Endurance racing - LeChampWRL

[revvhappy]

Let's get the conversation started: Suggestion for additional information will be added.

Car: 1985 Toyota Supra
Weight: 2540 without driver
Wheel size: 17x9 and 15x9
Tire size 255/40-17 245/40/15
HP/TQ: 160/175
Camber F: -3.0 R: -2.0

Comments: This car has completed 15 races and 15,000 race miles. I started on 16" wheels with cheap tires, but moved to 17" to get more rubber as the car got faster. I have used Dunlop Star Spec II and Bridgestone RE-71r tires in 255/40-17. The Star Specs were great, but the RE-71 were magic. The first race on the RE-71 was a 24 hour at Autobahn in Illinois, and we ended on the 4 tires we started with (90 minutes off track for a diff swap). I never tried anything else after that. Handling, braking, and wear were perfect for this car.

Last year I was looking for a gearing change and the only method available was moving to 15" wheels with 245/40-15 Hankook RS-4. There are only a few choices in this tire size and RS-4 seems to be the best for endurance racing. They take a fair amount of heat to work well, but once they warm up the grip level was similar to the RE-71. The car turned faster lap times at Road Atlanta than the previous year on the 17s. One problem that came up was front brake lock-up under hard braking. It was never an issue with the RE-71, but happened several times during the RA race. Maybe it was the lighter rotating mass or the smaller footprint, but it was an issue. The good news is that the RS-4 wears exceptionally well.

I'll add more data as I get to more races this year. I'm adding 40HP and losing 100 lb of mass with an engine swap.

Peter St Pierre
Hong North Racing

 

[Swoope]

peter,

thanks so much. this is just what we are looking for and you format is well done.

i think i will be seeing you around halloween.

please drop me an email.

beers

 

[revvhappy]

New data point for the Hankook RS4 after a 24-hour Lemons race at Carolina Motorsports Park - 4/27-28/2019.

Car: 1985 Toyota MR2
Weight: 2300-ish without driver
Wheel size: 15x8
Tire size 225/45/15
HP/TQ: 100/not much
Camber F: Not sure, but definitely at least -2.0 all around

The team has run 205-15 Dunlop ZIII at CMP with good results, but they get torn up in about 7-8 hours. The course is a cheese grater and eats tires. The RS4 has a good reputation for wearing well so the car owner decided to give them a try. The tires are much heavier than 205s and may have influenced a couple of things: 1. More rotational mass so harder to accelerate, and 2. Heavier steering. #2 didn't seem to be an issue once at speed, but the car definitely went a bit slower than the last race. I'm sure part of this was the level of grip, which I'll address next.

The RS4 tires need heat to work and the weather was perfect for a test: a 50 degree morning moving to 80 during sunlight hours, then back to the 50s again at night. We had no idea where to start with air pressures and they might have been a bit high but we never touched them during the entire race (Lemons doesn't allow things like this in the hot pit). Once the tires heated up in the 1st stint they stuck pretty well, but every experienced driver on the team remarked about the lack of feedback in terms of feel and noise when they were pushed hard. The grip was similar to the Dunlop ZIII but harder to manage without feedback. There was a larger contact patch which helped us to maintain cornering speed (this is a pure momentum car). During the heat of the day they got a bit greasy when over-driven.

The most amazing feature of the RS4 is the exceptional wear. We had one spare RS4 and some older Dunlops "just in case", and had a rotation strategy for when it became necessary to move them. It never became necessary! The tires stayed in the same place, with the starting air pressure for 23 hours of racing. The left front tire was the most worn, but still had tread sipes visible on the worn outer edge. The right side tires look like they can go another race.

Call me a believer. We finished 7th overall with all of our speed made in the corners - we beat them mercilessly.

So the choice will be: Incredibly long wear with less feedback, or more feedback and grip with RE71/Rival/Dunlop at the expense of wear (higher tire costs and time wasted changing tires during a race).

 

[Swoope]

would love to see what changing pressure would do. i have a set of the RS3 that i have only done one day on.. and have the same feeling about feel and grip. though i have had two really good drivers ride with me and comment on how good they felt. go figure.

do you have any idea of what the cold psi was when you started?

beers

 

[Tylervot]

Re: Body rooooooollllllllll

More pics from yesterday
That truck looks good Adam. Too bad you cant run without the numbers on the side. Or could you?