MB:)CS

I have moved up to the advanced group in DE's and would like to get some track tires for my car. I am having trouble with fitments. I have 235/40/18 front and 265/40/18 rear and have been using the stock PS2's but would like to try the Nitto NT-01. My problem is that these tires (and several others) only come in 275/40/18 for the rears and I am afraid that they might rub on something. Has anyone used the 235/40/18 and 275/40/18 combo? Thanks

FlyYellowRSA

275's work fine!

Jim Michaels

275's aren't too wide, but they're taller (larger in diameter) than the OEM rear size, which would result in slightly higher effective gearing. Approximate diameters shown below.

235/40/18 = 25.5"
245/40/18 = 25.7"
275/35/18 = 25.7"
275/40/18 = 26.7"

Bill Lehman

I'm considering track tires for my Cayman and have done some research. The stock PS-2s are 25.4" dia at the front and 26.3 in the rear. I've noticed several Caymans and Boxters running Toyo R888 using 245/40 on the front (25.5") and 275/35 on the rear (25.7) Also available is and 274/40 @ 26.7". Nitto are available in those sizes from Discount Tire.

Jim Michaels

A minor point, but my R888 spec sheet shows the 245/40/18 to be 25.7". I'll probably get R888s in 245/40 and 275/35 sizes (on 9 and 10" rims) when I'm done with the Michelin Cups. I've been using Michelin Cups in sizes 235/40/18 and 265/35/18 on the OEM rims for three seasons (2 sets during that time) and they have worked very well on track (and driving on to and from), but are a little too cold natured at autocross. The 265/35/18 size is a little shorter than the OEM rear size, so they look a little funny, but effective gearing is lowered a bit.

Other "drive on to and from" tires to consider include the noisy Yoko A048 (235/40/18 & 265/35/18); the street tire class Falken RT-615 (235/40 & 265/35, and 245/40 & 275/35); the street tire class Dunlop Sport Z1 Star Spec (235/40 & 265/35, and 245/40 & 275/35, but shave them down from 10/32" tread depth); and the street tire class Bridgestone RE-01R (235/40, 245/40, and 265/35; also 10/32" tread depth).

The September issue of European Car lists all of the above track tires, plus some others, including the slicks with narrow grooves (e.g., Hoosier, BFG R1, & Kumho V710) that are not very streetable.

Jim Michaels

MB: I also considered the Nitto NT01. While they come with 6/32" tread depth, they are essentially slicks when worn down to 3/32". That's good for track and autocross, but bad for driving on to and from events.

MB:)CS

Thank you all for your input. I ordered Nitto tires in sizes 235/40/18 & 275/40/18. I spoke with one major retailer of tires and he suggested I use two different types of tires, front and rear. This did not sit well with me and I discussed it with other track friends and was told not to go with that advice. I spoke to a smaller supplier, Todd, who advertises in Grassroots Motorsports and he gave me a lot of help and walked me through what the numbers mean and sizes meant and what would work, so I ordered from him. I will try these new tires out at Mid Ohio in early November. Thanks again for all of your help.

FlyYellowRSA

I have a set of 235/40/18 and 275/40/18 Nitto's that are like new mounted on flawless OEM Boxster rims if anyone needs them . Tires have one day at LRP $1800 rs911@***.net

acadian_dad

These tire sizes results in slight errors (few %) vs. the OEM sizes. Does anyone know what is the max allowed mismatch between front and back before PSM / ABS starts to have problems ? Does PSM kick in sooner on the track when these "off" sizes are used ?

FlyYellowRSA

I did not notice any difference nor did two friends with Caymens running the same size.....

acadian_dad

OK thanks ! Nervous nelly here ...