NJ-GT

Monoball plates will reduce unwanted dynamic camber and caster changes. Arms will let you increase track, camber and caster.

In my car I run the plates half inboard for tire clearance, 10" front wheels and 285/30R18 Hoosier A6 (wider than a regular 285).

The 996 GT3 front arms can be used on all the 986/987/996/997 (1997-2007 Boxster any version, 2005+ Cayman any version, 1999-2007 911 any version). They're used on the 996 GT3 RS at the rear.

My 2-piece front and rear arms have an addition to the stock parts. The rubber from the eccentric hole was eliminated with ERP solid mounts (black metal) with a center hole. This reduces dynamic toe, caster and camber changes. The flange that attaches to the subframe (2nd piece), was replaced with the GT3 RSR monoball. This reduces dynamic changes on toe, caster and camber.

You can also buy the entire GT3 RSR arms (2 pieces). Cost with the solid bushing is around $1,800 per corner.

karlooz

no need. my left control arm ball joint boot was torn so it need replacing. i figured i would go with the gt3 control arms just in case i wanted a wider track.

karlooz

hey NJ-GT, what camber plates are you using? i have ERP plates that are flipped to give me more negative camber (rather than adding shims). the ERP plates are camber/caster plates... i wonder if flipping the plates change the caster and clearance much. if i run a 10 front wheel there would be no way to turn the wheel, it would just hit the fender liner/radiator mount... how do you do it? i'm thinking about re-flipping the mounts and just slotting the top mount holes to get less caster (i'm at ~8.5degrees right now).

Evil Bunny

I stumbled upon this thread using the search function, its 10 years old but the best I found on the topic.

I am currently fitting GT3 LCA's to my 996 C2, one side partially complete, and thought I would add to the thread for the benefit of others, as well as seek additional advise from those that have completed the change.

As discussed you have to reverse the LCA's on a C2, I flipped mine and started with a 5mm shim, with this setup I could only get the tuning fork arm into the centre hole on the LCA.

With a 5mm shim and using the centre hole my 225x40x18 Yoko AD08R rub ever so slightly on the front wheel arch liner on full lock.

By adding additional shims and increasing the camber it will further push the tyre towards the wheel arch liner and increase the rubbing.

To counter this I will look at add an addition 2mm shim to the LCA and look to located the tuning fork arm in the eccentric hole in the LCA which will serve to push the tyre away from the front arch liner. - This method I believe has been used by other with success.

I believe ride height and suspension strut position also factor, my car runs on coilovers and is between M030 and X74 height, I will confirm.

Could someone confirm the effect lowering the ride height has on camber and caster?

In relation to the strut top mounting holes, mine are slightly elongated, again I under stand by moving the strut within the slots the geomotry is effected, again could some comment on how moving in-board / outboard effect?

Cogito_Ergo_Zoom

I also found this thread helpful when I was learning and building out my suspension.

You didn't mention what your application was, ie. street car, track only, race car, desired camber values, spring rates you are running, ARB rates, etc. but a few things I would suggest to keep in mind based on some of the lessons I've learned tuning and setting up the suspension on my 996 C2 race car:

-Suspension setup is the art of the compromise. There a lot of ways to skin a cat. Some recommendations & ways of doing things might result in better outcomes in some aspects but worse in others, eg. ultimate cornering grip with one vs. putting the power down better with another, but still result in roughly equally capable performance and laps times in the hands of the same driver. There is no ONE TRUE WAY to setup a car. Driver preference also plays a huge part.

Not necessarily. If you don't shim the lower wishbones significantly, there isn't a absolute requirement to swap the wishbones from side to side.

This is normal on a C2 with GT3 wishbones and the thrust/control arm mounted on the center bore. Also, how often are you driving the car at speed on full lock? While the rubbing isn't ideal, even with the 245/40/18 R1s I run in the tightest radius hairpins like Turn 11 at COTA, I rarely have more than 225 degrees of steering lock on, ie. less than one full turn of the wheel. Don't worry about excessive rubbing at full lock when the only place you'll ever see it is in the parking lot.

Yes, in that case the eccentric mounting bore position can be used to reduce caster slightly and reduce rubbing. Better yet, you can replace the center thrust bearing on the wishbone with a solid adjustable caster puck such as the one manufactured by ERP. The benefit will be finer caster adjustment and increased steering feel. Unfortunately I can't use these for my application due to the fact they're not legal for spec racing in PCA.

Yes, also keep in mind that that you won't need to "force" the thrust arm into the eccentric hole. It will be evident which bore to use based on how the thrust arm aligns with it due to the shimmed wishbone length.

Ride height primarily affects overall suspension geometry by relocating the inner suspension pickup points and balljoints relative to the outer balljoints (wishbone and tie rod ends) at the wheel upright. This really isn't something you can improve upon unless you're willing to convert to the GT3 or Cup wheel uprights, in which case you could go lower. I won't get into a long explanation of the relationship between ride height, Cg & roll center location, but excessive lowering is one of the biggest mistakes people make and will result in many undesirable steering and handling characteristics.

Caster is important but not the most critical of settings compared to camber and toe. This isn't something you should waste a lot of time worrying about. Go no lower than the X74 ride height specs and keep within manufacturer specs on caster and you will be fine. Consult a skilled alignment specialist in your area to get it right.

Again, many ways to skin a cat. You can reach desired camber settings by either shimming the lower wishbones or by adjusting the orientation and position of the camber plates. There are pros & cons to both methods and you'll get many diverging opinions here.

There's more I can share but I'm not willing to do it in a public forum. PM if you want to discuss.