todinlaw

I am thinking about doing the last DE of the season for the cold Midwest. I think the air temps are going to range form 35 degress to 55 degrees. Can I get away with running Pirelli Corsa Rcomps or should I go with the PS2's I thought I saw some postings that they do not recommend Rcomps under 40 degrees ?

Bryan Watts

On the contrary...when it's cold outside, you want an even softer compound than you would run when it's hot. Since you don't always have compound options in R-comps, you would still run R-comps since they are softer than street tires.

va122

+1

Make sure you warm those suckers up! Take up the entire out lap to do it if you have to. Don't forget to heat your brakes too!

todinlaw

Thanks guys. Not as much fun in the cold but unlike the both of you who get a much longer track season that we do, I got to get my licks in before the snow fly's

North Coast Cab

Run the Hoosier A6's or Hankook C71's.

Bryan Watts

I don't get the feeling he's looking to purchase a set of tires speficially for the event, but yes, A6's will work. We've run them when experimenting with classing out car down a class in NASA GTS racing.

DM993tt

Your grip level will vary much more with R comps in cold ambient temps. When you start out you will have very little grip as they work very poorly when cold, and will work well when track surface and tires heat up.

You would have a much more consistent level of grip if you went out with PS2's.

DanR

consistent, but consistently less! give the R's a lap or 2 to warm and feel your way!

RonCT

My guess is you'll be faster / safer on the PS2s... While R-comp is "softer", it also needs temperature to work. Think about a PSCup that's cold - like driving on ice. Fold in that the track temperature probably won't get about 35 degrees all day and while friction might get some heat into the tires, the surface they are on will still be cold.

I have the same dilemma... November 8 DE at Lime Rock and I'm torn between my 19" PS2s, my 19" Cups (which are faux-cups, basically PS2 compound in a quasi-cup tread design), or 18" Hoosier R6s...

I'm no scientist, so please, somebody with experience please chime in. My gut is based on my belief above - that you need heat for R-comp, even the hybrids like the Corsa and 19" Cup...

dan212

Cups still have more grip. If you drive them hard and get some speed in, they will warm up just fine. I find that the PS2's don't stick as well even after a few laps of abuse.

Bryan Watts

It may vary more, but you'll still have MORE grip with cold R-comps than you could have with cold street tires.

38D

The MPSC work just fine at 30 degrees, you just go a little slower than normal. Heck, I driven them in at ~40F in the rain, and they weren't even that bad.

RonCT

What I'm trying to say is that if you have to drive a Cup at 8/10ths because it's way below the compound's optimal operating temperature and you can drive a PS2 at 9/10ths instead, you will be quicker around the track. This only applies to the OP's question about late season track days in the 30s.

Every time I'm at Lime Rock or Watkins Glen and it's either pouring or freezing, I bring my PS2s and are turning much lower lap times than my buddies that are on Cups, Hoosiers, etc. -- where when it's warm / dry and we're on the same tires, we're all running comparable lap times that are quicker than the PS2s.

I also remember how BMW would not put the PSCup on the M3 here in the US because it had no grip in the cold and they were nervous about litigation. Porsche was equally concerned and that's why they redesigned and reformulated the 19" Cup for the 997. This has been covered elsewhere in the forum, but it's been clearly determined that the 19" Porsche approved "Cup" is not actually a true Cup, rather it's a hybrid street tire that looks like a racing tire. I've driven PS1, PS2, 18" PScup (true), 19" Cup, RA1, etc. and the 19" Porsche Cup is equivalent to the PS2 compound with a different tread pattern.

Bryan Watts

So what you're saying is that a harder rubber compound has more grip on a cold track?

RonCT

The hardness of the rubber all depends on it's scientific formula at different temperatures. That's why even in warm weather a "cold" PS2 will be quicker on the 1st lap than a cold Cup. Cups need 2 laps to warm up when it's 80 degrees out, and on a 35 degree day they may never warm up which is why everyone is "skating" around the track spring and fall up here in the northeast. That's also why up here people on PS2s are quicker when it's 28 degrees at Lime Rock.

R-comp appears to be very sensitive to temperature. When it's cold, they are like hockey pucks and "harder" than PS2s. But when they are hot, they are goo and very sticky. PS2s, however, are formulated to work in a different temperature range and while they never get as sticky as a hot PS2 on a warm day, they also don't get as "un-sticky" when it's 30 degrees at the track.

I'm no scientist / chemist, but that's how I understand it works, what we all see up north when it's cold, why BMW / Porsche either refused to supply or reformulated, etc.