rockitman

Great job on the paintshop w/ the K58's Metal!!! Thanks...
I meant no disrepect with the Champion's..it's just that if I get another set a wheels, I want something very different from stock. My rear Yoko's just came in. They are sweet, although they just don't look complete w/o the wheels...
Guess I need to do something about that. Looks like K58's black anodized (shot peened finished) with a polished lip.

Just curious, I have adobe photoshop elements 2.0... What tool(technique) or what topic under help do I need to use or read up on to do that wheel replacment thing on already existing photo's???

rockitman

Is this black shot peened anodized or is this considered dark grey shot peened anodized???

MetalSolid

You may have to read the whole book... Try topics:
Layers
Marquee
History
Lasso
Filters
Eraser
Image Adjustment

rockitman

Hey...That's my car with my babe Anne Coulter sitting on it...Awesome!!!!

Thanks...

Todd Serota [TracQuest]

Hi Guys:

I was taking a brief break to see what's happening on the GT2/GT3 forum, saw this thread and thought I would add my comments on the subjects discussed.

STREET TIRES:

Yokohama AVS Sports are great tires, especially for the money, but they're not the fastest street tires out there. Keep in mind that I don't know what sizes you GT3 guys need and what's available from the various manufacturers, but that aside, BFG G-Force KD's (dry) and Goodyear Supercar F1's (which come on the Z06 Corvette) are the stickiest street tires going. For great value, Falken Azenis (sp?) and Kumho Ecsta 712's should also be considered.

TIRE PRESSURES:

Most tires work best at 40 psi hot, so Andrew's pressures weren't far off at all. One huge exception is the Michelin Pilot Sport Cup, which works best at much lower pressures - around 32 psi hot. Either way, your cold pressures will vary dramatically depending on how hard you drive so you need to check your hot pressures often to see where you are. For example, I generally start at 29/31 front/rear cold because my pressures increase about 10 psi on average. At Willow Springs, though, because the corners are faster, I see about a 12 psi increase so I have to start at about 27/29 cold.

DOT LEGAL R COMPOUND TIRES

As one poster said, R compound tires like the Michelin Pilot Sport Cup, Pirelli P-Zero Corsa, Hoosier R3S03, Kumho V700 (Victoracer and Ecsta), Toyo RA-1 and Yokohama A032R are significantly faster than street tires, some more than others. HOWEVER, I don't recommend that anyone get R compound tires until s/he has refined his/her car control skills and is comfortable at or close to the limit of traction. There are 3 reasons for this:

1) R compound tires don't make much noise when they reach the limit, so there's no audible warning when they're about to break away like there is with street tires.

2) Generally speaking, R compound tires break away more suddenly than street tires, making it harder and riskier to explore the limits of traction.

3) You're going faster with R compound tires, making it that much harder to control the car when you start to lose traction.

Here are some other things to keep in mind concerning R compound tires:

4) Most R compound tires (all but RA-1's) need to be put through an initial heat cycle before they're ready for use. Unless you're comfortable driving really hard on a twisty road so you can get the tires really hot, you're going to have to get the tires from some place like Tire Rack and pay them $15 per tire to do this on a machine.

5) R compound tires need more negative camber to work well than street tires do. Unless you plan to change alignment settings, if you drive them on the street you'll wear out the insides faster than the outsides unless you do a lot of switching side to side and flipping them on the rims. Even though they're supposedly unidirectional, some can be run any way you want (as long as you don't mind giving up some water evacuation ability), but some can't.

5) R compound tires don't last nearly as long, so it can get pretty expensive to run them, especially if you use them on the street as I always have (until I got the GT2 and an extra set of wheels). Also, note that if you do use them on the street, they're not as good in the rain as street tires.

6) The sidewalls on R compound tires are generally stiffer, making them harsher and/ noisier on the street. It didn't bother me, but it has bothered others.

rockitman

Hi Todd:

GT3 tire size requirement:
Front 235/40/18
Rear 295/30/18
I found not too many tires out there other than Pirelli's, Michelin and Yoko's in those sizes. I can't even get Mich PS2's...The rear's are always on back order, so after hearing Metalsolids review of the Yokes, I elected to try them out on a second set of wheels for daily drivers...Right now I am deciding on my new wheels. Most likely black shot peened anodized Kinesis. The way Michelin is with the supplies, if I ever got a flat, I would be dead in the water, hence a second set of wheels and rubber was in order. The yoko's worked out to be $350 less per set as compared to the PS2's. The tread design for the rain looks to be superior to the PS2's. They were designed after yoko's racing rain tire that was run on many of the GT3's at the 24 hrs of Daytona last year. That is according to Yoko's web site...

