Todd Serota [TracQuest]

I agree 100%, Bob - well stated. Taking temps and pressures promptly is critical if you're really going to rely on the info to make fine changes. In fact, many people look at this data when they get into the pits even though they didn't have a hard lap immediately before pulling in, significantly tainting the data.

I often get into this discussion when people talk about IR pyrometers, which, of course, only measure the temperature on the surface of the tire. I wouldn't say they're totally worthless, but they're nowhere near as accurate and useful as a probe pyrometer because the surface of the tire cools much faster than the rubber even 1/4" underneath.

macfly

Can you suggest a really good place to go to set up my suspension / camber/ swaybars, so I can get the best expert input and have the car set up as well as possible for my next track day next at Willow next Tuesday.

I'll have a pyrometer, and be running 40psi hot, all details will follow.

Todd Serota [TracQuest]

Hi Andrew:

You want to talk to Steve Alarcon at Johnson's Alignment in Torrance - (310) 370-6301. He's been doing all of the alignment/suspension/brake work on all of my cars since 1986 (when we met in POC) and he's great. Tell him I sent you.

Also, if you've never used a pyrometer before we should talk. Aside from making sure you physically use it correctly, there are nuances to interpreting the data. I'll be happy to discuss it with you.

Btw, did you get the voicemail message I left on your cell phone a few days ago?

Bob Rouleau

Bob_D Agreed that 40 Lbs hot is a starting point. If the car feels weird then play with pressures - lower not higher.

Mac - My GT3 did not feel really great on track until I went for a track alignment which has neg 2.5 degrees all around. This wears out tires on the street though. Todd has elsewhere suggested neg 2 as a street/track compromise and my experience with that set up has been good. I would play with tire pressures more before I started to play with the sway bars. I was able to do a back to back test on track with two brand new GT3s. Mine with the track alignment and another (same color even) with the OEM set up. The difference was very pronounced. One other thing I've seen, even with the stock alignment, a set of R compound tires transform the car. It feels as if the car was set up to use a stickier tire than the PS2 N2. MOst of the GT3 competitors come with R compound tires as OEM, the M3 and the Stradale for example.

Best,

Sun Ra

Uncle Bob,

you said "even with the stock alignment, a set of R compound tires transform the car. It feels as if the car was set up to use a stickier tire than the PS2 N2. "

think this is true of GT2 as well?

Todd Serota [TracQuest]

Bob's got lots of good points:

1) Alignment is critical. The factory alignment is a joke from a performance standpoint, designed to make the car (all cars) push for liability purposes.

2) Tire pressures make a huge difference. When I took my GT2 to Willow Springs to play for a day it was an evil handling beast, oversteering everywhere, even under moderate throttle coming out of Turn 9 at 110 mph. I figured it was anti-sway bars so I adjusted them for less oversteer, but it didn't make all that much difference. Finally, after 3 sessions of showing off my car control skills at 100+ mph, I stopped being lazy and checked my tire pressures. The rears were at 48 psi! I lowered them to 41 psi and was eager to go back out when the rain it, and that was all she wrote.

That said, a small anti-sway bar adjustment can make a significant difference as well. At Laguna last Friday, Mike Schuster (MDS on this board) was kind enough to let me drive his GT3. We only got in a lap and a half before the checkered, but it was enough for me to get a pretty good feel for how the car handled. Aside from having Michelin Pilot Sport Cups rather than Corsas, it felt very similar to mine (not more nimble, I have to say, as Bob R. feels it is) but pushed more. I asked Mike what his set up was, including anti-sway bars, and he said that his front bar was one position off of full stiff (and his rear bar was also one position off of full stiff, where mine is). I suggested that he move the front bar one position to the middle, thereby softening the front bar and decreasing understeer. After I got home Mike sent me an email saying that the change made a very noticeable difference. Of course, Mike is here so I'll let him elaborate further if he so desires, since the actual experience was his.

3) Since Mike's is the only GT3 I've driven, I obviously haven't driven one on street tires, but I did drive my GT2 on the stock Michelin Pilot Sports for a session at Infineon and I agree wholeheartedly with Bob's observation. Certainly the GT2, with a lot more hp and even more of a torque differential as compared with the GT3, begs for stickier tires than stock. That said, I reiterate my comments from another post that novices should not put on R compound tires until they have a fair amount of experience, have pretty well mastered car control and are driving at or close to the limit. It will make it that much harder to learn, thus slowing down the learning curve.

