Tyre sizes-what's the difference

[nos4ra2]

Probably a dumb question, but what's the difference sizewise between a 265/70R15 and a 31x10.5R15? I've got the 265s on mine at the moment and am looking to stick the Runway 31x10.5R15 ATs on there.

[Twisted Instigator]

Not that dumb a question. I still get confused by it all!!

Looking forward to hearing the answer!

[Karma Supra]

The first number is the width
i.e. 265 mm wide.

The second number is height of the side wall, as a percentage of the width, i.e. 70% of 265

the R15 is the wheel diameter (in inches dispite the width being mm...)

When people talk about 31x10.5R15 they are simplifying it.. i.e. 31" dameter, 10" wide for a 15" wheel.



Here is a handy link....

http://www.etyres.co.uk/tyre-size-calculator.htm

[puddlesurfer]

OK - this is from memory so if I get it slightly wrong forgive me.

265/70/15 is a metric size

265 is the width of the tyre in millimeters
70 is the profile of the tyre (from where the tread is on tyre to rim) and is a percentage of the width (70%)
15 is the rim size in inches

31/10.5/15 is an Imperial size

31 is the diameter of the tyre
10.5 is the width
15 is the rim size in inches

There is a tyre (or tire for our american friends) size converter here:

http://www.1010tires.com/tiresizecalculator.asp

[Twisted Instigator]

I know about the width/height/diameter etc, but I still get confused when they start quoting the different measurements! That link you put up is a great help. Makes it much more understandable!! Cheers for that....

[MWS]

Probably a dumb question, but what's the difference sizewise between a 265/70R15 and a 31x10.5R15? I've got the 265s on mine at the moment and am looking to stick the Runway 31x10.5R15 ATs on there.

Hi All......I always use this for tyre sizes and comparisons....www.tacomaworld.com/forum/tirecalc.php .....Cheers....Mick.

[stormforce]

one is bigger than the other



Simples....

[nos4ra2]

one is bigger than the other



Simples....

That's basically what I was asking-sorry, already know about the numbers and sizes, but... Is a 31x10.5R15 bigger diameter and/or width(on the running surface-I know they are on 15" rims ) than a 265/70R15?

<edit> MWS, thanks for the size calculator-bingo, question answered, 31x10.5R15 are bigger and should get my speedo close to the truth too.

[Apache]

I know about the width/height/diameter etc, but I still get confused when they start quoting the different measurements!

Finally your signature makes sense...