OldSchoolHatch

I read a post about this Tire Size Calculator page, and it tells you how changing the size of your wheels and tires affects your speedometer. It's on a website for miatas, so is this accurate for our cars too? When I got new tires for my 13" stock wheels, the guy ordered 175/70/13 instead of 175/60/13. When I put that info in on the site, it says that my speedometer's 6.5% too slow and when it shows 60, I'm actually going about 64. I've had these tires for a while so I'd like to know if that's true. Here's the site:

http://www.miata.net/garage/tirecalc.html


[Modified by OldSchoolHatch, 2:27 AM 5/16/2002]

vansterdam

Here's a better tire calculator that lets you enter up to 5 sizes. The thing you have to remember with those calculators is that they are not exact. Each model tire in a certain size is not the exact same size. Then throw in factors like tire wear and tire pressure and the number is way off. They are still a good guide for choosing a replacement tire size.

bagpipe goatee

yep, that site applies to us just as well. It relies on exact math, like vansterdam says. However, different brands of tires labeled the same size are surprisingly very different. Then tires change size noticeably as the tread wears off. Basically that site is perfectly accurate, but tires are not.


Edit -> I'd kind of be mad if that happened to me. Not that the size he gave you is a bad size to have on these cars, they can actually help your gas mileage slightly by increasing your gearing. But I'd be angry because either (A) He was incompetant/lazy and didn't care about putting right size on or (B) He was out of the right size and knew the size he gave you was a decent alternative. It would be ok if he'd have asked you, explaining the differences and why it's ok, but it sounds like he was afraid of losing a sale by telling you a problem. Oh well.

Edit Edit -> I read the sizes you have. I looked it up. the two correct sizes for this car are 175/70/13 and 185/60/14. 195/50/15 is also the right size, but these cars never came stock with 15 inch rims. Either you mistyped or you had the wrong size on before.