ltcjmramos

Did a 250 mi drive yesterday with the Monterey Bay PCA club. In garaging the car ('04 GT3), I did my usual after action check, and have discovered exposed cording on the inner edge of the driver side tire. I'll need to get the rear tires replaced ASAP.

Having taken the car off the track, I had taken it to TRG for installation of their toe links, and to get a more streetable alignment. They did that with these alignment specs:
Front: Camber 1.8 both sides / Toe-in .50 both sides
Rear: Camber 2.1/2.0 / Toe-in 1.5 both sides
According to them, the difference in rear camber is to accommodate the curvature of most roads and helps the car drive straight.

Previously, with a more track-oriented alignment, I had corded the inner edge of the pax side rear tire.

Might I have a problem not directly related to alignment?

Porsche917K

I'm no expert but those setting seem a little aggressive for an all street car.

ltcjmramos

I'm no expert either. Any suggestions for street settings?

enthusiast

As you know, that rear wheel camber is more than what is recommended for street use and is most likely the problem.

With the rear cambers you posted, driving a lot of normal easy turns and going straight you will have the most wear on the inner portion of the tire patch.

The other thing is the inner shoulder tire wear can really sneak up on us. When we take a glance at the outer and middle tread areas they normally look great but the inner shoulder could be getting close to the cord. Then a few miles later, cord is showing.

Ahmet

If there's not a typo on your rear toe settings, that's your problem.

mooty

^ i told joe that as well.
2.0 camber is very little. i run 2.5 on my street cars. 3+ on track.
also you have way too much toe up front as well.

you NEED to see tony.

viperbob

Joe, it is not the camber that is killing the tires but it is that with the combination of toe in. With tire off the car roll it down the street. Rolls fine. Now sort of roll it with it on the inside edge. Not bad. Now try to get it to roll in a straight direction, but pointed sideways. The more it is pointed sideways (toe) the more that is has to scrape across the ground in order to move forward. This is what causes your issue.

va122

Yea what bob said. Toe is the likely culprit.

To add, you really don't need more camber in the rear then in the front.

Jetmech

The best way to tell, is to take a pyrometer and measure the heat across the tire after a hot lap, with no cool down, this way the only way I was able to get my car aligned to maximize tire life. but each track is different, and the GT3 does jump around. I ended up with neg 1.8/9 for rear camber and I have even temps across my tire. My toe was fine, but yes, that does need to be within spec as well.

Good luck.

MetalSolid

According to them, the difference in rear camber is to accommodate the curvature of most roads and helps the car drive straight.

va122

Not sure how that works. Considering most roads are banked or sloped for water runoff.

enthusiast

Yes, they were referring to just that, the crown being along the center line of the road (for water drainage).

CSPorsche

I actually have negative toe in, in the front of -1mm, and positive 2mm in the rear. I couldn't tell if you corded your rear or front this time, but if its the front your positive toe in might account for that. TIRE PRESSSURE is the first thing I would look at. Everyone overinflates their tires! There's a fine line though for too little air on the street as there are a lot of bumps and holes that may damage your rims, so find the sweet spot and check with other people running your exact tires. That's all I have for you! Good luck

Chris

va122

Huh. Guess you learn something new every day.

ltcjmramos

New tires are on the car, and taking the car back to TRG for them to check the alignment, and, probably, realign. What specs for street use should I have them put on the car?

My driving is all street. Some backroad drives 130-140 mph. Most posted 25-40 mph turns at double the posted speed.