How to Read an E-Bike Tire Sidewall

Your tire's sidewall holds a handful of separate codes, and they're easier once you sort them into groups. Size, pressure, direction, build and e-bike rating. Each group answers one question, so you don't have to decode everything at once.

The size code

Size is the code most people notice first. Michelin says a bike tire's size is probably printed in one of three ways: ETRTO, imperial or metric. Its examples are 23-622, 29 x 2.10 and 700 x 23C.¹

Many tires print two of these, or all three. They aren't different tires. They're the same tire described in different "languages."

The ETRTO style is the modern one. It's defined by an international standard, ISO 5775, and the older inch and French-style codes can be ambiguous.² Michelin says the ETRTO code gives the tire's inflated width and the rim's bead seat diameter, both in millimeters, in one code.¹

That second number is the one that must match your wheel. The page ETRTO and Inch Tire Sizes Explained goes through it slowly.

The pressure marking

Look for words like "Maximum Pressure" or "Inflate to." The maximum pressure rating of a tire is usually stamped on the sidewall.²

It's a limit for the tire, not a promise about what's right for your bike. Your bike maker's manual is the place to check. Max and Min Pressure Markings on a Tire covers how the two fit together.

The arrow

Most Schwalbe tire sidewalls carry a "ROTATION" arrow, which indicates the recommended rolling direction.³ There are also treads without a specified rotating direction, so a tire with no arrow isn't necessarily missing anything.³

If you do find one, Rotation Arrows and Mounting Direction explains what to do with it.

Build codes

Short letter codes tell you how the tire is made. Michelin's glossary lists several:

• GW (Gum Wall): the sidewall is coated with a layer of rubber to give it stiffness and protect it.¹
• WB (Wire bead): the bead, the edge that grips the rim, is steel and cannot be folded.¹
• TLR (Tubeless Ready): Michelin says these tires can be fitted without an inner tube provided that a tubeless wheel is used, the maximum pressure is not exceeded, sealant is added and the tire pressure is checked before each ride.¹

Other makers use their own abbreviations. If a code isn't in a glossary you trust, look it up on the tire maker's own site rather than guessing.

E-bike marks

Some tires carry an E-25 or E-50 mark. Michelin describes E-25 bikes as electric-assisted bikes with assistance until 25 km/h.¹ Continental says tires marked E50 are also certified for S-Pedelecs.⁴

These labels get their own page: What 'E-Bike Rated' and Speed Labels on a Tire Mean.

What if a code isn't on this page?

Check the tire maker's own technical page for that model, and read your bike's manual. When a general guide and your own tire's maker disagree, go with the maker.