# How to Read Motorcycle Tyre Sizes: 120/70-17, Load Index, Speed Rating and DOT Code

> The size on a tyre sidewall gives width, aspect ratio, construction and rim diameter. Learn to read load index, speed rating, TL/TT and the production date, and what happens if you fit a different size.

- **Author:** Motorsiklet Parçası
- **Published:** 2026-10-09
- **Updated:** 2026-11-08
- **Tags:** lastik, jant, güvenlik
- **Cover image:** https://motorsikletparcasi.com/uploads/blog/covers/motosiklet-lastik-olcusu-nasil-okunur.webp
- **Page:** https://motorsikletparcasi.com/en/blog/how-to-read-motorcycle-tyre-sizes

**A [motorcycle tyre size](https://motorsikletparcasi.com/en/glossary/tyre-size) reads like “120/70 ZR17 58W” on the sidewall: 120 mm width, 70% aspect ratio, radial construction, 17-inch rim, load index and speed rating.** When replacing, use the front and rear size, load index and speed rating in your manual or on the frame label.

## Metric size: 120/70 ZR17 58W

| Part | Meaning |
| --- | --- |
| 120 | Tyre width (mm) |
| 70 | Sidewall height as a percentage of width (70% → about 84 mm) |
| R / ZR | Radial construction (ZR: radial rated above 240 km/h) |
| \- (dash) | Bias-ply construction, e.g. 90/90-14 |
| 17 | Rim diameter (inches) |
| 58 | Load index (maximum load per tyre) |
| W | Speed rating (maximum speed the tyre can sustain) |

The **130/70-12** size common on scooters means 130 mm width, 70% aspect ratio, bias-ply construction and a 12-inch rim.

## Inch sizes: 3.00-10, 2.75-18

Older and smaller bikes give the width in inches. A **3.00-10** tyre is about 3 inches (76 mm) wide for a 10-inch rim. These sizes don't state an aspect ratio; it's usually close to 100%. Inner tubes use the same system.

## Load index table

| Index | Max load (kg) | Index | Max load (kg) |
| --- | --- | --- | --- |
| 46 | 170 | 58 | 236 |
| 48 | 180 | 60 | 250 |
| 50 | 190 | 62 | 265 |
| 51 | 195 | 65 | 290 |
| 54 | 212 | 69 | 325 |
| 55 | 218 | 73 | 365 |

## Speed rating table

| Symbol | Max speed | Symbol | Max speed |
| --- | --- | --- | --- |
| J | 100 km/h | R | 170 km/h |
| L | 120 km/h | S | 180 km/h |
| M | 130 km/h | H | 210 km/h |
| N | 140 km/h | V | 240 km/h |
| P | 150 km/h | W | 270 km/h |

A new tyre's load index and speed rating must not be lower than the values in the manual.

## TL, TT and other markings

- **TL (Tubeless):** used without an inner tube; the rim must also be tubeless-compatible.
- **TT (Tube Type):** used with an inner tube; common on spoked wheels.
- **Rotation arrow:** fit the tyre so it turns in this direction. Front and rear may have different arrows.
- **TWI / wear indicators:** raised bars in the grooves; replace the tyre when the tread reaches them.
- **M+S, Reinforced:** indicate a mud/snow pattern or reinforced construction.

## Reading the production date (DOT)

The last four digits of the DOT code give the production week and year: **2524** means week 25 of 2024. Even unused, rubber hardens over time and loses grip; a tyre with ageing cracks should be replaced regardless of tread depth.

## What if I fit a different size?

- **Speedometer error:** a smaller-diameter tyre makes the speedometer read high; a larger one makes it read low.
- **Handling changes:** width and aspect ratio affect turn-in and stability.
- **Clearance:** a wider tyre can rub on the chain, swingarm or fender.

To see a different size's diameter, circumference and speedometer deviation, use our [tyre size calculator](https://motorsikletparcasi.com/en/tools/tire-size-calculator). For pressures, see our [tyre pressure guide](https://motorsikletparcasi.com/en/tools/tire-pressure-guide).

## Tyre buying checklist

1. Size: front and rear size from the manual
2. Load index and speed rating: not lower than the manual
3. Construction: radial/bias match (don't mix front and rear)
4. TL/TT: suits the rim and tube situation
5. Production date: as recent as possible

Browse compatible products in our [Motorcycle Tyres](https://motorsikletparcasi.com/en/category/motorcycle-tyres) and [Wheels & Hubs](https://motorsikletparcasi.com/en/category/wheels-and-hubs) categories.

## How tyre pressure affects wear

- **Too low:** sidewalls flex and heat up; the shoulders wear quickly, fuel consumption rises and the steering feels heavy.
- **Too high:** the contact patch shrinks; the centre wears quickly, wet grip drops and the ride gets harsh.
- **Correct:** the tread wears evenly and braking and cornering grip are as designed.

Check pressures cold, at least monthly and before long trips; with a passenger or luggage use the manual's loaded values.

## Don't forget when changing tyres

- On tubeless rims, renewing the valve reduces the risk of leaks.
- New tyres must be balanced; an unbalanced wheel vibrates at speed.
- A tyre change is a good opportunity to check wheel bearings and the brake disc.
- New tyres grip less for the first 100–200 km because of release agent on the surface; avoid sudden lean and hard braking.

## Frequently asked questions

### Can I fit different brands front and rear?

It's possible, but handling characteristics can differ, so manufacturers usually recommend the same brand and range. Radial and bias-ply tyres must not be mixed front and rear.

### How often should tyres be replaced?

Rubber ages even with enough tread. Replace tyres with ageing cracks, hardening or deformation, and have older tyres checked by a specialist.

### Can I fit a tubeless (TL) tyre on a tube-type (TT) rim?

A tubeless tyre can be used with an inner tube, but a spoked (tube-type) rim isn't suitable for tubeless use, so an inner tube must be fitted.

### How often should I check tyre pressure?

At least once a month and before every long trip, with the tyres cold. Motorcycle tyres have a small air volume and can lose pressure quickly; low pressure hurts both grip and tyre life.

---

- Source page: https://motorsikletparcasi.com/en/blog/how-to-read-motorcycle-tyre-sizes
- Last updated: 2026-11-08
- Türkçe sürüm: https://motorsikletparcasi.com/blog/motosiklet-lastik-olcusu-nasil-okunur.md
- Site overview: https://motorsikletparcasi.com/en/llms.txt
- Append .md to the URL of any product, category, motorcycle, brand, blog or company page on this site to get its Markdown version.