We all have intentionally or unintentionally observed a code-like embossing of alphabets and numbers on the tires. If you belonged to that category of kids at a younger age who would see themselves as James Bond, you must have tried to understand that. Even if you are least interested in knowing the language, we all have wondered why this language is exactly and why is it there on a tire?
Today, we will help you understand the message written on the dirt bike tire and its tells. Stay connected with it, and you will feel yourself a true detective by the end. Let’s get into the hidden message reading.
What do the Numeric Signs Tell on a Dirt Bike?
When we observe closely, several numeric characters are showing on a dirt bike. To better understand, let’s take a regular-sized dirt bike tire and break down all the numbers one by one. You will notice a numeric string vertically embossed over the tire’s sidewall.
Usually, these numeric characters are placed in the same order on dirt bike tires. So when you are looking at the rear-wheel, you may see 120/100-18. The hidden message here is “from left towards right.”
Height, Width, and Diameter of the Tire
As we can see that the code is pretty simple to understand, but of course, it means that you have much more to sort out. There are several quirks which you should know. Luckily, all the dirt tires have the same way of measuring; you will start to enjoy reading as soon as you understand it.
When we see the width measures in mm, that tells 120 mm. When you check the vertical height, that shows a percentage figure. Sidewall represents vertical height as a tire’s width percentage.
Here, the height of the sidewall is 100 percent the width of the tire. It simply tells that the height of the sidewall is also 120 mm. For measuring, Rim diameter measures the reading in inches. Let’s take an example that a tire that belongs to a nineteen-inch rim.
It tells that the tire’s internal diameter is nineteen inches.
Learn it with an Example
Suppose you are looking to purchase a 90/90-21 tire for your dirt bike. The tire must have a width of 90mm. The second figure you take would be the width percentage. So here there 90 percent of 90 equals 81 in this case. Therefore the height of the sidewall would be 81mm.
The diameter is measured in inches to measure the rim size. Here the tire will fit the rim of 21 inches.
Understand it with the help of table
The following table makes it more straightforward for you to understand how to read the numeric signs. Have a look at the table below.
| Metrics | Inches |
| 110/100X18 | 4.50X18 |
| 120/100X18 | 5.10X18 |
| 130/100X18 | 5.3X18 |
| 110/100X19 | 4.50X19 |
| 120/100X19 | 5.10X19 |
What do the other Alphabetic and Numeric Characters Mean?
Other than the manufacturer’s name and the model details, there are some other alphabets, numbers, and marks. Alphabetic characters have a different meaning; numeric characters and marks denote different meanings. When you see the letter “R,” it denotes that the dirt tire is a radial tire.
There is no alphabetic character or the letter “B” that denotes the tire as a bias-ply tire. These details refer to the inner meshing direction of the dirt tire. It would be that all the dirt tires are Bias ply. However, many manufacturers have started to introduce radial tires.
The actual reason behind it is that the sidewalls of a dirt tire flex differently than usual, which causes the steering anomaly. In past times, people had observed many car accidents with vehicles turning over due to it.
There are always a lot of people who love to perform stunts in the middle of the road. Several riders claim that it doesn’t matter on a dirt bike whether the wheels are unusual things anyway. It has been observed that the dirt tires work together by the make of design.
Everybody agrees that if you want to risk mixing the bias and radial on a motocross or a dirt bike, then there will be the adage: Rear: Radial.
*Note*
You cannot use both radial and bias tires in your bike. If you opt for the bias tire for the front-rear, then the back tire should also be biased. In simple words, you must match both the tires.
Other Coded Information Embossed on a Tire
You might have noticed a dotted rating spread over the tire. The dotted rating is to help you know whether the tire is legal to use or not. Many dirt tires state that they should not be used on a highway.
Such tires are not legally allowed to use on the street. Suppose you doubt whether the tire is road legal or not, and we suggest you check this with the manufacturer. In Europe and the UK, to ensure that the tire is road legal, check if the following code is embossed over it.
M/C and a number followed by an alphabet; 91V. M/C means motorcycle. V is the maximum rating of speed, and 91 is the rating of load. You will need to check a chart to understand it clearly.
Conclusion
There are a series of alphabets, numeric figures, and marks embossed over the dirt tire. They seem to tell a hidden message to the reader about the tire’s specifications. It is all impossible to understand until you do not know what it is exactly.
Once you learn what does each sign denotes, it will be easy sailing for you. It seems to be so tricky, but you will enjoy reading it when you follow how to read it. Here we have tried to cover every tiny detail that could be of help for the reader.
Hopefully, you will find it more helpful to understand and read the dirt bike tire size.
