Hank Cohn

I did a search and it looks like both of these topics have been covered at great length. I've read several castor threads but none are quite like mine. My car is way down on castor at 6.5 degrees. The camber measures 3 degrees and there is one large shim ~7 mm in the control arm.

All the other threads I read indicated that more camber = more castor not less. I took some pictures of the strut top and the castor eccentric. Can anyone tell if my strut tops are rotated from these pictures and wouldn't moving the eccentric adjuster to the middle hole pull the wheel forward and increase castor?

All pictures are of the left front suspension.

Thanks in advance,
Hank

By the way, I believe the rubber bushing has been pressed out of the lower arm and replaced with a solid bushing. Perhaps that means that the only adjustment to castor would have to come from moving the upper strut mount?

Rickard 993 Turbo

You should change caster in the adjustable castermount in the lower control arm

Billy Wyatt

Hank, I thought I taught you all those adjustment do not make you faster??Did you sell the 07 gt3??

Hank Cohn

You did teach me a lot! I had a bout of temporary insanity and sold the 7 GT3. I boought an 04 GT3 that is set up really nicely for the track save for the castor setting. Don't sell the your 7.

Hank

Rickard 993 Turbo

You do not have a problem, adjust the caster in the solid mount and you are ready to go

NJ-GT

Hank,

If that picture is from the driver's side suspension (left side), it explains why your caster readings are way below factory specs.

The stock rubber bushings were pressed out, and new aftermarket solid bushings were installed in your car. Your solid bushings allow caster adjustment. However, whoever installed them, did the opposite of what should have been done.

Your control arms were pushed back, and that decreases caster. If you use the center hole you will see your caster going back to the factory numbers, and the stability will increase. But even better, if you rotate that solid bushing, so the hole used gets as close to the back section as possible, you will gain extra caster. I run my car with over 9 degrees of caster, and it gives me the benefit to run less static camber (good for braking, and slow turns).

I can't tell you if the top is rotated unless I get to see one of my spares at home, but to obtain 3 degrees of camber with 7mm of shims, that top should be fully inboard when looking at it from the top. If that's not the case, then it's rotated. My car didn't get more than -2.5 camber with 7mm of shims.

Hank Cohn

Rickard 993 Turbo and NJ-GT,

Thanks for the input. I have a question. In reading through the Workshop manual I came upon the following illustration. If the workshop manual is correct then someone flipped the control arms side to side as the center and eccentric hole are reversed from the illustration in the manual. Is this wishful thinking or do you agree?

Hank

Now that I look at the illustration I see that it is too small to tell anything. In the illustration, there are two holes. One that is approximately in the center and one that is toward the rear of the car. In the picture of my car there is one in the center and one toward the front of the car.

Hank Cohn

NJ-GT

You're saying that the castor adjustment plate (don't know what else to call it) is aftermarket and can be rotated in the outer control arm. Is that right?

In my initial post I was trying to say that the inner bushing, the one that attaches directly to the subframe of the car has been pressed out an a solid bushing has been inserted. I just want to make sure I understand.

Thanks again,
Hank

NJ-GT

Inner Control Arm:

The attachment to the subframe uses a rubber bushing that can be replaced by a monoball bearing from Porsche MotorSports, ERP Racing, etc.

Outer Control Arm:

Your outer control arms have aftermarket solid bushings with adjustable caster. They were not setup properly. The stock part has two holes, a center one and an eccentric one surrounded by rubber. The stock bushing cannot be rotated, yours can be rotated. Just get it adjusted in the right direction, and your caster will read better.

Hank Cohn

NJ-GT:
Thank you for your patience and very informative feedback. As you are aware, I am not the original owner of this car, and, as such, have a lot to learn about both the car and the previous owner’s modifications.

I believe that the car has numerous great performance mods, however, the implementation seems to be a bit off on several of them. It’s nothing that can’t be readily fixed, mind you, but a nuisance until I do.

Part of the fun of ownership for me is sorting the car and making it handle the way I like it. The trick, I think, is trying to avoid the really obtuse mistakes.

Thank you again for your help and for very selfish reasons I hope you keep your current car as I can see numerous questions from me in your future. If you do decide to trade for a 7GT3 you will be pleasantly surprised. A lot of things have been written about the car, but the fact is that the car is blindingly fast at the track straight out of the box with no mods.

Thanks,
Hank

Hank Cohn

Rickard 993 Turbo and RAD:

We rotated the castor biscuit to the proper orientation and relocated the diagonal to the center position. The front lines up perfectly with 8.4 degrees of castor at both corners. The steering wheel now weights up nicely and gives the whole car a noticeably more stable feel.

Thanks again for the help.

Hank

NJ-GT

That's great.

By the way, based on your pictures, your strut tops are rotated compared to the stock position. This gives you extra negative camber and more space for wider tires.

Next time, use the eccentric hole on the right direction, and shoot for 9.6 degrees of caster. Trust me, you won't regret. The car will feel even better on straight line.

Hank Cohn

Rad, It looks like 3.0 degrees is all the camber we can get and there is a 7mm spacer installed. I thought you were going to tell me that the tops weren't rotated. Wouldn't you expect something closer to 4 degrees with rotated tops and a 7mm spacer?

Hank