Help required on tyre sizes

[papacroft]

Why are tyres sometimes specified as 31x10.5xR15?
Does the 31 mean 31" diameter, 10.5" wide?
How much can this figure vary by from manufacturer to manufacturer?
Will 265x75xR15 mean an overall diameter 30.65"?
I have a KZN130 with standard 7J's. Will the sizes above be suitable (no obstruction to steering, or by bodywork), provided they are suitable for the rim?

Vanity and my friends new kZN185 force me to consider a bigger size than the standard 265x70.
Thanks
Mark..

[openback]

Why are tyres sometimes specified as 31x10.5xR15?
Does the 31 mean 31" diameter, 10.5" wide?
How much can this figure vary by from manufacturer to manufacturer?
Will 265x75xR15 mean an overall diameter 30.65"?
I have a KZN130 with standard 7J's. Will the sizes above be suitable (no obstruction to steering, or by bodywork), provided they are suitable for the rim?

Vanity and my friends new kZN185 force me to consider a bigger size than the standard 265x70.
Thanks
Mark..

31/10.50 r 15 is the american/imperial measurement,
approx31" diameter 10.5"wide radial tyre plys 15"rim,
265x75xr 15is metric convention,
265mm wide tyre profile 75% of width rest as before,
31s will fit on a 7" rim no probs, my IFS truck came with this when i got it, don't need wider wheels unless you go bigger than 10.50 wide

[papacroft]

31/10.50 r 15 is the american/imperial measurement,
approx31" diameter 10.5"wide radial tyre plys 15"rim,
265x75xr 15is metric convention,
265mm wide tyre profile 75% of width rest as before,
31s will fit on a 7" rim no probs, my IFS truck came with this when i got it, don't need wider wheels unless you go bigger than 10.50 wide

Thanks for that. One puzzle to me seems to be with the Colway tyres. They do a 31/10.5 r 15 on their website, but equate this to a 255/75 r15. Is it just a typing error (should be 265) or am I missing the point?
Any help much appreciated.

[Gizmo]

Thanks for that. One puzzle to me seems to be with the Colway tyres. They do a 31/10.5 r 15 on their website, but equate this to a 255/75 r15. Is it just a typing error (should be 265) or am I missing the point?
Any help much appreciated.

No it's correct..as stated before imperial vs metric sizes. 31./10.5/15 are a little less in width but higher [spect ration of the tyre wall]

[TonyN]

tyre sizes like 31" are just a general class guide, they often differ by 1 or 2" overall diameter depending on make. This is why telling someone a certian size tyre will rub or not is very vague.