Review: Rotor REX 1.1 cranks

First published in Singletrack Magazine issue 99

Firstly, let’s talk about wibbly chainrings, as no conversation about Rotor will avoid it. Elliptical, or oval, chainrings are designed to even out the power output of that high torque, low-rev powerhouse that you run. While you may think that your pedalling action is that of a perfectly balanced washing machine on spin cycle, in reality, you’re barely doing more than mashing the cranks up and down, twice a second.

Oval chainrings are designed to subtly (and sometimes not so subtly) even out your pedal stroke, so that the strong part of the cycle (the bit where your thighs are extending) has a higher, harder gear than the ‘over the top’ bit where your legs can struggle to keep that power delivery smooth. Rotor has been singing the praises of elliptical chainrings for years. The Rex crank is a one-by chainset that provides a handy pre-packaged single chainring chainset with huge 30mm bottom bracket axle and outboard bearings (in this case, there are press-fit bottom bracket versions too).

Installation was simple enough (removal is another matter, but we’ll get to that) and I was soon off on a ride and waiting for the weirdness to kick in. You can definitely feel the effect, but the initial sense of ‘this is different’ disappears after, or even before, the end of your first ride on them. This is then replaced by something very different; the regular changing of the gear size is not felt as a stiffening and relaxing of the effort, as I thought it would be, but instead there’s a much quieter, calmer sensation. The pedal stroke is suddenly far more even-feeling and instead of getting a binary big gear/small gear feeling, instead I could see how choppy and up/down my regular pedalling motion was compared to with this oval ring. While it’s easy to imagine a smoother power output at the tyre, I couldn’t measure that – but I could really feel that there was no longer an easy and hard part of each pedal stroke: just a single smooth flat line.

That’s the mechanics of the pedalling. The mechanics of the cranks are also interesting and it’s very obvious that Rotor is a company run by bronzed cyclists who care about getting the miles in and saving weight on their bikes. The cranks are a very impressively low weight, although this is achieved at the expense of a little ease of maintenance – removing the cranks means much faff swapping bolts and washers around, and though it’s not something you’re going to do regularly, it’s a right pain.

The chainring, meanwhile, is bespoke. Although four chainring bolts hold it on, the bolt pattern is proprietary – which makes it impossible to install the chainring in the wrong orientation, as well as making it harder for aftermarket firms to knock up replacement rings. Saying that though, this ring I have seems to be lasting well and, when clean, the cranks look great and are still running smoothly despite my usual lack of aftercare.

Overall:

I was looking forward to complaining about how odd it felt to ride this oval ring, one-by set-up, but in reality, I think I’ve been converted. As a lifelong gear masher, I’m looking forward to the new, smooth-pedalling future me.

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