Tyre sizes

brianr70 · Post by **brianr70** » Sat Dec 08, 2007 2:54 pm

how does one convert metric tyres sizes back to inches

this slightly old fart still works in inches for tyre size and maths was never my strong point.

for example what does this size mean
LT255/70R16 :?:

figured 16 is 16"

smurf182 · Post by **smurf182** » Sat Dec 08, 2007 3:08 pm

255 is the width in milimetres from sidewall to sidewall.

70 is the height of the tyre sidewall as a percentage of the width. (0.70*255=178.5)

16 is the wheel diameter.

LT means Light Truck.

R means its a radial.

timotheus · Post by **timotheus** » Sat Dec 08, 2007 4:30 pm

This might help others.

http://www.4wdbits.co.nz/tyrecalculator.aspx

brianr70 · Post by **brianr70** » Sat Dec 08, 2007 6:22 pm

Thanks

MAHINDRACJ4A · Post by **MAHINDRACJ4A** » Sat Dec 08, 2007 6:29 pm

Tyres have three important sizes to consider the first is the height, second the width and thirdly the rim size the tyre will fit. Now this can be confusing because tyres come in metric and imperial sizes. I use 31 x 10.50 R15 ATâ€™s. This means that my tyres are 31 inches high from the ground to the top, 10.5 inches wide and fit on a 15 inch wheel rim. Standard fitment to Mahindra Jeeps are metric 235 / 75 R15. This means that the tyre is 235mm wide, the distance from the wheel rim to the tread of the tyre is 75% of the tyre width and fits on a 15 inch rim. Notice that metric tyre sizes still use imperial rim sizes !!

so to convert 235/75 R15

235mm / 25.4 = 9.251" (this is the width converted to inches)

235 x 0.75 = 176.25mm ( this is the sidewall from the rim to the tread)

176.25mm x 2 = 352.5mm ( this is the sidewall x 2 because we have the bottom side wall and the top)

15" x 25.4 = 381 ( the rim diameter in mm )

381mm + 352.5mm = 733.5mm ( the total height from ground to tread )

733.5mm / 25.4 = 28.87" ( the height in inches )

so the size is : 28.87 x 9.251 x R15

28.87 x 9.251 x R15 is the same as 235 / 75 R15

Shit that was a lot of writing lol hope it helps you

H2OLOVA · Post by **H2OLOVA** » Sat Dec 08, 2007 8:16 pm

MAHINDRACJ4A wrote:
so the size is : 28.87 x 9.251 x R15

28.87 x 9.251 x R15 is the same as 235 / 75 R15

Shit that was a lot of writing lol hope it helps you

will also depend how hard you pump up the tyre :wink:

MAHINDRACJ4A · Post by **MAHINDRACJ4A** » Sun Dec 09, 2007 9:47 am

thats a variable

then you also must think about all the other variables such as amount of tread