As a machinist who has in the past needed to nail axial positions of shafts relative to their tapered sections I can vouch for every statement you made about the production of a part like this. Very tricky! In fact I might wager that they may cut the tapered section in one operation then locate that part on that section to cut the corresponding shoulder. Even then, most lathes would be at or beyond their ability to position a cutter accurately enough to put that shoulder where it needs to be. If it’s a steel axle, I would be looking at cylindrically grinding that to size. I too have swapped out my Shimano crank for a modular design but I went with Easton. Their solution to this is quite different in that the chainrings get splined and bolted to the crank arm before that whole sub assembly gets mated to the spindle. Very clever and it works great despite its aluminum axle. (One piece Hambini bb ensures there isn’t undue wear from misalignment.)

I never thought of putting a pen mark on my male taper and then testing insertion depth, but this might be a good way of testing the dimensional tolerances.

Link to the cranks and axle in description. Copped both for about 200 quid. Let me know if you understood the bit about the taper geometry. I kept hammering it home but don't know how obvious or not it is to people. Edit: reading some of the comments, it seems this design isn't the most user friendly or clear to install. To help those with issues here are some vital points: 1. You MUST back off fully the preload collar before assembly otherwise you can deadlock the BB bearings. 2. If your BB shell (thus bearing stance) is slightly too wide, doing up the tapers to the full torque may compress the BB bearings and over preload (deadlock) them. In this case, remove the plastics 0.5mm shims and oring. This will give you up to 2mm more shaft to play with. 3. If the 35Nm wont fully lock the chainring spider or power meter, tell Rotor its out of tol. If they mess you around and chat bs, then gently heat the crank to 60c and reinstall with grease on the spline. This will slightly enlarge the female taper.

Just goes to show, if people in the bike industry want to put in the effort to make a product with high tolerances and QC it is quite achievable.

0:31 the subtle pause is absolutely amazing

The more I learn about modern crank and BB standards, the more admiration I have for square taper.

I have two ROTOR Cranks, one in 30 mm, one in 24 mm, both DM. They perform really well and I do not have any issues with them. They are not cheap, because they are high grade products. What I like about ROTOR cranksets is, the seem to be more quiet than Shimano ones I had previously (R8000). As I am not an expert, I think, less noise, less friction, better quality.

It could be that the tolerances don't need to be quite as tight as you think. There is a phenomena known as elastic averaging for coupling designs like this. Your analysis is correct if the material is assumed to be perfectly rigid. The shoulder sets the axial position, and the rest of the material will elastically deform to allow this to occur (which is why you need to use the force of the screw to draw the assembly together). To extend your comparison of machine tool tapers a little further - dual contact and HSK interfaces have a shoulder perpendicular to the axis of the spindle such that an accurate z-location is set regardless of differences in the tapers. The requirement for this is important as rpm of the spindle increases as the hoop strength of the outer "taper" (spindle) can actually open up and the draw bar can pull the tool holder further in to the spindle. Heat is also something of concern, which you note. I haven't gotten my hands on one of those Rotor shafts, but I would imagine that they are machined with a swarf style 5-axis strategy in a mill turn machine. In cycle probing and cutter compensation would make this a somewhat straight forward task with a straight fluted endmill (no custom tooling required),

Back in the Isis bottom bracket spindle days, Race Face cranks specced a particular torque but also said it had to bottom out. Their instructions said if the arm doesn't bottom out at that torque, to remove the crank and reinstall however many times until you did. I've installed several Aldhu cranks. Sometimes I need to remove and reinstall once to ensure it's bottomed out.

I love the power meter setup on these, and they have used the same interface for quite a long time so there are actually plenty good used power2max meters available online. You can also play with crank lengths quite easily. After spending years riding BMX where this kind of design is the norm, I have always found two piece cranks quite annoying in comparison considering how the whole thing needs to change if you change bike or damage something.

second

I have 2 of these both linked to powermeters- one on a power2max and one on an xcadey xpower-s. I haven't seen any problems so far and both read consistent with a quarq riken spider, and all 3 powermeters are within 5% of a elite direto trainer. Happy with the performance.