PogueMoHone

As far as flats are concerned, Michelin gives extremely high priority (from their own stock) for those needing replacements. Ask me how I know..I was in that predicament.

They came through, as did PCNA.

bob_dallas

Hi Todd, while I agree that some tires work best at 40lbs hot, that's a pretty big generalization. Alll the manufacturers are using different rubber compounds, etc. Pirelli PZ-Cs work great at 40 hot all the way around and from what I've heard Corsas do too. Hoosiers actually seem to like a little more than that (although I haven't tried them on the GT3) and the Michelin cups as you mention like quite a bit less (document I have says 32/36 should be a good target). I don't have any guidelines from Michelin on the PS2s like I do on the cups but in my experience they like a little less than that, at least in the front, as I mentioned in my message. It made a HUGE difference for me on the track (reduced the push) and the wear was more even across the tread. I haven't run the pyrometer on them and probably won't because I doubt I'll be running them at the track anymore...YMMV

Bob Rouleau

Bob and Todd,

I'm with Todd on this one. 40 hot will get you in the ball park with radial street tires ON THE TRACK - it is a generalization but it is a good one. I learned this trick from a Goodrich engineer at a seminar years back. It seems that all manufacturers design the tires for best performance at that hot pressure. So far my experience with a dozen different tires supports the theory. Note that on the road it is not unusual to see higher pressures on very low profile tires to avoid pinch flats and sideall damage.

I also agree that the P0 Corsa (unlike the P0-C) likes lower pressures, around 36 hot on my GT2 and the Michelin Cup about 34. Todd likes them softer - what can I say (grin) different tracks cause different behavior.

Still if anyone asks me for a starting point at DE I stick with 40 hot except on the two R compound tires above. Both of them have very stiff sidewalls and can handle lower pressure without squirming too much. Squirm not only makes the handling bad but builds heat and pressure in the tire.

As new tires with new construction and compounds show up, I might have to change my mind. Meantime I use the Corsa as my all around street and track tire. As always YMMV!

Regards.

macfly

Firstly, waht is this YMMV?

Second, on MPS2 running 40 hot all round on the GT3 does anyone else feel that the car is yawing and moving about on it's tires a bit too much to feel 'safe'?

I found the car to be very unsettled at any speeds much over 80mph, especially in turn 8 @ Willow, where my SO3 shod M3 would easily hold 115-120 and feel like it was on rails. The GT3 I worked up to just around 100mph, and it felt very unsure and unplanted. I simply didn't have the nerve to try and go beyond this.

Why does this car feel so much less able at high speeds than my M3?
Is it tires?
Is there something else I should know about these cars?

I was really surprised to be so much slower in it than the M3, and pretty much everything else out on the track. I know it goes fast around the 'Ring, but how?

mds

macfly, you said you stiffened the sway bar. Both? Front? Rear? That may be a factor. Also, what toe settings are you using? Can you double check the alignment?

macfly

The settings I gave my mechanic were the ones on your sheet, and he told me that that was what he did, with the exception of -2 in the rear, which he thought that was better for some reason. He did the rear sway bar one notch stiffer, and left the front as it was, on the 'standard' setting.

Below is the sheet I made up for him to do the work by. They have a very fancy alignment set up there, so I have no reason to think he did otherwise. To be honset I'm not sure how to check it accuratly.

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'

Todd Serota [TracQuest]

Hi Bob:

Your comment about using a pyrometer is really the key, even though I understand why you don't plan to use it on your PS2's. That's the only way to know exactly what your tire/alignment/suspension combination is doing. By definition my comment about most tires working best at 40 psi was a pretty broad generalization, but I've found from experience that it's pretty close - within a 2 psi difference either way (other than the Sport Cups, and, of course, the old, old BFG R1). As for Hoosiers, I believe Hoosier actually recommends the slightly higher pressures you mention, but the vast majority of my friends who use them (and are very experienced racers) have found that those pressures are too high, and right around 40 psi works best.

P.S. - To Macfly: YMMV = Your Mileage May Vary

bob_dallas

Yeah, I agree 40lbs hot is a good starting point for most tires - I guess I just hate for people to take that as the holy grail and not deviate even when it seems like things are not working properly.
Also - tire temps and pressures can drop pretty quickly depending on ambient temperature and the time it takes to get to the pits or even the time it takes to get around all 4 wheels. Even 1-2 psi can make a difference so if someone is reading 40 after it's dropped a few lbs then they could be over pressure even if 40 is right.
So I guess my point is - learn everything you can and don't just blindly trust guidelines if something doesn't feel or look right.

mds

macfly, both the stiffer rear bar and the slightly less rear camber will tend to reduce rear end grip relative to the front. Try putting the bar back to its orginal position first. And make sure the rear tires are not getting over 40psi hot.