Bill Dearborn

I have a set of Pirelli Slicks with 20 heat cycles on them. I only run HPDEs so absolute lowest possible lap times aren't critical. How many heat cycles can I get out of the set before they become too slippery?

Bill

Prop Job

I'm usually to the cords after about 12-14 on the front and about 24-28 on the rear. I don't notice grip significantly falling off until 1-2 sessions before they cord.

Bill Dearborn

I have about 1/32 tread on the outside edge of one front tire and 2/32 on the outside edge of the other. I have swapped them from side to side from one event to another to try and even out the wear. I am heading to a 3-day event after Easter and will have another person driving the car in student sessions so the number of track sessions will double that weekend. I have been thinking the front tires won't make it through the 3 days.

Bill

J79guy

The first 2-3 heat cycles is where the "magic" goes away. After that, I honestly can't tell the difference until they cord. I don't have a sponsor, nor do I race in the big-bucks events, so I run my P-Zeros until they cord. Like was stated, they will let you know when they do wear out, the grip goes away, but up to then, they feel fine.

Scooter70

With a good alignment, I've run the Pirelli scrubs for 5-7 weekends (6-10 heat cycles per weekend). I usually try to flip the tire on the wheels about halfway through but with a lot of camber, they really don't wear too unevenly. At the end of last year they weren't showing cords but they certainly weren't all that fast compared to fresh/soft rubber.

Poor-sha

I run mine until they cord also and as others have said they seem to perform about the same until they do. I'm only getting 2-3 days on a set these days.

For the folks flipping these, keep in mind that some of them are asymmetric on construction and they will handle very poorly if they are on backwards. The yellow stamp should be on the outside and the red stamp the inside. I believe it's the DHD2 tires that if you run them backwards on the rear they are prone to snap oversteer.

Bill Dearborn

Sean,
Do you know what the difference is between the Pirelli DHE and DHB compounds? I just purchased a set of tires from Todd and the fronts are DHE and the rears are DHB.

Bill

Dan H.

Interested in the answer, I also purchased tires from Todd and one pair are DHA and the other DHB, didn't think to ask if the different sizes that were recommended were different compounds, hope it doesn't cause an over/under steer condition

Bill Dearborn

I queried Todd as well in an email. This is what he replied:They are both hard compound. D = dry, H = hard, E,B,A etc = construction. Ok to mix front or rear just not on the same axle. They are not directional. Most guys mount the yellow to the inside to get max life. Yellow was to the outside from the pro car.

Bill

Poor-sha

Not exactly. The constructions are different but generally you will see that a given size generally come in the same "family" (DHA, DHAB, DHC, DHD2, etc.). I wouldn't worry too much amount mixing different from and rear family. I don't know that I'd mix different family on the same axle but it seems like direction is more important.

I posts about this a while back in the GS.R build thread after reading through some of the Pirelli docs I found online. I'll have to dig that up.

Dan H.

Thank you for sharing this Bill.

TopSpeedNeed

I went to Roebling Road this weekend for an HPDE. On Sunday I put my Pirelli scrubs on, I have 305/660r18's on the front, 325/680R18's on the rear. Outside temps was 70ish degrees, and cold air pressures were as follows, L/F 27psi, R/F 28psi, both rears were 30psi. I ran in track, sport 1 mode. after about 9 laps, tires were gripping well, but the psi was crazy, L/F 33 psi, R/F 34 psi, L/R was 41 psi, and R/R was 39 psi. Why would the rears pressures get to high and not the front. I watched the PDR, didnt look like I was spinning the tires anywhere? Any thoughts ? Has this happened to anyone else? This is my first experience with the Pirelli scrubs.

Prop Job

I go out at 22 cold, sometimes 20-21. I've heard or read somewhere that Pirelli recommends no lower than 22 for sidewall integrity. It feels to me that they work best in the 26-28 hot range.

Racingswh

I start 24 all around. Bleed down if needed. Clockwise track I see pressure build on the left side and depending on how many slow corners the rears can take a beating. I bleed down to 30 hot.

39 is too high. 30 is too high to start.

I know drivers that start super low when they are racing. I also had a friend in a powerful heavy car have a right rear failure and the shredded tire tore the corner off the car. The winnings aren't enough to cover a sandwich at lunch so I try not to start so low it will possibly compromise the integrity of the tire. That's why I bleed down after they get some heat and pressure in them. When it sits overnight we add back air in the AM.

