My car has the upper strut mount on the 3 holes that allow more camber, the standard 1mm shims and 2.6 degrees camber at the front.

Yesterday, I was working on the suspension (playing). I installed 11mm of camber shims (7mm, 2mm and a pair of 1mm) at each side, plus the stock 1mm shim.

When I dropped the car I found that the car won't turn. With just half turn on the steering wheel it will rub on the plastic inner fender cover badly. I got an increase on track of 22mm, but it only works on straight line, Great !!

I got to remove the 19mm bolt and 21mm nut that retains the control arm, in order to use the second caster adjustment hole and try. the control arm moves even forward (toward the front of the car), increasing caster even more, and by the time I was able to get the bolt back in there, the front tires were rubbing with the plactic inner fender cover with the wheels straight.

The one thing I noticed is that both control arms look the same (left and right), what looks different in the second caster hole position.

I didn't try this, but I think that if we swap the control arms, then the second caster hole (not the center one) gets relocated toward the front of the car, and in that case using that hole will reduce caster instead of increase caster. This should allow the front track increase by using plenty of camber shims.

Is this documented in the Porsche technical manual?

What do you think?

 

What are you trying to achieve by all this, more camber?

 

Alon - when you increase camber with shims you also increase caster and end up with the tire rubbing on the fender liner. The caster change moves the wheel forward, hence the rubbing. I gave up on the shims and ovalized the holes at the shock mount to get more camber without increasing caster.

NJ-GT I suggest you pm raceron. He has a GT3 and is an alignment expert.

Rgds,

 

I know how the shims affect the caster (and overall track I suppose) but I was more curious why he would be looking for more than 2.6 degrees of camber. Ovalizing the holes seems like a reasonable alternative.

 

Racing slicks maybe? DOT R's are happy with neg 2-3 deg. There are caster adjusters available from Motorsports for US$1,500 a side. Although as the rate the C$ is climbing they will soon lot cheaper for us than our US pals

 

That's why I was asking because anymore than 2.6 degrees seemed to be very excessive (except for racing, with the right tires). I do love this dollar exchange although I'm certain that in the end, we'll all suffer for it.

 

NJ-GT, I do not understand what is going on with your car. I rotated my upper strut mounts to gain more camber, and now have an adjustment range of -2 to -4.5 degrees, without having to ovalize any holes. I still have the stock caster. Are you certain that your upper strut mounts are positioned correctly? You have to press out the studs and turn the housing 60 degrees.

 

With the strut towers rotated I can get up to 3.9 degrees of negative camber with just 1mm of camber shims.

The idea of using the camber shims is to increase front track to help the car turn better in very slow turns. I managed to increase the front track on 22mm, but I had the problem with the caster. Increasing front track is a good thing to defeat understeer. Increasing negative camber is good as well but up to a limit, where braking is drastically affected and the outside of the tire won't be used on slow turns.

 

Gotcha! What ever means you can use to lengthen the control arm, or relocate it's chassis attachment point rearward or outboard should work.