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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 01-02-06, 06:48 PM   #1
EGreen
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I thought maybe the limit needed to be adjusted on my FD, sounded like it was rubbing, but on closer evaluation the noise was coming from my newly replaced cranks when pedaling hard. Then I realized a clunking feel/sound on the occasion when I step hard on the pedal.

Insufficiently tightened cranks? (no apparent play, though)
Insufficiently greased?
Is this what a broken BB sounds like?
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Old 01-02-06, 07:29 PM   #2
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Maybe you need some Locktite on the BB cups(or teflon tape),water in the bb, Your cleats may be loose, Chain ring bolts maybe loose, Those are some good starters
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Old 01-02-06, 07:31 PM   #3
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what kind of BB is it. Cartridge or loose bearing style?
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Old 01-02-06, 07:46 PM   #4
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i would check through all the possible problems you and others listed. make sure the bb threads are greased and also make sure the pedal threads are greased. make sure everything's really tight. if you check through all this there shouldn't still be a problem, other than if your crank is starting to get hosed out (stripped out) although since you said its new that probably isn't the case unless it was ridden alot without being tightened down enough which can hose one out, especially an aluminum one, especially an isis one, but i dont know what your running. the clunking thing you describe sounds like a problem with the BB spindle, though, while the screeching sounds like not tight enough or not enough grease somewhere. greasing threads lets you get them tighter anyways.

you should not have to use loctite. it should only be used for certain things, because permanently locking something that is having a problem is just going to temporarily lock the problemed parts in place for awhile, at best (not actually fixing the problem). you really should not have to use it anywhere in your bottom bracket. teflon tape sounds good but i would stay away from the loctite.
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Old 01-03-06, 12:40 AM   #5
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Based on the clunking sound that you mentioned, I'm going to take a shot in the dark and guess that you have an imperfect interface between a square taper bottom bracket and crank.

Did you install new cranks, or just swap used cranks?
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Old 01-03-06, 10:42 AM   #6
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Quote:
Originally Posted by spunkyruss
Based on the clunking sound that you mentioned, I'm going to take a shot in the dark and guess that you have an imperfect interface between a square taper bottom bracket and crank.

Did you install new cranks, or just swap used cranks?
As I didn't do the work myself -still haven't put those tools in my toolbox- you all are giving me valuable input, (a clue), that I'll take to my LBS guy. That said I don't know what kind of BB I have in there and no way to know for sure. The cranks aren't new, but to my eyes, are in pristine condition showing little signs of wear (I did inspect them [Campagnolo Record] prior to purchase and installation.)

The LBS is small and I'll have every opportunity to look over the guys shoulder and suggest the possible issues that you guys have brought up.

BTW, is the clunking sound/feel always an indicator of a problem? I experienced this with my new RB from time to time from day one, always when I step down hard on the pedal, such as if I start (or climbing a hill) in a too high gear.

Thanks!
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Old 01-03-06, 11:05 AM   #7
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Moreover, if there is a need for a new BB ... I'm looking at the online Catalogues and seeing quite a range in price for them. What are you getting for spending more, performance or durability or not much at all?
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Old 01-03-06, 03:53 PM   #8
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Noises from the nether regions can be some of the trickiest things on a bike to diagnose. all these ideas are good places to start. they can come from anywhere between shoes, cleats, pedals, crank/spindle interface, chainring bolts, the bottom bracket itself, or the frame.

One possibility, though: You said you got Campy Record cranks, which have a square tapered spindle interface, which is slightly different from that on a Shimano. I.E. you have to use them with a Campy bottom bracket. It will go on, but won't work right. If you're getting a new one, a more expensive one will be lighter and last longer. Make sure to check the BB shell width and spindle length against the one you have now---though the cranks may need a different spindle than your current ones. Lastly, be sure to not grease square tapered spindles (only splined). hope that helps
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Old 01-03-06, 04:47 PM   #9
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Jrcal is correct in saying that any number of gremlins can cause noises that sound like they originate from the bottom bracket/crank.

He's also correct about the different taper profiles used by Campy (ISO taper) and Shimano (JIS taper). Both the crankset and the bottom bracket must have the same taper profile. The two don't play nicely together.