This business with the tapers is quite bad on SRAM GXP and others. It messes up the chainlines and you end up having to mess around with spacers. The "average" bike mechanic can't get their head around it.

It looks like this design has even more in common with plastic cups then with a lathe rear tool post mount: cranks must be undersized and considerably soft to press onto the axle with plastic deformation

Thanks so much for doing this and confirming that Rotor makes quality stuff! I'm seriously considering Rotor cranks with Power2Max power meters and don't wish to risk having a damaged crank with Ultegra or Dura Ace!

I've been seriously considering the Aldhu for some time. Thank you very much for making this video. Cheers!

Hey, first of all, thanks for the video. I recently bought a Xcadey powermeter (PM from now on) for Rotor aldhu cranks. As you said, the interface was not perfect between the powermeter, the cranks and the axle, so there was an unnaceptable amount of play. I took it to my local bike shop, thinking that maybe I did not know how to assemble it correctly, and they returned it to me assembled, and said that more force was needed in order to get a snug fit. Weeks go by and the PM starts returning some wonky readings until it eventually dies completely. After dismounting all the pieces I discover that the PM outer cover is cracked, undoubtedly because my LBS applied too much torque. I have to add that Xcadey sent a new one, almost no questions asked. This second unit I mounted myself (not going back to that shop) and had no troubles, in fact it´s still going on trouble free after 6 months. I guess that the problem lied within the first PM mounting interface, since that´s the only thing that changed, but that´s my expierence.

I had more than one problem with these: 1. Two sets produced vastly different chainlines and Crank q on the same bike, also cranks were not centered in reference to the frame. 2. The crank bolts loosen over time, and there is no fail safe that prevents the cranks from coming off (did not happen to me, but it happens acording to the forums) 3. less space between the crank arms and pedal than with Shimano, Quarq (relevant for me during winter when wearing overshoes) 4. Preload ring is an absolute fail! The ring gets compressed when turned. It's really tricky to dial in... need to place a flathead where the ring opens (which does chip the material and introduces splinters into the fine threads. 2 cents of thinking would have at least yielded to put some knurling on the opposing side of the preload ring pinch bolt. 5. Rotor support just stopped responding when asking for support with this. So in summary: I can't recommend those. Really wanted to like them, because they were the only option to stay with a 24mm spindle and using a power2max. Really wish there was a better option for Shimano BBs. Imho they should keep the modular design, but a) change the spider interface b) use a similar design to Shimanos for attaching the cranks

It is worth pointing out that if you had any play on the powermeter spider it would not all have beeb Rotors fault. Its a 3rd party power meter so if that would be out of spec then Rotor could have got is 100% right but not get it clamped down because of it.

A fantastic modular system I run myself on the TT bike, with interchangeable spiders/PMs/chain rings. You can get the Vegast crank arms for about half the cost of the Aldhu's too.

I have the previous version of ALDHU labeled 3D24 I think. I like them. Durable and nothing really to go wrong. They replaced shimano 105 cranks.

Great video. My big 1x11 Vegast chain ring came lose on a bike trip. I never fastened it with a torque wrench. So now I understand why it came lose. I found a guy with a big enough Allen wrench and tightened it very well. Back home it came lose with a lot of force and squeeking sound. Now I know that the tapered side caused this. I will use a torque wrench next time, this is precision work!

I just replaced a brand new Easton C=chainset, because it has bend chainring, or axle, for a Rotor Vegats, and it is absolutely perfect and stiff. Chainset is made of milled single piece of aluminum. No rubbing no issues.

Long-term review would be interesting, i.e. if you’d have any play eventually e.g. from wear. It’s of course normal to torque down chainring bolts time to time, but here it’s quite an exquisit setup.

