It often happens that when you have to change tires, the usual question comes up: How can I know the measurements of my tires? Many of you are already familiar with some of the nomenclatures that appear on the side of the rubber, especially with those that indicate the size and construction (and that appear as something like 120/70ZR17), but we can know a lot more about our tires just by looking at them carefully.
In today’s post, we are going to show you the basic and necessary information to know the measure or measures that we have to ask for to get the right tire on our bike, but also to differentiate a little more complex data such as the load index or homologation.
Each motorcycle model requires specific tire sizes that are indicated by the manufacturer in its technical data sheet. It is very important to try to stick to the recommendations for safety and to adhere to the regulations of the road. You can see these measurements by looking on the side of the tire, where you will find something like this: 120/70ZR17 or 90/90-21.
Although we are going to focus on some of the most common sizes, we must take into account that there are also other types of sizes such as: 3.00-19, or MT90B16… The first are designations in inches and are still common, although less and less,while the latter can be found on V-Twin motorcycles, such as Harley Davidson or Indian. In this case they are alphabetical designations.
Going back to the example size 120/70ZR17, in this case 3 types of measurements are combined: 120 in millimeters, 70 in percentage and 17 in inches. To understand what each of them means, we must imagine a cut tire as in the following picture:
We can see the width (called nominal), which is not visible to the naked eye and measures 120 millimeters. Be careful! It is not the same as what we appreciate visually when we look at the tire from the front, that is something else and it would always be a larger number.
In this case, it corresponds to the tread width or real width, which, as can be seen in the measurement, could vary several millimeters depending on the manufacturer. In this case 126 mm (3 mm on each side).
Now let’s see what is 70 (120/70ZR17). This number designates the height of the tire section, but as a percentage of the width (120mm). This means that the section height will be 70% of 120. In other words: 120 x 70 / 100 = 84mm. And what is the section height for? You may ask… To be able to calculate the total diameter of the tire if necessary or if you want to change the size.
Finally, let’s look at the 17 (120/70ZR17). This measure, denominates the diameter of the rim, which is the part where the tire is fitted. In this case, the measure is designated in inches and first of all, we have to know that 1 inch is 25.4mm. Now we must imagine the whole wheel (the tire and the rim) cut.
We would be left with this section.
In the image, we can see that corresponds to the measure 17 inches or what would be the same 431.8 millimeters. Anyway and as we have said before, you can always consult the technical data sheet of your motorcycle to see the approved measures and that there is no doubt.
You may have noticed that we are still missing a piece of information from the previous sizes (120/70ZR17). These letters indicate the type of internal construction of the tire, whether it is radial or diagonal. If it is radial, it is indicated with a letter R or ZR, while if it is diagonal, it is usually not indicated, i.e. it is not indicated at all. If you want to know the difference between these constructions and how they affect the performance of the tire, you can read all about it in the following article.
On the other hand, on Continental tires you will usually find the letters M/C, which indicates that it is a MotorCycle tire.
If you find M+S it means that they are tires with a special grip for mud and snow.
In this section we are going to look at the load capacity index and the speed category symbol, i.e. numbers and a letter after the tire size. In the photo below, which we take as an example, we can see that after the size (130/70-12) and the tire type designation (M/C= MotorCycle), we can see 62L, “62” is the load capacity index and “L” is the speed category symbol.
And what does each of them do? In this case, the 62 indicates the load or weight that a tire can support in operating conditions. In this case the tire can hold 265 kg, as long as it does not exceed the specified maximum speed, which is determined by the letter “L” and corresponds to the Speed Category Symbol.
The speed index is always represented by a letter, starting with “A” for low speed tires and going up in alphabetical order.
On motorcycles, the easiest to find are M, N or P for off road tires (130, 140 or 150 km/h) and U or V for racing bikes (200 or 240 km/h). The highest letter we can find is Y, which corresponds to 300 km/h.
If we take a closer look at our tires we will see that there is even more information about them on their sidewall, although with somewhat smaller letters. If we look closely we will see that they also indicate their load capacity (but this time specified in kilograms and pounds), the pressure in Kilopascals (KPA) and Pounds per inch (PSI), their homologation code after the acronym DOT, the date of manufacture or if they are tubeless or not.
