One of the most important parts of a motorcycle and motorcycle safety that is often overlooked is tires. Tires are what keeps you and your motorcycle firmly on the road, rain or shine.
In order to prioritize safety and reliability while riding your motorcycle thought and consideration should go into tire selection and inspection. What are these considerations? How do you choose the right motorcycle tire for your bike? Let’s dig in and find out.
Understanding Tire Codes
There are a variety of tires that motorcyclists should be aware of when selecting tires for their bike. These variations are made for different styles and speeds of riding, cosmetic purposes, and even race applications. Since this article is geared towards Harley-Davidson motorcycles, the main things to consider are:
- Tire Size
- Speed and Load Ratings
Let’s start the discussion on tire size by first breaking down how motorcycle tires are sized. What do all of those numbers and letters mean? There is a lot of information conveyed in a tire size code.
The tire size is the most straightforward thing to consider when choosing a motorcycle tire and reading the sizing code. Different brands use different codes and the two codes above are the most common styles we see in the Harley-Davidson dealership. We’ll start with the first code type.
In the first code style the tire size is represented by the first three numbers in the code.The first numbers tells you the width of the tire at its widest point(130mm) followed by what’s called the Aspect Ratio. The Aspect Ratio is the profile or height of the tire compared to the width. It indicates the ratio of height to width. Therefore a 90% aspect ratio means the tire is 90% as high as it is wide. The importance of these first two numbers is of course to remain clear of wires or the fender wall of the bike.
The third number is the rim diameter, which is the easiest and most straightforward to understand. Only one size will fit your rim since your rim is but one size, while your width and aspect ratio can change depending on fitment and clearance of the fender(s).
A take away that we see at the dealership more often than we’d like is the fact that guys are trying to squeeze wider and wider tires under their factory fenders. You DON’T want to squeeze oversized tires underneath your fenders despite if it appears to fit or how good it looks or what your friends tell you. There is vital wiring underneath the fender and depending on your motorcycles suspension if you hit a big enough bump and the suspension compresses enough you run the risk of rubbing and tearing up your tires of the wires to the brake light and turn signals. Hitting a bump and losing a brake light or turn signal randomly without you knowing it can get your ran over at night
Make sure you have adequate room underneath your fender for the tire size that you decide to go with and also be aware of how/where your wiring is ran. There’s no science to this, it’s just something to figure out. Ask your local Harley-Dealership for tips as to what size they see working for similar applications to yours if you aren’t comfortable with making the determination yourself.
Load and Speed Ratings
We then get to the load and speed ratings of the tire. You always want to load your motorcycle within the confines of how much weight the tire can handle at certain speeds. Below are two charts. One is the Load Index or Rating conversion table and the second is the Speed Rating table.
Since we are talking top speed and weight let’s consider a typical Dunlop tire for a
Harley-Davidson Touring bike. bike easily capable of 100+ mph and a bike that is relatively heavy and has the capacity to carry weight in various compartments and saddlebags.
The rear tire on a 2020 FLHXS is a Dunlop D407T 180/55B18 80H. This tells me that the tire is;
- Dunlop 407 Touring Tire with the “D407T” indication at the beginning. This is make and model of the tire essentially.
- The tire is 180mm wide with a sidewall that is 55% as tall as it is wide. This is a relatively low profile tire.
- Rim Size is 18”
- Load Rating is 80, which converts to 992lbs
- Speed Rating is H, which is 130 mph.
As you can see just by the coding on the motorcycle tire, the load rating is more than adequate as the bike weighs 795lbs and the top speed of a stock bike is about 105-110mph.