35 vs 40 series rear tires, 987.2S PDK for auto-x

Use this forum to discuss car maintenance, building track cars, and modifications

Moderators: David Leong, Andrew Forrest

Post Reply
Rocky J
Posts: 8
Joined: Wed Oct 25, 2017 4:01 pm

35 vs 40 series rear tires, 987.2S PDK for auto-x

Post by Rocky J » Wed May 02, 2018 8:09 pm

Hey guys,

I recently acquired a 987.2CS that I'm trying to setup for autocross. Need some help picking the more ideal rear tire size for autocross, 35 or 40 series for better gearing...? There's a 1" difference in overall tire diameter.

- 987.2 CS
- 18" wheels
- PDK

Only reference I have is from last year's AX08 in October. I drove an '08 Cayman S with manual transmission and 275/35/18 RE71R rear tires. I was hitting the rev limiter at the end of the 2-cone slalom after the big horse-shoe before approaching the left hairpin turn. I felt if the car had 40 instead of 35 series rear tires then it would have been perfect. But again, different car, different tranny, etc... Any tips? TIA!

User avatar
superhighperf
Posts: 24
Joined: Wed Nov 01, 2017 10:19 pm

Re: 35 vs 40 series rear tires, 987.2S PDK for auto-x

Post by superhighperf » Mon May 07, 2018 7:40 pm

i think the taller tire is a better choice but. if you want to compete using the re71r in the showroom class you are limited to a specific width and profile. i think its 235/40/18 and 265/40/18 and tire rack does not show that the rears are available. if you are limited to an 18" wheel and want to compete in points based class and run the re71r you could use a 265/45 or if you want a wider rear you would need to go down to a 35 series. i think the sweet spot for 18" is 255/35 and 275/35 but they recommend at least a 8.5" wide front wheel and 9" rear.

last year on my 06 CS i used 245/40/18 on a 8.5" wheel and 265/45/18 on a 10" wheel. i got close to red line but never hit it. this year i got some points back and went with an 8" front and 9" rear wheel using 245/40/18 F and 275/35/18 R. i figured i would rather have a wider tire than a taller tire and i have a manual so a third gear shift would slow me down quite a bit. with a PDK i would recommend going with the 255/35/18, 275/35/18. you might need to press the shift button a couple extra times. no big deal :roll:
if you don't care about fast times get some HARD tires and fill the fenders

Rocky J
Posts: 8
Joined: Wed Oct 25, 2017 4:01 pm

Re: 35 vs 40 series rear tires, 987.2S PDK for auto-x

Post by Rocky J » Wed May 16, 2018 2:11 pm

Thanks for the input superhighperf.

Anyone running 18" wheels on a 987.2 CS PDK?

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests