Wheels

Wheel size

Mountain bikes roll on 26′′, 27.5′′ or 29′′ wheels. Bigger wheels roll over obstacles more easily and carry speed; smaller ones are quicker to turn and throw around.

Also known as: 29er, 27.5, 650b, 26 inch wheels

Key facts

Standard
ISO 559, 584 and 622 mm bead seat
Size
26″, 27.5″ and 29″

The three sizes

  • 26′′ (ISO 559) — the original mountain-bike size; today mostly on dirt-jump bikes.
  • 27.5′′, also called 650B (ISO 584) — playful and strong; common on smaller frames and in the back of mullet bikes.
  • 29′′ (ISO 622) — rolls over roots and rocks, holds momentum and grips; the standard on most new mountain bikes.

What a bigger wheel changes

A larger wheel meets an obstacle at a gentler angle, so it rolls over instead of stopping, and its longer contact patch grips better. The price is a little more weight and a bike that asks for more effort to flick from side to side.

Mixed wheels

Many enduro and downhill bikes run a 29′′ front and a 27.5′′ rear — the mullet. The big front wheel rolls over the trail; the small rear one leaves room behind you on steep ground.

Related articles

  • Hardtail — A mountain bike with a suspension fork and a rigid rear end: light, simple, cheap to keep running — and the bike that teaches you to ride well.
  • Full-suspension bike — A mountain bike with suspension at both ends. The rear shock keeps the back wheel on the ground over roots and rocks, which means more grip, more control and less fatigue.
  • Tubeless tyres — Tyres that seal directly to the rim with no inner tube, holding liquid sealant that plugs small punctures as you ride. Less weight, fewer flats and more grip at lower pressure.
  • Mullet — A bike with a 29′′ front wheel and a 27.5′′ rear: the big wheel rolls over the trail, the small one keeps the back end agile and out of your way on steep ground.
  • Frame geometry — The angles and lengths that decide how a bike rides: stable or nimble, easy to climb or eager to descend. Every model publishes them in a geometry chart.
  • Boost — The hub-width standard of most modern mountain bikes: 110 × 15 mm at the front and 148 × 12 mm at the rear. Wider hubs make stiffer wheels and leave more room for tyres.