I'd like to see you analyse the carbon version (unfortunately only 30mm axle).

which cranks can i use with sram red etap chainring dub system? would like to go for shorter than 170mm cranks... cant find sram cranks anywhere shorter than that

Speaking of tapers, what is your experience with square taper bottom brackets, and do you have a clear favourite among them? Always love these engineering analyses.

I have the 24mm model with Power2Max power meter and also the 30mm track model. Both are very stiff and superbly made.

Aldhu 24 + Power2Max NGeco + Praxis Buzz 10/11/12-speed chainrings + AXS road 2x was a nightmare. 1) The cranks hit the derailleur cage when set up to SRAM’s spec. 2) The 5mm wide flat-top chain is can get stuck in between the chainrings because the NGeco mounting tabs are >3.5mm thick. 3) That >3.5mm thickness causes shifting problems because the FD overshifts to a lesser extent while the rear is in the smaller sprockets.

24mm axle works only with specific 24mm cranks and 30mm with 30mm cranks and afaik carbon one is only 30mm last time i checked (have both of them 24 and 30mm axles)

I am on my third Rotor crankset. On the first one the left arm came loose and destroyed itself. The second one was DOA. The axle had terrible burrs and so the surface on both arms was destroyed. The third one is working so far.

Whenever I've looked at Rotor cranksets, I've been shocked at the prices, so that has ruled them out for me. I have wondered about the machining of the tapered splines in cranksets that I own (FSA and SRAM). There's quite a few standards for straight cylindrical involute splines, but I don't know about for tapered splines. The exposed spindle length a.k.a. distance between crank arms (as Hambini calls it) can vary quite a bit due to manufacturing variations.

Can't wait for the full review... Been looking at switching!

Been using Power2Max with the 24mm Aldhu for 2 years with no issue. Just about to fit 30mm aldhu+p2m combo on a new bike.

Thanks for the video. I was recently looking at getting a power2max power meter with the aldhu cranks, so I imagine this video will be useful.

I don't deny that that is a very nice piece if machining but modern CNC machine tools should easily be able to hold 10micron tolerance on those size parts so the 50micron you use as an example is a bit excessive. Also - there is always an also - the simple trigonometric analysis does not account for the elasticity of the crank spline hole (and I suspect a lesser extent the axle) which will allow axial movement when tightening the bolt. I have not run the analysis but on my crank-set (see the first link below) once the taper is 'nipped-up', tightening the retaining bolt can push the crank about 1mm onto the taper on the axle. Also, you should have considered the thickness tolerance on the power meter spline area which is also important for the fit to be good enough - how well so Sigeyi control this? I suspect the tolerances on the tapers are not as critical as your analysis might suggest. I bought this Sigeyi power meter about one year ago (kzfaq.info/get/bejne/rb55lKR92rO0c5s.html), I have not been able to test its accuracy (its not that important to me) but so far it has worked reliably and the battery lasts a long time. The only real issue I have had is getting a firmware update transferred to the power meter. I'm looking forward to your full review of the power meter. OK, I've been a bit critical. If you want to get your own back, I'm look to get engineers to critique is video (kzfaq.info/get/bejne/h5p4esujp76oeYE.html). In particular comment on what I found in the seat-pin would be welcomed.

Yeah, it’s impressive tolerance but, but also kind of demonstrates how the sram or race face style chainring attachment are better. With repeated assembly and wear, the rotor style is likely to reach a point where the chainring isn’t clamped tight and a shim would be needed.

My takeaway - apply boiling water to male parts for a more impressive size.

I had the center bolt that affixes the NDS crank shear off inside the axle on a ride. Rotor attributed it to me not installing it properly (I had put a few 1000mi on it since the last time I had taken anything apart) but ended up sending me a full set of new arms and axle. I had only needed the center bolt, but oh well. Otherwise I've been happy with these married to a power2max spider and praxis chainrings. The old rotor setup I had prior to this (the 3d+) had a catastrophic failure at the pedal spindle interface and I broke the whole end off the crank arm.

