Liquidcooled

I still have a few trackdays left and was wondering what the coldest outside temperature would be before you should stop running MPSCs. It's about 60 degrees were I am and getting colder every few weeks.

I run them at 36psi hot in warm weather, is there anything I should do differently when running them in cooler weather?

Thanks

924RACR

Yes - make sure you warm 'em up good before you lean on 'em.

bobt993

When I ran MPSCs the lowest temp I ran them at was 40degs (even wet track at times). Just get them up to temp.

RonCT

Depends on which Cups you are talking about. If "real" cups then I'd say not to go below 40 as they are like hockey pucks. If the Porsche N-rated cups, then pretty much any temperature. I've run those as cold as 28 degrees without any trouble (love those early spring / late fall days at Lime Rock).

Nordschleife

the real one's I only use in the summer months, I suggest Contis for the 'shoulder' period before and after winter. For me the cut-off temperature is 6°C that is 6*(212-32)/100 +32=42.8°F (any chance of switching to SI this side of the next millenium).
Its not just the temperature, its slippy things like Fall leaves on the road, and nasty damp patches, and the interaction with ABS. If you want a nightmare experience, try brakingwhilst approachimg a junction covered in slippery leaves.
On the plus side, three sets of wheels anhd tyres is 50% more cool than two sets, or to put it another way, you need twice as much rack space...... 'Look at THAT rack!.......

R+C

certz

I have run them with frost on the ground but those first few laps are hairy. Like it was said above, just get them hot before you start pushing them. Also, watch the pressure as you get them hot - I had big swings in pressure that day...

R+C - I wish, I have given up on us ever changing over.

Nordschleife

You know, I think Nitrogen would help here - can you get N at truck stops? Also remember to switch over to green valve caps if you do use N (its less hygroscopic than air and therefore more stable pressurewise)

R+C

KOAN

I try not to us them below 60 degrees! It is very hard for me to get enough heat into them to make them stick. "Hairy" doesn't begin to describe it ( 55 degrees at the kink at Road America at 105 mph, I thought I had enough heat, but guessed wrong. I survived, proving it is better to be lucky than good) Anything below 60 and I use Hoo R6.
I start at about 25 lbs cold even on warm days, What do you start them at at 40 degrees? How many laps does it take to get them to stick, and how many laps are left in the session (or race)?

Bob Rouleau

Up here we see temps very near freezing in the fall. I have run real Cups in those temps. No problems driving to the track - just drive prudently since the rubber is essentially frozen. On the track, a few laps to get heat in them and they are fine. FWIW on the 996 GT3 I used 32F, 34R hot pressures. Anything above 35 lbs and the tires felt greasy no matter what the air temperature.
Best,

KOAN

What are your cold, starting temps?

Liquidcooled

I am running the ''real'' MPSCs on the car.
Braking while entering a junction covered in slippery leaves doesn't sound like much fun at all. I might have to start thinking about purchasing another set of wheels and tires for the colder months.

We only have regular air at gas stations, no nitrogen. I'm not familiar with green valve caps, how are they different from regular valve caps?

On warm days I start with 29psi cold tire pressures and keep bleeding the air out of the tires till they are a solid 36psi hot tire pressure.

bobt993

I agree with Bob on the front pressures and for a little lighter car 964/993 I run 36psi rear. You need to induce excessive slip angle on these tires during your warm up in slower speed corners eg 50 to 70mph apex speeds. They warm up nicely then. Typically 8 lbs lower starting pressures.

DrJupeman

I've run them when ambient was around freezing. They are fine once you get heat into them.

Liquidcooled

Do you feel running 32F and 34R hot tire pressures like Bob would work good on a heavier 996TT?

bobt993

I would go with the staggered setup. Bob has alot of experience so start with that target. Dr.J and Collin had them dialed in very well some years back when they ran them using the staggered pressures ( I believe they were using 32/36 on the advice of a Michelin Engineer). This tire likes to be hot and it is almost impossible to get them too hot in the cooler weather. Bring a pyrometer to the track and follow the Michelin performance guide for track temps. I think it is a really good learning tire since it has a variety of behaviors during the warm up phase.