Last fall I purchased a complete set of RSS toe links, control arms & steering links from a buddy who had them on his 996 Cup Car. My shop installed them while they had the motor out to pin the coolant lines. He also dialed in -3 degrees in the front of the car. I was finally able to get the car out for the first time today since the work was done. When I would brake hard out on the highway I could hear rubbing. I came home and the Hoosier R7's in the front were destroyed on the outer edges from rubbish against the top of the inner fender to the point that it actually bent the inner fender edges & will need to be rolled out. We did not lower the car any & the tires are what I always run (18" Hoosier R7 slicks). The rims are 18 Turbo Hollow Twists. Any quick ideas as to what to look for. I am at a loss why this would have happened.

 

bummer on the tires... how many times did you hear the rubbing before it dawned on you that it could be terminal? that much shaving of the tire should have given some sort of steering wheel feed back i'd think??


with increased camber you might expect that the rubbing would come from the inside of the wheel. you don't mention your toe setting, if you are towed out a ton & it occurs under hard braking when toe will increase as the suspension compresses that could be it. especially with where your show the fender damage at the leading edge of the wheel well.


or, and im completely speculating here,,, are any of the cup parts you installed longer to make for a wider track desired in a racecar. meaning pushing the entire front assembly out some creating the opportunity for tire/body contact.


I still find it hard to fathom that you did not sense the wheel feedback and sound alerting you to such a severe contact episode. was the radio up real loud?


jb

 

My first thoughts are the parts you installed are not compatible with the Turbo front suspension. My second thoughts are your spring rates are too soft allowing too much compression under braking. My third thoughts are why didn't the shop that installed the parts check for proper clearance. From you pics, it looks like your wheels and tires stick out too far and rubbing the fender lips is inevitable. If your shop is Porsche savvy they should know in an instant. I assume the -3 is camber which should tuck the tops of the tires in a bit more. I'm assuming the Cup LCA's are adjustable for length. Maybe they are too long pushing the wheel carriers outboard and everything else was adjusted from there to get proper alignment. So now your front track is wider. My guess.

 

^^^^^ what we said.... it makes sense that a 911 cup car might want an expanded/wider track for front side grip even in the tail happy platform a 911 can be...


cup cars are also not AWD...

 

What's the thickness of shims in LCAs? Are top mounts rotated or not, if they're "GT3 style"? What's the width of those tires? Were fenders rolled or not? How much caster you have?

Ie if you have std turbo strut top mounts you need to have lot of shims in LCAs. With std top mounts the caster adjustment range is 0 to -1.5 deg. So then you'd need about 20mm shims to reach -3 deg camber (1mm = 4,5' ---> 10mm = 45' ---> 20 mm = 1.5 deg). That amount of shims will push wheels forward a lot, increasing caster , unless you have either adjustable caster pucks on LCAs (Cup LCAs have them, but in which hole the caster arms are set?) or have adjustable caster arms. Pucks are a crude way to push wheels back, with adjustable arms caster can be fine tuned. Actually they're the only way to adjust caster in these cars.
All that above leads to the fact that your front wheels are more forward than they're supposed to be and outer tire will contact fender when cornering hard. Rolling fenders would help a bit, but basically the reason is altered front geometry.

 

Find a competent shop. They gave you more front camber via shimming the LCAs which is the proper way to do this. As you add more shims you are thereby lengthening the LCA (widening track) the whole wheel assembly will naturally be pulled forward (more caster) due to the fixed length of the trailing arm. What they should have done is installed the trailing arm in the alternate hole on the GT3 LCAs which I assume you have. The street GT3 arms have two positions which can be used. It's not precise but does the job. If you have Cup style arms, they will have solid adjustable caster pucks which can be rotated to precisely bring caster back into spec. I do not recommend adjustable trailing arms.

 

I made an experiment today by adding 10 mm shim to the LCA, without touching the track rod. Wheel center moved forward about 20mm. It was easy to push it back with an adjustable caster arm.

 

Thanks guys for the feedback. As a side note, I was simply taking the car out on the first decent day to do some durametric data logging to send to Kevin at UMW since I upgraded to larger injectors/fuel rail, new tune & secondary fuel pump. The issue never showed up till I did a long 3rd/4th gear run & hit the brakes hard. I heard a rubbing that actually sounded like the tire rubbing on the inner plastic fender well. I "gimped" home & the tire had shredded on the sidewall area & there was a slight bend in the lip of the inner fender as you can see in picture one right of the front side marker. That was the only damage to the car itself which I think can easily be "rolled" back into place & touch up with some paint. I thought the shop I dealt with was very competent & they have set up many race cars in the past.

 

A note away from the suspension stuff. Modding the front radiator brackets may be a helpful thing in your case as well. Pwdrhound just did his to fit 275s in the front and I did mine to fit my 255/35/19s. Not overly hard to do and give about 1 inch more room on the front of the fender liner.

 

How did you modify the radiator bracket to give you more clearance. Thanks guys for the feedback. I'm taking the car to a dedicated shop here in town as soon as they can fit me in.

 

Some pics of the front/rear set up

 

https://www.6speedonline.com/forums/996-turbo-gt2/252887-255-35-19-fitment-front-how-i-did.html

I didn't even completely remove the brackets when I did mine. Just took the bolts out , pried the radiator foward, did the cutting, put 3 washers behind the one stud, couple Hite with the hammer, then some touch up oant.

Pwdrhound I think did a little nicer job on his than I did to mine.

 

Here is the radiator bracket mod flewis763 alluded to. I just posted it up here:

https://www.6speedonline.com/forums/...big-tires.html

 

Thx Pwdrhound. I took the car over to my local shop tonight & sent him the link to your radiator write up.

 

Great pictures, sorry you went thru that, beautiful car !!!!