Always loved Rotor stuff. The 3DF made the BB30 on my old bike actually usable. SRAM DUB looks like a not-so-cheap knockoff of 30mm Rotor down to the preload adjuster. Difference is the Rotor one is beautifully machined whereas the SRAM one is a piece of plastic tat.

I had to torque more than 35nm to remove the play and still have creaking with 24mm and Hambini BB. Doing my head in. Think need to speak to Rotor as Power2Max were responsive but not helpful.

Funny that you say this. Just got an Aldhu 24mm and no matter what I do, the spider is loose. I also tried googling this but didn't find anything. I guess I'm the only one with this issue... I called Rotor, they told me to go to 40Nm and it still wouldn't compress. I can't seem to win with any brand.

A similar review of SRAM’s cranks would be a good video idea. They have a much higher torque spec of 54Nm. I think they may have more issues with cranks coming loose despite the higher torque spec.

I think Rotor headquarters are in a little village outside Madrid(Ajalvir). They build their stuff at home. I had a few Rotor products in my hand,very good looking but never try one.

Hello, I have this wobble too. I screwed the crank, the shaft and the Power2mx together, but there is 1-2mm play and the crank wobbles, what could that be?? In your video you can see it at 8:45, thanks for help

Personally had trouble with the taper, vegast crank, had to go above the 40nm to get it the lock correctly the chainring

I have those on my TCR and 8-Bar fixed gear. They are lovely cranks.

Hey PT! Many thanks for the video. I had Vegast version if the crank (cheaper version) and I had this very problem. Crank arm wasn’t pressing all the way to the spider and had this terrible creak going on. I contacted Rotor and they eventually replaced it-they tried to convince me there was some bb/bearing misalignment but I did try other 30mm crank which worked fine. In the end, I sold it as I wasn’t keen anymore.

Not to disagree on the general importance of getting tolerances right in over-constrained interfaces like this one. But even if the male part was just ever-so-slightly too big (or the female part too tight), you could probably still torque it down flush against the lateral stop; the crank-arm portion of the interface would likely just stretch a little more. With my set (30 mm), I can kind of tell as the preload pinch nut, while being very (like, very!) loose on the pinch bolt before torquing down the left* crank arm, will seize considerable after doing so. Also, the 3 plugs in each arm will usually become clearly visible after torquing down the cranks. And stretching holes (of cranks, way beefier around the hole than the rotors) has been a thing for decades ... well, ok, this might be easier with a tiny square taper compared to a huge spline taper, but still(?) * I was told by some Rotor person that the left arm, pretty much the same as the right one, bottoms out against a lateral surface when mounted as intended. Side note: Sram has been mass producing that kind of over-constrained interface (tapered spline + lateral stop) since the introduction of gxp. Now, by no means, am I trying to say they nailed it or that there weren't people having issues with it in the field, just that, by and large, it kind of can work. Another side note: I still find it somewhat funny how we went from 3-piece cranks, some designs with detachable spider, to integrated/2-piece to, now, fully modular (kind of 3 piece again). (Sorry for shitty English. Also, not really an engineer. I like your videos much more than the ones from the French aerospace guy :D)

there was a reason we abandoned tapered axle and cranks long ago. I used them through the 70's and 80s. . Shimano engineered the new axle design - and we have no problems.

The Aluminum Aldhu turned out to be to flexible for me, the pedals end up at a jaunty angle under the force of standing pedaling. The new carbon ones are supposed to be better but haven't tried those yet. Rotor are bad at q-factor. On my carbon road bike there is >1cm on EACH side between the arm and the frame. They could easily have narrowed the q factor with straighter arms and increased stiffness at the same time.

Very interesting and I always learn something from your reviews (as a total layman engineering wise). Personally I have two bikes with Rotor InPower 1x cranks and they are bulletproof (aside from the single A battery which is relatively short lived) and easy to swap chainring sizes. . Quality machining and really not that expensive especially when they have them on sale. By far my favorite cranks.

i have a Aldhu 24mm and even when torqued to way above the torque setting the chainring still wobbles. tried the chainring on my aldhu 30mm crankset and it fits perfectly. i might need to get a spacer to make the crank arm compress the chainring enough to keep it tight.

