Thumping noise when pedaling
11-25-16, 08:55 AM
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Thumping noise when pedaling
This past week, I'm hearing a thumping noise around the bottom bracket area when the crank is pedaled under load to a certain area. Load meaning when I'm going up hills, but trying to not mash. It almost sounds like a flat tire thumping kind of noise, but when I coast, the noise isn't there. Only occurs when pedaling.
I'm planning on seriously looking at this tonight, was curious if anyone can give me tips on what I should be looking at specifically. I replaced the bottom bracket a year ago with a Shimano UN55 on my 2015 Crosstrail Sport. I have about 1000 miles on this new bottom bracket, it shouldn't be going out already, should it?
Thanks!
I'm planning on seriously looking at this tonight, was curious if anyone can give me tips on what I should be looking at specifically. I replaced the bottom bracket a year ago with a Shimano UN55 on my 2015 Crosstrail Sport. I have about 1000 miles on this new bottom bracket, it shouldn't be going out already, should it?
Thanks!
11-25-16, 10:42 AM
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First and easy checks are for loose arms on spindle and loose BB within frame shell. Andy.
11-25-16, 02:24 PM
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Loose crank arms will tend to shift at the same point on each pedal stroke. If the thumping happens throughout the pedal stroke, or not at the same point each time, check that the bottom bracket is properly adjusted and then check that rear hub and bottom bracket bearings are good and don't need re-packing.
Last edited by JohnDThompson; 11-25-16 at 02:27 PM.
11-25-16, 02:41 PM
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Loose crank arms will tend to shift at the same point on each pedal stroke. If the thumping happens throughout the pedal stroke, or not at the same point each time, check that the bottom bracket is properly adjusted and then check that rear hub and bottom bracket bearings are good and don't need re-packing.
Thanks, I noticed this morning it was thumping at a specific part of the stroke when the left crank was at the 10 oclock position.
11-25-16, 02:50 PM
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Depending on the pitch it means that your bike is ripe, and should be eaten tonight or tomorrow at the latest.
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11-25-16, 02:55 PM
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Sometimes a slightly loose crank arm can be hard to detect. If it isn't obvious stand the bike along a wall, sit on it holding the wall to stay upright. Now apply the brakes hard to keep the bike from moving, place the cranks horizontal, and stand on them. Do a small hop to press them down hard, then reverse the position and repeat. If there's any play at all between the cranks and spindle, you'll hear and/or feel it.
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11-25-16, 07:42 PM
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Sometimes a slightly loose crank arm can be hard to detect. If it isn't obvious stand the bike along a wall, sit on it holding the wall to stay upright. Now apply the brakes hard to keep the bike from moving, place the cranks horizontal, and stand on them. Do a small hop to press them down hard, then reverse the position and repeat. If there's any play at all between the cranks and spindle, you'll hear and/or feel it.
Oh, and it was too late to eat it, this bike is spoiled......I've been buying too much stuff for it to feel too good that it got spoiled!
11-25-16, 08:39 PM
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Check the chain rings too. Recently I tracked an occasional creaking noise to a couple of loose bolts in the triple chain ring. There are a couple of lock nuts I can't reach without disassembling the entire chain ring set so it still creaks occasionally on hard downstrokes while climbing or sprinting.
11-25-16, 08:59 PM
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Check the chain rings too. Recently I tracked an occasional creaking noise to a couple of loose bolts in the triple chain ring. There are a couple of lock nuts I can't reach without disassembling the entire chain ring set so it still creaks occasionally on hard downstrokes while climbing or sprinting.
11-25-16, 10:37 PM
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one more thing to check - pedal sliding side-to-side on its spindle
most mfgs of new pedals sell rebuild kits
most mfgs of new pedals sell rebuild kits
11-26-16, 07:22 AM
#12
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Sometimes a slightly loose crank arm can be hard to detect. If it isn't obvious stand the bike along a wall, sit on it holding the wall to stay upright. Now apply the brakes hard to keep the bike from moving, place the cranks horizontal, and stand on them. Do a small hop to press them down hard, then reverse the position and repeat. If there's any play at all between the cranks and spindle, you'll hear and/or feel it.
Last edited by cny-bikeman; 11-26-16 at 07:58 AM.
11-26-16, 11:00 AM
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11-27-16, 07:26 PM
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Well I tightened, or torqued the left crank to the specification that Specialized listed. No more thumping noise.
After carefully looking though, I noticed that my chain rings on the drive side are slightly bent but still working and is why I sometimes have chain rub. That might be early next years project to replace the crank-set if necessary. The chain rings unfortunately are riveted rather than bolted together. I'm betting it wasn't exactly a high priced item for Specialized to use for building this bike.
After carefully looking though, I noticed that my chain rings on the drive side are slightly bent but still working and is why I sometimes have chain rub. That might be early next years project to replace the crank-set if necessary. The chain rings unfortunately are riveted rather than bolted together. I'm betting it wasn't exactly a high priced item for Specialized to use for building this bike.
