The only way to work these out is by checking a chart. M/C (motorcycle) and then a number followed by a letter 91Vĩ1 is the load rating + V is the maximum speed rating. In the UK and Europe, if a tire is to be road legal, it will display the following code: If you are in any doubt as to whether a tire is road legal or not, you should check with the manufacturer. Most dirt bike tires are not street legal, and will state “Not for use on the highway”. A DOT rating lets you know that the tire is legal for use on the road in the USA. Other important information on your motocross tire – Motocross Advice advises against riding mixed ply tires. One thing everyone agrees on is that if you want to take the risk of mixing radial and bias on a dirt bike, or motocross, then remember the adage: RADIAL: REAR We feel that tires work together by design. A few riders are saying that on a dirt bike, this doesn’t matter, as the wheels are doing different things anyway. There are always people who like to experiment. Back in the seventies, there was a spate of severe accidents with cars turning over because of this. The reasoning behind this is that the sidewalls flex differently and cause a steering anomaly. If you go radial on the rear, you should match that on the front. The most crucial point here is that you cannot mix radial and bias tires on your bike. Recently, however, some manufacturers have started offering radial options. It used to be that all motocross tires were Bias (cross) ply. These descriptions refer to the direction of the inner meshing of the tire. If there is no letter, or you see a B – then that tire is a bias (or cross) ply tire. If you see the letter R – this denotes the tire as a radial tire. So far, so good! What are the other letters and numbers on a dirt bike tire?Īside from the manufacturer’s name, and the model of the tire, you may see other letters, marks and numbers. In this case 90% ofĩ0 = 81 – therefore 81mm sidewall height.įinally, the last figure is in inches and refers to the rim. The second figure is a percentage of the width. What if we were looking to buy a 90/90-21 front tire for our dirt bike? Therefore the INTERNAL diameter of the tire is 19 inches across. So, in our example, the tire is meant for a 19inch rim. The final figure, (Rim diameter) measures in inches.In this case, the sidewall height is 100% of the tire width. It represents the height as a percentage of the tire width. The Sidewall aspect ratio (height) is a percentage figure.The width measures in mm – in this case 120mm.Thankfully, all tires have the same weird way of measuring, so once you understand these points, it is plain sailing. There are a couple of quirks about tire sizing which you need to now. Of course, it is never as simple as it seems. These numbers represent (Left to right): Tire width/Sidewall Aspect Ratio (height)-Rim diameterĪs you can see, the code is straight forward enough. So if you are looking at a rear-wheel for a dirt bike, you might see: 120/100-18 These numbers sit in the same order on most dirt bike tires. On the sidewall of any tire, you will see a string of numbers. Let’s take a typical dirt bike tire size and break the numbers down, one by one. In the following paragraphs, we will make sense of all of the variations, so that you can buy the right tire with confidence. You have probably asked yourself “ what tire should I buy for my dirt bike“? What are all of the different types of tire compound? Enduro, adventure, dirt bike and motocross all have a bewildering amount of tires for different surfaces and applications. While we are at it, we may as well deal with another matter of much confusion. By the time you have finished reading, you will be able to look at a dirt bike tire and make sense of it – you will understand dirt bike tire sizes. In this article, we will attempt to break that code. This Dirt Bike Tire Sizes Guide will make your life much easier! Just what do all of the numbers and letters on a dirt bike tire mean! Trying to break the code on a tire feels like you are trying to read some secret code or foreign language. Whatever walk of life you are from, and no matter vehicles you have owned, there is one thing that has likely confused you at one time or another.

Motorcycle tire comparison chart