I run Pirelli scrubs 305/645/18 front and 325/680/18 rear.

I also run them down to the cords. For me fronts typically wear at a 2 to 1 pace. 2 fronts for every 1 rear. I probably get 12 sessions out of the fronts so a 3 day weekend usually if I swap them left to right during the weekend. 2 weekends out of a set of rears. Really depends on how hard I am driving and the temps.

EmJay108

I have extensive experience with Pirelli slicks both racing and HPDEs and have spoken with Pirelli engineers many times. I've mostly run DHs, and DHBs a handful of times, DHE once. All of these tires are of asymmetric construction, yellow facing out, dot at the valve stem. As far as I know, the compounds feel mostly the same, and the main difference between the DHs and DHBs are that the DHBs have a larger belt and are a little stiffer than the DHs. Many people online are saying that there is a very stark difference between the two, however they're using the same chassis setup, and not changing alignment, dampening, or bars to accommodate the differences. I don't have enough experience with DHEs to confidently convey my thoughts on the tire. Don't mix different constructions on the same axle, but DHB in the front and DH in the rear with the proper chassis setup is no problem.

While racing, typically they heat cycle out past 2-3 cycles depending on run times and temperatures. After that, you'll be slightly below pace by a couple of tenths. After the initial fall off, grip gradually declines until about 8 heat cycles, of course by this point you're not racing on them, we're talking about DEs. You can definitely notice that they're a bit greasy and you can't push as hard, but still perfectly drivable. After 12 heat cycles the tire is pretty much toast, but I've probably pushed 14 heat cycles on DEs if I'm just wanting to drive, not going for time. They feel all over the place and slippery. Maybe good for doing lead-follow or working on racecraft.

HPDEs and races I typically start DH and DHB tires around 18-20 psi in hot-hot Florida. Clockwise tracks 18 left side, 19 right, or 19-20. For races I've even started as low as 17-18, but for any pressures below 22, you have to be very careful until they're warmed up not to smack any kerbs or potholes (sebring) or else the tire will fail and bubble or wart on the inside. Colder days (40 deg) I've started 21-22 cold pressure, bleeding air to 28 and have seen good results with cold grip. These Pirellis see their optimal grip around 28 PSI hot. 30-31 is acceptable but not as good as 28. Much of this is subjective and depends on chassis setup, and which chassis you're running on, but heat cycle info and pressures are consistent between chassis for the most part.

If anyone is running Michelins, or doing two different series where they're running both Michelins and Pirellis at different events, I also have some good information that I'm able to share about the differences between the two of them, and chassis setup.

Racingswh

Good information in your post. Thank you!!

What car? Weight with driver? Aero or no? Lap times?

How do you get away with starting them that low at Sebring? I would be scared.

EmJay108

Most of my experience is with 718, 981, and 997.2 Cup Porsches, however I also have much experience in my C5. The 718s weigh 2900 (2897) dry, 981 is maybe 150 pounds more, and the Cup is closer to 2700. My C5 is around 3000 pounds. Add 150 for driver, 140 pounds for full fuel (100L) in 718 competition. In the 718s I'm running consistent 2:12s at Sebring, 981 is 2:15ish, 997.2 cup fastest I could to is 2:07. C5 has no aero and 2:22-2:24 times.

You really have to be patient with the Pirellis that low. Getting them warmed up on your outlap and pace lap before the race, heavy on the brakes to get some heat in them and build pressure, avoid potholes! Stay off the kerbs for 2 race laps, and slowly start getting more and more aggressive during your third lap when you'll be seeing ample pressures. It's the only way to stay relevant during a 30-60 minute sprint race. If you start at 22-24 psi, you'll be around 33-35 psi and sliding around when they reach thermal equilibrium. Using nitrogen helps keep pressures consistent between corners with heat different.

Racingswh

Thanks for the info. Nice lap times. Flying in the cars you mention.

I might try starting the pressures lower just to see how they feel.

Citation

I am far from the fastest guy in HPDE, probably not the fastest guy on this thread. I can verify the Pirelli slicks definitely cycle out in my case long before the tread is gone.

clubracer23

I’m interested in what you have to say about Michelin vs Pirelli slicks. My own experience I bought a set of each (scrubs) and tried them on my car on the same day/weekend. I could get the same lap time with either tire but the Michelins were good for more laps in a row.
I ordered a new set of Michelins based on my unscientific test.