ADias

My point was that the Michelin rec seemed to be generic, independent of car. That does not make sense, as diff cars have diff weights and pressures should depend on corner weight. Grip=CornerWeight X ContactPatch.

Mike in CA

A valid point. When I was buying my MPSC's, I was confused by the lack of specifics in the Michelin literature too, so I called them. I was told that, in fact, the Sport Cups were designed to perform optimally in the range of 32F and 36R and a temperature range of 180-220 degrees. On our cars that works perfectly, as it does for another car which uses MPSC's as OEM, the BMW M3. The implication from the person I spoke to was that Porsche and BMW owners were the primary users of these tires and they were engineered for applications where f/r tires and pressures were staggered. For other vehicles the tires will work fine but maybe not to the optimal spec. I didn't get into a long discussion with the guy; it was enough to know that the tires would work for me. You can take this FWIW.

mdrums

*Remember* 19" MPSC are NOT as good as all the other 18" MPSC. The 19" stock sizes for a Porsche are of a different compound (harder) and different tread pattern. Toyo R888 in the stock 19" size is a much better tire for the track then the MPSC 19" stock sizes.

cbzzoom

Hmm.. interesting.

Like a lot of people here I got a "RoW performance" alignment on a stock 997, getting as much negative camber as possible front and back. That means the rear is a lot more negative than the front. (I think I have -1.2 front -1.8 rear)

I found that compared to stock, the front end does hook up way better now, so there is less understeer. But from what you're saying, if I left the rear end without so much camber it would understeer even less.

I guess I really need to go for the GT3 LCAs at some point.

I wonder with the C4 which naturally understeers if it would be best to really bias the camber to the front, like -2.3 front and -1.5 rear or something.

atr911

Two things to consider:

1. The response was in reference to someone running r comp tires which make significantly better use of neg camber. The quoted -2+ degrees of camber was far too much compared to the front.

2. The common advice to remain within 0.5 degrees front to rear would still apply to your situation and you're probably okay with your setting.

Here's the real issue; Driving style cannot be determined online. We can point you in the right direction but FAR too many variables exist to really tweek a setup. Tires, track, any and all suspension mods, rim size and most importantly, driving style/skill.

There is no e-substitute to a pyrometer and some seat time. Keep in mind that as your corner speeds improve the balance may be upset. Ideally, at the true limit you enter a corner at maximum speed and hold it under balance until the apex where you would unwind the steering wheel as you apply throttle. Usually, one would want a slight under steer at this point so maximum throttle can be applied at corner exit.

Your C4 may have a LSD which increases push as well.

atr911

P.S. -2.3F -1.9R is a great comprimise street/track setting to start with. Just remember to toe the rear in a little.

acadian_dad

Just a brief followup. I had the 996 GT3 LCA's installed by AutoImport and both the front and rear camber were set to -2.3 deg. Spent Saturday at Calabogie shaking things out with some fresh MPSC's (stayed with the 34/35 hot pressures) and the improvement in handling was exceptional. 3 hours of fairly aggressive track time later (chasing atr911 a little ... ), there is still significant wear on the rear driver side outer shoulders and assymetric wear across the driver front tread blocks (not so much on the shoulders) but not as bad as before.

So while the increased camber did improve the wear somewhat, the change in handling was eye opening. Lap times dropped from the 2:29 range to the 2:25 range and just felt smoother. When driving at 7/10-8/10, the car was just carving into the turns like butter - so very nice ...

atr911

Yeah, I'll attest to the fact you were moving!

I didn't want to offer someone elses tool but one of the guys I was up with (my next door neighbour) had just bought a tire pyrometer. I suppose it's only slightly helpful unless you use it each time you come off but it gives a pretty good indication of how to set pressure (along with mfg specs of course) and will tell you how your setup suits your driving.

If you take a look, I posted about my Hoosiers running thin on the outside front left after only 2 days so I'm going to be flipping tires left to right after each day up there to even out wear. Too late for me now as they're corded but not a bad idea for all the right turns at bogie.

On another note, what a GREAT day. Lots of guys running mid and low 2:20's to play with. Did you check out the pics?

http://picasaweb.google.ca/117413030...OV5a-Du46L4QE#

acadian_dad

Nice photos !

tcouture

I have a 2009 C2S Std-PASM with adjustable LCA's (RSS).

I am trying to align for -2.2 front and -1.9 rear of camber and it looks like I now have 9.5' of caster, which may cause fender rub (among other things).

How did you guys solve that one?

T.