Manifold

My understanding is that the front camber is adjustable, but comes from the factory nearly maxed out (negative) at about -1.3. That seems odd, but does it fit what you all understand?

If so, and assuming shims are the only way to get more neg camber, does anyone know the required total shim thickness to add about 1.5 degrees of camber? That should give about -2.8, which can then be backed off through adjustment.

My understanding is that shims aren't needed to get the rear camber to be in the -2.3 range, and that Porsche doesn't recommend using rear shims because of the RWS.

orthojoe

You can get about -2.5 without using shims up front. Anymore than that and you need shims.

In the rear my guy guessed that you can get about -2.6 without shims, although I will find out next Friday for sure since the car is going in for an alignment adjustment.

Keep in mind the shims in the front and rear are not the same shape.

Manifold

Dealer says factory setting was -1.3 in front, which can only be increased to about -1.4 without shims. That roughly fits what Macca said in another thread, but contradicts what you were told.

Mike in CA

Stock camber is -1° 30' which is -1.5° I just had front camber maxed out to almost -2 degrees (-1° 55').

I was told that there are locating holes at the top of the strut that can be used to get a bit more negative camber (by flipping the strut?), and beyond that shims are required. For my purposes, -2° was adequate.

Todd B

If it's the same as the 997.2's, you rotate the strut mount, by removing the top plates. Pressing the mounting bolts out. There's a different set of mounting holes 180 degrees, which rotates the strut to allow for more camber.

Mike in CA

That's exactly what my suspension guy at the dealer must have been referring to.

m3irish

I don't believe the 991 carried that feature over from the 997.

Macca

Thanks Mike. I was going to step in and clear that point up.

It will vary on individual cars and alignment equipment. With my car we achieved a maximum of -2.15' at the front using the factory gear without upsetting castor. Rear max out was -1.55'. I dont believe he top mounts are rotatable and if so would alter castor? castor is really important on the 991 GT3 as there isnt alot of room under there to push the wheel forward or back without fouling the guard liner on hard lock.

I was told using Porsche Motorsport shims on the LCAs was the way to do this properly so I bought the shims. They are no cheap for what they are.

I understand that 10mm shims total = -1.0 camber approx.

My car sees far more road miles than track miles (assumes average of 7-8 full track days a year). I do not think I need to go out to -2.7 front and -2.5 rear like the more dedicated track guys here as the MPSC2 are very expensive in NZ (3200 usd a set) and tyre wear becomes the issue for the sake of maybe less than 0.5s on our short tracks here....

Mike in CA

Thanks guys, for the clarification. I was told initially that there were additional alignment holes with the 991 but it's possible that the suspension guy was making an assumption based on his knowledge of the 997.

Regardless, I didn't pursue the issue further as for a street car that will be used for autocross I didn't feel I wanted more negative camber than the -2 degrees in front that was obtainable with the stock set up, at least for now.

Macca

Problem is I think it looks different up top Mike?

doba_s

Yes top mounts on 991 GT3 can not be rotated.

To increase the camber beyond what you can get on the top you need to add shims. Also you want to make sure when adding shims you are not widening one side more than other, meaning you need to add the right size shims and maintain the same distance from the center line of the car to the left and right.

Decent alignment machine would be able to show you this information and based on that you can add shims to both or just one side. Fine tune it by adjusting on the top.

Manifold

Looks like Tarett has shims, but I haven't confirmed their application to the 991 GT3:

http://www.tarett.com/items/991-981-...him-detail.htm

Their website notes about 10 mm of shim for 1 degree of camber, as Macca said.

I'm still baffled by the wide differences in adjustability people are reporting without shims. On my car, without shims, my dealer said he can't even get to -1.4 F but can get to -2.3 R without difficulty. Others are reporting more than -2.0 F but not being able to get to -2.0 R. Are the manufacturing tolerances really that wide?

BigT

Guys, took delivery of my 2015 just before the snow arrived in the Mid Atlantic so only have a few hundred miles on the car and of course as you all say it is wonderful. Now in garage on lift keeping warm so have taken time to check alignment, and inspect. My car came dead on to factory specs== -1.5 degrees camber all four wheels, front toe 0.5mm in on both wheels, 1.5mm in on both rears, ride height within a few millimeters of spec front and rear.

So now my question; does anyone know how to set rear toe?. This will need to be done if changing rear camber. For years I have done my own alignments on 996 Cup, 997 cup and GT3RS so understand the kinematics, but with the motorized adjustable rear toe, how does one either lengthen or shorten rear toe link when changing camber? (Front looks pretty straight forward and like prior models with adjustable length steering arms.)
Thanks, Tom

Macca

Manifold. You dealer is wrong I believe. I spent time talking with Chick Moreland at Elephant racing about this before my alignment guy even touched the car. As you are aware Chuck was an early 991 GT3 owner and did some great work on his site explaining the 991 GT3 suspension and even comparing it to a 991 Cup car. He told me max would be around -2.0 front and rear but rear maybe less. Sure enough he was almost spot on and everyone also has found the same.

There isnt a wide range of difference between cars as you say. I think you will find most of the 991 GT3s will get close to -2.10 F and -2.0 within 5 minutes which is very small.

I did not want to mislead. The top mount can be moved as mine was to get get maximum front negative camber without shims (-2.15) and perhaps there is another few tenths. However the movement is only via the 5-7mm of slot on the top mounts where the bolts go through so is very little and of course the risk is changing castor/wheelbase etc.

Here are the Shim part numbers you need from Porsche Motorsports. They are not cheap! The Tarrett ones will work fine and Im sure Elephant make them also (they do great stuff IMO and get my vote).

Tom - I believe the important thing for the rear is you have the steering wheel dead centre with he car on before switching off so the RWS motor and arm are locked into the 0 degree offset position.

orthojoe

Tarret and RSS shims will work in the front. They are all the same shaped shims used on the cup cars.

I am not aware of an aftermarket source for the rear shims. We ordered these from the dealer.