The most obvious piece of information is the big numbers and letters that usually look like this – 130/90 17, or MT90 17.
These numbers are a metric designation that indicates the size of the tire and the rim that tyre is designed to go on.
The question is what do those numbers actually mean?
Let's start with the first series of numbers, 130/90 17 which in this case are a metric designation. This is the most popular nomenclature used in the motorcycle tire sizing world today. What do those numbers actually mean?
THE FIRST NUMBER – WIDTH
The 130 indicates the width of the tire in millimeters. This is measured as a straight line through the tyre from one edge of the tire's tread to the other edge.
THE SECOND NUMBER – ASPECT RATIO
The second number, the 90, represents how tall a motorcycle tire is in relationship to its width. This is the aspect ratio between the tire's width and its height indicated as a percentage. In simple terms this means the larger this number is, the taller the tyre will be. In the example the tyre is 90 percent as tall as its width which we could calculate to be 117mm.
THE THIRD NUMBER – RIM SIZE
The last number, 17, refers to the tire's rim diameter expressed in inches.
The width on some tires may be expressed in inches. In those cases the aspect ratio is usually not included.
An alphanumeric designation such as MT90 17, represents the same tire size as 130/90 17. It's just expressed in a different way. M means the tire is for motorcycle use, T is the tire width code, 90 is the aspect ratio and 17 is the rim diameter.
You'll notice the tables do not go any further than 150/90 tyre sizes. Here's why.
The alpha numeric method of tire sizing is older than the metric system. Way back when … motorcycle tires didn't get much larger than an MV85 which is equivalent to a width of 150mm. Modern tires larger than 150mm wide now only carry the metric size designation.
| Front | ||
| INCH | METRIC | ALPHANUMERIC |
2. 50/2.75 | 80/90 | MH90 |
| 2.75/3.00 | 90/90 | MJ90 |
| 3.25/3.50 | 100/90 | MM90 |
| 4.00 | 110/90 | MN90 |
| 4.25/4.50 | 120/80 | MR85 |
| 4.25/4.50 | 120/90 | MR90 |
| 5.00/5.10 | 130/90 | MT90 |
| Rear | ||
| INCH | METRIC | ALPHANUMERIC |
| 4.00/4.50 | 110/9 | 0 MN90 |
4. 50/4.75 | 120/80 | MP85 |
| 4.50/4.75 | 120/90 | MP90 |
| 5.00/5.10 | 130/90 | MT90 |
| 5.50/6.00 | 140/90 | MU90 |
| 6.00/6.25 | 150/80 | MV85 |
| 6.00/6.25 | 150/90 | MV90 |
It's likely you'll find other letters mixed in within these motorcycle tire sizing numbers. They'll look like: 120/70ZR17 or 170/60R 17V, or even in other combinations. The two extra letters designate the tire's speed rating and construction.
The letter R or B indicates the construction used to create the casing of the motorcycle tire.
An R stands for radial construction and a B indicates the casing has a belted bias.
The other letter refers to the speed rating and indicates the maximum speed a motorcycle tire can sustain under its recommended load capacity. For example, U is indicates a maximum speed of 200 kmh / 124 mph.
In the examples the Z and the V are both speed rating indicators.
| SPEED RATING | MAX SPEED – MPH | MAX SPEED – KPH |
| J Type | 62 | 100 |
| N Type | 87 | 140 |
| Q Type | 99 | 160 |
| S Type | 112 | 180 |
| T Type | 118 | 190 |
| U Type | 124 | 200 |
| H Type | 130 | 210 |
| V Type | 149 | 240 |
| W Type | 168 | 270 |
| Y Type | 186 | 300 |
| Z Type | Over 149 | Over 240 |
Introduction
How to decipher the marking of motorcycle tires
Correspondence table for metric and inch tire marking systems
Conclusion
Motorcycle tires are impossible to choose correctly if you do not understand their sizes.
