First Look: Rotor Rex 1.1 crank and 1x chainring

Oval rings and lightweight cranks in the 1x Narrow/Wide configuration


Rotor Rex Set

Rotor has successfully brought back the oval chainring with proven science and results. This Spanish company has continued to innovate with incredibly light and stiff cranks mated with their oval rings. For us, the oval rings relieve stress on the knees and hips and increase output, while decreasing pain. In a nutshell, our experience can be summarized as it’s “like having a 39 tooth chainring when going over the top of the pedal stroke, but having a 42 tooth ring at the most powerful part of the stroke.”

Rotor Narrow Wide Ring

We’ve found two downsides though and they are:

  • All the other bikes in the fleet with round chainrings feel unnatural/odd after getting used to the Rotor oval chainring. The solution for this is to buy chainrings for the other bikes in the fleet.
  • The front shifting is compromised as it is indeed harder to shift and tune the derailleur for the front oval rings.

Well the onset of 1×11 drivetrains is here to the rescue for the front shifting issue as it is totally eliminated with a 1x setup. Rotor came up with a Narrow/Wide oval ring and we were excited to try it out. They sent us their Rex 1.1 setup with a PressFit 4130 bottom bracket. They also insisted we try a 172.5mm crank length, since they’ve found that to work well with their rings and with these new bikes with lower bottom brackets.

Rotor Crank with Massive Spindle

So we put it on and so far so good. There’s no dropped chains and no shifting issues of course. We are seeing the benefits of the oval ring. With only one ring in front, the oval ring gives us a more ideal ring with good top end, but we seem to have an extra gear on those very steep wall climbs. The crank is incredibly stiff as well, and we like the more direct and efficient power transfer.

Rex 1 Crank Specifications
  • Arm Material: 7055 Alloy
  • Arm Length: 170 mm, 172 mm, 175 mm
  • Chainring Sizes: [not included]
  • Rings: 0
  • Spindle: 30mm, 24mm
  • Compatible Components: Rotor QX1/No-QX1
  • Claimed Weight: 489 g
  • MSRP: $500
QX1 Chainring Specifications
  • Material: aluminum
  • Number of Rings: 1
  • Teeth: 28 t, 30 t, 32 t, 34 t, 36 t
  • Compatible Components: SRAM XX1, [with adapter] Specialized , Rotor REX 1.1, 2.1
  • Claimed Weight: [28t] 50 g
  • MSRP: $125

Actual weight photos are shown below.

Rotor Crank Weight for 172mm

System weight with 172mm length cranks.

Rotor Ring Weight

30 tooth chainring weight.

Rotor BB Weight

BB weight with all the spacers.

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About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a dirt jumper, singlespeed, trail bike, lugged commuter or ultralight carbon road steed. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. Francis also believes that IPA will save America.

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  • Peter Cain says:

    I wonder how the clutch derailleurs would deal with that constant chain length change.

  • Cheese says:

    @ Peter Cain, I had the same question. I didn’t want the clutch derailleur to be constantly pumping, eating up energy. It has turned out not to be a problem though. The difference in chain tension is BARELY noticeable. The tiny amount of movement in the hanger probably didn’t even engage the clutch. I now use the Qring singlespeed and itworks perfectly for that too.

  • Banshee956c says:

    I wish they’d offer their oval n/w ring in a 104bcd format, I like rotor cranks, I have one on my road bike, but I’m not going to spend that kind of money on the cranks when I already have a set of sixc

  • joeshmoe says:

    Are they available without the fugly graphics? Seriously, that’s a deal breaker.

  • Sun says:

    I just wish this chain ring was available for my GXP XX1 as I’d have ordered it 6 months ago.

  • David says:

    A 104 format would limit choice of rings to 34t and up or 32 if you go offset like the 30t round ring. If you want the 104 format go with 34T ss non-NW + MRP 1X. I did. XX1 and Sram X0 compatible with QX1 adaptor. The longer downstroke gives me more traction on my trail bike and I can maintain a lower rpm too. My 2 cents.

  • Endless Bikes says:

    Interesting, I think we have a 1x chainring that’ll work for it.

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