THSCC Forums

I’m looking for new tires (for DD use).

I am looking at a slight price difference for various sizes and wanted to ask a few questions.

195 vs 205's. on a 15x6 rim. Some say the 205's will have a negative affect because the width of the rim is so small. of course that’s internet talk and everything there is true. Can anyone confirm this?

Also, what does the second part of the number mean? For the tires I am looking at, I have 55, 50, and 60, with 60 being the cheapest. (a variance of 5 bucks per tire)

With these being daily driver tires, I am mostly looking for long life and price as the first factor points followed by wet grip and then dry grip. noise and comfort I can care less about as its a sport car with sport suspension... it was never meant to be quite or comfortable.

Please help me understand the tire sizing thing so I can make a halfway decent decision. experience will tell me if I want to use the same tire size next time.

For a 15x6, 205's are perfectly fine. 225's might be a bit much, but are done by people all of the time, yet is sort of a waste for DD tires. The 50, 55 and 60 are the aspect ratio. Take the tread width in mm, in this case 205 mm, multiply it by the aspect ratio 50=.5, 55=.55 and 60=.6, and that determines the sidewall height. The taller the sidewall, generally the worse the performance, but the best quality of ride (comfort).

I would look what is the OE size and try to stick fairly close to that. If you check out the specs of the tire, go by rotations per mile. That will give you a very good idea of what that tire size will do to your speedometer. Otherwise, I would mainly go by the average consumer reviews of the tires. TireRack and Discount Tire Direct all have great review tools with millions of miles for each tire to give a fairly accurate review. I like to read through the user comments and see if I see a lot of common issues, like road noise as a tire wears, or a lot of tire balancing issues due to out of round tires. If I see stuff like that, I tend to move on. - AB

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'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

205/50 is what most people go with for miatas isn't it?

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

This should help you figure out overall diameters of tires. You generally want to stay pretty close to stock rolling diameter unless you are intentionally trying to change the gearing of your car. Bigger diameter=speedometer off in a way that will get you in trouble hurts acceleration (probably helps gas mileage though) and lower revs per mph. Smaller diameter keeps you out of trouble, improves acceleration, but more revs per mph. Smaller diameter can look a little funny if you take it to an extreme though.

I'd say keep it +/- 5% and you're fine.

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2012 MX-5 Sport SUV

I prefer this calculator since you can have the side-by-side view:
http://www.wheelsmaster.com/rt_specs.jsp

Since most speedometers read a bit fast from the factory, you can get away with a bit larger diameter if need be, but you are probably best to keep the tire height stock for aesthetic reasons and again keeping the diameter the same. If you increase the width then just decrease the ratio to get the same height.

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2003 Subaru WRX Sportwagon = daily driver/boost and booster seats
2000 BMW 540iT = wife's kid hauler
2012 Toyota Highlander = the boring reliable vehicle

I think 195/55/15 is the stock Miata 15" size. But yes, I've run nothing but 205/50/15 on my 15x6" wheels since I got the car (well, excluding the 225/45/15 Hoo$ier$, anyway).

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Dustin Fredrickson
-- I'm a nobody --