Otherwise, at best, you risk bringing just a useless piece of rubber from the store. To determine the sizes, we have prepared a short decoding method and a comparison table of tire dimensions.
Any motor rubber has a sea of information on the sidewall about the properties, purpose and, of course, size. We need to figure it out, and then compare the readings with the table. You can learn more about motorcycle tire labeling in our previous article.
As a rule, the main marking on the side of the tire looks like this: 120/80 R16 59S. This is the so-called metric marking. Let's understand it in more detail:
120 - profile width from edge to edge of the tread, expressed in millimeters.
80 - profile height, expressed as a percentage.
R - radial type of construction.
16 - diameter of the landing area. This indicator should correspond to the same diameter of the rim on which the tire will be put on.
59 - load index, or the maximum weight that the tire can withstand without loss of performance. We are looking for it in the table:
| Tire load index | |||||||
| 40 | 140 | 53 | 206 | 66 | 300 | 79 | 437 |
| 41 | 145 | 54 | 212 | 67 | 307 | 80 | 450 |
| 42 | 150 | 55 | 218 | 68 | 315 | 81 | 462 |
| 43 | 155 | 56 | 224 | 69 | 325 | 82 | 475 |
| 44 | 160 | 57 | 230 | 70 | 335 | 83 | 487 |
| 45 | 165 | 58 | 236 | 71 | 345 | 84 | 500 |
| 46 | 170 | 59 | 243 | 72 | 355 | 85 | 515 |
| 47 | 175 | 60 | 250 | 73 | 365 | 86 | 530 |
| 48 | 180 | 61 | 257 | 74 | 375 | 87 | 545 |
| 49 | 185 | 62 | 265 | 75 | 387 | 88 | 560 |
| 50 | 190 | 63 | 272 | 76 | 400 | 89 | 580 |
| 51 | 195 | 64 | 280 | 77 | 412 | 90 | 600 |
| 52 | 200 | 65 | 290 | 78 | 425 | 91 | 615 |
S is an index of the speed at which the bike can move without losing ride stability, grip and other useful tire characteristics.
The value is also in a special table:
The models in the top are arranged in terms of price / quality ratio. In the process of writing it, we were guided by the reviews of amateur bikers, professional tests, and were also guided by our own subjective opinion and many years of experience with tires.
| Speed index | Maximum speed, km/h |
|---|---|
| A | 40 |
| B | 50 |
| C | 60 |
| 65 | |
| E | 70 |
| F | 80 |
| G | 90 |
| J | 100 |
| K | 110 |
| L | 120 |
| M | 130 |
| N | 140 |
| P | 150 |
| Q | 160 |
| R | 170 |
| S | 180 |
| T | 190 |
| U | 200 |
| H | 210 |
| V | 240 |
| W | 270 |
| Y | 300 |
| VR | >210 |
| ZR | >240 |
| (W) | >270 |
| Z | >300 |
This method of marking tires is followed by most manufacturers, but there are those who prefer alternative types, where the dimensions are indicated in inches.
For example, this one is 3.25H-19. Everything is simple here: 3.25 is the tire width expressed in inches, H is the speed index, 19 is the bore diameter.
Sometimes an inch designation can be used instead of the usual millimeter, for example, like this: 4.60/80 R16.
There is a rather rare alpha system created mainly for sports tourists. For example, this type of MM90S-16, where: MM - profile width in inches (3.75), 90 - profile height in percent; S - speed index, 16 - diameter of the landing rim of the tire.
| Marking alpha | Width in inches |
|---|---|
| MG | 2.75 |
| MH | 3.00 |
| MJ | 3.25 |
| ML | 3.50 |
| MM | 3.75 |
| MN | 4.00 |
| MP | 4. |
| MR | 4.50 |
| MS | 4.75 |
| MT | 5.00 |
| MU | 5.50 |
| MV | 6.00 |
To make it easier for you to determine what the inch size corresponds to in the metric system and vice versa, we have prepared a comparison table for you.
