# How Do Tire Sizes Compare? P265/75-R15 To 31x10.5-R15

You will find that the P265/75-R15 is what they call a regular road tyre and is a standard size for a road car. However the 31x10.5-R15 is actually an off-road tyre and is designed to be wider with more grip to help with the rough terrain.

If you are wanting to research tyre sizes then you should find a lot of helpful advice from car forum websites or even car tyre specific forums. To search for these forums you are best to head to google.com and type in keywords such 'Car Tyre Forums' or 'Car Forums'. You should find a wealth of options and so a great way of narrowing down which forums to join is to see how many members they have and how often it seems to be updated.

Most forums will allow you to start your own thread and so you will be able to post any tyre-related queries on the forum and wait for the responses. It is also worth heading down to the local garage, even if you do not know the mechanics that well, I am sure they will be happy to offer any advice on different tyres. It is always worth doing your research to make sure you are getting the tyres that are best suited to your car and needs.
thanked the writer.
The first tire is a regular tire, the send are used for off road use. They have deep grooves and are wider than regular tires.  The r15 for both is the rim size, the 31 on the second 1 is for overall size of the off road tire and the 10.5 is the width. Where 265 is width for the first one and 75 is the distance from the top part of the rim to where the tired ends. Hard to compare since they both use their own measuring system
thanked the writer.
Anonymous commented
The P265/75-R15 is approx. Equivalent to 30.5x10.4-15 30.5 being the diameter and 10.4 the width.

The 75 is the aspect ratio. In other words the height of the sidewall is 75% of the width.

265x75% = 198.75 mm or 7.79 inches. Double this since the height of the tire includes 2 sidewalls. 15.58. Add this to the rim diameter of 15 and you get a total diameter of 30.5 inches.

The 265 is the width in mm. Divide by 25.5 to get 10.4 in width