[CyberColorado]

I would like to run a tire that is not offered in the OEM size. I understand that the second number is the height. So, I would be going with a slightly taller tire. Has anybody done this? How much of a difference between a 65 height and a 70 height? Or is that amount nothing? Slight spedo error? This is what I am interested in. https://www.walmart.com/ip/Kumho-Ro...75035&wl11=online&wl12=55012347&wl13=&veh=sem

 

[KMW]

You'll be fine. Colorados also come stock with 265/65-17, Trail Boss, ZR2. That 255/70/17 will be about the same height as that, and a tiny bit narrower.

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[CyberColorado]

Thank you KMW

 

[hand foot maneuver]

You can always check your math at miata.net, they have a good tire size calculator. Youll be fine though.

 

[GH1618]

The second number is the profile, not the height. For a given width, a larger number will be higher.

Here is a good tire size calculator: https://tiresize.com

 

[KMW]

Correct. The first number is section width in millimeters. The second number is sidewall height in percentage of section width, called aspect ratio.

So a 265/65/17 has a section width of 265mm. And the sidewall height is 65% of 265mm, or 172.25mm.

A 255/70/17 has a section width of 255mm. The aspect ratio is a higher percentage, but of a smaller number. So 70% of 255mm is 178.5mm.

That's only 6.25mm difference. But you have to remember, these numbers are all general. Every brand of tire is a little bit different. But you should be just fine with the 255.

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