| Tire size in. | Load index | Permissible rim width, inch. | Tire size | ||||
| Alpha | Metric | ||||||
| Standard | Reinforced. | 100 | 90 | 80 | |||
| 2. | 40 | 46 | 1.50-1.85 | MH 90-16 | 80/100-16 | 80/90-16 | 90/80-16 |
| 3.00-16 | 40 | 48 | 1.60-2.15 | MH 90-16 | 90/100-16 | 90/90-16 | 100/80-16 |
| 3.25-16 | 48 | 55 | 1.85-2.50 | MJ 90-16 | 100/100-16 | 100/90-16 | 110/80-16 |
| 3.50-16 | 52 | 58 | 1.85-2.50 | ML 90-16 | 100/100-16 | 100/90-16 | 110/80-16 |
| 4.60-16 | 58 | 59 | 1. | MM 90-16 | 100/100-16 | 110/90-16 | 120/80-16 |
| 2.75-17 | 41 | 47 | 1.50-1.85 | MH 90-17 | 80/100-17 | 80/90-17 | 90/80-17 |
| 3.00-17 | 41 | 50 | 1.60-2.15 | MH 90-17 | 90/100-17 | 90/90-17 | 100/80-17 |
| 4.50-17 | 50 | 67 | 2.15-3.00 | MR 90-17 | 110/100-17 | 130/90-17 | 140/80-17 |
| 4.60-17 | 50 | 62 | 1. | MS 90-17 | 100/100-17 | 110/90-17 | 120/80-17 |
| 5.10-17 | 50 | 67 | 2.50-3.50 | MT 90-17 | 110/100-17 | 130/90-17 | 140/80-17 |
| 2.75-18 | 42 | 48 | 1.50-1.85 | MH 90-18 | 80/100-18 | 80/90-18 | 90/80-18 |
| 3.00-18 | 47 | 52 | 1.60-2.15 | MH 90-18 | 90/100-18 | 90/90-18 | 100/80-18 |
| 3.25-18 | 52 | 59 | 1. | MJ 90-18 | 100/100-18 | 100/90-18 | 110/80-18 |
| 3.50-18 | 56 | 62 | 1.85-2.50 | ML 90-18 | 100/100-18 | 100/90-18 | 110/80-18 |
| 3.60-18 | 51 | 62 | 1.85-2.50 | MH 90-18 | 100/100-18 | 90/90-18 | 100/80-18 |
| 4.00-18 | 64 | 69 | 2.15-3.00 | MN 90-18 | 110/100-18 | 120/90-18 | 130/80-18 |
| 4.10-18 | 60 | 69 | 1.85-3.00 | ML 90-18 | 100/100-18 | 100/90-18 | 110/80-18 |
| 4. | 64 | 69 | 1.85-3.00 | MM 90-18 | 110/100-18 | 110/90-18 | 120/80-18 |
| 4.25-18 | 66 | 69 | 2.15-3.00 | ML 90-18 | 110/100-18 | 120/90-18 | 130/80-18 |
| 4.60-18 | 63 | 69 | 1.85-3.00 | MR 90-18 | 110/100-18 | 120/90-18 | 130/80-18 |
| 3.00-19 | 49 | 54 | 1.60-2.15 | MH 90-19 | 90/100-19 | 90/90-19 | 100/80-19 |
| 3. | 54 | 54 | 1.85-2.50 | MJ 90-19 | 100/100-19 | 100/90-19 | 110/80-19 |
| 3.50-19 | 54 | 57 | 1.85-2.50 | ML 90-19 | 100/100-19 | 100/90-19 | 110/80-19 |
| 3.60-19 | 52 | 54 | 1.85-2.50 | MH 90-19 | 100/100-19 | 90/90-19 | 100/80-19 |
| 2.75-21 | 45 | 54 | 1.50-1.85 | MH 90-21 | 80/100-21 | 80/90-21 | 90/80-21 |
| 3. | 51 | 57 | 1.60-2.15 | MH 90-21 | 90/100-21 | 90/90-21 | 100/80-21 |
Keep this chart for yourself and you will always have data on how to determine the size of motorcycle tires. In the BlackTyres online store, the selection of new clothes will be much faster and easier, because you can choose tires according to the model and size of the wheels of your bike. Just sort them using filters and choose your favorite tires.
