Contour Enthusiasts Group Archives Forums Modifications Wheels & Tires Tire size change vs. height variation of the SVT.

If you change the CSVT tires form the stock 215/50/16 to the 225/50/16 size (on the stock wheels), does the variation of the height of the ride noticeable? Do you have to lower the car?

Well the first number-225 is how wide in millimetres the tire is so its 22.5 cm wide. You aren't changing the height at all, just the width

So it goes Width/Percent of width=Sidewall height/tire in inches

The only way to get a lower car with same rim would be getting a small sidewall. So a 215/45,40,35,30/16

Specification Sidewall Radius Diameter Circumference Revs/km Difference
215/50-16 108mm 311mm 621mm 1952mm 512 0.0%
225/50-16 112mm 316mm 631mm 1984mm 504 1.6%


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

You may be right but the overall diameter of the stock 215/50/16 tires is 24.3" while that of the 225/50/16 tires is 24.9" (unloaded), a difference of 0.6" in diameter or 0.3" in radius. This should, in principle, affect the height of the ride by an amount smaller than 0.3" when the tires are loaded. Am I wrong?

Thanks for the reply.

The reason I asked the question is that last week I installed a set of Firehawk SZ50 EP in the 225/50/16 size. The listed overall diameter is 24.9". The original BFG g-force tires had an overall diameter of 24.3", thus a difference of 0.6" in diameter or 0.3" in radius.

However the 24.9" overall diameter is measured on a 7" wide rim while the 24.3" diameter is measured on a 6.5" rim. This would increase the listed diameter of the Firehawks by about 0.2" and the radius by 0.1".

According to this simple calculation, the radius difference between the new and the old tires is then 0.4" which is also the increase in the height of the car.

This is indeed a small height difference but I think I noticed it.

I wonder if other SVT owners who have installed a new set of 225/50/16 tires on stock suspension agree with this observation.

Ive got 225/50/16's I think it depends more on the design of the sidewall than it does the actual diameter. I had kumhos to begin with on the rears and they had a very flat/plain sidewall, which made them look larger than the Dunlop A2's that I have on there now. Some tires the tread actually wraps around the edge of the sidewall a little more, making the sidewall appear smaller.