A Guide To Making Sense of Motorcycle Tire Numbers

What do Motorcycle Tire Numbers Mean

If you have ever studied a motorcycle, looked at the tires, or maybe never noticed until you went to put air in your bike’s tire, you probably saw some numbers and perhaps even letters on the side. If you are curious as to what this means, it is relatively simple. These numbers list information about your tires regarding the size.

First Number

The first number inscribed on a motorcycle tire is there to indicate the width of your tire in millimeters. This width is measured by way of a straight line through the tire. It goes from one edge of a motorcycle tires tread to the other side.

Sometimes this measurement can be denoted in inches, but the metric system is conventional for the first number. If at first glance, you see letters instead of a digit, you have a tire that is written with alphanumeric measurements. The codes are translated for you if you read on.

Second Number

The second number imprinted on your motorcycle tires represents the aspect ratio. The aspect ratio describes the height, or how tall the tire happens to be in relationship to the width of the bike’s tire. This aspect ratio can be found amid the tire width and the tire height and is written as a percentage.

In other words, the larger this second number is, the taller your motorcycle tire will be. For example, a tire that is written 130/90 means that it has a width of 130 mm and it is 90 percent as tall as the given width. When you calculate 90 percent of 130, that means it is 117 mm tall.

Third Number

The third number on your tires indicates, more simply, the rim size or the circumference of your wheel. So, if the number is 18, that means your tire rim is 18 inches. A tire with a 16 as the third number has a rim size of 16, and so on.

Alphanumeric Numbers

Some motorcycle tires have alphanumeric numbers, for example, MJ90 17. This is basically writing the same thing as the digital example only in a coded fashion. The M stands for a tire that meant to be used on a motorcycle, the following letter is the width code, and the number (such as 90 in this case) still stands for the aspect ratio. In this example, 17 stays the same and represents the rim size.

The alphanumeric system for motorcycle tires states back before the metric system. In those days, motorcycle tires were not designed to be much bigger than an MV85 or a tire with a width of 150 mm. Tires that are made for modern bikes that are also more substantial than 155 mm in width will have the metric designation and will not have an alphanumeric code.

Alphanumeric codes can be interpreted in metric (mm) or in inches. There are codes for both the front and rear tires, as motorcycle usually have different sizes for the front and the back. These codes are as follows.

On the front tires:

• MH90 is 80/90 metric and 2.50/2.75 inches
• MJ90 is 90/90 metric and 2.75/3.00 inches
• MM90 is 100/90 metric and 3025/3.50 inches
• MN90 is 110/90 metric and 4.00 inches
• MR85 is 120/80 metric and 4.25/4.50 inches
• MR90 is 120/90 metric and 4.25/4.50 inches
• MT90 is 130/90 metric and 5.00/5.10 inches

On the rear tires:

• 0 MN90 is 110/90 metric and 4.00/4.50 inches
• MP85 is 120/80 metric and 4.50/4.75 inches
• MP90 is 120/90 metric and 4.50/4.75 inches
• MU90 is 14/90 metric and 5.50/6.00 inches
• MV85 is 150/80 metric and 6.00/6.25 inches
• MV90 is 150/90 metric and 6.00/6.25 inches

These may not be the only letter on your tires. Speed ratings can also be listed but are not spelled out in a way that a novice would initially be able to interpret. If an extra M is listed, this can simply mean the tire is intended for a motorcycle, as opposed to one for a different type of vehicle or trailer.

Speed Rating

To further add to (and possibly confuse) the code of reading tires, there are also speed ratings denoted by letters. Speed ratings list the maximum pace the tire is designed to handle, and should not surpass that. These speed rating marks are smart to be aware of if you like to test the limits of your bike because having a blow out at top speed can be lethal. These ratings are listed as follows.

New style:

• J – 62 mph
• K – 68 mph
• L – 75 mph
• M – 81 mph
• P – 93 mph
• Q – 99 mph
• R – 106 mph
• S – 112 mph
• T – 118 mph
• U – 124 mph
• H – 130 mph
• V – 149 mph
• W – 168 mph
• Y – 186 mph

Old style:

• J Type – 62 mph
• N Type – 87 mph
• P Type – 94 mph
• S Type – 112 mph
• H Type – 130 mph
• V Type – 149 mph
• Z Type – 149+ mph

Once you have your first, second, and third number down and understand the speed ratings, you will be able to interpret the numbers on a motorcycle tire much more straightforward. You will also be more equipped to know how much speed your bike can handle—the engine isn’t the only factor in that equation, tires play a role in the maximum pace, too.

Motorcycle tire quality can be part of the listing when you are buying tires. Several options exist for different conditions and diverse bikes. For instance, you could get the same size motorcycle tire in a sport touring, a performance road or cruising, off-road, motocross, desert, or city version, along with numerous other options.

Cost

As with anything, the options you select in your tire will determine the value. Generally, the prices will range roughly from $70 to $160. Some shops charge for installation of the tire, some don’t, and many will charge a small balancing fee. Retreaded tires can cost around 30 to 50 percent less than brand new tires. However, these must be carefully inspected to be sure the constitution of the tire is still sound.

The prices of motorcycles will generally influence the range your tires will cost, as tires for something like a Ducati can cost more than something based on used motorcycle values. Getting specialized tires with premium treads will naturally up the price tag.

Load Rating and Date

Not all, but some motorcycle tires may have a load rating for the given size. This can be more often the case with rear tires or four more substantial touring bikes. You may have also noticed a date stamped on your tire sidewall.  You will generally see a four-digit number after the word “DOT, “ and this indicates the week and year your tire was made. For instance, the 37^th week of 2018 would be written as 3718.

Other Terms

If you need to brush up on further tire construction terminology, there are only a few terms that are absolutely essential to know. More research can always be done to learn further details within these terms, but the basics are as follows.

Tread

The tread is the portion of your tire that touches the road. Generally speaking, smoother tire tread will grip better on even, slick, and dry services. While thicker or chunkier treads are better for off-road conditions. There are various patterns designed for streets that perform best in wet and slippery weather. Many off-road tires also are available in a vast array of different surfaces, ranging from packed down soil to loose sand.

Bead

The bead of a tire is the portion that connects to the wheel. Generally, this is a steel wire that is coated heavily in rubber. The bead of your tire is meant to have a snug fit against the wheel to avoid your wheels from slipping within the tire.

Carcass

Your tire carcass is essentially the body that is underneath the tread. In the case of motorcycle tires, they can be bias-ply or radial. This refers to the way the carcass of your tire is designed. In radial tires, reinforcing belts run from a bead on one side to the bead on the opposite side across your tread.

Additionally, tires with bias-ply contain belts running from each bead to the other at 30° to 40° angle. These cords are often made of fiber chords of fiberglass, polyester, or aramid and help to add strength to the integrity of what you are riding on.

Sidewall

The sidewall of your motorcycle tire explains itself and its name. It is the wall that runs between the bead at the wheel and the tread of your tire, basically the side surface.  Your sidewalls offer your tires a lot of their handling capability and load transfer performance.

What do Your Tires Say?

Now that you know how to read a motorcycle tire take a look at your bike and make yourself comfortable with the exact size and dimensions of your ride. It can be beneficial to know tire-speak next time you need to balance them or get a new set.

Furthermore, it can help you better understand what speeds you can safely ride at and where you should cap out, even if the engine technically could go faster. Staying within the limits of your tires should always be done.