Castor adjustment

[audiman]

Had the alignment done on the beast today and it now drives perfectly. Bill came to 188 inc vat, but whatever, 18" tyres aint cheap to wear out.

One problem with the car tho, the castor on the front right is out of spec and of course this isnt adjustable. Anyone know if there are products out there to adjust castor and also what part of the car this might be??

Am i right in thinking the top mount of the strut is involved here?? I did crash the car into a hedge 3 years ago, but it hasnt ever shown up before today. Wonder if the extra power has distorted the shell? Maybe having solid bushes for the subframe and poly bushes for wishbones, together with stiff shock settings has paid its toll on the 14 year old nail?

Any thoughts

[steve930]

castor is the angle at which the front strut is situated, If you look directly at your front strut through the wheelarch, you'll notice that it sits at a slight angle and not verticle. This is your castor angle.

As you increase the castorangle, you change the camber angle of the front wheel hub as you turn a corner.

The main effect of adjusting castor is the amount of intitial bite as you throw the car into a corner, and how the car balances out, under acceleration coming out of the corner.

you can get adjustable top-mount platforms to enable you to alter the castor value, not sure whether you can use universal one's or whether you will have to get audi-specific one's, (if anyone makes them)

[S2 Ant]

If something is bent still surely that would also throw the castor out too.

[ericd]

Had the alignment done on the beast today and it now drives perfectly. Bill came to 188 inc vat, but whatever, 18" tyres aint cheap to wear out.

One problem with the car tho, the castor on the front right is out of spec and of course this isnt adjustable. Anyone know if there are products out there to adjust castor and also what part of the car this might be??

Am i right in thinking the top mount of the strut is involved here?? I did crash the car into a hedge 3 years ago, but it hasnt ever shown up before today. Wonder if the extra power has distorted the shell? Maybe having solid bushes for the subframe and poly bushes for wishbones, together with stiff shock settings has paid its toll on the 14 year old nail?

Any thoughts

Tom,

I got my alignment done today at my local Audi dealer (£80 + vat, no discount , fixed price), my castor on the right was/is also slightly out.

I got mine done about 18months ago after fitting new top mounts & tyres (just to check how things were looking) and at that time the castor was within spec !, recently I did w/bone & arb bushes + plus drop links and 2 new bolts in the steering rack after the gbox saga.

I was thinking (probably complete rubbish) but could the castor reading be affected by and be indicitive of the condition of the top mounts , I know replacement of them shouldn't (AFAIK) change the alignment , just thinking out loud !

when I checked mine recently there wasn't any excessive play so I left them , but still thinking of trying out the QRSport mounts...


B.T.W.
I just checked the printout regarding castor , initial reading 2deg 40 , (spec is 2deg 10 +/- 0deg 30), final reading was 3deg 21 , so whatever else was done during alignment significantly changed the castor reading ?!?,

[mcandmar]

Could it be the subframe position? From memory the mount under the passengers feet is fixed and the other three are floating so its possible to mount the subframe out of line with the car. I remember playing with its position for ages until i was happy it was straight.

I would guess that if the position was wrong the subframe would sit slightly turned to the right, that would possibly give you less castor angle on the right hand side vs the left.

[audiman]

Ah, yes, that could be the reason as i have changed those mounts

[Error404]

Bump to a very old thread - did you ever get to the bottom of this Tom?

I got my alignment done today and my castor is slightly out of spec side to side to the tune of about 0º31' or just over 0.5deg.

I wondered if it was either subframe out of alignment from putting new bushes on, or whether top mounts have seen better days?
When I changed the subframe bushes i did try and see if there was any movement in the chassis mounting points but they all seemed solid

Need to dig out the last alignment sheet from after I fitted the new front subframe and wishbone bushes and see what the castor spec was then to see if it has manifested since then.

[audiman]

no, it never made the handling different so left it. Didnt cause any tyre wear either.

[jogi730]

Following loads of mods, ie bushes, top mounts, coilovers etc, how does one determing the best alignment for wheels? Or is this a skill that should be left to 'experts'?
Obiously, using OEM setting would be pointless?
Cheers
Chris

[Error404]

Cheers Tom, the alignment centre said it wouldn't make any difference to tyre wear or handling, but it would be better to get it spot on I think. The place i used after fitting the refreshed front subframe 18mths ago didn't measure the castor angle so no hint there - My castor difference is just outside the maximum factory tolerance so not ideal IMHO. I noticed on the sheet that my set-back is also not perfect, about 5.5mm out so subframe alignment could well be the cause I guess.

Chris factory settings are defiantely the starting point - a real alignment specialist will be able to work with you to improve them according to what you want and how your car is set up. Somewhere like Wheels in Motioin or Centre Gravity are two places with excellent reputations that spring to mind

[Rusty]

The lower ball joints can be rotated slightly in the clearance holes, this is how mine was adjusted and it was the only time it's driven truly straight.