Rotor QX2 110/74 Inner Chainring

When you’re crawling up a brutally steep incline covered in scree, you want power and traction. This is where Rotor’s  QX2 74mm Inner Chainring excels. This ring fits on five-arm spiders with a 110/74mm bolt circle diameter.

Mountain biking might be one of the best places to apply Rotor’s Q-Ring concept. At low rpms riding over a surface that your tires are barely clinging to calls for steady power application if you’re to get through without dabbing. The ovality of the rings, here 10%, means that your legs will speed through the dead spots in your stroke, where you’re least able to apply power, and power through the points where you’re strongest. While the effective chainring diameter is constantly changing, the power you’re applying is nearly steady. And this means that the bike is rolling at a more constant pace rather than lurching and stalling. Interestingly, and very much to the point, this is not the much-maligned Shimano Bio-Pace that appeared and disappeared years ago. It’s very much the reverse, and it’s much more effective.

Rotor offers the 74mm bcd QX2 in 25 or 27 tooth options. The 25 varies from an effective 26.25 at your strongest to a 23.75. Basically, a 26at the most powerful point in your stroke to a 24 at the weakest. This might give you the mind to ride a bigger big than your current round ring, but Rotor recommends sticking with the same size.

Getting the most out of these rings requires tuning them. Rotor makes them adjustable-that’s what all the extra bolt holes are about. There are three adjustment points. There’s a guide that comes with the rings explaining how to tune them to your stroke.

Mountain bike chainrings take lots of abuse. That’s why Rotor CNC-machines them out of 7075 aluminum plate. They are relieved of all excess material to minimize rotating weight. The precision work at the factory results in longer life and better shifting on the trail.

The QX2 Inner Ring can be mated to a round (noQ) or QX2 outer ring.

The Rotor QX2 110/74mm Inner Chainring not only powers you up hill, but improves your traction.