They use this fine spline for spider mount interface just to allow 1 degree clock of direct mount oval chain ring. Want to dial oval chainring orientation a bit? No problem, take it out and reinstall it rotated one degree clockwise or counter clockwise at a time until you find the perfect angle. As we use round rings, this design complexity give us no benefit.

I'm hearing a lot of good things about Praxis cranks. I'm hoping you get a chance to review that.

At first look, it looks the same as XCadey, but they're different aren't they? I think the XCadey power meter is mounted with 8 screws.

My Rotors click (30mm DM version) and haven't been able to resolve it until this video. I've had them for over two years now but it was already clicking under each (driveside) pedal stroke after a few months from new so I suspect the DM and crank interface developed some give resulting in the click. Oddly my older Rotor 3D+ cranks (24mm) on another bike have been silent. Both of my Rotors have Q Rings if that makes a difference?

Nice explanation! I recently bought a power2max NCeco with the aldhu 24mm for my 18 scott foil (PF86 BB) . My drivetrain is a r8050 ultegra di2 so I kept the shimano chainrings. However, when I first installed the aldhu crankset, I noticed the crankset is sitting slightly further than my ultegra crankset. I noticed that because the chain is rubbing the front mech when I am on the big chainring. So I thought no big deal, I will just adjust my FD. So I got it to work, but since then, my drivetrain is super noisy when in the big chainring (worst when cross chaining). It's been a few months and still the same. Any ideas? Appreciate for your input!

Ive not long but the cheaper version for my 2007 cannondale Caad 9 and what a great idea, rap going forward as can fit most bbs and if you buy the spider any chainrings!

My challenge in clanging my chainset to rotor was in the quality or compatibility of the chainrings. I will not do that on my new bike. I will opt for a 4iiii powermeter rather than rotor

Good review and well explained. I have the same combination on my bike and will check it out later. My question: If the chainring is lose like you described at 8:47 and can angle would that not result in a better more straight chain line?

hey, nice video. Any update on it after year of use? thinking of swapping to it

I wonder, is the taper issue described the reason for the failure rate I've seen (2 sets of my own) in the rotor flow cranks. Cracks in the crank arms at the spindle interface.

Sugino offers Shimano compatible 24mm road cranks, though I have no idea about availability where you live(or where I live for that matter)

That’s good. I’ve been considering these cranks for more 1x chainring options

Great style of explanation of the important engineering details. Subscribed. I saw this vid as I was looking at these crank sets for a power meter. I really don't like the idea of taper and spider clamping combined as you describe... Even if they do manage to get it to work in this case. I'll probably look for other brands. Is this the only option for these style power meters for shimano rings?

What should you do if you have some play when mounting the spider on the spindle. I have a aldhu24 crank for my BB90 Trek. And when mounting the spider it is not totally play free :(. I can remove the play when tighten the crank into frame but that can not be good, is it? Any one this issue? @PeakTorque?

Great video, good explanation about the taper!

@Peak Torque I have just purchase at 24mm Rotor crank set and 1-piece chain ring. The machining on the chain ring is outstanding! When you torqued up the arm, did you apply force to the pedal with a chain attached to mate the splines in the best position as there's a fair bit of lash between the ring and spindle. Thanks!

If I ever have a Shimano crank fail, I'll get these. #prawnwatts

Could a cheaper axle be made that used a wave washer to give the correct fit , or would that preload the power meter and bias the measurement?

I have noticed that you went back to quarq on gxp I suppose, any reason why you chose gxp over 24mm aldhu. I m currently choosing my crank set up and can't get passed by disadvantage of gxp

Hey, i just watched this and this product is awesome looking

After watching your video I felt the need to yank my crank.

Does rotor crank arm compatible with the sram red direct mount chainring?

