Tire Numbers

[WhiteGalant]

well I thought I knew what they meant but apparently not. So help me get this right, for example, 225/50/17. Now the first 3 digit number is width, the 2 digit number is the height of the sidewall, and the last is the rim size. So say your rim is 7.5 wide could you use a 225 tire. Basically what im asking is, does the width of the rim have any correspondence with the width of the tire. how big is the difference between a 205 and a 215

[RAZ_76]

205 to 215 is 10mm. Width for tires is measured in mm. Hope that helps. I have 225 tire on a 7inch wide rim.

[dknight3]

i could be wrong but i thought the middle number was the ratio of height to width, not just the height.

[WhiteGalant]

yeah ive heard that too, im just trying to clear some things up

[Reelax]

example = 225/40r18

225 = 225mm wide
40 = sidewall height expressed as a percentage of width = 40% of 225mm ( 90mm tall)
18 = 18" diamter tire

so the above tire is a 40 "series" but a wider tire of the same series will have a taller sidewall height (actual height does not stay constant when varying the width).

225/40r18 vs. 305/40r18

40% of 225mm is 90mm, whereas 40% of 305mm is 122mm

additionally 2 tires of different width and different series can have nearly identical sidewall height:

225/40r18 vs. 255/35r18

40% of 225 is 90mm, and 35% of 255 is 89.25mm (0.75mm is a negligible difference.)

[RedGalant2k1]

well I thought I knew what they meant but apparently not. So help me get this right, for example, 225/50/17. Now the first 3 digit number is width, the 2 digit number is the height of the sidewall, and the last is the rim size. So say your rim is 7.5 wide could you use a 225 tire. Basically what im asking is, does the width of the rim have any correspondence with the width of the tire. how big is the difference between a 205 and a 215

Yes the tire width has direct correspondence to how wide (or skinny) a wheel it can be put on.

In an example: You can not physically mount a 215 width tire on a 9" wide wheel. The tire itself is only 8.46" wide. If you look at the tire manufacturers website or data books you'll see recommended wheel widths for a tire to fit on properly.

I think Reelax explained the rest perfectly.

[dknight3]

yea reelax, you da man! haha