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

A motorcycle 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. For pressures, see our tyre 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 and Wheels & 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.