Wednesday, June 18, 2008

R-Comp Tars

One thing I learned at Miller is that Khumo MX’s are not R-Compound tires. A few years ago they were among the ultimate track tires even though they carry a treadwear rating of 220. But today there are a slew of sticky new track tires available.

I now have 4 track days and about 800 street miles on the Kuhmos and they are almost half gone (4-5mm remaining of the 7.8mm original depth). This seems to be pretty reasonable wear for the performance they provide.

Because my stock suspension doesn’t have enough negative camber, it causes some extra wear on the outer shoulder of the front tires. Rotating fronts and rears only prolongs the inevitable. While at Miller I also experienced a little chunking on the middle of the outside front tire. This is typically caused by overheating. It was warm there and there are a number of corners that really loads the outside front tire.

Scott is running Nitto NT01s on his 3600 Lb, 400+ HP BMW 335i and recently got 9 track days from his first set. That is really good wear -- on par with what I will get from my Kuhmos. Oh, he’s like 17 seconds a lap (at Miller) faster than me too.

Replacing the Kuhmos with Nittos seems a no-brainer, however there is one more twist. Nitto doesn’t make the NT01 in the 245/40-17 size I use, they do however offer it in a 255/40-17. This is a little wider and a little taller than the Kuhmos. Luckily this is a very small amount and it should fit without any mods. Worst case a 5mm spacer up front.

Size....Tire...Size.....Width...Diameter
Nitto...NT01...255/40...10.35....24.92
Kuhmo...MX.....245/40....9.90....24.80

1 comment:

mark said...

I'm running the Nitto's in that size. Lots of stick. I did a series of brake test this weekend on some relatively clean, warm asphalt.

Mmmm ... deceleration.

I'm still not happy with the brakesfeel though. New braided lines. New master cylinder. Multiple flushes. I'm looking at new calipers. I could do a rebuild for much cheaper. But with a tight window between track days, new calipers is the easy way out.

I'll probably do this work myself, because, a) I need to spend some time under the car, b) I need to practice pad swaps, and c) I need to practice fluid bleeds.

Turner seems to have some good prices. $150 each for front calipers. Rears are more expensive.

The brass caliper guides look like a nice upgrade. I also need to refresh the hoses in my ducting.

http://www.aircraftspruce.com/catalog/appages/ceet.php

I bought some spare rotors to carry to events. Damn they're heavy. I'm thinking the floating rotors may be a good upgrade to get rid of some unsprung weight.