Track Tires and Cold Weather
 

I have booked my first HPDE of the year for 04 March. I am getting ready to order Michelin PSS 4S tires in the next few days. I know that summer only tires get very marginal at or below 40 degrees ambient, but I have always assumed that in a track situation, once the tires come up to temp, they are good to go. Then I read a disclaimer on TireRack that says that the compound on summer tires should not get below 40 and that if the tires are that cold, you should not air the tires, work the tires or put the weight of the car on the tires. The disclaimer states that the compound in the tires can fracture.

What are the thoughts on that disclaimer? Is it just legal butt covering or is the fracturing of the compound a real concern?

Thanks

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Iirc I've tracked PS4S in similar to described conditions as well regular PS4 (non S model) and Primacy HPs too. I've never seen any cracks or fracturing on any of them so I'd say that you should be good as long you take your first few laps easy (as you probably should anyway in such low temperatures).

The cracks or fracturing can happen at lower temperatures. Let's assume you drive on them at 0 or 10 degrees - there's going to be a higher likelihood something happens to them than at 40. Last year, our first autox event was in early April and it was 20 degrees that morning. I chose not to drive on my tires to the event and put them on there. Out first runs were 35+ degrees, so it wasn't a big deal at that point. Other people drove on them and they were fine.



They tell you not to go below 40 degrees for safety. At 40 and below, you're not going to get enough heat in them nor is the pavement going to be hot enough. When we're autocrossing and it's even 50, you're not really going to get decent grip.

I got a set of PS4S and hunted around for better guidance than "don't use below 40F". I found a TSB online from GM that gave pretty good guidelines (they came stock on some hi-po GM cars). Basically below 40F you have less grip and below 20F you get cracking. In my experience with summer tires in general, they don't work at all in any sort of freezing precip, and my take on the TSB is to be careful below 40 until you get some temp in the tires, and once overnight lows drop below a hard freeze take them off the car.

Like most safety warnings, they have a big margin of what I call bullshit. Yes its not ideal for summer tires to work on cold temperatures, but they are not going to magically explode.

For context, I store my car on a trailer outside (not heated) in Canada, temps go below 0F often and the car needs to go in and out of the trailer sometimes for maintenance/repairs. I use 200TW street and 100TW entry level rcompound tires, and I leave the tires I finished the season with on the car for winter. I use those same tires on spring for shakedown and tests before the season starts, I have yet to see a single crack in them.

So the TL;DR is, your tires will be fine, just bring them up to temp progresively (dont peel at 10/10 from the pits).

I attended an HPDE at VIR back in November. Both mornings the ambient temp was high 20s °F for my first sessions. I treaded lightly (literally) for about 2 laps, at which point all the grip seemed to be there. This was with Hankook RS4 tires. My avatar pic is actually from that event, and on the short drive from the lodge to the paddock (lodge is on site) my tires felt like they weren't round, lol. Lump lump lump lump...

Likewise, during a practice session for a Lemons race a few weeks ago at Barber the ambient temp was 37° and the track was damp. I THOUGHT I was being cautious with throttle, but looped the car halfway through the first lap and came to a rest just feet from a barrier. Again, RS4 tires.

You should be fine if careful. The first morning session for an HPDE (for each group) is usually run under yellow flag for first 2 laps. If the sun is shining that's usually enough time for the tires to come up to temperature.

All that aside, concerns about actually damaging the tires is unfounded at the 20-40°F temperature range. If it was 0-20° out I would start to be worried (and such a state seems highly unlikely to occur at a scheduled HPDE event).