Incorrect Ackermann: Why does my outside wheel scuff wide on full lock?

[re2500]

Ive noticed this since putting my coupe back together. The Ackermann angles are all wrong???

When turning on full lock the outside front wheel turns too much causing it to scuff wide (or drag when reversing) making a noticable bang boom noise and causing the car to rock as the wheels fight and then slide and give in.

The car has been 4 wheel aligned and is perfect in a straight line. I dont understand how this can be adjusted or have changed other than the steering arms being incorrect on my KW's??

Or have 1 F**k*d it by lowering it too much cos i think it looks cool innit

The other think i can think of is that its always been this way (due to non conventional ackermann of our steering arms pointing forward) and the solid bushes are just exaggerating it all, the old jelly bushes absorbed some of the noise of the wheels scuffing??

The spec is:
KW v2 galv coilovers lowered till there is a slight tyre tuck in the arch.
Spherical compbrake top mounts
Alu subframe mounts
Black poly wishbone bushes
ABY rack with Bambridge Delrin Trackrod bushes
ABY strut brace
BBS RK 17x8 ET35 with Goodyear eagle F1 225-45-17 tyres

[Rusty]

Mine has always done the jumping thing on full lock, stock, lowered, 16s, 17s etc. etc. Not sure why

[stocious]

all 4 hubs are aligned at 0* toe ??

http://www.s2forum.com/forum/showthr...rame+alignment i dont know how to make link yet sorry, have a read about toe. unless your subframe front or back is out of alignment bent or other the akerman angle shouldnt be your problem. i bet its still alignment. car rolls straight but dont turn good is not aligned at all

[stocious]

toe in for quick turn tou out for high speed staability, but in reality you want just enough toe that when you acc hard the hubs are pulled into around 0* toe, if you have poly bushes up front this wont happen.

[stocious]

just one last though, when you hung your front subframe did you do it by the front' bolt first?

[re2500]

Reading the thread linked above it sounds like this could be fairly normal behavior on our cars. Having a good old think and drawing some diagrams there's no real way that the ackermann angles can be changed. I have read in the Net that ackerman angles are sometimes deliberately incorrect to improve dynamic alignment during hard cornering and improve turn in using the extra weight transferred to the outside wheel.
Im going to put it down to the fact its always happened its just the new tight/solid bushes are exaggerating the noise.

i bet its still alignment. car rolls straight but dont turn good is not aligned at all

How is this, can you elaborate
All the alignment of the car (Toe,camber and castor) are all within tolerance. This was done on a Hoffman optical 4 wheel alignment system only 2-3 weeks ago. Im not sure how this can all be good in a straight line but its not aligned because it doesnt turn well? What alignment could be the culprit

[re2500]

I understand there is one fixed and 3 floating subframe mounts. But i didnt know of a way to align it so when i hung the subframe i mounted it loosely on all 4 bolts and jiggled it to the centre of its allowable adjustment and tightened it up. Could this be the cause, would it effect the ackermann angles?

[stocious]

my own car dont do this, and my last 80 saloon didnt either. correct ackermans angle is for slow speed, if they moved the front and rear subrame two differnet direction to adjust camber would not that exagurate the problem. i handed back the 80 twice till they got it right how far out was the camber when you got it done and what is the toe set at now up front ? out of curiosity. i saw alignment because i dont trust most alignment places, most people dont in my opinion. personaly i have not had this problem/or has it been noticeable "banging" . which is odd. ill pop in when passing its fairly local. but i know they fixed it.

[stocious]

I understand there is one fixed and 3 floating subframe mounts. But i didnt know of a way to align it so when i hung the subframe i mounted it loosely on all 4 bolts and jiggled it to the centre of its allowable adjustment and tightened it up. Could this be the cause, would it effect the ackermann angles?

i would think so yes, my brain is telling me that compensating for an adjusted subframe/whishbone for correct toe , leads to problems on full lock, my 2 cents . as i said ill ask the guy that did it. hope that makes sense

just spoke with the guy, camber, then measure castor, then set toe - his own words. and recheck after a drive. as it can change ever so slightly, due to setup being so crude - his own words. hope this helps

[Error404]

toe in for quick turn tou out for high speed staability, but in reality you want just enough toe that when you acc hard the hubs are pulled into around 0* toe, if you have poly bushes up front this wont happen.

Don't you mean toe in for stability and toe out for turn in response


James they all do this IMHO. My old standard 2.8CQ did it, and my CQ now does it, Helen's S4 also does it although to a lesser extent. Its compounded by the rear wheels pushing the car forwards as its trying to turn. I think it is amplified by slightly increased scrub radius with the lower offset and wider rims, also as you said the solid mounts and poly bushes mean that there is no slop to cushion the pushin' as it were

You can adjust the set-back with the subframe mounts, the alignment gear should measure that and your alignment man can start by setting that up.

[re2500]

Cheers for your input guys! uve put my mind at rest.

[stocious]

[QUOTE=Error404;680725]Don't you mean toe in for stability and toe out for turn in response


yes thats what i meant, good eye. my bad

[stocious]

anyone try these before ?

http://www.jcwhitney.com/caster-wedges/p2020830.jcwx?filterid=c11304d82y1991g190u0j1

curious ?

[Error404]

WTF are they supposed to do?

[stocious]

just spotted them, was wondering that myself. i presume between sub and chassis. looke a bit agri huh lol, or a door stop