Teardown: ROTOR 2InPower Crankset 30mm
One viewer of the Hambini YouTube channel sent in a bike for service and a new bottom bracket. This bike was fitted with a Rotor power meter crankset. In the process of making a new BB for this bike, the rotor crankset was measured and checked. This post covers the engineering and a general opinion of the construction. If you want a review of the Power meter accuracy, this will not be covered in this guide.
A hot topic in many internet forums is which power meter to get. This situation is muddied because of the varying axle and bottom bracket combinations that exist.
Introduction: Rotor Bicycle Components
Rotor are a Spanish company that have long been associated with cranksets and more recently entire goupsets. Their offerings have not always gone well. Their UNO groupset came out when there was a paradigm shift from mechanical to electronic and finally wireless shifting. It was left languishing and very few have been spotted out in the field.
Mechanically, this crankset represents a complete overhaul of the Rotor crankset system. Large elements have been copied from Shimano’s Hollowtech 2 system. Here are some of the mechanical bits in brief:
- 30mm Aluminum axle
- 90-92mm DBCA (Distance Between Crank Arms)
- Axial preload adjuster integrated into the non drive side crank arm.
- Single pinch bolt system for the non drive side crank arm
- Lightened aluminum alloy crank arms
- Accepts standard 130BCD rings and Q Rings
- This particular unit has an integrated power meter
This crankset is a different animal. From the outset it is well engineered
Geometrical checks were carried out to establish the true quality of the manufacturing. The axle appears to be pre-machined before a final grinding process on the bearing landings.
The diagram below is an approximation of the measurements taken. A is the datum, P and Q are measures of roundness and indicate the bearing landings. X and Y are run outs and they indicate the amount of bend, strictly speaking the runout at X is the same as the out of roundness of P
For all practical purposes, the runouts and deviation were less than 0.01mm which can be considered to be zero and thus very good.
Improved Preloading system
A common theme across bike cranksets is poor preloading systems. The displacement type preloading systems such as those used by Shimano are the best. Wave washers are effective but adequate knowledge and use of shimming is required to obtain the best performance. This is often beyond the scope of expertise of most amateur mechanics and even some bike shops.
This rotor crankset has a preload system which is a larger version of that found on the Shimano Hollowtech cranks. A preload bolt on the end of the non drive side crank moves the crank arm in and out and provides displacement level preload adjustment. This is easy to use and mechanically effective.
Installation into a Cervelo Frame with a Hambini Bottom Bracket
This crankset was installed into a Cervelo bike frame with a Hambini Bottom bracket. The final fit and finish were very good. No shimming of the crankset was required
This is a well engineered product. Rotor have really made some vast improvements, the quality of the machining and geometrical accuracy are amongst the best out there. If you are in the market for a 30mm crankset, then this is recommended.
Phew. I have two of these and when I see something show up on Hambini I brace for the inevitable news that I’ve bought something with great marketing and poor engineering!
You have to give credit where it is due. This is a well engineered product
Same here… was ready to throw it away..
Any thoughts on this catastrophic failure of an Aldhu 24? Includes pics.
Next but one post after that is also a bit concerning.
Both relate to the steel 24mm system as opposed to their newer 30mm alu system as reviewed here.
It looks like the drive non drive side bearing has been misaligned and fatigued the axle from the photographs. There are running tracks on that side.
Reassuring to see…
I have an older Rotor 3D24 which I got via P2M with a power meter spider several years ago – it’s fitted on a 2014 Cannondale Supersix hi-mod (one of the older CPC frames that got through the Hambini roast without too much of a kicking).
I use an outboard bearing BB86 because it originally had a Shimano 6800 crank (BB30/PF30 narrow span also makes no sense to me).
The rotor crank seemed nicely machined, particularly the idea of machining the NDS arm in it’s closed position then spreading it to fit the spindle.
The bearing diameters seemed to be ok (not sure about axial alignment, concentric between sides or circularity etc as I only had calipers and buttered fingers to measure it with); plus I like the pre-loading method that’s similar to shimano as it’s easy to fine tune.
Worth putting a dab of medium duty thread-lock on the alu. pre-load cap (Loctite 248 or similar); mine bounced out one day and it was a cock on + expense getting another from Rotor.
A slight issue I have is with the double threaded bolt, due the the way it is designed – when you are turn anti clockwise to slacken the bolt to remove the crank arm the bolt will slacken initially (like a cotter pin) then tightens again to spread the crank arm to release from the axle.
I becomes impossible to to know if you are un tightening the initial phase (that has maybe been over tightened) and the bolt is tight or coming up to the end stop of the crank release phase.
Unfortunately the bolt is steel and the crank arm is aluminium, their is a sacrificial sleeve on the course thread, however on the finer thread end in the crank arm, the crank become the sacrificial portion as the alu thread is easier to strip, than the steal of the bolt. to compound the problem – the crank thread being a finer thread it loads that end higher than the course thread with the sacrificial insert – leaving the fine thread in the crank as the weakest point
It should have an inset at both ends if you are going to use an insert or just do away with the DTT and remove the bolt – insert from the other side to spear the crank arm to release. Trying to be too clever. You would think they realised that by slapping warning stickers all over it saying ‘do not remove bolt’
Hi David, is this on the non drive side of the bike you are referring?
Hello Hambini, sorry to bump this old review. I was wondering why the preload bolt needs to be tightened to 5 nm while the shimano counterpart is below 1 nm or basically by hand. Isn’t that too much preload for the bearings?
The Rotor is on a 30mm bearing axle. The Shimano is on a 24mm Axle. The preload is per ball, the bigger bearing would thus require more torque to achieve the same preload per ball.