×
Offers now live ends in 0d 14h 15m 42s
Up to 15% off even more tyres
More deals added from Michelin, Continental, Bridgestone, Pirelli and Goodyear
Tyres  /  Tyre NewsHelp and Advice  / Motorcycle Tyre Dimensions Explained

Motorcycle Tyre Dimensions Explained

Motorcycle Tyre Dimensions Explained

Motorcycle tyres have slightly different dimensions and features compared to car tyres.

There may be numbers and letters on your motorcycle’s tyre sidewall that you might not understand, not being familiar with the ZRs or M/Cs scattered across the tyre.

We’ll be covering every motorcycle tyre dimension and explaining what each mean to give you a better understand on general motorbike tyre sizes.

A tyre's sidewall outlining a tyre size

Motorcycle Tyre Size

On the surface, motorcycle tyre sizes are confusing – but they don’t have to be.

As shown in our visual guide to motorcycle tyre dimensions below, the sidewall of your tyre will display key specifications for that particular model.

Graphic explaining motorcycle tyre sizes

Each displayed words, numbers or letters have meaning, so let’s explore what the main dimensions are for a tyre size.
 

Tyre Width

This number indicates the tyre’s section width in millimetres, measured from sidewall to sidewall.

For example, in 120/70 R17 M/C (58W), the “120” refers to a width of 120mm. This is a nominal value and can vary slightly depending on the rim width the tyre is mounted on.
 

Aspect Ratio

This is the height of the tyre’s sidewall expressed as a percentage of its width. In our example, the aspect ratio is “70”, meaning the height is 70% of 120mm – which is 84mm.

A lower ratio like 55 would result in a lower-profile, sportier tyre, while a higher ratio like 90 is typically found on touring or classic motorcycles.
 

“ZR”, “R”, or “B”

If your tyre has “Z” on its sidewall, it indicates a high-speed rating, meaning the tyre is approved for speeds exceeding 149mph (240km/h).

“ZR” means a high-speed rating and that the tyre has a radial construction – the "R" standing for radial.

Many high-performance bikes use ZR-rated radial tyres, especially in sizes like 180/55 ZR17, whereas typically road bikes will tend to use standard radial constructed tyres, such as 120/70 R17.

If a tyre has a “B” marking (e.g. 170/80 B15), it indicates a bias-belted construction – a hybrid between bias-ply and radial – offering increased load capacity and improved ride comfort, commonly found on cruisers and touring motorcycles.
 

Rim Size

This indicates the diameter of the wheel (rim) the tyre fits, measured in inches. In 120/70 R17, the “17” means the tyre fits a 17-inch wheel.

Common motorbike rim sizes range from 10" on scooters to 21" on off-road bikes, but 17" is the standard for most sport and street motorcycles.
 

Other Tyre Dimensions Explained

While width, aspect ratio, and rim size make up the core of a tyre’s sizing, several other markings on the sidewall play an equally important role in safety, fitment, and performance.

These include construction types, compatibility, load ratings, and directional fit – all essential to understand when choosing the right motorcycle tyres.
 

“M/C”

This stands for “Motorcycle” and confirms that the tyre is designed specifically for motorbikes.

It’s important not to confuse motorcycle tyres with scooter tyres or car tyres, which may have similar markings but are engineered differently.

 

“Tubeless” or “Tube-type”

This tells you whether the tyre is designed to run without an inner tube (Tubeless) or requires one (Tube-type).

Tubeless tyres are common on modern bikes with cast wheels, such as the 190/50 R17.

Tubeless rear tyre found on many sports bikes, while Tube-type tyres are often used with spoked rims on off-road or adventure bikes.
 

“Load Index”

The load index is a numerical code that indicates the maximum weight a tyre can safely carry.

For example, “52” corresponds to a maximum load of 190kg per tyre.

See the following tyre load index table for reference:

Table of a tyre load index from 20 to 99

Always ensure the replacement tyre has an equal or higher load index than what’s recommended for your bike.
 

“Wheel Rotation”

The direction of wheel rotation is usually marked on the tyre with an arrow.

This ensures the tread pattern performs optimally for water dispersal and braking.

Fitting the tyre against its marked rotation can impact handling and safety, particularly at high speeds or in wet conditions.
 

Final Thoughts

Motorcycle tyre dimensions might seem like a maze of numbers and letters at first glance, but once you know what each part means, it becomes much clearer.

From tyre width and aspect ratio to speed ratings and construction types, understanding these markings is key to choosing the right tyres for your bike.

So next time you’re browsing for new motorcycle tyres, take a moment to check what’s written on the side of your current tyres and make sure to order the right size!

Buy motorcycle tyres
Buy new tyres at Blackcircles.com
Want exclusive motoring news?

Subscribe to our newsletter for the latest EV, Performance, SUV & 4x4 content

Join our mailing listSign up
Back to news

Join the conversation

We love to hear from our customers. Connect with us today and let’s start a conversation.

PayPal
Representative Example: Purchase rate: 23.9% p.a. (variable). Representative: 23.9% APR (variable). Assumed Credit Limit: £1,200

PayPal Credit and PayPal Pay in 3 are trading names of PayPal UK Ltd, 5 Fleet Place, London, United Kingdom, EC4M 7RD. Terms and conditions apply. Credit subject to status and approval, 18+ UK residents only. PayPal Credit and PayPal Pay in 3 are a form of credit, so carefully consider whether the purchase is affordable and how you will make the repayments. PayPal Pay in 3 is not regulated by the FCA. See product terms for more details and FAQs. Learn more about PayPal Credit.  Learn more about PayPal Pay in 3.