dmilzoff

DJF1
I like your recommendation of using MPSCs for dedicated track tires and my street tires if weather is bad. (I can go to Hoosiers after another dozen DE day.)
What pressures would you recommend for a 996TT (18" stock tires)? Should I be checking for tire pressure after a run or should I be checking tire temperature? Is an infrared temp gauge sufficient or do I need a pyrometer?
David

joey bagadonuts

David,

I've driven in the rain on both MPSC's and Kumho's and I'd have to give the Victoracers the nod for wet-weather traction. Like yourself, my AWD car tempts me to just keep a set of R's on the car and forget about it. As long as it isn't a daily driver, I think it's doable as long as you take it easy in the rain.

Pressures for my 3,200-lb car usually end up in the mid 30's--that's determined by a pyrometer. I would recommend you buy a probe-type pyrometer (the infrared models are not as accurate) and determine for yourself the best numbers. Each driver and track works the tires differently, so using a pyro will help you determine what's right for you and your car.

As for street driving, Factory numbers work fine: 36 psi cold. BTW, I use 17" wheels and a 225/255 tire combo.

DJF1

For the track shoot for HOT temps between 32 -35. More than this and the tires feel a bit slippery.
I usually start COLD 26 front 27 rear and end up 33 front 35 rear HOT.
So after your run check your HOT temps and it would help if you have a probe type of pyro to see the temps accross the tire. If you have more than 15 degrees difference between the edges then adjust the tire pressure accordingly in 1 pound increments.
One think to be aware of is that with the low cold temps your out lap will be slippery and you will feel actually the tires flexing a lot. This is normal as they heat up. Once you do about a lap then start putting your foot down.
The MPSC's stick very well and they are progressive when they let go. Not very audible I must say so always increase your performance in increments to find your limits.
Also bear in mind the track temps, when on a cold day obviously start with a pound or so more COLD and reverse when the track is really hot. If you must run with them in light rain or very damp condition run close to OEM pressures cold as Michelin recommends.
When you run them on the street stick to OEM tire pressures, on 18's I would run anywhere from 34-36 front and 36-38 rear COLD temps.

We are all very hopefull on the new incoming Hoosiers, with the present ones IMO stick with the MPSC's due to their wear characteristics and general construction. The Hoosiers are not steel belted, blow outs do occurs which can be very damaging as you can appreciate...Not to mention the wear... Unless you do competition then the 1 second per lap or so that you may find in the Hoosiers it does not translate in a any advantage for cost per mile or even fun factor when you do only DE's...

Good luck and enjoy them!

Mark in Baltimore

Danny,

When you say hot tire pressures, are you taking a reading after a cool down lap or do you come in after some hot laps and immediately take pressures? I've noticed that the pressures can drop very quickly while the car is sitting, especially win cool weather.

My MPSC's are running at about 34F/35R hot after a cool down lap. Think I should go lower? Should I end up with 32F/33R hot for optimal stick?

DJF1

You really have two choices.
1. to have a buddy check on the spot temps and pressures as you come in to the hot pits after a few hot laps
or
2. Your last "cool down lap" can also be used to maintain temps up. While I do not use almost any brakes on this lap that does not mean I take it easy in the corners. In other words I will try even on the cool down lap to take the corners almost as fast as on a hot lap, i will not accelerate out of them so when the next one comes I can decelerate or accelerate as I see fit to take the corner fast without using brakes and most times I'm up a gear as well to give a break to the engine. I have tried this and compared results with method nbr 1, on a normal hot track I did not find any drop in temps doing this.

To tell you for a fact that 33/34 is the best I cant. It also depends on the track surface, temperature and layout. What is good on one day it could be different the next. I have even noticed differences as the tread goes down or even as the day goes by. Most of the adjustments that you will do will be on "feel" and lap times. A certain track might have a lot of tight turns so you may want to add or reduce pressure according to what your car is doing overall. The only clear indication that you have over/under inflation would be uneven temps ( more than 15F between the ends) and ofcourse if you overheat them more than 200F you may see some chunking. In general they will "feel" slippery if they are over inflated.

I would say that a good starting point is 32F 34R Hot. The you play and look at the lap times.
BTW if you feel confused dont worry you are not the only one

Adam Richman

Hubert, some R3S04 feedback (disclaimer, this is a 2175 lbsish FF):

We have been running effectively the same suspension setup, toe, camber for the last two years. The end-of-the-day differences between the R3S03, RA1, R3S04 are pretty much indistinguishable but this is a big picture statement. I do not buy that there is any more than a half second difference between these tires over the course of a lap at most tracks. We did an impromptu comparo of the RA1 and the R3S04 down the back straight at Road Atlanta during the ARRC practice day about a month ago. What we found (and we ran the tires on both cars over two sessions with pretty much identical weather conditions) was that the Toyo was notably faster down the straight than the Hoosier (irrespective of who led or followed, the Toyo could either pull away slightly or catch up slightly on the straight and we swapped postions a couple of times per session). It was equally notable the difference at turn-in for 10A as the Hoosier throughout the sessions had significantly more turn-in grip. We were both running good quality RA1s as well (both were shaved to 4/32nds and had plenty of life left - I believe he ran one of the qualfying sessions on his). In the turns, the Hoosier was much easier to place the car throughout the sessions. BTW, both the 04s and RA1s were 225/50s. I won't knock the Toyo, its a damned good tire, but it does give up some overall grip to the 04s and they don't have the feel of the new Hoosier.

