I am probably soon going to get coil overs for the miata. I primarily autoX and the car has been running 14" star specs. STS/CSP guys seem to use 15"s usually? but CP etc guys run 13"s?
I am not sure the trade offs. I know if I wanted to I can get take off racing tires in 13x10
It's all about tire and wheel availability. The 13s used to be popular in CSP because Hoosier sells a 255-width A6 in a 13 inch diameter, and wide 13 inch wheels were available relatively cheaply and were light. Since the 6UL 15x9 wheels came out, most of the CSP cars I see have switched to using those with the 275-width 15 inch A6s. The 13 inch setup is still lighter (and offers a gearing improvement), but most people seem to think the 15 inch setup is faster.
STS uses 15 inch wheels because you basically can't get good STS-legal tires in 13 or 14 inch diameters.
What class are you running?
13's are shorter and change the gearing, the shorter tires are easier to get under the fenders and thus allow wider widths to be run wthout hitting. The downside is that some 13's won't clear the later 1.8 car's rear brakes.
Yep, 13's won't clear the 1.8 brakes, front or rear, the 20" tall tires make for interesting gearing and lots of 2-3 shifts. If you're restricted to DOT tires then the 275's are definitely faster. The DP cars run either 13 or 15, it seems to be a toss up, but the tires aren't. Avon A11 is the magic words there, and should be on a 13x10 wheel.
the gearing advantage is that the car will accelerate like you wouldn't believe .. as tpwalsh pointed out the down side is that you're often caught between the need for 3rd vs 2nd gear
I run BMW in X class which is all non BMW
If I went to 13"s they would be dedicated wheels while right now the car lives on its 14"s for day to day and autoX/track
I only intend at this point to make 1 or 2 track days a year just because of logistics with family etc but I do autoX about once a month. If I run 13"s I will get some used avons which will put me in "gold class" which is vs instructors
I do have 1.8 brakes on the front currently. Besides that rollbar/swaybars/seat is it
Running a smaller tire will keep geometry the same but drop the cg of the car over an inch.
13's will pretty much require 1.6 brakes.. which probably aren't up to trackday snuff, but I'd double check that.
You'll need to log in to post.