| Tire size in inches | Tire size metric | ||
| 100 | 90 | 80 | |
2. 75 | 80/100 | 80/90 | 90/80 |
| 3.00 | 90/100 | 90/90 | 100/80 |
| 3.25 | 100/100 | 100/90 | 110/80 |
| 3.50 | 100/100 | 100/90 | 110/80 |
| 3.60 | 100/100 | 100/90 | 100/80 |
| 4.00 | 110/100 | 100/90 | 110/80 |
| 4.10 | 100/100 | 110/90 | 120/80 |
| 4.25/85 | 110/100 | 120/90 | 130/80 |
| 4.50 | 110/100 | 110/90 | 120/80 |
4. 60 | 100/100 | 120/90 | 130/80 |
| 5.10 | 110/100 | 130/90 | 140/80 |
Explanation of rubber marking abbreviations:
120/70 Z 12 m/c (58W)
| Maximum speed | |||||||
| MPH | km/h | ||||||
| V | 149 | 240 | |||||
| (V) | over 149 | over 240 | |||||
| W | 168 | 270 | |||||
| (W) | over 168 | over 270 | |||||
| Z | over 149 | over 240 | |||||
| Y | 186 | 300 | |||||
| Tire load index | |||||||
| 40 | 140 | 53 | 206 | 66 | 300 | 79 | 437 |
| 41 | 145 | 54 | 212 | 67 | 307 | 80 | 450 |
| 42 | 150 | 55 | 218 | 68 | 315 | 81 | 462 |
| 43 | 155 | 56 | 224 | 69 | 325 | 82 | 475 |
| 44 | 160 | 57 | 230 | 70 | 335 | 83 | 487 |
| 45 | 165 | 58 | 236 | 71 | 345 | 84 | 500 |
| 46 | 170 | 59 | 243 | 72 | 355 | 85 | 515 |
| 47 | 175 | 60 | 250 | 73 | 365 | 86 | 530 |
| 48 | 180 | 61 | 257 | 74 | 375 | 87 | 545 |
| 49 | 185 | 62 | 265 | 75 | 387 | 88 | 560 |
| 50 | 190 | 63 | 272 | 76 | 400 | 89 | 580 |
| 51 | 195 | 64 | 280 | 77 | 412 | 90 | 600 |
| 52 | 200 | 65 | 290 | 78 | 425 | 91 | 615 |
| Dimension conversion | |||||
| bar | psi | Bar | psi | Bar | psi |
1. 2 | 17 | 1.9 | 28 | 2.6 | 38 |
| 1.3 | 19 | 2.0 | 29 | 2.7 | 39 |
| 1.4 | 20 | 2.1 | 31 | 2.8 | 40 |
| 1.5 | 22 | 2.2 | 32 | 2.9 | 42 |
| 1.6 | 23 | 2.3 | 34 | 3.0 | 44 |
1. 7 | 25 | 2.4 | 35 | 3.1 | 45 |
| 1.8 | 26 | 2.5 | 36 | 3.2 | 46 |
| Rim section height. Motorcycle tire width. Rim width. Disc width | |||
| Rim width, inches | Tire width, mm | ||
| 6.50 | 200 | ||
| 6.25 | 200 | ||
| 6.00 | 180 | 190 | 200 |
5. 5 | 180 | 190 | |
| Tire profile height 60, 65 and 70% | ||||
| Rim width, inches | Bar width mm | |||
| 6.50 | 230 | |||
| 6.25 | 200 | 230 | ||
| 6.00 | 200 | 230 | ||
| 5.50 | 170 | 180 | 200 | |
| 5.00 | 160 | 170 | 180 | |
4. 50 | 140 | 150 | 160 | 170 |
| 4.25 | 140 | 150 | 160 | 170 |
| 4.00 | 130 | 140 | 150 | |
| 3.75 | 120 | 130 | 140 | |
| 3.20 | 120 | 130 | ||
| 3.00 | 110 | |||
25 
75-16 
85-3.00 
85-3.00 
85-2.50 
25/85-18 
25-19 
00-21 