The new Hoosier comes at a mold depth of 5/32nds. I ended up running 2 qualifying sessions, 1 20 minute practice session, 1 20 lap sprint race and measured 4/32nds outer edge and inner tread depth (the outer edge - this is the front left tire btw - was harder to measure due to debris and melt of the lip but looks to be a good 3.5/32nds). Basically, I ran two full qualifying sessions, 1 20 minute practice very hard and a 20 lap sprint (where two of us finished .02 seconds apart so this was very hard driving) and used 1/5th of the tire and this is alot for a weekend as I never run all of qualifying (let alone two full ones) or more than a handful of laps in practice. I forgot to ask Rodney (App Tire, www.racetire.com - they supply our SE Div SCCA races) how much is usable if any below that mold depth so it might have more life than that to it. The new Hoosier, despite its quickness, is appreciably heavier than the older R3S03 - this same front left R3S04 weighs as much as my Toyo RA1 intermediate rain tires (shaved to 6/32nds) making it heavier than my dry shaved Toyos. In talking to App Tire, they had a report of a driver saying the R3S04 fell off during his race, he backed off and they came back in w/in a half lap (he won the ARRC enduro in a 2850 lbs. ITS car so it was being pushed very hard). Another item of note (and I think this is hillarious), I have to drive up onto 2x6s to get under the airdam/splitter w/ my race jack. I was trying to get the car up in the air quickly (this might have been after the initial heat cycle - can't now recall) and it picked the boards off the ground a good couple of inches before they fell to the ground (these are ~2' 2x6s ). It must be the stick of these tires that makes them as quick as the R3S03s while weighing more. A word of warning however as they are wider than the old R3S03s in the same size. The tread width is the same (maybe a smidge narrower) but the section width is 1/2" wider so if you have rubbing issues w/ a R3S03 which is wide to begin with, you might want to take note of that. Otherwise, they are fantastic tires (and I happen to think they are a fantastic company in their support for motorsports) and you will not go wrong with them.

On another note, I would not talk anyone out of an RA1 either. These are great tires. They have very good rolling resistance, they are extremely durable (unintentionally qualified on a flat left rear at RA in '02 due to a puncture and didn't damage the tire and didn't exit the track, was slower than I'd like but eh ) and they are very fast. The turn-in is not too far off the R3S03 but it doesn't feel _as_ good but the upside is they never seem to go off (its certainly not as good at turn-in compared to the R3S04 but I already said all that stuff) which we found the R3S03 prone to during longer races and/or on rougher surfaces. This is actually the tire I'd choose (will choose again) to run at Lowes MS for my ITA car for the straightline speed (we spend probably nearly half of that track at WOT) and Roebling Road due to the abrasiveness of the surface (although I am inclined to try the 04s there after hearing reports of App Tire's testing there w/ the new compound). Over the last two years, we've found that we (co-driver and I) can turn w/in tenths of our fastest times on either the RA1 or the R3S03 so I don't buy the global comments that these tires are seconds apart - my experience is that this is simply not the case. I also do not buy that a Michelin or Goodyear DOT is _seconds_ faster than either of these. The RA1s wear well also and running our schedule this was a great benefit last year - I think we ran 19 races for the year, seven of these were 1.5 hours or more and I *think* it was done on 10 RA1s (and Roebling ate a couple of them well before their time ). In contrast to some comments, I would not suggest an unshaved RA1 as they will wear quicker than one shaved. You can call up Vilven Tire about their recomendations for your car's weight and I believe shipping is free (can't recall now) - I would think somewhere around 3 to 4/32nds but its something I'd ask _them_ (because they know this stuff) if I were you. On our intermediates we will see minor chunking from a drying track. The shorter tread blocks will not generate as much heat and chunk off and you'll get longer life from the shaved tires vs. the full treads.

I have run the A032Rs also. I like them. Not as a race tire but as a DE/Auto-x tire they are fun but do give up a good bit on the grip department but you can still get around a track PDQ with them. The will wear very well and are relatively insensitive from my experience except for extreme high tire pressures. I also think they make a pretty good wet tire. I tried that street tire thing in the wet thinking they had better depth and such but found the A032R significantly quicker in the wet (and that's what one should expect). I think these tires come at 5/32nds depth and I feel pretty secure that heat cycling (especially from a dealer) is not necessary. If I had a preference however, I'd run the RA1 for a wet tire vs. this but that's just my preference.

Sorry for the long post. Not sure if its of any help and I am neither a professional on a closed course nor did I sleep in a Holiday Inn Express last night

Oh one last note; you mention a concern about the learning curve of each tire. I cannot speak to the Michey but as for the RA1 vs. R3S04, the Toyo is less easy to damage

C4FDR

I have Toyo proxies RA-1's on my 01 C4. I have 8 track days, averaging 2 hours a day and I should get another 4 to six track days out of them. I purchased them from American International Motorsports in Sonoma, CA (Infineon/Sears Point). I drove Infineon in the rain and they were great. I did not shave them and I just fliped the tires on the rims and rotated side to side since the outside was wearing faster then the inside on the fronts.
They do get faster when the cross treads on the edge get smooth.
These tires telegraph well.
They were about $1100.00 tax and shipping unshaved.
225 ZR 40/18's on the front and 275 ZR 35/18's on the rear
Todd from Trackquest wrote a good article on these tires on his 996 Cab.
I'll buy them again.

Hubert

Wow. You guys are amazing. Thank you for the wealth of knowledge you've shared. Hubert
PS: I decided on the A032R's for my 1 set of R's for the wear , linear feedback and grip and general availability. Thanks again to all those that counseled and advised.

Mark in Baltimore

Danny,

Thanks for all of your advice! I need to get a hot lap so I can see if my changes make a difference. Timing my videotapes a day later just isn't cutting it.