• Rotor Rex 2.1 MTB Crankset

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Rotor Rex 2.1 MTB Crankset

With a growing demand, Rotor is committing to a separate mountain bike crank line named “Rex”. The additional line, with its own designation and design will help to clearly distinguish the Rotor MTB from the road crank line.

The new Rex MTB cranks are based on the same successful “Trinity Drilling System” technology as all Rotor cranks, which help reduce weight and maximize stiffness. The Rex 2.1 crank, the first number indicates the level, the first number indicates the level, and the second number indicates the number of rings, in this case it is 1 single chainring, the new QX1 ring.

UBB30 axles ensure maximum frame compatibility, and cranks are available in several arm lengths including most common 170, 172.5 & 175mm. In addition, Rex 2 cranks are manufactured in 7075 alloy, making them even more durable.

UBB30 technology

The REX 2 uses ROTOR’s ultra-rigid and UBB30 technology (developed for the 3D+), offering a performance upgrade opportunity for almost all bikes on the market – whether they were designed for 30mm cranks or not.

Cold forged, trinity drilled

The REX’s cold forged, trinity drilled arms and aluminium UBB30 axle ensures serious rigidity and performance to face anything you can throw at it, while saving weight in regards to the majority of 24mm cranksets.


The REX 2’s axle technology comes from our UBB concept, which is compatible with most bottom bracket standards on the market. This allows for surprising and unexpected new options for upgrading bikes of any BB type: our groundbreaking UBB30 axle concept is compatible with BSA (68 & 73), ITA, BB86, BBB89, BB92, BB30, & BB386 evo.



ROTOR's trinity drilled crank arms resist bending and twisting forces better than classic hollow tube crank designs can. ROTOR’s crank arms are stiffer than the competitions products due to our Trinity Drilling System and material. This process drills three full-depth holes from axle to pedal. This gives our crank arms superior rigidity and an exceptional stiffness-to-weight ratio.


Adapts to all.

The UBB (Universal Bottom Brackets) concept is simple: it fits everything. UBB is a design concept that Rotor applies to all its cranksets to make them compatible with all BB standards and frames on the market. It allows installation of almost any crank with a 30 or 24mm axle from ROTOR on the bike you have, regardless of its BB type.


  • 511 grams REX 2.1, 170mm.
  • 170, 172, and 175mm.
  • REX 2.1 BCD 76mm x 4.
  • 100% CNC, extruded, T6 7075.
  • Q-Factor 163mm, Chain Line 56mm (REX 2.1).
  • Ultra stiff steel 30mm UBB axle compatible with BSA, ITA, BB86, BB90, BB94, and BB30 frames.
  • QX1 chainring not included.
  • Rotor chainrings & road cranks compatibility chart (.PDF) - Here you will find the specific Rotor chainring designed to work with your crank.

Buy Rotor Components from Chain Reaction Cycles, the World's Largest Online Bike Store.

  • Delivery costFREE
  • Delivery toUSA
  • 365 Days return or exchange

    If you're not completely satisfied with an item you may return it within 12 months of purchase. We'll give you a full refund if the item hasn't been used or the component hasn’t been fitted.

    More information on returns
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Buying Guide

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