How to Determine Your Rim Size

June 1st, 2012

Here at we help people determine which wheel they need for their car every day. The biggest question is always determining what size of rim they have on their vehicle.

When someone asks you what size something is, your first thought would probably be to go out and measure it. Unfortunately, you can’t just take a measuring tape to your wheel in order to determine the size. It was always measure larger than what people say the wheel is.

Why is that? It’s because the measurement is based on where the tire actually sits, not where the edge of the rim is. So now you’re probably wondering “How can I figure it out without taking the tire off the wheel!” It’s actually very easy. You’re tire will actually give the diameter of the rim. For example, imagine your tire says P275/55R20. That “R20” at the end actually indicates that this tire is for a 20” diameter wheel. The wheel on this vehicle is a 20” Chevy truck wheel which unfortunately doesn’t narrow it down a whole lot because there are lots of 20” Chevy truck rims available but now you know to only look at the 20” when looking for your style.

This same thing can be used to determine the size of hubcap that belongs on your vehicle. If your tire says R16, then you need a 16” hubcap! It’s as simple as that.

How can I find out the width of the wheel?

Well, this part is a little more difficult. Unfortunately, your tire won’t tell you exactly what the width is and it would be almost impossible to measure it – especially with a tire on it. Some wheels, like steel wheels, give the dimensions on the front of the rim, either toward the outer edge or near the center around the lug nuts. But most wheels, especially alloy wheels, only show the dimensions on the back side.

It is usually located on the back of a spoke along with the factory numbers, or engraved into the inside of the barrel.  The dimensions will always be written as something like 20X8.5J indicating that the wheel is 20” by 8.5”, the width being 8.5”. Some imported brands will list the numbers in opposite order, but the same concept applies.

Why it is Important to Know

Many times, the size of the wheel helps us determine exactly which wheel our customer needs. Sometimes there can be a few styles of wheels that all look very similar, but are available in different sizes. By knowing the size of the wheel, our customers need we can narrow it down to a single part number and assure we get out the right wheel. Some companies even offer the exact same style of wheel in multiple size variations, so it can be very important to not just know what the wheel looks like, but the size as well.


Please Comment