Is the left crank axially restrained on the face (similar to the drive side) using the bearings (I'm thinking with a spacer keeping the inner races apart) or is the tapered spline the only thing holding it in place? EDIT: It doesn't seem to be this way looking at it. But does the end of the spindle bottom out against a face on the inside of the splined crank? I'm worried about the splined fit ''squirming'' under load if you will, and fretting wear occurirng between the crank and spindle due to elastic backlash under load.

@peak torque just seeing how your going with these cranks?? I'm building up a new bike and leaning towards these cranks. Do you have any feedback please after 6months. Cheers

@Peak Torque how much clearance have you got between the drive side crank arm and the outer derailleur cage? I've got P2M +3d24 and there isn't enough clearance. If this works well I might go down this route instead. Are you using Mechanical or Di2? Thank you. GP

Got it 35Nm but no mention of how you got the cut on your thumb? 😁

Rotor Aldhu/Vegast 24 is a nightmare. I have two spindles with bad threads and during a casual ride a brand new Vegast crank arm fell off. It was one week old and I used a torque wrench. The quality is just horrible. Same for their web shop that sends mails with template placeholder and customer supper that promises replacement parts but never sends a return label, wants me to cut the crank in half. Do I own a machinery shop?! Ridiculous.

Thanks. I learnt a lot from that one.

what kind of big torque wrench do you use? Looking for a reasonably priced one. Thank you!

One thing that bothers me is the use of o-rings on the axle. O-rings eventually dry-rot and fall off/out of things like this. Usually when you still have sixty miles to go before reaching civilization. Also, they crush during assembly and use, then when you go to replace the bearings or swap the crank to a different bike, they don't fit properly anymore.

Would like to hear your thoughts on the Cannondale si series cranks. Same concept, although the spider is screwed down onto the arm, which is then bolted on with the aforementioned taper

If I'd ever tried to put something like this design into production it wouldn't have got past the first design review. It's just dumb engineering design requiring stupid levels of machining accuracy to dig themselves out of a hole created by a fundamentally stupid concept.

Hi Peak, Only cranks I have run on road bikes for years. :)

While i’m not officially an engineer, I worked in the airspace industry for 10 years and been around Bikes for 30 years doing my own Maintenance. I don’t like the party trick of such a refined setup. Everything gets slack with time and this really isn’t the way to go for me.

My bike shop asked if I wanted these cranks or the Ultegra 8000 cranks, didn't hesitate and said rotor. I don't like my cranks splitting in half, I don't like the look and availability is very bad for the shimano chainrings.

I ordered the carbon crankset. 100g LIGHTER than Dura Ace

Update: I got the carbon arms a few days ago and the increase in stiffness is pretty dramatic. The carbon arms feel like a crankset should, without the noodly flex of the aluminum arms.

Have an ALDHU and it isn't a straight swap with my Ultegra... chain-line is vastly different so I need to adjust the front derailleur always by a lot when switching

Is rotor any good then??

Excellent video! The question is, as always…why is almost nobody making a 24mm steel spindle crankset? Especially with carbon cranks they all go for aluminum…

Hi!! Did you used all the washers and o-rings that are shown in the video when installing the crankset in the Giant Tcr BB86?? I’m asking because I bought a set of Aldhu’s second hand and thet came without any washer and o-rings, to know what to buy to install them properlly in my Giant Tcr.

Always replace a Shimano part. Replace it with some Campagnolo instead! Preferably replace all Shimano for campy:) Problem solved!

@Peak Torque, I went with a 24mm 3-bolt setup, but full Chinese - Sigeyi AXO with Zrace Hardrock cranks. I'm preparing to install and have found there is a bit more backlash than your splined Rotor setup. How concerning is backlash with these power monitors' accuracy? Is the issue that some level of accuracy is lost for a moment in each pedal stroke?

Very good qulity. I have the full power meter crank from rotor. Baught it for a fair price from bike24

Shimano cranks seem to be splitting.....

Has there ever been a crankset with a threaded interface to secure the crankarm to the spindle? (As in you turn the whole crank arm to affix the crank arm.)

What is the answer to the question? Should I replace Shimano cranks and, if so, why?