MM-Racing

I need your advice because I can not find proper setting for more agressive caster. I know that stock is 8,00 -/+ 30'. But there is second hole in the arm which makes caster more agressive.
How set the car using the second holes? What advantages and disadvantages are from more caster?

thanks
Marcin

GT3 Chuck

there is no reason to fool with the caster setting (if it is in spec) unless there is an understeer or oversteer problem that you cannot correct with tire change, toe, camber or track bar adjustments...if that is the case there is probably something wrong with your suspension or chassis geometry....technically, you can reduce understeer and increase oversteer with more positive caster - you can reduce oversteer and increase understeer with more negative caster....usually, the amount of positive or negative caster is a design decision and when it is within spec it allows the rest of the suspension to be adjusted (aligned) for optimal performance

Bob Rouleau

Using the second hole (and changing nothing else) will give too uch caster and your tires will rub on the fender liner. It may be used i you rotate the struts to get negative camber (2 degrees or more) and end up with too little caster. Most rotate the struts and use shims in the lower A arm to get 2.5 degrees negative and keep the caster in 8 to 8.5 degree range.

Best,

MM-Racing

I have not measured the caster yet but car turns noticable faster and more agressive. I m going to aligne and measure car again tommorow. But your advice is max 8,50, I ve seen somewhere on RL that some users put 9,00.

DanH

Don't the manthey top mounts give an extra degree castor? Thought that was the point?

MM-Racing

Dan may be you are right but I thought that their mounts gave only more camber in the front. I m going to aligne again my car after changing the possitiions into back holes of front arm.

MM-Racing

I ve measured the caster after changing and it apeared right 9,02 and left 8,53. Durung slow corners (till 80m/h) is quite ok but in high speed in the corners the car in not so stable and a bit oversteer. I will go back with caster.

With Manthey camber plates the castor in first hole is caming back about 20 min.

MM-Racing

Dan, you are right. I compared aligments and MM camber plates add +1 degree caster.

DanH

That makes sense then - I didn't think you could get 8 degrees plus without them...

I've got castor adjustable top mounts in my intrax 4 ways but the guy stopped at 8 degrees too as he didn't want to foul the arches.

Bob Rouleau

MM
My experience is that caster greater than 8.5 will cause the tires to rub against the fender liner. at 9 degrees, mine rubbed as did my wife's 996 GT3.

Caster in the 8 - 8.5 degree range is the correct setting. More does nothing for handling in my experience. If you have oversteer issues, I suspect something else is wrong. First suspect is rear toe which should be 16 to 18 minutes toe in per wheel. Much less than that causes instability on hard braking and can provoke snap oversteer on hard cornering. PM me if you want to discuss in detail.

best,

mjb

I concur with Bob on caster at about 9. I had my camber increased in the front to -2.0 using shims which pushed the caster out to 9deg. Now the tires rub on the fender liner near lock.

BTW, I didn't think caster was adjustable on the 6GT3 anyway. How do you "set the caster"?

MM-Racing

I pushed the wheel a little back by using the back holes in control arms. Than it resulted in caster greater about 20 min. This tendency to turn faster maybe is a result now of smaller distance between the wheels (front vs rear). But it is not comfortable at higher speed.

ArcticFox

Hey DanH, I am looking for a solution to adjust the castor...you mentioned adjustable top mounts....can you tell me what they are, and were to find them??? I have found nothing domestically that will do this. I would love to hear what you did/puchased!

I have slightly lop-sided castor and would like to get her perfect. Adjustable top-mounts/plates would be my preference.

Thanks in advance!

DanH

Tim I replied to your mail.

For anyone else interested they are made by Intrax, but came with my Intrax by Oakley Design 4 way titanium dampers. Development work is being done with them on my car as they were originally setup for the 997 so I'm the guineapig. So far I'm very impressed. Not only quick on track, but better ride on the road.

ArcticFox

Thanks Dan, got your reply.