Offset front subframe bushes - increased castor

[Rusty]

Anyone running offset subframe bushes on the front and if so, what do you think?

[mcandmar]

Wasn't aware of these, got any links?

[Flat on my back]

.

Think 034 do them...

[Rusty]

The centre holes are offset thus pushing the subframe forward 10mm or so and increasing the castor angle. I think that the effect is sharper turn-in and mid-corner performance but there must also be downsides? Twitchyness perhaps? They're help in place with some pins to stop them rotating whils ton the move. Thinking of getting a set for mine up front.

[mcandmar]

I always thought the greater the castor angle the more stable the steering, or more inclined to track in a straight line. Result being less nervous steering, and increased camber angle while turning. Both a benefit for high speed driving. For slow speed tight turns i always understood you want the opposite, as little castor as possible. ....having said that my only experience with castor angles is confined to computer games

[S2central.net]

I think mcandmar is right - I have an old rally car prep book that covers this one...

Rally car - tight turns - thats what the handbrake and throttle induced steering is for

Way too much castor could be a real PITA on a daily driver thru traffic thouigh - all about compromises and prioritahs again.

[Rusty]

linky[/URL]]Increased caster is advantageous for racing and, in some cases, street driving. The only disadvantage is the added steering effort. While camber gain due to caster is generally good for increasing the grip of the front tires in a corner, too much camber gain will cause the tires to heat up, lose grip, and wear out prematurely. Therefore, do not use more than a few degrees of caster. If your car uses a MacPherson Strut suspension, it may be necessary to modify or install new strut tower mounts to be able to adjust caster.

Justg something I found through Wikipedia...

[S2central.net]

Oh if its on wiki, it must be right - LOL

[stiglet]

You are indeed correct Mr Casey.

Increased Castor good for low speed tight cornering, whereas actual camber is better for high speed not-so-tight cornering.

Side effect is increased straight line stability but it will be harder on the PAS pump.

[Rusty]

Oh if its on wiki, it must be right - LOL

Hence the "..." mr. Nugent

So basically:-

Increased castor leads to increased camber when turning and this can help grip.
Increased castor leads to heavier steering and so more load on the PAS pump.
Increased castor leads to more straight line stability.

Nit sure it's really worth the effort for my little banger

[S2central.net]

Andy - I think its worth a try - and you are the guinea pig for many a thing... Its especially interesting in your case as its a car that gets regular road use and more than the average amount of track thrashage !

[Rusty]

Requires drilling the subframe to rotationally lock the bushes in place. They're £20 more than the standard ones, I'm guessing this is due to economies of scale. If I can get a template then I can get some made at work though...

[A1QSHIP]

Ahem... see this thread.

http://www.s2forum.com/forum/showthread.php?t=11983&highlight=alloy+subframe+bushings

[stiglet]

Ahem... see this thread.
http://www.s2forum.com/forum/showthr...frame+bushings

This is intriguing.

I did not realise the camber of the wheel became POSITIVE with enough steer. I always assumed the factory caster would prevent this. Does this mean Audis have a massive KPI angle? Downside to having Mcpherson i guess...

Anyway, if this is so then i can see increasing the caster would be a benefit.

Also, Paul - I noticed you were asking about caster on the rear. I don't know if this will have any effect as long as the left/right are balanced. As far as i know, caster only has an effect on steered wheels? Hence porsches were mentioned, i think the 928has 4 wheel steering (that must be a b*tch to set up!).

Can anyone shed any more light on this?

[GT500]

This is intriguing.

I did not realise the camber of the wheel became POSITIVE with enough steer. I always assumed the factory caster would prevent this. Does this mean Audis have a massive KPI angle? Downside to having Mcpherson i guess...

Anyway, if this is so then i can see increasing the caster would be a benefit.

Also, Paul - I noticed you were asking about caster on the rear. I don't know if this will have any effect as long as the left/right are balanced. As far as i know, caster only has an effect on steered wheels? Hence porsches were mentioned, i think the 928has 4 wheel steering (that must be a b*tch to set up!).

Can anyone shed any more light on this?

ISn't KPI and castor the same thing? KPI is not a relevent term anymore as most on here won't have even seen a King Pin!
The more castor you induce,, here is the shiit bit,,, the less steering feel you have (not something any Audi needs less off!). As stated above the weight increases, not so bad on ours with power steering. On the race cars I have set up we try and run as much castor as the driver can cope with, Yes you gain mid corner grip/speed but poor begger turning the wheel comes back knackered!