Choosing the right motorcycle tires is crucial to improving your bike’s overall performance. This post will provide you with all the basics to help you understand your motorcycle a little bit better.
Understanding Basic Motorcycle Tire Terms
Choosing the right type of tires involves three things. You should understand how you ride, know how you plan to use them, and most importantly, safety.
Let’s start this article with the basic tire terminology:
- Tread – this is the part that hits the road. A smoother tread generally works better on smooth and dry surfaces while “chunkier” tires are more ideal off-road. Most street tread patterns are made for wetter environments and off-road tires are made for different surfaces, from sand to hard-packed dirt.
- Bead – this is the part of the tire closest to the actual wheel. It has a snug fit to the wheel to prevent the wheel from slipping rotationally in the tire. Moreover, the bead is typically a steel wire heavily covered with rubber.
- Sidewall – this is the part of the tire that connects the tread and bead. It’s a small yet crucial part as it gives the tire most of its handling and load-transfer characteristics. This is the part you refer to when talking about profile, height, or aspect ratio. A shorter sidewall usually has a stiffer sidewall and thus, a lesser flex. This also means better handling and turning, bad bump absorption, and a more difficult mounting.
- Carcass – this is the “body” of the tire under the tread. Motorcycle tires differ based on how they’re made and can either be radial or bias-ply. Radial tires have reinforcing belts (often made of steel) that run from bead to bead across the tread. Bias-ply tires, on the other hand, have belts that are usually made of fiberglass, aramid, or polyester. These run from bead to bead at an angle of 30 to 40 degrees.
How to Read Information on Motorcycle Tires
You can find everything you need to know about a tire, like its size and other components, by its sidewall. Additionally, there are two ways to show this information: alphanumeric and metric.
Since radial tires didn’t exist back then, alphanumeric was the only way to determine tire sizes. This resulted in a limited number of sizes available and therefore an uncomplicated system. But, as the tire technology became complicated, a new system had to be made to provide that information to motorcyclists. This led to the birth of the new metric system. Here are two examples of tire sizes. Let’s break down what they mean:
A: 130/90 – 16 67 H
B. M T 90 – 16 Load Range B
In the first example, 130 represents the width across the face of the tread in millimeters. The number 90 refers to the aspect ratio (%) while 16 refers to the rim diameter (in.) Then, 67 refers to the load rating while H stands for the speed rating.
How to Read Alphanumeric Motorcycle Tires:
In the second example, which uses the alphanumeric system, the width is conveyed by the letter “T.” M, on the other hand, means motorcycle—every alphanumeric tire will start with this letter. 90 stands for the aspect ratio, which is the height of the sidewall expressed as a percentage of the width. Thus, the height of the sidewall is 90 percent times 130 mm or 117 mm.
The next number refers to the rim size expressed in inches. If this were a radial tire, the rim size and aspect ratio would be separated by the letter “R.” But, since it’s not, you can be sure that it’s a bias-ply tire. If this were a bias-belted tire (a bias-ply tire with stiffening layers of fabric over the body plies,) a “B” would separate the aspect ratio and rim size. You can also see that this tire should be placed on a 16-inch wheel.
Other information refers to load ranges and speed ratings. Load ranges are the maximum weight a tire can carry. Speed ratings refer to the maximum speed a bike can carry the maximum load.
Motorcycle Tire Width
Diverse size numbering systems show widths in different sizes. You can use this table as a guide when determining the width of a motorcycle tire:
|Permissible Rim Widths||Metric||Alpha||Standard Inch||Low Profile Inch|
|2.15, 2.50, 2.75||110||MN||4.00||4.60|
|2.15, 2.50, 2.75||110||MP||4.25||4.25/85|
|2.15, 2.50, 2.75||120||MR||4.50||4.25/85|
|2.15, 2.50, 2.75||120||MS||4.75||5.10|
|2.50, 2.75, 3.00||130||MT||5.00||5.10|
|2.75, 3.00, 3.50||140||MU||5.50|
Motorcycle Tire Speed, Size, and Load Rating
|Front Tire Size Conversions|
|Rear Tire Size Conversions|
Note: Always use the tire size, load rating, speed, and type on your motorcycle’s manual. This information is for general use only, so never use it as your main basis for choosing motorcycle tires.
Motorcycle Tire Service Descriptions
A tire’s service description is the number and letter combo you see after the tire size. It includes information like the load and speed index, which you can see in the table below:
|Speed Rating||Max. Design Speed (MPH)|
It can also provide additional and optional information but these vary per manufacturer. For instance, they can further clarify what belongs to the tire or what the tire was designed to do.
Most modern motorcycle tires feature a load index and speed rating. Say you’re looking at Michelin tires: the code, which consists of a letter and two numbers, appears after the size. Therefore, if the code is 67H, 67 stands for the maximum weight while H refers to the maximum speed.
What Tube Size Do You Need?
You can refer to this table to know the exact tube size you have to buy:
Motorcycle Off-Road Size Conversion Chart
What Size Valve Stem Does Your Tubeless Motorcycle Tires Need?
You can choose from two types: 8 mm and 10 mm. The former type, with an actual opening of 8.3 mm, is found in most BMWs, Buells, and aftermarket wheels. The latter, which can fit an 11.3 mm, is more common and used by Japanese manufacturers and Harley-Davidson.
Can You Use Motorcycle Tires With Different Load or Speed Ratings?
A downgrade in load or speed rating is never a good idea. Manufacturers consider maximum load and speed ratings and they always specify the tires they think your bike needs.
Upgrading a speed or load rating won’t hurt. However, it can give a bad riding experience due to sidewall stiffeners added to the tire. Manufacturer-recommended tires can handle the load a bike is approved to carry. Trying to exceed that means the tires won’t be the only weak point—other parts can break, too!
While a higher speed rating is rarely dangerous, you may have to give up fuel mileage or tire life. Just stick to the OE speed rating when possible. Also, while upgrading is allowed, keep in mind that other riding characteristics can be affected.
Plus, when considering weights, don’t forget to factor in the weight of the rider, passenger, etc. Japanese motorcycle brands are notorious for assuming that their customers are all lightweight.
Does the Age of Motorcycle Tires Matter?
Yes! Luckily, it’s very easy to tell the age of your tire.
All sidewalls normally contain a DOT code, which is around 12-16 digits or so. The code starts with the letters “DOT” and is then followed by a series of numbers. Take note of the last block of numbers.
Four-digit numbers usually reference the week of production in the first two digits, then the year in the last two. So, if 4218 are the last four digits in your tire, it was made in the 42nd week of 2018.
If your motorcycle tires are around five years old, we suggest bringing them to a professional to have them checked. On the other hand, if they’re at least ten years old, you should replace them immediately no matter how they look.
Following your bike’s manual is the easiest way to ensure you’re getting the right motorcycle tires. Unless you know what you’re doing, stick with the stock sizes and you’ll always end up with the right decision.
Happy shopping and stay safe on the road!