Rotor 3D+ not spinning freely

Valdezzzz
Valdezzzz Posts: 4
edited June 2018 in Workshop
Hi there:)

I just got a Rotor 3d+ crankset for my BMC slr03 which has a BB86 bottom bracket. Therefore I installed a Rotor PF4130 bottom bracket in order to make the 3d+ crankset fit in my bike.

My problem is that when I give the the cranks a semi powerful spin with my hand, it only spins for 3/4 of a revolution. I have already had a pro bike mechanic check that the new bottom bracket had been installed correct. I have also tried to loosen the bolts to make shure I had not overtightened anything. I have also tried spinning the cranks for about 10 minutes with my hand but it did not help.

So my question is: Does the resistance in the cranks dissaper/decrease when I use it or is there anything I might have done wrong?

(Btw. The 3d+ crankset is from one of my friends who took it of his new bike so I don't have any spacers or manuals. As far as I can see it does not need any spacers seeing as the preload bolt is easily able to tighten enough)

Hope you are able to help and thanks in advance:-)

Comments

  • StillGoing
    StillGoing Posts: 5,211
    The preload bolt should only be used to take the small gap out and not to make up for the lack of spacers.

    https://youtu.be/VbkbXl8XRXI
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • timothyw
    timothyw Posts: 2,482
    As above, try refitting the cranks with the preload bolt a bit looser.

    Also true is that new bottom brackets will usually be quite firmly packed with grease, this means they won't spin particularly freely until they've been ridden for a few dozen miles.
  • keef66
    keef66 Posts: 13,123
    I always take the fact that my Shimano BBs don't spin freely to mean the seals are still doing their job.
  • Valdezzzz
    Valdezzzz Posts: 4
    I have just tried measuring the gap between the buttom bracket and the non-drive side crank arm when the preload bolt completly loose. The gap is only about 1-2 mm which is why I wouldn't say any spacers are needed. I only need to turn the preload bolt about 1 revolution and the gap is completly gone.

    I also tried removing the crankset to check the bottom brackets for grease and they are exatly as described filled to the brim with grease. I think that is very likely to be the cause of resistance.
    I will do a 30 km ride on the cranks to see if anything happens and report back.
  • Valdezzzz
    Valdezzzz Posts: 4
    I have just been out riding a 30 km ride and I can already feel the difference.
    However, when I got home and looked at my cranks I noticed that the bottom bracket was leaking grease. Is this normal?
  • sungod
    sungod Posts: 16,501
    if you fill a ball race with grease a fair amount will get squished out in use
    my bike - faster than god's and twice as shiny