"X" inch wheels ....how do you convert?

Trevor, There is a website somewhere that explains all this, but in the absence of knowing what it is, I'll do my best to explain.......

The size you quote is 265 (is the nominal width of the tread....265mm). The "70" is the aspect of the tyre. Basically it means that the height of the tyre, from the rim to the outer circumference, is 70% of the first number....265 in this case. So, the height of the tyre from rim to outer edge is about 185mm.

The "16" is the diameter of the wheel....in bloody INCHES....just to confuse the issue.

So, to calculate the total diameter, you divide 185mm by about 25mm to get it in inches. Say 7.5 inches in this case. This is only one side of the tyre, so you need to double it....becomes 15 inches; then add the wheel diamter to give you a total overall tyre diamter of 31 inches (approximately).

Hope this helps.

Roachie

Trevor

A little lite reading Tyre Bible

Regards

Paul

Trevor,

I Googled tyre size and came up with this.

Tire Sizing

Passenger Tire sizing is typically displayed as:

P215/65R15 89H

The "P" stands for "P-Metric" or "Passenger". This means that it is a North American tire sizing designation. European tires typically don't have the "P" attached to the size. Tires with higher ply ratings will generally start with "LT" which stands for "Light Truck". This indicates the tire is an LT metric and will always have a Load Range indicated. It is important to note this for vehicles that call for LT metric tires. Never substitute a P metric tire for an LT metric tire, even if all the other dimensions are the same.

The "215" is the width of a tire, also known as the "section width". This is the width of the tire in millimetres at its widest point from sidewall to sidewall when mounted on the recommended rim width. The actual tire width can vary depending on the rim width it is mounted on.

The "65"is known as the Aspect Ratio. It is calculated by dividing the section height by the section width and multiplying by 100. (In this example, the sidewall will be 65% of 215)

The "R" stands for Radial, meaning it has a radial construction. Radial tires have ply cords that extend to the beads and are laid at 90 degrees to the centreline of the tread, the carcass being stabilised by a circumferential belt. Other possibilities include "B" for belted construction and "D" for diagonal construction. This means the ply cords extend to the beads and are laid at alternate angles less than 90 degrees to the centreline of the tread.

The "15" stands for the diameter of the wheel in inches. This is the exact size that this tire will fit. There are some older rims called "TRX" which are metric measurements like 390. You CAN NOT mix TRX rims with regular tires or vise-versa.

The "89" is the load index

The "H" is the speed symbol.

This is the same as Roachie said but I was in the middle of cut and paste and I was not going to waste it.

With 15" tyres it is very easy, 31 x 10R x 15
31" tall x 10" wide on a 15" rim

Wayne

Look here: Site Link

265/75/16=32
285/75/16 = 33
305/70/16=34
315/75/16=35

This website does it all, awesome. www.1010tires.com

This link takes you directly to the tire size / converter calculator

www.1010tires.com/TireSizeCalculator.asp

here's another.
" target="EOF" class="lbg">www.miata.net/garage/tirecalcold.html
(I'm not as smart as the other dudes, you'll have to cut & paste)