Mountain Bike Size & Fit Guide — Frame Size by Height

The right frame size is the difference between a bike that disappears beneath you and one that fights you on every climb. This guide covers the basics — and the mistakes we see most often.

The quick height chart

Rider height	Frame size	Typical use
155–165 cm	S	Teens, smaller adults
165–175 cm	M	All-round trail
175–185 cm	L	XC & trail
185 cm+	XL	Tall riders, endurance

Inseam beats height

Stand against a wall, measure crotch to floor. A longer inseam lets you size up for stability; a shorter one means size down for clearance. When standover is tight, always go smaller — you can't unclip fast enough otherwise.

Reach and stack

Modern geo is described by reach (horizontal distance, drives roominess) and stack (vertical, drives upright vs racy). A longer reach with a short stem is the current trail standard; the MEIRX TJ985 uses exactly this.

Dirt jump sizing is different

DJ frames run small and stiff on purpose — you want control in the air, not stretched-out comfort. See the MEIRX Dirt Jump geometry notes.

Still unsure?

Send us rider heights and inseams for your order and we'll spec frames per rider — that's what OEM and bulk programs are for. Or run the Bike Finder for a recommendation.