Manifold

Sorry if this has already been covered, I don't usually keep up with the GT4 section ...

I tried RE71R tires for the first time with GT4 on track this past Friday. I liked them. They seem about the same grip as the Cup 2 (or maybe a little more?), grip doesn't fall off too much in the session, and not overly sensitive to tire pressure. That said, two questions:

- What's the optimum hot pressure?
- How do the tires behave at ambient temps in 35-40F range?

I tracked the GT4 because the GT3 was having an engine issue (), and it was fun to get back to tracking a manual mid-engine car. Comparing with the GT3, I do think the GT4 could benefit from slightly stiffer springs. The GT4 doesn't feel quite as buttoned down as the GT3.

BillC3

I find that 34 psi hot all around seems to work best on 19" RE71Rs on my GT4.

Errsomeone

Agree. Though, in my case I use the stock sized 20s.

Yargk

I'm on my second set of RE-71R s. I don't think they are any faster than cup2s because some of the cup2 lap records haven't fallen, but I agree that they are more consistent and more fun for 20 minutes (perhaps last longer too). I run 30-31 front and 32-33 psi rear, hot. The front tires are proportionally a little wider than the rears, considering how much lighter the front of the car is, so 2psi difference f/r seems ideal.

At 35 F they work fine. (Cold day last year at Thunderhill!)

Manifold

Thanks all for the input. How many cycles/days are you guys getting out of these tires?

Yargk

I surprisingly got 600 miles out of my last set. There was a little tread left, but the tires were slower after perhaps mile 450. It is driver dependent whether the fronts or rears wear first. It was rears for me. (I had -2.5 / -2.2 camber at the time, now -2.8 and -2.5)

I run perhaps 22-27 miles a session, so that's about 26 HC. I think I'll replace after 550 miles now, so 24 HC. I take it easy and do 3-4 sessions a day on average so I get 6-8 days. If you run the full day, you'll get 5 days.

Others have gotten fewer miles though.

orthojoe

I've found that higher pressures hot (34-36) give more consistent performance thoughout the session and the day whereas lower hot pressures (32-34) give a slightly faster first few laps and then degrade. Lower pressures also led to slower laps as the day went on whereas the higher pressures were consistent through the day. I like to set at 27psi dead cold and then never adjust again the rest of the day.

As far as life goes, I don't think it's number of heat cycles but rather the amount of tread left. The center section always seems to wear first. When that center section is close to flat on the outer side, performance drops substantially.

For me, the first 2 days are the fastest. Slight drop 3rd day, 4th day is 2-3 seconds slower (center is almost flat). This is why I plan to stick with stock alignment now. No gain in tire life despite increasing camber. No gain in performance.

Oddly, when running 19" size the front wears faster and when running 20" the rear wears faster. Happened with multiple sets.

MarcD147

I like them at 32 psi hot and find that at 34 or above they get greasy and slide a bit more.
I start at 26 (stay of the curb till they are 28 or above) and bleed during first session in hot pit and then down to 31 after 1st session
then for subsequent sessions I bleed after session to 31 (assuming it keeps getting hotter weather during day)

if its 35-40F outside I would prob start first session at 28 and bleed in hot pit during session and only bleed to 32psi after sessions (as their is likely more wind chill during the day)

moveswiftly

I agree with this recommendation. 24-26 PSI Cold. stay off the curbs until 2 laps in. Anything above 34 PSI hot - very greasy.

ExMB

I can see that happen since the sidewall will be taller (if you are maintaining OEM circumference/DIA) and therefore will flex more.

orthojoe

Thanks. I was wondering why that might be happening

Manifold

That plus more load on the fronts during heavy braking may contribute to more wear in the fronts. Adjusting tire pressures may help even out the wear, but of course that would affect the car balance. We ran our GT4 with factory alignment and settings, and the RE71R are on the 20" wheels.

Perimeter

MPSC2 change characteristics halfway through wear, I won't buy them again

Jim Cobb

STLPCA

FWIW, my setup which has worked well, apart from the well discussed klag/occasional small stone interference between the front caliper and the inside of the wheel barrel:
OZ Racing Leggera HLT w/Bridgestone Potenza RE-71R
F: 245/40x19 (27#) 8.5Jx19 ET53 (20.75#)
R: 285/35x19 (30#) 10Jx19 ET40 (22.5#)