Bob Rouleau

The street tires like 40 lbs hot. Start around 32 cold and bleed down as needed. Brand new tires squirm more and generate more heat and pressure so you may have to bleed them down to 40 hot more often at first.

Philip in AL

Bob, is that 40 lbs, front and rear?

Bob Rouleau

Phil in Al - Yes all around. Fine tune from there. Some prefer a few pounds less in front,i.e., 38F 40R. I prefer to start with equal pressures all around and tweak if needed.

Rgds,

curtsm

There are a couple of files from Michelin on CB Racing's website:

http://www.cb-racing.com/boxster_links.htm

A PDF and PowerPoint presentation describe various technical aspects of the MPSC (tire pressures, etc.):

http://www.cb-racing.com/pilotsport_technical.pdf
http://www.cb-racing.com/PilotCup_Presentation.PPT

- curt

MetalSolid

Running MPSC 37-40lbs hot, worked better for me. Pressures measured after a hot lap, not after a cool down lap.

Bob Rouleau

Metal - I think you and I run about the same pressures as mine are based on measuring after a cool down lap. Still, track condition counts and I dial mine in based on how the car handles usually over a range of a couple of pounds.

dave morris

macfly,

you noted earlier that you got 50 heat cycles on a set of MPSCs and never noticed them going off or losing grip. fwiw, my experience has been somewhat otherwise. first, i love the MPSC tire. i'm probably on my 8th or 9th set. they wear like iron and are a great tire for a heavier car like my '84 911 ... and probably a GT3. but after about 25 - 30 heat cycles they definitely start to go away. after 50 or so they are pretty darn slippery. and i generally don't have much rubber left at that point. i took a new second set of tires to the track last weekend ... ran on the old ones that had about 45 cycles until the last run ... and changed to the new set. the difference was dramatic and immediately noticeable. grip in turns and braking, turn in, you name it.

still hoping to buy somebody's used GT3 as soon as i grow up.

dave morris
'84 911 coupe
'97 993 coupe

macfly

45 cycles until the last run ... and changed to the new set.
I've never been able to do that, I've always come home, changed the tires and then gone back a week or so later. My times however are considerably off the possible maximum of the car on these tires, (I'm around 10 seconds a lap slower than the pro drivers like Cort at my local tracks) so maybe that explains why I feel so little alteration in the performance of the tire over it's life. However I'm keeping a log of everything on this set, cycles, times, temps etc to see if I can notice any difference, and I'll post that too once I've used up this set.

Also I have been sticking to the letter of the law (32-36 hot) on the MPSC's and haven't thought to vary from that. I have noticed that they seem to slip and slide a bit more when they get hot and the pressure goes up to around 36-40 which happens here in SoCal in the hot summer days, but I'm guessing that it could be as much the tarmac going off too.

I'd love to hear what everyone else has found with these tires, because I really hadn't thought to go outside of the 'specs'. Are they crisper and better a couple of pounds over, what happens if you run them a bit softer? Kevin and John, Cort has done very fast laps in both your cars, what pressures where the MPSC's at then?

4 Kurves

Well, yesterday at the POc event I did quite a bit of fiddling. First of all I just got my car back from having the camber increased again. With -2.8 in the front the front tires rubbed a lot so I put the 5mm spaces back on (making the offset stock) and that helped although they still rub a bit.

I also went to full stiff on the rear anti-sway bar to help cure slow speed understeer - this worked beautifully but resulted in more oversteer. After my first session the tires were hotter then I normally find them - 35/39 without a cool lap so I bled them down to 34/36. Next session after a cool lap they were still high so I went down to 33/35. Oversteer seemed less so that is what I stuck with most of the day.

Ironically I turned what was to be my fastest lap of the day on my second hot lap in the very first session of the day - a 1:14.23 (this is without the bowl as POC runs it) and spent the rest of the day trying to break 1:15 as was never able to do so. Closest I got was a 1:15.63

What really sucked was that the first two sessions don't count towards your fastest lap so I ended up finishing 2nd in my class to my friend Hennrick (also a GT-3) by just 2 10ths.

So now I am wondering about the higher pressures....

Maybe the higher pressure produces better grip but the car did feel more nervious? Or maybe I was just more relaxed in that session and didn't overdrive (a distinct possibly) and was therefore faster. In addition to the 1:14 lap and I had a number of laps in the first session that ended up faster then my best "counted" lap - the others were marred by traffic.

I've been taking the 32/36 Michelin recommendation for granted and haven't fiddled too much but now I'm thinking I need to experiment more. I'll do some of this on Thursday at Button Willow and let you guys know how it went.

Other factors come into play of course - for one it was 20 degrees cooler in that first session then the late afternoon session when I was over a second slower. And the anti-rollbar setting - I not convinced that this is best - sure the understeer went away but the rear end is more nervous now. Ok on the slow tracks but I wouldn't want that for a fast track.

-Kevin

MetalSolid

It took me until the very last session to figure out the pressures, because of the very cold track. By simply adding 2lbs to each tire the handling was absolutely transformed.

4 Kurves

Noel - what you and Bob have been saying has me thinking the same thing - I've been running too low of a pressure. Time for some experiments!

Where you at the big track on Sunday or just Saturday. There was a heck of a wreck there but one of the Muller EVO's on Sunday. I didn't see the crash (I was at SOW) but heard about - turn 9, mud and a cartwheel. Heard the driver was ok. I saw the car be DRAGGED into the transporter Sunday night and it looked like a total loss to me.

MetalSolid

I was only there Saturday.

macfly

I'm very happy to hear that no one was hurt.

My Sunday was much calmer, took the Zee out for it's first drive of the year.

4 Kurves

It has a twin! Or am I seeing double?

macfly

It was one of the other posters from the Z8 board who came out to see what the scene was like at the Village Coffee Roaster, it was a simply stunning day out all round!