The OE 14" is usually 195/75R14 I think.
I think the tire books recomended 205/70R15 as an alternate. that one won't screw up either torque or the speedometer by much and still holds correct sidewall shape on the 6" rim. It's only 1 tenth inch taller than stock.
215/70R14 is starting to push minimum rim width for allot of brands/types. I'd check the spacific tire's info with the manufacturer. Many of them have the acceptable rim widths listed on their web sites and it does vary some from one tire to the next. This tire is 4 tenth inch larger than stock.
Do remember that as you increase tire outside diameter, you alter speedometer readings and reduce effective torque. The speedo isn't such a big deal for racing but lossing torque would be bad in autocross.
A few tenths of change in tire diameter isn't usually a big deal but in autocross it could make the dif between a win or lose.
there's a good tire calculator at www.miata.net the numbers above are based on that calculator. (Real tires can vary slightly from specs. Again. check the tire makers data.)
Info on how tires can alter performance is in the tranny section of my cave in the gear ratio article.
Also.... look up the tread width for a given tire.... that can very by as much as 1 inch from one tire to the next even tho they are the same 205/70R14 size. (or whatever size your looking at...) I've seen tires that are listed as 195 but have the same tread width as some 205s. (Remember... that first number is the widest point thru the center of the sidewalls. NOT the tread width.
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11-Sept-01, The day the world as we knew it ended.
