs to be 1/16" (very important, NEVER toe out unless you want dangerous instability), and is set at the same time as any corrections for minor subframe tolerances. You can shim the radius arm brackets, but that only gives you toe out and positive camber, so you generally need to file the hole for the radius arm pivot (or the inner hole in the subframe web), and when the alignment is correct, fill the remainder of the hole with weld and/or weld on a thick washer in the correct position, so that the pivot can't move.

[Dan]

.....it's very obviously not driving straight

Then the first thing to do would be to check the subframe positions, especially given the non-standard body. Get it on stands, sitting reasonably level over a flat level floor and drop plumb lines from key points on the subframes, the same points each side. The centres of the mountings are a good start but get a few other points too like the corners. Mark these points on the floor. You can do suspension point measurements at the same time, if you mark them in a different colour it makes it easier. Move the car away and then measure side for side and opposing diagonals, each symmetrical measurement should obviously be the same. If you start to find discrepancies you can start investigating why. If you do find things to look into, first off check that the parts you have measured from aren't just bent or twisted. If it seems you really do have a problem, it should be a fairly simple matter to see exactly what is out of line once you have got an idea of exactly what measurements are off.