Trouble getting crankset spindle into bottom bracket

Hi all,

I recently purchased a Rotor crankset with a 24mm spindle, I confirmed a few times with Rotor that this would fit my BBR60 Shimano bottom bracket.

However, even after greasing the spindle it is extremely difficult to push the spindle into the BB. Now I did have to use a soft mallet to extract the old Ultegra crank, but I’m worried that I may damage the BB by force the Rotor spindle in.

My only other experience with replacing a crankset was on a 105 and that was with a press-fit BB, the new cranks slid in without me having to force it in. Does anyone have a similar experience and is it safe for me to take a mallet to the Rotor crank?


Does this scene look familiar?

I had the same issue (Rotor aldhu) and was nervous about hitting it hard with a rubber mallet, especially the p2m spider that was on there.
I realised with Rotor you can take the DS chainset off and fit the axle on its own, then refit the NDS and DS.

This way you only have to hit the axle with the mallet.

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Try putting the crank in the freezer prior to fitting it, the metal will shrink slightly. Never done this with a bike but I’ve used this with reasonable success when dealing with tight tolerances while working on cars.


Wow that is EXACTLY what I’m looking at now! How hard did you have to hit the axle to get it to seat?

Yeah, that’s what rubber mallets are for (just on the axle).

The freezer idea is interesting… just degrease it first, then grease it cold… might be worth a shot.

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It’s a hard thing to describe over the internet but it was firm, once it got going it went in easier.
It certainly felt wrong, is my first carbon frame.

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I had similar issue with Rotor Aldhu 24 crankset and rotor BB. They surely should be compatible parts, but it was very hard to to push the axel through the BB. First, I thought something was wrong and contacted Rotor customer service. They said you should be able to push it through without tools. In the end I managed to do it with enough determination. The beginning was the hardest part but after that it went through relatively easily.

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So glad to find this thread. I’ll use some more determination and get it done.

Noticed this same issues as well. Few weeks ago i was installed P2M NGeco with aldhu crankset to Ceramicspeed BSA bottom bracket. I was surprised how tight the fit was, despite of grease on a spindle. In my case drive side bb was tightest. I need to remove crankset few times to test do i need spacers or not. Remove the crankset was more scary than install it. Didn’t test it if it’s better idea hit the spindle in first and after that attached the spider and crank arms. I will probably do that next time when i need to replace bb.

I think the same terminology applies here as when asking how tight some screw should be tightened, you need to use “man power”. As in baby power is not enough and gorilla power is too much.

Maybe get some calipers and measure. There were incompatibilities in the past between FSA 24mm and Shimano 24mm due to the “24mm” measurement not being exact. Since getting some Mitutoyo calipers, I’ve started measuring all things like this…seatposts, inner diameter of carbon forks, headset bearings, wheel bearings. Essential piece of kit in my opinion.

A set of calipers will probably reveal that the Shimano BB is in fact 23.9 and designed as interference fit, with its plastic sleeves, whereas the Rotor BB I am guessing is an exact 24mm and steel, if its like my 30mm Rotor BSA.

Why not get the dedicated Rotor bottom bracket? Doesnt really seem like a great saving to use a BB which is maybe a bit cheaper and then risk damaging the power unit on installation.

Full disclosure, I’m a massive fan of Rotor kit.