Don't forget that the first step in correcting this noise is determing what the source of the noise is. Don't ignore any of the possible sources that jrcal mentioned. I only took a shot in the dark by guessing that it was a problem with a square-taper crank/bottom bracket. I wasn't even sure that you had a square-taper bottom bracket when I made the guess.
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Old 01-03-06, 06:09 PM   #10
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Thanks guys. I'm thinking he eyeballed the BB that was in it, wasn't broke didn't replace it, and made the fit, possibly an imperfect fit leading to the noise.

Thing is I'm not sure what was in there. It's a older steel framed Motobecane, all (originally) French but for the original cranks that were Japanese manufactured - so I'm guessing shimano.
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Old 01-03-06, 06:56 PM   #11
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Thing is I'm not sure what was in there. It's a older steel framed Motobecane, all (originally) French but for the original cranks that were Japanese manufactured - so I'm guessing shimano.
I doubt it. I've seen a lot of SR cranks (Sakae Ringyo) and some Takagi Tourneys, but no Shimanos. Doesn't mean they don't exist, but if the bike is anything less than a Grand Record, I'd bet on SR as the maker of the crank.
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Old 01-03-06, 08:07 PM   #12
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Quote:
Originally Posted by Motofan
I doubt it. I've seen a lot of SR cranks (Sakae Ringyo) and some Takagi Tourneys, but no Shimanos. Doesn't mean they don't exist, but if the bike is anything less than a Grand Record, I'd bet on SR as the maker of the crank.
No, I wasn't referring to the original cranks as Shimano but trying to guess (put it out to be speculated on) what type of BB is in there and that it may be incompatable with the Campy cranks.
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Old 01-05-06, 06:57 AM   #13
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The BB had been replaced by lbs, said I had limited choices given the French sizing, most bb's available were not long enough ... but it is definitely square tapered as suggested here it can only be.

Basically he tightened everything up- today, I'll see for sure if that's all that was needed.

Thanks for all your help. Thanks to this mechanics forum I've learned to effectively harangue lbs - hopefully in time I'll avoid it entirely.
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Old 01-05-06, 01:02 PM   #14
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Hey E,

Don't know if you've already taken the bike, but I just want to reiterate what someone said. If the problem is an imperfect interface between the spindle and the crank (say it's a little small), which your symptoms say that it could be, do NOT ride it until you make sure. I accidentally rode about 5 miles on a bike with a loose crank, and I ended up messing up the square hole and having to replace it. I found out the hard way that aluminum cranks can be that soft, especially in the face of your stepping force and the hardness of a steel spindle.

Good luck.
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Old 01-05-06, 01:34 PM   #15
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Quote:
Originally Posted by peripatetic
Hey E,

Don't know if you've already taken the bike, but I just want to reiterate what someone said. If the problem is an imperfect interface between the spindle and the crank (say it's a little small), which your symptoms say that it could be, do NOT ride it until you make sure. I accidentally rode about 5 miles on a bike with a loose crank, and I ended up messing up the square hole and having to replace it. I found out the hard way that aluminum cranks can be that soft, especially in the face of your stepping force and the hardness of a steel spindle.

Good luck.
Peripatetic's post is perhaps the most important thing that anyone has had to say about this. I don't know how we've gone this long without mentioning it.

I messed-up a set of cranks in a similar fashion. Riding a bike with loose or ill-fitting cranks is the type of mistake that you only make once.

Last edited by spunkyruss; 01-05-06 at 01:36 PM. Reason: clarification of what I meant by 'mistake" in the final sentence
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Old 01-05-06, 01:45 PM   #16
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Quote:
Originally Posted by peripatetic
Hey E,

Don't know if you've already taken the bike, but I just want to reiterate what someone said. If the problem is an imperfect interface between the spindle and the crank (say it's a little small), which your symptoms say that it could be, do NOT ride it until you make sure. I accidentally rode about 5 miles on a bike with a loose crank, and I ended up messing up the square hole and having to replace it. I found out the hard way that aluminum cranks can be that soft, especially in the face of your stepping force and the hardness of a steel spindle.

Good luck.
Thanks for the warning, I'll remember it. He claimed that it WAS insufficiently torqued and gave assurances that no such incompatability exists.

I've not had the opportunity to ride it today, but when I take it out tonight I'll listen closely.
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