SLROC Forum

Hey guys

I have a set of BF Goodrich Mud T/As on my disco and they have a slightly strange size format

They are 31/10.5 r15. Im assuming 31 is the outer diameter, 10.5 the width and 15 the rim size. Now compared to a usual measurement of say, 235/75r15 i thought it seemed strange. Is it an American sizing or something?

Can anyone shed some light on the subject?

Cheers

Ally

hello

yeah 31 is the tyre size, its quite a common size of tyre lots of brands do them.  hope this helps

If you are old enough that is how they all used to be.
You might find this useful.
http://www.members.shaw.ca/jbarge/tires.html

You know that is actually good old imperial size & easy to understand.
often use with bigger tyres & in the good old USA, & nice to see sometimes because you know what you are getting, 31", 33", 35" etc etc
http://www.etyres.co.uk/tyre-size-calculator.htm

a tyre 31 inch tall, with a tyre width 10 1/2 inch wide approx (not tread width) that goes on a rim of 15".
That doesnt tell you the rim width you need, but you get to know what a 9.50, 10.50, 11.50, 12.50 needs,
5.5, or 7", 8" 10" even, same as if you are needing rims for a 215 mm or say a 285 tyre)

The metric size, 235/70/16 is just about the same height & width as a 235/75/15 just with a bigger hole in the middle.
*they both measure about 29" tall, but how does somebody know that unless they know, they look it up or someone tells them. or measures the tyres !!*

Tyre 'profiles', are like, 35,40,45,50,55,60,65,70,75,80,85.
If a tyre is 195 R15, then that is full profile and will be 195/80/15 probably.

235 mm wide tyre (about 9 1/4") with an aspect ratio of the tyre wall 75% of the tyre width that goes on a 15 inch rim.
So that is like a 235/70/16 measure about the same height as a a 225/75/16 but it has a narrower tread.
that really doesnt quickly tell you how tall that tyre is.
www.tyresdirectuk.co.uk
www.camskill.co.uk

Google 'tyre bible' and it will be explained better than by me.
Plenty of online tyre conversion tables available.
www.kouki.co.uk/utilities/visual-tyre-size-calculator
www.onlineconversion.com/bigger_tires.html


george