This was a Dukes of Hazard from a GT3 RS that decided not to change out 6 year old tires. He drove straight off a country road in the corner with no grip. A passenger at that point. Nobody was hurt and the shock tower survived. The front shock, camber plate, and some body work however did not. I think it was about $20k to fix. The Porsche struts are far thicker than most other cars, but everything has its limits.

 

My GT4 went in to install the rear toe links (Tarett).
I am running the new Apex Forged VS-5RS 19 x 9/ 19 x 11 wheels with 255/35 front and 305/30 rear MSC2’s
Sharing my alignment set up which is 95% for the track. No camber plates, only shims.
Feedback welcome. Will report back after my upcoming double Pitt Race/ Mid Ohio weekend.

 

That's a lot of caster... Do you have any rubbing? Try going out of a driveway (decline / incline) at full lock, both directions.

I never really understood the different camber left vs right thing... Can someone explain?

 

No rubbing, at least not driving the car on the street and going out of my driveway, even at full lock, both directions.

The tech at the performance shop explained me why the different l v r camber settings but I forgot, will ask.

 

Get a set of Tarrett camber plates which will take you to -3.0, that will also dial back your caster which is too high. You can then add shims to get around -3.5 which is what I would go if no street driving at all. You also want a small amount of toe out, which you have currently.
For the rear -2.5 is good, I would go around 2.0 deg of toe in per side but no more than than. This is my current alignment for reference, I drive it on the street too no issues. I run -2.0 camber on the rear and get good tire wear so have not gone higher.. Apex Autowerks in clifton are v. good for setting up Caymans, although they will suggest going the thurst arm bushings route rather than camber plates to correct caster.

 

Two years ago after adding 7mm of shims on each front arm also my caster got to 10° (stock was 9.5°) and I never understood if it's good or bad for front handling...

 

2.5 degrees up front is as far as you can go with just shims before you start having clearance issues. Clubsport strut tops allow you to go to about 3.2 degrees before the caster starts to get too much again. I preferred the clubsport strut tops to caster pucks as I like to use Porsche Factory components at every opportunity where I can.

 

From my experience, the biggest change I noticed with the high caster numbers were an odd on-center steering feel. The wheel liked to sea-saw left to right when dealing with any road irregularities.

 

I find the front toe setting affects the on center feel more so, adding to that the type of tire, street/comp being much worse than all season or winter tires.

 

I am hoping you are right. I had my caster corrected when I added my MCS dampers and it helped a lot with the sea-saw issue, but I still get some steering wheel crosstalk on broken pavement. I have an appt. next week to add more front toe in on my car. It has a little now, but not much.

 

I just put on motorsport front camber plates with the swift springs. It lowered the caster from 9.75 to about 9.25 degrees. I can readjust it with the thrust bushing, but we are going to see how this caster runs at the track this weekend.

Both camber plates and solid thrust bushings can correct a caster problem, but they also each have their own specific attributes as well. With my 9 inch rims, 265 tires, maximum shim, and wheel offset reduced from the OEM 60 to 50; a camber of -3.0 degrees can be achieved on the front axle. However, the tires stick out a bit too far and rub ever so slightly on the upper inside fender when at the track. So adding the camber plates tucks the front wheel and tire back into the wheel well, can further increase negative camber, and helps correct the caster by a fixed amount (.5% in my case). This will allow for up to -3.5 degrees of camber in the future, while still keeping the tire inside the fender. LCA thrust bushings can't accomplish all of that, but they do give you fine adjustment over the caster, which is unavailable without them. A nice thing for a GT car. Now we have full control over the camber, toe, and the caster. Beyond that, the solid thrust bushings take the slop out of the rubber bushings and further tighten up the front end of the car making it more precise. This is what you see on the RS cars, and I definitely noticed it.

The rear of the car already has solid LCA thrust bushings as standard. Porsche chose the rubber ones up front for the GT4 to make it more compliant and pleasant for street driving. So in the end, a good route to go for a person who wants to maximize the performance and adjustability of their GT4 for the track, would be to do both upgrades. If you are mostly on the street, I would start by add some shim and try to make a -2.5/2.2 to -2.5/2.0 setup work for you.

 

My question was a little different:

If we take two 718 GT4 or Spyder with same rear camber/toe (let's say -1°30' and +1.5mm each side), same front camber/toe (-2° and 0mm), but one has 9°30' (stock) caster, while the other has 10°... what are the differences in handling? Who can say accurately which is better? With more caster you should gain more camber as your front wheels turn, but maybe too much (dynamic) camber is bad and you get understeer. I think it's hard to answer.

Stock non-GT 718 has shorter front arm so the caster is a lot lower like 8°30' or 9°... GT 718 already has 9°30' ... MAYBE if we move too far away from the starting design the suspension doesn't work very well.

 

I have seen a few different specifications for the 718 GT4/Spyder, but not one verified specification from the factory manual for these numbers. I would like to know what Porsche actually lists, not the myriad of after market 'proven', preferred' settings always quoted here on Rennlist.

For example here are two (neither mine), note the specified ranges:

 

Those “specified ranges” from the alignment machine databases are definitely wrong. Stock caster is supposed to be around 9.5 degrees (+- 0.3 degrees roughly).

Getting -2.5 degrees front camber with shims alone would push front caster to 10.3-10.7 degrees, at which you start running the risk of rubbing.

My car is at -2.0 degrees front camber with roughly 10.0 degree caster, shims only.

 

Wizee, your reply is what I am talking about, you say they are wrong and even give other specifications, who is to say that you aren't wrong? Do you see my point? The front camber on my car is -2.4 and the caster is not in the 10 degree range.

How about a scan, PDF or photo of the actual Porsche manual/document?