I have a Mazda that takes an uncommon tire size. A friend once pointed out that I might have better luck trying a smaller tire tire profile, IIRC. Now, I’m not out to have some cool-looking set of wheels, but how do I know what my options are? What part of the nomeclature tells me the profile measurement? Granted, I know the low-profile tires are more expensive…
Also, what other options do I have? Can I vary tire width or other options? Again, please fill me in what part(s) of the nomenclature describes these various aspects of the tire.
Now, if only I could get rid of my own spare tire!
Thanks all!
Changing the tire size will likely affect your speedometer, and might affect the vehicle’s handling. I wouldn’t listen to your friend, stick with what is recommended in the manual.
Changing only the tire size can indeed alter the speedometer reading as well as the final drive ratio. However, how much it changes both depends on the difference in diameter. A good place to get tire specs is: www.tirerack.com. If a different size tire fits in your wheel wells (to include at full turn) you should be ok assuming the tread width is no more than 2" wider than the wheel.
You’ll have lots of options if you change your wheel size, especially if you want a different aspect ratio.
My car takes 205-55-16 tires. They are 205 millimeters wide, 55% as high as wide and fit on a 16’’ rim. Over all they are about 24’’. Some crazies replace them with say 205-35-18 tires which work out about the same. There are web sites that do all the calculations for you, but I don’t have the links.
A 205/55 x 16" tire should be 24.9" in diameter. You sure about the 205/35 x 18? Tire Rack doesn’t show such a size. There is a 215/35 x 18 which is an inch shorter at 23.9. Assuming this is correct, you’re turning more RPMs per miles and your speedometer is reflecting a higher MPH than actual.
Usually you can safely go up one size (IE - you can replace a 195 with a 205), I assume you could safely go down a size too. Since the height of the sidewall is a percentage of the width a wider tire would need a lower sidewall height (number) to be the same size. (1st number tread width, 2nd number sidewall height (as a percentage of tread width), 3rd number rim diameter). Always check with someone knowledgeable to be sure it is safe to mount the tires on your rims. I believe tirerack.com will show you sizes that are safe for your rims.
This calculator will help you determine if the overall diameter is close, the default shows a wider tire with a lower profile on the same rim size – Tire size calculator
