Clonking noise on every pedal revolution

ChrisEyles

Veteran
Location
Devon
My commuter recently developed a slight "clonking" noise when pedalling against resistance. As well as being kind of annoying, I don't want to ignore a warning sign and end up with an expensive trip to the LBS!

The noise occurs once per revolution of the pedals, when the left (non-driveside) crank is pointing more or less straight down. It doesn't occur when back pedalling, or pedalling gently - for example I can't replicate the noise lifting the back wheel off the floor and turning the cranks by hand. It only happens when some effort is being applied e.g. up hills or maintaining speed on the flat etc. The noise is slightly quieter if I get out the saddle on a climb, but still happens at the same crank position.

I had a look on Sheldon Brown's site, and it seems the most likely culprits are the BB or the pedals themselves. I've checked both of these, and they seem to be good and tight, with no play anywhere that I can detect. The BB is a cartridge type, so I guess I can't adjust this like I would do on an old style cup/cone setup. It has done around 4,000 miles without any attention - is it likely it simply needs replacing?

I also checked the chainrings, and they aren't coming into contact with the FD. No kickstand or anything for the cranks to catch on either.

Any suggestions gratefully received!
 

Hugh Manatee

Veteran
Tight link in the chain?

Is the cassette tight?

Check the tyres.
 
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al-fresco

Growing older but not up...
Location
Shropshire
Sounds similar to a problem I had a few years back which turned out to be a worn pedal. Have you got a spare pair that you could stick on to see if the problem goes away?
 
OP
ChrisEyles

ChrisEyles

Veteran
Location
Devon
@Hugh Manatee - I don't *think* it would be a tight link in the chain, since wouldn't this make a noise every chain revolution rather than every pedal revolution (these won't generally match)?

@Sittingduck - Yes, the noise occurs at the same crank position in all gears

@al-fresco - Unfortunately I don't have any spare pedals, though this does seem like a possible cause. Again, these have only done 4,000 miles or so, which doesn't seem like a lot to wear out!
 

RebornBumbler

Senior Member
Location
Barnstaple
The BB and pedals are definitely top suspects, but as it's at the bottom of the stroke it could also be related to your movement on the bike - think stem, bars, wheel bearings, seatpost (if seated) - intermittent noises on bikes can be hard to pinpoint.
It's a process of elimination - I'd try the pedals first (worst case you'll have some spare pedals which you'll need at some point).
 
Location
Bucks
BB or crank then, I reckon. Remove crank, clean re-grease could be worth a shot? If definitely no play in BB and smooth then I guess thats' ok. Seat posts often the cause of noises but if it's still happening out of the saddle then it's unlikely unless you're still applying pressure on the saddle with your thighs, out of the saddle...
 
OP
ChrisEyles

ChrisEyles

Veteran
Location
Devon
@RebornBumbler - interesting, I'll check the stem and bars to see if the noise could possibly be coming from there.

@Sittingduck - Sadly I don't have a crank puller to remove the crank myself, otherwise I would definitely do this.

Now I come to think of it, I think I *do* have an uber-crappy pair of spare pedals somewhere in the shed. Wouldn't want to use them long-term, but they'd do for eliminating/confirming the current pedals as the source of the noise. Just need to see if I have a spanner that will fit or if I need to order one for the purpose.
 

Gravity Aided

Legendary Member
Location
Land of Lincoln
Some Shimano sealed BBs have a plastic cup on one side. Might it be cracked?
 

mjr

Comfy armchair to one person & a plank to the next
My top suspect (because I've killed several left-hand cranks this way, including some me-not-on-bike falls thank to a duff kick-stand) is the crank coming loose on the BB spindle. Hold both cranks and try to wobble them gently side-to-side: is there any play? Holding left crank and frame? If you've not ridden far, you may get away with tightening the crank bolt or remove/serious clean of the facing parts/reattach, but the left crank may well be dead. New alloy left crank £8.39 at Raleigh dealers, but I've bought them as low as £2 from some local bike shops.
 
OP
ChrisEyles

ChrisEyles

Veteran
Location
Devon
@Learnincurve - the FD is definitely clear of the chain and chainrings, this was one of my initial suspects too

@mjray - I couldn't detect any play/wobble in the cranks, but I guess this is possible. I did have a small off on this bike a few months ago in the ice, which could have done for the crank :S If this is the case, does the BB spindle usually need replacing too, or is this made of sterner stuff than the crank interface?

My plan now is:

1) Does a little look-no-hands riding cure the problem? If so I guess I need to check if my stems/bar need replacing, that could be nasty!
2) Most likely: do my cheapo old pedals fix the problem?
3) A trip to the LBS for a new crank (or for tools to do the swap, depending on relative price!)

Thanks all for the helpful feedback!
 

mythste

Veteran
Location
Manchester
Happened on my Charge Fixie. Had the BB replaced and problem was gone. the LBS could replicate it by holding both pedals where the clunk noise was, pushing down hard and wobbling back and forth.
 
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