Thread: How To MEASURE WHEEL OFFSET

Originally Posted by Disco_owner

Ron;

With 255/85R/16 or bigger , I was Recommended Rim Size of 16x8 " with a -1" ( -25 mm) off-set, I spoke to Andrew Richmond this morning from Rangie Spares , but from what you're saying I need a +33mm offset

I'm confused.

No, I'm saying that the standard offset is +33mm and it is stamped on the rim so you don't need to measure it.

To get the offset, what I do is:

sit the rim on wood, but the tyre off the wood so that you are literally measuring the rim only and nothing to do with the tyre.

The measurement from the very outside of the rim which would go on the inside of the car when fitted, through to the surface where the rim mates onto the axle hub is the backspace.

The offset as you already know is a measurement that is based from the hub mating surface of the rim to the mid point of the rim. So an offset of -25mm means the hub mating surface is 25mm inboard of the rim centre line and so the rim/tyre sticks further out when mounted on the vehicle. When measuring the offset, its important not to try to covert the measurement from a backspace, as an 8" rim when measured from outside to outside is actually around 9" due to the outer bead flanges on the rim and unless you make allowances, then your calculations will be all wrong.