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Clunk in Bottom Bracket
#1
Lately I have been getting a clunking sound which seems to be coming from bottom bracket; it gets worse the longer and the harder I pedal (especially long uphill climbs), only happens while pedaling, happens while pedaling seated or standing. LBS guy removed pedals and bottom bracket, greased them up, reinstalled them, and the clunk is about 90% gone but still there. But LBS guy is convinced it can't be the BB because nothing seems to be wrong with it. I think I should replace BB (am considering SKF); any thoughts?
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#2
Before you do that, try replacing the pedals. Does this happen when you pedal with one leg? Try pedaling with a single leg while on a flat area if you don't hear the sound, switch legs and see if the sound appears. If you are not clipped in or riding with toe clips, single leg pedaling is a bit harder to do, but it is doable.

Did the LBS check for chain skip? You should really feel a chain skip, but not all riders know what it is. Also, if you have access to a bike trainer, put your bike on the trainer and turn the crank by hand about as fast as you would if pedaling but put pressure on the pedals while turning the crank. If it is the BB, you should be able to hear it while off the bike.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Giant
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#3
Thanks. They are actually new pedals, $120 Axioms with less than 300 miles. They were removed, lubed, and reinstalled. There's no chain skip. Before removing BB, one could reproduce the clunk by pushing very hard on either pedal while preventing bike from moving, but moreso on left side. After greasing and reinstalling BB and pedals, the clunk is almost gone but still there. BB and pedals seem very smooth spinning with no load, but there is also a significant amount of flex and warp in the front crank (enough so that front derail cannot be setup without chain scraping at least one side of it), which would be worse under heavy load. I was going to be replacing front crank next spring (summer bike season here is like 4 months tops) but am thinking now would be the time.

Bike is Electra Townie 21, which other people have experienced strange BB noises that go away when BB is replaced. Because of the geometry of the bike, and because of my being a former bodybuilder, I can push extremely hard on the pedals and am really wanting something that I won't be able to bend. At this point, I am pretty much set on the SKF BB, as their industrial bearings last forever.
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#4
Well, if the bike has a history of doing this, then I would change the BB. They aren't that expensive as compared to other parts on a bike. Not difficult to replace if you have the tools for it.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Giant
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#5
Thanks again. LBS is putting in new BB after 3 trips there of me telling them that's what I wanted done in the first place. Having a hard time finding a good LBS, so I'll be spending my winter learning everything I can and rebuilding the bike myself. It's little things that bother me, like using Locktite where manufacturers recommend using antiseize, not using torque wrenches, etc., that I've been seeing in LBSs.
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#6
I'm in the learning phase myself. My big problem is that I don't have space (nor the tools) to actually work on the bike unless its outside and I can't do that because the mosquitoes down here swarm year round. I live pretty much in the woods and I can't even wash my car without using repellent. Maybe some day, I'll get a small shop in the back yard where I can work on bikes.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Giant
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#7
I don't have the space either; I do have access to a fully equipped machine shop (including an auto dyno, I wonder if I could use that as a trainer to track down the clunk), but it's a very busy place; I could take parts there to work on and borrow tools, but couldn't leave anything behind, so I'd be dragging stuff back and forth. With only being able to bike from end of May to early October, I don't really want my bike spending its summer in pieces, so if I rebuild it myself, I'd have to over the winter.

And after all that... LBS guy removed old BB to measure spindle length for new one, and now he says it does feel like some of the bearings in it are slipping which is what I told him the first time I went there.
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#8
Glad to see you've got that fixed.

Troubleshooting skills are a whole different skill set and just because someone claims to be a "mechanic" or "technician" doesn't necessarily mean they know HOW to fix something. More often than not, poor technicians just memorize symptoms and fixes for those specific symptoms. In those cases they are just parts swappers and can get expensive! Smile

I think there a number of people here that actually possess good troubleshooting skills.

Steve
Junkyard Tools rescued from the junkyard!
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#9
Thanks Steve. As it turns out, that particular LBS was unable to get the proper size bottom bracket, so they put my bike back together with the old one. In doing that, they dented the fender and scratched the paint quite noticeably, then tried to claim they didn't do it. So I took the bike to another LBS who inspected the bike, found that in replacing BB/crank, etc. the last shop didn't tighten anything up but left everything loose (but rideable); within about three minutes of looking at the bike, they said the freewheel/hub thing at the back needed replacing (can never remember what that's actually called), so I just replaced that along with new chain and better quality BB and the clunk is now gone.

I had a feeling I should have went to the second LBS first, as they are quite popular around here, but thought I'd give the smaller shop a little business. But they've only got one guy fixing bikes, and it's obvious that he's being rushed to get things done. Second LBS is actually Electra dealer and they claim they've never replaced a BB on an Electra bike, but I insisted that it be replaced.

So, yea, bike is fine now, actually almost like having a brand new bike. And I have brand new Brooks saddle and new handlebars with better reach to put on this weekend. Really enjoying the forums and videos, learning lots from this site and from the Park Tools site, so hopefully the next time I need worn out stuff replaced, I'll be doing it myself.

Victoria
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