track oriented suspension

[Quadcammer]

Originally Posted by edc

You probably won't quite get -2.5 unless you lower the car. I understand US cars are higher than UK/Europe ones so I can get it reasonably easily on old saggy M030 suspension and lowered suspension.

the car will be lowered on h&R springs

[rastta]

Originally Posted by Topless

Pick your poison.

I chose Porsche GT3 arms because that is what comes on a GT3 Cup car. No bling, just proven technology putting cars in the winner's circle all over the world. My setup shop does a LOT of track car setup and this is the choice they recommend over aftermarket alternatives. I really didn't bother shopping anything else for my 987.2. Working good so far...

YMMV

Actually the cup arms are different than the regular GT3 arms - they are forged and more expensive and also have monoballs from the factory.

I'm not knocking them - but the whole idea of shims turns me off - especially when having to dial in camber.

[jsceash]

Originally Posted by rastta

Actually the cup arms are different than the regular GT3 arms - they are forged and more expensive and also have monoballs from the factory.

I'm not knocking them - but the whole idea of shims turns me off - especially when having to dial in camber.

The split arms and shim are no different than solid arms except, when your frame side eccentric bolt bottoms out you add a shim and then you regain the adjustment of the eccentrics. I use a 3MM shim on the street and a 7MM shim on track. then adjust the toe link to get your toe back in.

[rastta]

Originally Posted by jsceash

The split arms and shim are no different than solid arms except, when your frame side eccentric bolt bottoms out you add a shim and then you regain the adjustment of the eccentrics. I use a 3MM shim on the street and a 7MM shim on track. then adjust the toe link to get your toe back in.

I'm familiar with how they work. The issue is - when I'm looking to get an exact camber number - how do I know what shim to use? With a bolt - I can simply move it slightly to accurately dial in what I want. I guess if you have a variety of different sized shims this isn't a problem - but they aren't cheap.

[MaxD]

The GT3 arms increase the track width of your car while adding camber. You get two enhancement (increased track and camber) for the price of the arms. Both are advantageous to your cars performance.

The shims are silly expensive but there are many non factory less pricey alternatives (tarett for instance). Once set up you will normally only use 1-4 mm shims for changes.

[jsceash]

You still have the eccentric bolt for fine adjustment. That gives you about 1-1/2 degrees of fine adjustment after installing a shim.

[rastta]

Originally Posted by jsceash

You still have the eccentric bolt for fine adjustment. That gives you about 1-1/2 degrees of fine adjustment after installing a shim.

Front has no eccentric.

[jsceash]

My 2003 had chamber adjustment eccentric screws all four wheel. I've installed K2 coil-overs with chamber plates all four corners and split arms. If I wanted I could get -4.5 degrees chamber without rubbing, but that's excessive.

[MaxD]

My 2003 had chamber adjustment eccentric screws all four wheel.

Can you show us a photo of the front set up. Are the control arms factory parts?

[rastta]

Originally Posted by MaxD

Can you show us a photo of the front set up. Are the control arms factory parts?

Yeah - would love to see that - no Boxster or Cayman that I know of ever had a front eccentric from the factory. I know both my Boxster and Cayman don't.

[thstone]

Originally Posted by rastta

Do most go GT3 arms because spec boxster rules only allow them?

Correct. The 996 GT-3 adjustable lower control arms are the only legal part allowed in the rules to increase negative camber. Also this is how the factory Cup cars adjust camber so every Porsche race shop already knows how to set them up.

Of course, there are pro's and con's to everything;

Slotting the shock tower to get more negative camber is fairly easy but has limited adjustment range and could hurt re-sale value because the car has been permanently modified and a lot of potential buyers won't want to take the risk that it wasn't done properly.

Camber plates are affordable but have limited adjustment range.

Adj lower control arms and shims are expensive but they provide a wide range of adjustment and shops already know how to set them up. Some of the investment might be re-gained on re-sale to the right buyer but that cost can be a mouthful to swallow.

Pick your poison.

[thstone]

Originally Posted by rastta

I'm familiar with how they work. The issue is - when I'm looking to get an exact camber number - how do I know what shim to use? With a bolt - I can simply move it slightly to accurately dial in what I want. I guess if you have a variety of different sized shims this isn't a problem - but they aren't cheap.

A good race shop already knows the relationship of number and sizes of shims to degrees of camber. And yes, most shops have already have all of the various sizes in stock and only charge you for what is installed on your car.

When you change the camber setting, you might need to buy 1 new shim to get the correct camber but then the shop will give you the excess shim back in case you need it in the future. Over time you'll own a small assortment of shims and the shop will use your stock of shims so you don't have to keep buying additional shims each time you want to make a change.

If you wanted to learn this yourself, you'd buy a small assortment of shims and then test using different combinations to create a shim vs camber table. Once you had the table, you could make changes pretty easily and quickly.

[jsceash]

Well I have to take back what I said on the front you guys are right the front looks like this







Sorry for the confusion and the quality of the pictures the photos of the rear did not come out, to dark in my garage I try to take them again tomorrow.

[jsceash]

Rear suspension alterations.


Adjustable top plate coil over.


7MM shim in GT3 C arms.


Stock Adjustable eccentric bolts for fine adjustment.


Adjustable Toe Links From Ebay.


7MM spacer plate. 45MM studs from Rennline.

[Brad Roberts]

Holy S_T why did they drill holes in the top?? I understand it has an adjustable camber plate, but max it out negative and use the factory slots to fine tune!!

[Brad Roberts]

I'm familiar with how they work. The issue is - when I'm looking to get an exact camber number - how do I know what shim to use? With a bolt - I can simply move it slightly to accurately dial in what I want. I guess if you have a variety of different sized shims this isn't a problem - but they aren't cheap.

5mm shim .5deg negative
10mm shim 1deg negative

Hasn't changed in 18yrs since the arms have been out. New are are the same! Super simple to figure out once you have a selection.

[rastta]

Originally Posted by Brad Roberts

5mm shim .5deg negative
10mm shim 1deg negative

Hasn't changed in 18yrs since the arms have been out. New are are the same! Super simple to figure out once you have a selection.

First time I've ever seen anyone post the relationship between a shim and camber. Thanks.

[Quadcammer]

ok all, I ordered my parts, everything should be in in the next week or two and I'll probably start in early jan.

What are people doing for front track arms? Seems the only option is porsche @ $350+ each

[jsceash]

Originally Posted by Brad Roberts

Holy S_T why did they drill holes in the top?? I understand it has an adjustable camber plate, but max it out negative and use the factory slots to fine tune!!

Before I got GT3 arms on the front I had to slide the chamber plate adjustment to go back and forth between Street and track. I could not tighten the screw through the top openning. Now all I do is switch two shims. and adjust the tow.

[Brad Roberts]

Quadcammer.. I have seen another arm out there. Guy in Texas. I have not touched them.. but he is starting to run ads in magazines for the arms and outher pieces he makes.