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View Full Version : Advice on cranks not spinning freely after BB installation


bitt3n
05-29-2017, 02:16 PM
I just installed a Chris King 24mm ThreadFit BB and some Ultegra cranks, and when I give the cranks a spin (without a chain) they only turn about 2.5 times before stopping. My other bike's cranks spin for a dozen times when I spin them the same way, so I'm worried I installed something too tightly.

Video here. (https://www.youtube.com/watch?v=-vyNhA57mH4&feature=youtu.be)

The manual says to install the BB shell at 30ft/lbs, which I did, and then I hand-tightened the cranks with that little round plastic Shimano tool. I'm wondering whether I do indeed have a problem and how to diagnose what it is I'm doing wrong.

There is no play in the cranks and I don't feel any grit or unevenness or anything when I turn them. The BB was purchased used so I suppose it's possible there's something wrong with the bearings but I think user error is much more probable.

Cicli
05-29-2017, 02:18 PM
They will be fine. Tight seals and fresh grease slow things down a bit. You will never notice while riding.
Providing things are free and smooth, it dosent really matter how they spin in the stand.
They are fine.

11.4
05-29-2017, 03:28 PM
If the bottom bracket was already used, it should spin reasonably well. Bottom brackets don't have to just spin to a silly degree because it's all about how they perform when loaded, not unloaded like in your spin test.

However ... what could be happening is that your bottom bracket isn't faced properly and the two halves of the bottom bracket aren't quite collinear. That can cause the whole thing to slow down, and can also lead to premature failure of the bottom bracket. I see this all the time, so if you have any hesitation at all about whether your bottom bracket was tapped and faced to ensure that it would perfectly align the bottom bracket, I'd have a shop or a builder do so quickly for you.

bitt3n
05-29-2017, 04:16 PM
If the bottom bracket was already used, it should spin reasonably well. Bottom brackets don't have to just spin to a silly degree because it's all about how they perform when loaded, not unloaded like in your spin test.

However ... what could be happening is that your bottom bracket isn't faced properly and the two halves of the bottom bracket aren't quite collinear. That can cause the whole thing to slow down, and can also lead to premature failure of the bottom bracket. I see this all the time, so if you have any hesitation at all about whether your bottom bracket was tapped and faced to ensure that it would perfectly align the bottom bracket, I'd have a shop or a builder do so quickly for you.

It's a used Seven frame. On their website (http://www.sevencycles.com/buildingbike/techsupplement/framebuilding.php) they say they face the BB shell themselves so I assumed it would be ok.

AngryScientist
05-29-2017, 04:17 PM
is that a brand new king BB?

bitt3n
05-29-2017, 04:23 PM
is that a brand new king BB?

No it's used.

martl
05-29-2017, 04:34 PM
i once had a BB spindle that would stop to turn nice and smooth when i fastened the countering. In that case, the faces of the BB casing on the frame weren't perfectly parallel. Once that was fixed, all was fine.

oldpotatoe
05-29-2017, 05:14 PM
They will be fine. Tight seals and fresh grease slow things down a bit. You will never notice while riding.
Providing things are free and smooth, it dosent really matter how they spin in the stand.
They are fine.

Yup, what he said. In addition, put your hand on seat tube when you spin cranks(no chain) and if it feels smooth...go ride.

11.4
05-29-2017, 05:27 PM
It's a used Seven frame. On their website (http://www.sevencycles.com/buildingbike/techsupplement/framebuilding.php) they say they face the BB shell themselves so I assumed it would be ok.

Everyone says that and I would expect that to be the case with Seven. But I've seen Serottas, Pinarellos, Lynskeys, and plenty of other frames where that wasn't actually the case. A shop can run the right tap through the frame and face the bottom bracket, all in a few minutes. All it takes is a slight ding on the edge of the bottom bracket to make the bottom bracket settle in at an angle and that could happen after leaving the builder. Similarly, someone who mucked up the threads slightly on a previous installation could create a problem for you.

I suspect you just are feeling a little resistance in the bottom bracket bearings that isn't a sign of anything wrong. Not only do you have seals and grease and such that can slow it down, even in a used bottom bracket, but also King sets their bearing cartridges pretty tightly with the idea that they relax ever so slightly under load.

I only mention the issue above because it's always a good idea to double check how the headset and bottom bracket are faced and/or threaded. You'll probably never have to do it again, but it's about the only other issue that could be affecting your bike.

bobswire
05-30-2017, 12:36 AM
I think your BB is fine. When I went from square taper to outboard BB I thought I must have did something wrong, I didn't. It's in the nature of the beast, once you get on the bike you won't notice any difference