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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 08-24-11, 07:19 PM   #1
Binarycow
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Hearing / feeling a clunk

Hello,

I have a BSO (Yes, I know, sell it and buy a real bike), that is making a clunk sound whenever I pedal. I feel the clunk in my right foot, but not my left, so it seems as if it is a right side issue. It is usually a dull clunk, and occurs when the right crank is about halfway between the down tube and the seat tube.

It does not seem to impact riding experience, and seems to occur less when I speed up (haven't been running a computer recently, so not sure how fast exactly)

Any ideas?
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Old 08-24-11, 07:32 PM   #2
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Maybe the bottom bracket (the crank axle/bearing unit) isn't tightened against the frame properly. To check that, you'd remove the crankarms and confirm the bottom bracket is properly tightened against the frame. I don't know what a BSO is, so this may or may not be applicable, depending on what sort of BB it comes with. Photos might help.
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Old 08-24-11, 08:03 PM   #3
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its a crank arm or BB issue?
pics?
what is the name of the BSO (bike shaped object)
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Old 08-25-11, 04:04 AM   #4
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It is a Vertical Edge Runner bike. 26" tires, 18 speed, bought at the local PX (Post Exchange, like a walmart) for less than 100$... Having problems finding a pic online, and cannot take a pic of my bike quite yet.

Nothing is visibly wrong from the outside of the bike.

Now, I must say, this is really my first foray into bicycling, so I have no special bike tools... Anything which allows me to use a crescent wrench/toolbox, or the little bike multi-tools would be excellent... However, I guess I will buy tools if I have to.

So, tighten the bottom bracket? Any other ideas?
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Old 08-25-11, 09:19 AM   #5
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To give good advice, we'll need to know what style of bottom bracket you've got. Even a cell-phone picture could help.
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Old 09-02-11, 08:58 AM   #6
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Sorry it's been a while. I did a bit of research, and it looks like I would need to remove my crank, which needs a crank arm puller. Then I can tighten the BB, which requires a special tool dependent on the type of BB I have.

Now, is it possible to determine the style BB I have despite not being able to remove my crank? (I don't have a crank arm puller) If I'm going to buy tools, I'd rather do it all at once.
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Old 09-02-11, 09:04 AM   #7
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Sorry it's been a while. I did a bit of research, and it looks like I would need to remove my crank, which needs a crank arm puller. Then I can tighten the BB, which requires a special tool dependent on the type of BB I have.

Now, is it possible to determine the style BB I have despite not being able to remove my crank? (I don't have a crank arm puller) If I'm going to buy tools, I'd rather do it all at once.
Yeah, it's possible. Photos showing it from both sides would help a lot; a picture's worth a thousand words, etc etc.
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Old 09-02-11, 10:54 AM   #8
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If these pictures don't work, the album is at: https://picasaweb.google.com/1125081...eat=directlink






Last edited by Binarycow; 09-02-11 at 10:58 AM. Reason: Album link
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Old 09-02-11, 12:45 PM   #9
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Any chance the left crank arm is hitting the kick stand on the way up?
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Old 09-02-11, 01:34 PM   #10
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I don't think so... but I'll take it off to make sure. Anything else?
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Old 09-02-11, 02:15 PM   #11
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Binarycow: Try some different pedals on that bike before you start worrying about the BB, particularly if you only feel in in the R pedal.
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Old 09-02-11, 02:26 PM   #12
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I wouldn't be super surprised if it was the kickstand rub issue. Had that once or twice on an old bike and it took the longest time to figure that out. It didn't always happen unless I had my weight on the pedal (may have been some crank arm flex or a BB problem I never diagnosed), but a slight rotation of the kickstand and the problem went away. Though you'd probably feel that more in the left foot than the right, but it is the right position for that problem.
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Old 09-02-11, 02:34 PM   #13
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I did replace the stock platform pedals with the clips. I'll throw the stock ones back on, and remove the kickstand, and I'll get back to you on this...

Thanks for your help so far!
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Old 09-02-11, 09:26 PM   #14
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Ok cool, the photos are helpful. After checking for kickstand and pedal issues, you could move on to the bottom bracket. That bottom bracket is the traditional adjustable sort. It might clunk/thunk if one of the bearing cups were able to rock around on its threads.

The bearing cup on the driveside has a flange on it, and should be firmly cranked down against the frame so it can't rock around. From your photos, it looks like the type that has 36mm wrench flats, so you could probably get a thin headset wrench and slip it in there without having to pull the cranks. The driveside cup is reverse-threaded in this case, so lefty-tighty.

The other bearing cup has 16mm flats, and can be turned with a 16mm cone wrench. It's locked in position with that notched lockring, which you can turn with a lockring wrench or just make do with a big arc-joint plier if you have one. This site is right-hand threaded, and is called the "adjustable cup" because it can be adjusted until you find the "just right" setting where the axle turns freely, but doesn't have bearing slop. To check how freely the axle turns, lift the chain off the chainrings so it's not interfering.

Hope that helps Oh, and also make sure your crankarms are bolted to the axle quite tightly.
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Old 09-05-11, 08:13 PM   #15
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Well, I put the stock platform pedals back on. We'll see if I experience the clunk tomorrow. Kickstand is not an issue. I can't remove it (it uses a really large allen key or something), but it is NOWHERE near any moving part. I'll keep you posted.

As far as tools, which tools would I need to adjust the BB?
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Old 09-06-11, 01:59 AM   #16
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As far as tools, which tools would I need to adjust the BB?
I covered that in my previous reply. 36mm headset wrench for the driveside. 16mm cone wrench, and either a lockring spanner or something that can take its place, such as a big arc-joint plier, for the non-driveside. Fingers, eyes, cold beverage.
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Old 09-10-11, 03:24 PM   #17
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Hmmm... Seems putting my stock pedals back on removed the clunk. Which means its either an issue with the pedals, or how I put them on. Maybe I didn't tighten them enough.
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Old 09-11-11, 02:01 AM   #18
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That'd do it.

Also you can work the BB lockring with a hammer and screwdriver. If it's stubborn, lots of light taps in as many notches as you can reach, and you shouldn't make a mess of it. Even if you do, it'll only be cosmetic damage.

I've done ally cups (lots more resistance than rings) like that without damaging them... but I used a bit of plastic folded over the tip of the screwdriver and took my time. You can tap those cheap steel ones pretty firmly before they'll dent though.

Gonna have to get around to picking up a lockring spanner one of these days... so much nicer to have the right tools.

Last edited by Kimmo; 09-11-11 at 02:05 AM.
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