This is the first modification I'm planning on my car.

I want to set the negative camber to 3 degrees all around, in order to have something that works ok at the track and at the streets, and reduce the understeer.

There are 1mm , 2mm, 3mm, 7mm shims. Which one sould I get?

 

Get a few 1mm shims. You may need more than one but they can be used in combination. I'm running -3 up front and don't find the car is darty at all on the street. It worked great at Road Atlanta on street tires.

Karl

 

I needed 9mm total to get to -3deg up front.

On a related subject, with the widened track and this much camber, I'm getting a bit of low speed tire rub at full lock (right turn). Anyone experiencing the same? Admittedly I've raked the front down by another 5mm or so.

 

My car needed more: 7mm on one side and 8mm on the other to get -2.5° while keeping caster at 8°. Front is lowered 10mm to Euro spec. No rubbing with the Cup tires.

 

I note the monoball mount at the top of the front strut is designed to be turned 180 degrees to achieve more negative camber. The 3 mounting studs must be pressed out of their original positions and pressed into alternate positions in order to to turn the mount. This may be the best place to start in quest for more negative camber.

Anyone done this?

 

I had my GT2 at the dealer for an alignment check under warranty and since it was out of alignment they covered it under warranty. At the same time I had them set the front at -1.5 and the rear at -2.0 camber. The technician also mentioned the option to rotate the front struts/shocks 180 degrees to increase the camber, but I am driving mainly on the street with track days mixed in. I just finished a full day at Sears Point yesterday with good results, so for now I am sticking with this setup. I did hear from Johannes van Overbeek that the car would handle better with around 4 degrees of toe (negative I think) in the rear, but this wouldn't be optimal for the street. Moreover, he suggested that tightening up the sway bars can help. Please remember these suggestions are for a GT2, and I am not sure if they are applicable for a GT3. Good luck.

 

The issue is that there are 2 ways Porsche designed into the system to increase camber at the front, rotating the upper strut mount which tilts the strut in at the top and/or adding shims at the lower control arm which tilts the strut out at the bottom.

Literature I have says the limit is 5 degrees negative, presumably achieved by rotating the upper mount then adding shims until 5 degrees is achieved, a limit to the thickness of shims that can be added is not given.

If you rotate the strut mount, then the lower limit of negative camber is raised since it is permanently tilted in relative to the stock position unless the mount is re-rotated.

It would be nice if someone could post the range of adjustment possible if just the upper mount is rotated.

 

Not a range adjustment as such, but a quick report on the -2.5 achieved by rotating the shock mount.

My tech set me up
-2.5 front
- 2 rear
Stiffened up sway bar one position.

I just did three long run sessions at Big Willow, and came home through the canyons. This seems to be a very predictable and pleasant set up at both track and on the mountain roads. At the next service I may go more, depending how the cars feels over the next few weeks, and what I learn from the boads here.

My tech did say that he has several cars set up at -3 all round, but he said that was more suited to competition rubber, and I should get the hang of my car with this set up.

 

Cupcar, rotating the strut gives well over -3 degrees. I have not tried it on my car yet. Shimming has an advantage in that you get a small increase in track with increasing camber. By the way, there is another adjustment that can be made. According to both the USA workshop manual and the GT3 Product Information book, the longitudinal link can be attached at one of two separate points to maintain optimum geometry as camber angles change. I have not tried this yet either.

 

Thanks mds,

After asking my question, I read in Paul Frere's book: The Porsche 911 Story , 7th Ed., page 423, that the stock adjuistment set up is good for -1 to -2.5 degrees and turning the mounting plate allows for -3.5 to -5 degrees as you indicate.

He also mentions the shims are for: "final adjustment", but I would assume they are most useful to achieve adjustment between -2.5 and -3.5 degrees since this seems to be a window between "stock" and "turned" upper mounting plates.

Interesting on the longitudinal links, wonder how much negative camber prompts a change in mounting point.

I agree with advantage of increasing track with shims as well.

 

Uhmm.

It seems that shims are not necessary to get -3 degrees of camber all around.

Even better, rotating the strut mount 180 degrees, will allow for the installation of wider rubber at the front with no rubbing (265/35 R18)

Interesting.

By the way, I was running 245/35R18 Hoosiers for auto-x in my boxster all around, and 225/40R18 - 265/35R18 Michelin PSC for the track. The 265 Michelin is the same width of the 245 Hoosier. Therefore 265/35/R18 in the front of a GT3 is possible with no rubbing.

 

What is the stock camber and toe settings for the GT3 from the factory??? Is it 0 front, 0 rear??? What are the advantages handling wise for modifying these settings??? If my car is mostly driven on the street, is it really necessary to mess with the stock settings??? Will adjusting them cause uneven tire wear??? And finally, how does changing the toe fit into this whether changing it by itself or in combination with the camber settings???
Thanks

PS: Bottom line, I am looking for a summary of handling characteristics by modifying toe/camber for the front, rear or both, whether it's just camber or just toe or both in combination. Probably not an easy question as it is driver specific. A general guide would be helpful...Thanks

 

Okay, I have done some research. Camber is the tilt of the tire relative to vertical. If the top of the tire leans inward (towards the engine) the car has Negative-Camber...If it leans outward, that is Positive-Camber.
*Negative-Camber gives the car more cornering grip and improves steering response.
*A car without enough negative-camber will understeer and wear the tread off of the outside-corner of the front tire.
*Too much Negative-Camber will wear the tread off of the inside corner of the tire
So this harkens to one of my questions...Are the stock camber setttings negative and if so how much???

I am still confused on the toe settings and caster...Should these be played with??? I am interested in maximum handling characteristics witout uneven tire wear...

 

I agree, wider rubber beats a minimal increase in track any day. BTW, can you tell me what width wheels the 265s were on. It seems like the hot setup for the track is 9s & 11s with 245s & 305s

 

Rockitman,

After hearing from a number of people that their factory alignment settings were "off", I had my GT2 checked after buying it, and the settings were way off from specifications, so when they realigned it for me under warranty, I asked them to max out the settings based on the factory recommendations. I don't know if the GT2 and GT3 have the same settings, but the major issue I believe is that there is usually a .5 degree variation allowed. My local dealer has a new facility and the latest alignment machine, which automatically sets all of the remaining alignment specifications once camber is set. Mine is -1.5 in front and -2.0 in the back, which seemed to work quite well at Sears Point last Friday. Additionally, you can change the sway bar settings to improve cornering ability. I am far from an expert on this topic, but can tell you that after the realignment, the car "dives" for the corners when I turn in now. :d