Rotor 3D+ doesn't spin freely after tightening the pinch bolt

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siim
Posts: 72
Joined: Sun Nov 26, 2017 9:37 pm
Location: Estonia

by siim

I installed a Rotor 3D+ crankset on a C-Bear BB. At first all seemed fine:
1. I back up preload nut (the one on the non-drive side)
2. inserted nds crank arm and axle
3. install drive side arm
4. push crankset to the left side so there's no free space on ds
5. tighten preload by hand until cranks spin freely but there's no play anymore

Now I tighten the pinch bolt of the preload nut and as soon as it gets reasonably tight, cranks will not spin freely at one certain spot. Most of the turn is ok but at one spot it's clearly binding and not how it's supposed to be. If I back off the pinch bolt, crank spins ok again but then preload nut can be moved by hand again which means pinch bolt is not tightened enough.

What can I do about it? Is a washer needed on the nds? Right now I'm using no spacers or washers whatsover as the crank is Cervelo BBRight specific 3D+ with shorter spindle and the frame is BBRight as well. BB has dust caps on of course.

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themidge
Posts: 1136
Joined: Fri Jan 13, 2017 4:19 pm
Location: underneath sweet Scottish rain

by themidge

When I installed my 3D+'s I left the preload assembly where it was (probably just lucky with the way everything was spaced to start with) and then DID NOT tighten the little allen bolt that's supposed to lock it in place. There was no play and no binding and so far, nothing has come loose. I see no reason why the thing would come loose, so try riding it without tightening the bolt.
Or just e-mail Rotor..?

by Weenie


1415chris
Posts: 1273
Joined: Sat Apr 18, 2009 8:59 am
Location: Surrey UK

by 1415chris

It is weird, since the pinch bolt only locks preload nut in the position securing it from coming lose, that's it.
I had a couple of 3D+ cranks on Cervelo frames, never noticed or experiance what you are describing.
Preload nut is just too big to be deformed by this tiny pinch bolt, maybe it is...?

morganb
Posts: 667
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

I had this problem but the cranks barely turned. I needed to switch to thinner bearing shields and it worked fine. This was on an S3 so BBRight.

reedplayer
Posts: 472
Joined: Sat Nov 14, 2015 10:10 am

by reedplayer

siim wrote:
Wed May 30, 2018 8:50 pm
I installed a Rotor 3D+ crankset on a C-Bear BB. At first all seemed fine:
1. I back up preload nut (the one on the non-drive side)
2. inserted nds crank arm and axle
3. install drive side arm
4. push crankset to the left side so there's no free space on ds
5. tighten preload by hand until cranks spin freely but there's no play anymore

Now I tighten the pinch bolt of the preload nut....
maybe i understood you wrong, but i think you did it in the wrong order. first tighten the pinch bolt (thats no preload nut!), then preload by hand.

just watch the video:
https://youtu.be/VbkbXl8XRXI?t=118

reedplayer
Posts: 472
Joined: Sat Nov 14, 2015 10:10 am

by reedplayer

did you do everything in the rigth order? first tighten the central pinch nut, then preload nut.
https://youtu.be/VbkbXl8XRXI?t=118

siim
Posts: 72
Joined: Sun Nov 26, 2017 9:37 pm
Location: Estonia

by siim

When I say "pinch bolt" I mean the tiny 2.5mm hex bolt that's on the preload ring (on the non drive side). Can be seen at 3:05 in the linked video. This is also how it's called in the official Cervelo Rotor crank installation guide: https://ponbic-p.azureedge.net/en/cdn/m ... 9ae2-0.pdf

siim
Posts: 72
Joined: Sun Nov 26, 2017 9:37 pm
Location: Estonia

by siim

And yes, I've wathced that video many times and did stuff in the right order. Anyway, I also sent email to Rotor, waiting for their response...

srshaw
Posts: 175
Joined: Sun Apr 05, 2015 6:06 pm

by srshaw

That's weird. It shouldn't really effect anything. Perhaps back of the preload a little before locking it down?

I've got a rotor 3df using a bsa 30 bb. I couldn't get it to run quietly without clicking at all. I bought another bb and it's now fine. Perhaps I over tightened the preload and ruined the bearings.

by Weenie


siim
Posts: 72
Joined: Sun Nov 26, 2017 9:37 pm
Location: Estonia

by siim

Got some help from LBS. First, they pulled off the preload ring of a new aftermarket crank and gave it for me to try at home. I did it and results were the same - still binding at one spot. Took the new ring back to shop and got a 1 mm spacer (Rotor original) to try. I installed the spacer between preload ring and BB. Magic! Everything works as expected: I can tighten the ring so that there is no play and after tightening pinch bolt crank still spins as it should. Case closed.

Moral of the story: follow the manual and you don't have issues (most of the time).

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