American Motorcycle News

Here’s What the Weird Numbers on Motorcycle Tires Signify

Motorcycle Tire Wear

If you’re new to motorcycles, then you probably noticed that the tires have some strange numbers on them. These numbers and letters are essential to understand as a biker, since you can then choose out tires better.

And you don’t have to feel too bad about not knowing what those numbers and letters on a motorcycle tire mean, since most people don’t know. But with this post, you’ll learn about what these numbers signify.

Motorcycle tire numbers: what do they mean?

So the first thing that you should know about the numbers and letters that you’re seeing is that they’re code. Each number and letter represent specific information about the characteristics of the motorcycle tire.

The codes represent the load index, speed rating, construction type, aspect ratio and width of a motorcycle tire. When you look at numbers now after understanding what they represent, it’s actually impressive how manufacturers are able to present this information.

Here’s a more run down of everything that the numbers mean:

Width of the tire

The first number that you see in the sequence is the tire’s width, which is in millimeters. So motorcycle tires with a width of 200 mm will just be the numbers “200.” A better way to visualize the tire width, i.e the first number would be its thickness.

Aspect Ratio

The second number that you find in the sequence is the aspect ratio of the tire, which is in percentage. The aspect ratio is a percentage of the width of a motorcycle tire. So a tire with an 80% aspect ratio means that it is 80% wide as it is tall.

The higher the aspect ratio of your bias ply tire, the taller it will be. The motorcycle tire size can play a vital part in your handling of your bike, since wider tires can make your maneuverability more difficult.

You should also remember that the rim diameter is also a part of the aspect ratio of your tubeless tires or radial tires.


The next addition in the sequence will be a letter r, which might also be the first letter in the sequence depending on the tire manufacturer. Along with the information about the motorcycle tire size, the letter for construction can be R, B, or D.

All three of these construction types have different meanings, such as R is for radial construction, B is for bias ply construction, and D is for diagonal. Bias ply tires and radial tires are very popular choices for every tire size.

Bias ply tires are popular for the speed rating that it can support, often allowing motorcycle tires to reach a faster maximum speed. As for radial construction, these happen to be a lot more durable than its bias ply construction counterparts.

Speed Rating

The second letter in the sequence is the speed rating for tubeless tire. Along with having information about the tire’s width and the tire size, the tire sidewall will also has a letter for the speed rating, which will indicate the maximum speed that a bike can reach.

Motorcycle tire sizes play a major part in the load and speed index of your tires, since aftermarket wheels with improved width can handle a greater load capacity.

There are different letters for the speed rating which refer to the maximum speed that a tire can safely reach with reduced risk of tire failure. For example, the M speed ratings means that your touring bikes can safely reach top speeds of 81 mph. In the metric system, that translates to a top speed of 130 kmh.

Similarly, a motorcycle tire with a speed rating of N can reach a top speed of 87 mph, which translates to 140 kmh in the metric system. These speed ratings can change depending on the type of tires you buy.

Load Rating

The final number in the sequence is the load rating, which refers to the maximum load that a tire can carry. Most motorcycle tires have a load index of 73, which considering their tire size, aspect ratio, width means that it can carry 827 lbs or 375 kg.

When should you replace a motorcycle tire

Choosing tires for your motorcycle can feel like a very challenging task, since you have to consider the motorcycle tire sizes, width, rim diameter, speed rating, and aspect ratio. However, depending on your riding style, the tube type tire that you choose should feel like the right tire, since you might even take it off road.

However, there are a few general indicators that tell you that you should be getting new tires for your motorcycle.

Checking tire tread depth

The first thing that you should do to check if you should replace your tire is checking the tread depth of your tire. According to the standard inch system for tire sizes, if your tread depth is less than 1/16th inches, you need to replace them. You can check the tread depth of your motorcycle tires with the penny test too.

Take a penny and insert it into the tread of your tires. You should insert the penny Lincoln’s head first, and if you can see his head unobstructed, then its time to get a new tire with better inner tubes. How quickly your tread depth shrinks across the width of your tire really depends on your riding stye.

Checking for cracks signs of damage

The next thing that you check on bike tires are any cracks and signs of damage. Even if you were to check you owner’s manual, you can see that cracks other signs of damage can be a serious concern. It can lead to your tire blowing out, which could even lead to an accident. All things considered, if you see too many cracks throughout your bike tires, then you should look for new tires while keeping your rim size in mind.

How does your bike feel when riding

Finally, you should just check how your bike feels when you’re riding. Regardless of your riding style or the bike you have, even if it is a Harley Davidson, you should see if you ride in a straight line and if the wheel feels wrong somehow. If that is the case, you should contact your nearest mechanic.