MacGT3

I am tracking an 05 GT3 at VIR this weekend in a DE. The weather forcast is for sunshine and tempertures in the low to mid forties with nightime lows in the low twenties. Temps will be in the low thirties for the first run sessions both days. Car will be stored outside both nights in the paddock area.

I am running Pirelli P Zero D5 245/645/18 fronts and D3 305/645/18 rears. Are these forcasted tempertures too cold to run this tire safely or should I go back to R compound Hoosiers R3S05's or Michelin MPCS as I have this option.

I am experienced with this car but not with slicks at this temperature.

All help is welcomed!!!!!!

DCLee

I think you'll be fine in the mid-forties, I run the same combo; just get them warm.

If you ever need a spare set of Pirelli rears or a full set of Pirelli race rains (great for avoiding a lost weekend at a place like VIR), I have a new set of those I want to get rid of, as well.

Lee in D.C.
'04 RS Clone

Larry Herman

Low to mid 40's I'd rather run the Hoosiers. The MPSCs will be too hard, and you run the risk of cracking the Pirellis due to the low 20s at night. It is not an old wives tale, they will crack at low temps, just sitting there.

chrisp

Hoosier used to require that DOT-R's be kept above 32 deg F. This was 3-4 yrs ago. I don't know what the current temp limitations are.

eugene

Pirelli slicks can get fine cracks on the sidewall at freezing temperatures.( Not always) I have experienced this.

Probably not a good idea to have them on the car at 30's and 20's overnight temps.

eugene.

MacGT3

Thanks for the info, I am new to the Hoosier R3S05, what PSI's am I looking for when the Hoosiers are hot coming off the track?

DC Lee, I would be interested in the rain tires.

95m3racer

I'm curious how that setup works with softer compound in the front, and hardest in the rear.

Also, is 645 for rear use on porches, or is 680 recomended because of the extra forces from being mid engine/rwd?

Larry Herman

We ran the D5s in the front and the harder D4s in the back. Stay with the 645s all the way around so that the ABS works properly. The 645s also provide a little better acceleration.

MacGT3

95m3racer, D3/D5 setup was recommended by Bob Woodman Tire who I purchased the slicks from.

I hope they made the proper recommendation.

Due to the weather today and tommorow I will not have an opportunity to find out.

It is snowing and they are calling for 8 to 12 inches where we live.

Larry Herman

You should be ok with that. Maybe a little more oversteer than you might want, but better rear tire wear. I would probably soften the rear bar a hole or maybe 2 for that combination. It is my understanding that Pirelli did not ship any D4s in that size, and none will be coming until late spring.

MacGT3

Larry,
I watched you race at the PCA Club race at Summit, you are pretty good. My mechanic is one of the members of the Flying Lizard Race Team. (My dumb Luck!!!)

An outstanding and very bright young man by the name of Kenny Schreves. He has done all of my modifications over the past year based on my progress as a driver and he had set up the suspension for these exact tires for VIR. The setup was based on a car that they had tested at VIR for the 24 Hours of Daytona.

Unfortunately, as you well know, this past weekends weather was not very friendly for the track.

I look foreward to meeting you in person in the future.

bobt993

I usually like to see 40psi, sometimes a little more. Pyrometer helps, but with cold weather, you won't get a good reading unless you pit on a hot lap and have someone read temp/psi for you in the pits.