How to read a motorcycle tyre sidewall: size, load index, speed rating and date code

Read the sidewall left to right. A marking like 140/60 R 17 is the size: 140 is the section width in millimetres, 60 is the sidewall height as a percentage of that width, R is radial construction and 17 is the rim diameter in inches, as TVS Eurogrip sets out in its own tyre marking guide. The two characters that follow the size are the load index and the speed rating. The four digits stamped in an oval are the week and year of manufacture. Everything else on the wall is either an approval mark or a fitting instruction.

The size, and the letters mixed into it

Pirelli's example of a sports bike rear is 190/55 ZR 17 M/C (75W). M/C simply means motorcycle. The Z in ZR is part of the construction and speed group, with R meaning radial. On most Indian commuters you will see a dash instead, as in 100/90-17, which marks a cross ply or bias tyre rather than a radial.

Two words on the wall decide whether the tyre can run without a tube. Michelin lists TL for tubeless, and Pirelli says the word TUBELESS appears on tyres suitable for tubeless use. An arrow shows the direction of rotation, and an asymmetric tyre carries a marking for the side that must face outwards, which TVS Eurogrip flags as a fitting error riders do not notice until the tyre wears oddly.

Load index and speed rating, in kilograms and km/h

This is the part most owners skip. Michelin India's example, 120/70 ZR 17 M/C 58W, works out as a load index of 58, which it gives as a maximum load of 236 kg, and a W speed rating, which it describes as a speed above 270 km/h. Pirelli's 75 is 387 kg. A rating in brackets means "above" that figure.

The speed letters are not alphabetical, which is why they confuse people. TVS Eurogrip's table runs J at 100 kmph, L at 120, M at 130, P at 150, S at 180, T at 190, H at 210, V at 240 and W at 270. Note that H sits between U and V, not next to J. TVS Eurogrip's advice is to use a tyre whose speed rating matches or exceeds what the bike can do, and it says makers normally pick a rating around 20 per cent above the vehicle's capability.

So if your owner's manual calls for 54P and the shop offers a tyre marked 54J because it is in stock and cheaper, you are buying down two steps of speed rating for the same money saved on one service.

Date code, TWI and the ISI mark

Michelin explains the DOT code as a sequence ending in four digits, the first two being the week of manufacture and the last two the year. Pirelli's worked example is 0320, meaning week 3 of 2020. Ask for the code before you pay. A tyre that has sat in a godown for two years is still new, but it is not fresh.

For wear, look for the tread wear indicators. ATMA, the Indian tyre makers' body, defines them as projections inside the tread grooves, present in the main grooves and in the shoulder at a minimum of six places around the circumference. Michelin says these indicators stand 0.8 mm high. ATMA's limit is the same figure: tyres with a non skid depth below 0.8 mm on two and three wheeler tyres are unsafe to use, against 1.6 mm for other motor vehicles.

Two more Indian checks. ATMA says fitment must conform to Indian regulations, including ISI marking on the sidewall, so look for it on anything sold here. And it warns that tyre and rim components must match, because a mismatched assembly may explode. That is worth remembering the next time someone suggests a wider rear tyre on a stock rim.

Sources

• TVS Eurogrip: how to read a two-wheeler tyre marking
• TVS Eurogrip: motorcycle tyre speed rating and load rating
• Pirelli: tyre markings, tips to choose the right ones
• Michelin India: motorcycle tyre speed rating and load rating
• Michelin: how to read a motorcycle tire
• Michelin India: motorcycle tyre tread depth and the legal limit
• ATMA: tread wear indicator
• ATMA: selecting the right tyre