Correct, raising the ride height is another option, with cup shocks being so short though you wont have a lot of room to work with.

Heavier springs or even stiffening the sway bar could help prevent rear squat, however you would only be putting a bandaid on the problem, not solving it. I've run those ride heights with no problem and my carriers are stock. Bumpsteer kits really make life easier at low heights.

 

Are you suggesting bumpsteer adjustable toe links or also control arms as well?

 

The bumpsteer ends usually work with most adjustable toe links so all you would need is the end portion. Worst case you could buy toe links with bumpsteer and sell yours. I think tarret sells ends. Who does the work on your car?

 

 

Well, tire wear is not more important than lap times. This isn't about sacrificing handling for tire wear. But my tire wear IS an alignment issue or bumpsteer issue. Or maybe other. There are plenty of much more competitive drivers that don't wear tires into icecream cones. I am trying educate myself on the mechanics of the alignment on the finer level so that I see where I need to be. So if I see what other people align their cars to I can understand and break that down on a fundamental level if underatanding. Versus just saying "Jim Bob likes this alignment setting, do that on mine!" Not trying to sarcastic or a dick. Just trying make sense of it. I am not one of these people who just eats what is fed to them without understanding the principle and making an educated choice. Make sense?

 

 

The lower shot tire is sub 3000 miles aggressive street driving. Note the corded inner.

 

Wise words, I'm the same way. I need to see for myself. Gather as much info as you can and make an educated decision for yourself. Too many variables to copy others. FWIW, all I do is time trials. So I'm all out most laps. You can get even tire wear if you tune your setup for both wear and your driving style at the same time. I would not run slicks on that setup. Slicks are far more sensitive and will blow out on you while driving, literally within a couple of sessions if super heated on that edge. Hoosiers are durable and will withstand for a while. Check tires regularly if you see cords, time to change tires immediately.

 

Thanks. I have somewhat minimal understanding of how if you have a low ride height that the angle(up or down relative to the subframe attach points) become basically a gain setting to how much toe change you get as you load and unload the suspension. But where does camber come into play with that? So in other words if I have adjustable control arms, all monoball and adjustable toe links I should not have to compromise toe for camber or vise versa. So I can essentially get my toe and camber exactly where I want. But is camber going to also effect toe steer with suspension compression and decompression?

I guess where I am getting with this is if I know that based on a specific camber, ride height and toe setting what the curve is based on shock travel then I can fine tune that. Of course all that changes as soon as RSR spindles, subframes and such come into play.

 

Look up PMNA memorandum 202/2004. It'll shed some light why you may be having issues with inner tire wear. Heavy weight, low ride height, and soft rear springs in combination of the low pick up points of the TT subframes will all put an extra load on the inside of the rear tires as the suspension compresses under load. This is one of the reasons the later Cups (997 on) lowered the pick up points on all 3 wishbones at the rear wheel carrier and raised it at the subframes thus improving the geometry of the rear suspension. The angular position of the rear wishbones relative to the subframes have everything to do with how much the wheels camber in under load which directly translates to the load transferred to the inner tire. The 996Cup which shares the rear wheel carriers and subframes with your TT (minus the 7mm thick rubber spacers), so basically a street suspension adapted for race use along with its geometry shortcomings. As a result, due to rear tire failures, for the 996Cup running on the oval at Daytona, PMNA recommended a change to the RSR rear carriers which raised the pickup points 20+mm which reduced the load on inner part of the rear tires. Hope that makes sense. You may have more at play here but it's worth looking into. Good luck getting it sorted.

 

How do you plan on gathering this curve? Sounds expensive and time consuming even if you already have motec or something with shock travel sensors etc and the means and time to make a curve. Best way is to drive and take tire temps. Hire a mechanic to stay trackside. Change the easy things like ride height and rear stiffness. Pwdrhound has a point, however more spring rate makes things, well springier and harder to control, hence the reason many Porsche shops remove factory springs and go lighter for their club drivers. Heavier springs and harder to compress and make for a handful of a car. Especially on anything less than slicks. If you like the way your car handles now, it behooves you to keep it that way.

 

Thanks! I look into that memo. Great point. The 996RsR and latter 997cups I believe have the same raised pickup point rear spindles. Different brake bolt spacing though I believe. For now i’ll raise the rear as I have enough droop with my shock spacer. Also am looking to up spring rates and bumpsteer for the rear. Fronts are wearing great.

 

The brake spacing is different on the RSR and the Cup. It's the same casting but milled slightly differently.

The 996GT3RS was the homologation platform for all the motorsport suspension components used in the 996RSR and the later 997Cups and RSRs. I have those on my car now. At static ride height, the front LCAs and tie rods have a slight negative declination and the rears are just about level. If you look at your car, you will see that both the front and rear arms have a significant positive inclination which is far from ideal. It is like this on the 996Cup but they minimize the negative effects of this thorough the use of relatively heavy springs and light weight of the car. You can see the detailed comparison here where the standard 996GT3(Cup) suspension parts are compared to the 6RS motorsport carriers.

https://rennlist.com/forums/996-gt2-...omparison.html

 

As always your detailed knowledge is impressive and your willingness to share is commendable.