4) Finally, while I run 2 degrees negative all around on the street and track, I wouldn't call it much of a compromise. If you do a lot of street driving it will chew up the insides of your tires much faster than you'd like. A good compromise setting is 1.25 or 1.5 degrees negative all around, but one must realize that tires which like a lot of negative camber won't perform well at those settings. For such tires, even 2 degrees negative is at the very bottom of the acceptable range.

NJ-GT

I drive with Michelin Pilot Sport Cups for 8 months a year, and with Dunlop Winter Sport M2 for 4 months in my Boxster S.

My R compound tires feedback is not good. It is kind of an on/off grip. I remember that my factory Pzeroes and my GForce K/Ds were very progressive, but their dry grip was not close at all to the PSC. I can deal with that on/off grip feeling, because the emotion of the g-force generated during braking and turning is amazing.

For auto-x the PSC are as bad as any street tire, because you don't get a chance to heat them up. A typical auto-x is a 45 sec lap, with a 15 minutes rest. For those events I use Hoosiers A3S03.

My camber is -1.2 F and -2.0 R. I maxed out camber with the stock suspension and camber plates, because I was running A-Stock class at SCCA events (practically no mods allowed).

There is not a perfect setup for street and racetracks. But one thing for sure: The best negative camber setup on street tires won't catch the grip of factory camber settings on R-compound tires, even with Hoosier R3S03 who love negative camber.

I prefer the negative camber setup with R-compound for my daily driver. My first set of PSC lasted 8,000 miles and my second set is practically new with less than 1,000 miles on them. PSC treadwear is rated at 80, when PZeroes are rated at 140. This means that you should expect half the life on PSC compared with PZeroes.

MetalSolid

Macfly, how are your tires wearing?

Todd Serota [TracQuest]

Hi NJ-GT:

A quick comment about tread wear ratings. There is no standard, so there is no way to compare ratings across manufacturers. Put another way, the ratings are totally arbitrary. Each manufacturer is consistent within its own line, but that's as far as it goes. So, one manufacturer's tire to which it has assigned a tread wear rating of 100 could have completely different wear characteristics than another manufacturer's tire with a tread wear rating of 100. In fact, some manufacturer's have been known to adjust tread wear ratings on specific tires for specific purposes - for example, making a tire legal in a stock competition class that has a tread wear restriction.

macfly

The wear looks even now, at 2K miles. My guess is they'll make another 2-3K at this rate of wear, though it's hard to guess at this point how long they'll last, as first 1,300 miles I was keeping it easy for break in. As I'll be doing quite a lot of track days and DE maybe not that long, we'll soon see.

I still haven't figured out what set next, seems there is no perfect tire, NJ-GT's report of the on/off feeling of the MPSC is a little disappointing, as I was thinking that would be the next set up. I'd prefer something with stiff sidewalls and progressive feel near the edge, not an on/off switch that could land you in a wall!

996TwinT

Well I, for one will NEVER buy Michelin tires again. I had the complete opposite experience that Colm had. I had a flat rear PS2 on my GT3 and it took 15 days to get a tire! When I called Michelin Customer Service to expedite it, they made up every excuse in the book. I also had a severe steering issue with my car which I believed was a bad front tire. They tried to tell me that it was because there is a coating on the new tire that has to wear off. When it's time to buy replacement tires, it won't be Michelin.

MetalSolid

I have slightly more wear on the inside of my tires, especially the rears. Your wear patterns seem to indicate that you are close to the correct alignment and pressures, where as mine don't.

macfly

What camber/caster/toe are you running?

MetalSolid

The dealer tells me it's pretty much within factory specs but didn't supply numbers...

rockitman

Does everyone still consider these the reference standard factory spec for alignment settings??? I think mds got this from a french shop manual...

factory specs for the 2004 GT3:

Front axle height: 115 + 5mm (115 to 120mm)
Rear axle height: 128 + 5mm (128 to 133mm)

Front axle:
Toe unpressed (total): +8' +/- 2'
Toe difference at 20° lock: -1°30' +/- 30'
Camber: -1° +/- 5'
Max camber difference, left/right: 10'
Caster: 8° +/- 30'
Max caster difference, left/right: 40'

Rear axle:
Toe per wheel: +13' +/- 2'
Max toe difference, left/right: 5'
Camber: -1°50' +/- 5'
Max camber difference, left/right: 10'