It'll be fine. 245/40/18 and 275/40/18 are pretty normal tires for 981's. I'm going 255/35/18 and 275/35/18, but it's out of necessity rather than choice since they don't make RE71 in the sizes I wanted. Your tire sizes proposed are actually what Apex recommend on their new 18's for street/track.

 

 

 

 

I'm sure they'll be fine, but your sons' experience is an outlier. It's pretty well established that on average RE71 are 1-2 seconds quicker than RS4 at the expense of tire life. To Pep!, I wanted more meat up front than 235.

 

Did you choose 275 for the rear out of tire availability, clearance, or dynamics? I went OE 19" 235/265 sizes with RE71's on my new 1/2" wider wheels and regret it. The speedometer is accurate, but the are too narrow for the wheels. I feel like the sidewalls being non-vertical is degrading the performance. Definitely going wider with the next set, but was thinking 285 in the rear.

 

Availability and dynamics. 285 will fit for sure, but RE71 doesn't come in that that'll fit. With the low torque these cars have, 275 should be plenty. Going wider on front compared to rear should increase rotation, especially at -2.7 front and -2.0 rear camber. 285 would be fine too.

 

OP, your comment about the tires becoming greasy after 8-10 laps makes me wonder about your tire pressures. Nitto NT01's and RE71's I've tracked like to be in the low 30's PSI hot. If you're letting them get over 35 PSI, that could be why they feel out of sorts.
Bern

 

Thanks Bern...that's probably it! I was at IMS on the F1 road course configuration last weekend and was getting pressures of 36-38 PSI after 30 minute sessions. With the two long straights at Indy, theres very heavy braking in turns 1 and 7 which really heats the tires. Next month I've got another event at Putnam Park and will give the lower pressures a try.

On another note, I flew out to Sacramento back in May and did 3 days at Laguna Seca and two days at ThunderHIll with my son in his Spec E46 BMW race car. Loved LS, but really loved TH. What a great complex. We ran the Cyclone bypass day one and the Cyclone day two at TH. We had a wet track one day at LS and I now know where all the creeks run across the track when it rains! No car damage, just a little landscaping work :-) :-)

 

I have been using RE71R for a few years on a 987S. They are very grippy, and they do wear quite fast for the track I go to (mosport). The point about being greasy, I find these tires are best at 30-32psi hot. anything higher they do get greasy.

I am planning to try Toyo R888R next year.

 

My experience with RE71Rs on the cayman are for factory 18" wheel size (235/45 265/45) and they lasted around the equivalent of 11 track days between Pacific Raceways, The Ridge, and ORP. I'm saying equivalent because that's counting days my wife and I shared the car as 2x. I did flip the tires on the wheels at about 5 days to help balance out that the most common tracks (Pacific and the Ridge) are both anti-clockwise.

Unfortunately once I wore them out they weren't available for replacements, I'm trying the firehawk Indy 500 as that's what we run on our endurance car and I thought it would be worth being more familiar but I'm guessing it'll be slower.

 

I get the same wear out of RE71R on my 981 BS in OEM 19" sizes, about 11 track days. So far running -2.0 front and rear camber, changing to -2.3 front at next track alignment.