Weird rumble, silent pop when pedaling - Solved

[R3awak3n]

This one is hard to describe. I thought it was maybe the pedal bearings or some play in the pedals so I took them out this weekend, new grease, no play but this is still in there.

When I pedal sometimes I can feel it on my feet, some rumbling or pop but its silent I can only feel it. Sometimes its on one foot, sometimes the other and only at certain times, sometimes its smooth. I am thinking maybe crank bearings? The cranks are super record with ceramic bearings that I got from someone here in the forums. How long do ceramic bearings last? Could it be something else?

[ColonelJLloyd]

I would switch pedals and see if the issue persists. It's a process of elimination these things. Sucks.

[parris]

Could it be slightly loose bb, chainring bolts, etc?

[jtakeda]

Does it happen when you wear sneakers?

[R3awak3n]

@coloneljloyd - I need to do that and should have been what I did this weekend instead of re greasing the bearings. Will start there for sure.

@parris - thought that too, the campy cups look tight enough but might need to remove the crank and really check. I know that the C clip was coming out last week and I just put it back in. I checked chainring bolts by hand they all seem to be there, also chainrings not moving around.

@jtakeda - Have to try this. I did try to not clip in and still felt it.

@Mark McM - Could be chainring wear but the chainrings don't look like they have many miles to be honest. Definitely not chain or cassette wear as they both have less than 500 miles.

[Mark McM]

Originally Posted by R3awak3n

This one is hard to describe. I thought it was maybe the pedal bearings or some play in the pedals so I took them out this weekend, new grease, no play but this is still in there.

When I pedal sometimes I can feel it on my feet, some rumbling or pop but its silent I can only feel it. Sometimes its on one foot, sometimes the other and only at certain times, sometimes its smooth. I am thinking maybe crank bearings? The cranks are super record with ceramic bearings that I got from someone here in the forums. How long do ceramic bearings last? Could it be something else?

The notchiness of bad bearings is usually too small to notice when riding.

A stronger possibility is a worn chain and/or sprockets, and or chainrings. When one (or more) of these are worn, the mismatch between the pitch of the chain and sprocket can cause a vibration as the teeth engage with the rollers. The larger magnitudes of the forces involved will make any vibrations caused larger and easier to notice than bearing notchiness. These vibrations will also vary between different sprockets and different chainrings, depending on the degree of wear difference between chain and sprocket/chainring.

In particular, chainrings wear can wear unevenly, with more wear on the teeth that are engaged during the power portion of the pedal stroke. There can be a very distinct 'jerkiness' (for lack of a better term) felt in the pedals as the chain transitions from the more worn to the less worn portions of the chainring.

[Ken Robb]

Originally Posted by Mark McM

The notchiness of bad bearings is usually too small to notice when riding.

A stronger possibility is a worn chain and/or sprockets, and or chainrings. When one (or more) of these are worn, the mismatch between the pitch of the chain and sprocket can cause a vibration as the teeth engage with the rollers. The larger magnitudes of the forces involved will make any vibrations caused larger and easier to notice than bearing notchiness. These vibrations will also vary between different sprockets and different chainrings, depending on the degree of wear difference between chain and sprocket/chainring.

In particular, chainrings wear can wear unevenly, with more wear on the teeth that are engaged during the power portion of the pedal stroke. There can be a very distinct 'jerkiness' (for lack of a better term) felt in the pedals as the chain transitions from the more worn to the less worn portions of the chainring.

This makes a lot of sense to me and I had never thought about uneven wear on chainrings before.

[spoonrobot]

I know you solved your problem already but FWIW KMC chains have always been "rumbly" on SRAM cassettes for me.

[R3awak3n]

Originally Posted by spoonrobot

I know you solved your problem already but FWIW KMC chains have always been "rumbly" on SRAM cassettes for me.

yeah, I noticed right away and KMC on sram cassette sounds really grumbly and metally compared to the same setup but with a ultegra cassette (on my other bike). Still works fine and shifts fine but lowder and just not as.... how should I put it, refined.

[Mikej]

I know that rumbling happens on the clutched shimano mtb rd if the top jockey pulley is too close - happens in all gears, check you b-screw, or whatever thay call it now.

[Mark McM]

Originally Posted by Ken Robb

This makes a lot of sense to me and I had never thought about uneven wear on chainrings before.

Uneven wear is most noticeable on the small chainring. All else being equal, smaller chainrings wear faster than larger (just like small sprockets wear faster than larger). That is why many people rotate their small chainring mounting. Large chainrings must be used in specific orientations, due to the positions of the chain pick-up rivets and anti-jam pin, but small chainrings are fairly agnostic about their orientation. On 5 arm chainrings, the chainring mounting orientation can be shifted in increments of 72 degrees (1/5 of a circle). Periodically shifting the small chainring orientation can even out the wear and extend chainring life.

[oldpotatoe]

Originally Posted by R3awak3n

This one is hard to describe. I thought it was maybe the pedal bearings or some play in the pedals so I took them out this weekend, new grease, no play but this is still in there.

When I pedal sometimes I can feel it on my feet, some rumbling or pop but its silent I can only feel it. Sometimes its on one foot, sometimes the other and only at certain times, sometimes its smooth. I am thinking maybe crank bearings? The cranks are super record with ceramic bearings that I got from someone here in the forums. How long do ceramic bearings last? Could it be something else?

What rear wheel? Mavic krysirium by chance? Could be BB, crank off(remember clip on RH cup, you DO have a clip on RH cup, yes?)...spin in hand...feel smooth or not?

[David Kirk]

If it's crank-rpm related my money is on the bottom bracket bearings or the interface between the two side of the crank.

dave

[R3awak3n]

Originally Posted by oldpotatoe

What rear wheel? Mavic krysirium by chance? Could be BB, crank off(remember clip on RH cup, you DO have a clip on RH cup, yes?)...spin in hand...feel smooth or not?

wheels are hunt (so some sort of taiwan generic hub).

clip is on the RH cup. I won't have access to tools for a couple of weeks so would be able to take crank off but I will do that. I know that crank, without the chain on it spins like butter. I remember when installing, the bearings felt AMAZING.


@David Kirk - it does seem to be rpm based, I think. and I feel usually at a certain angle on the crankset.


edit- also thank you to everyone so far for the help and time!

[shovelhd]

I'm thinking chain/cassette/link/chainrings/chainline. Is the bike new to you? What kind of chainrings, chain, cassette, and chain link (if any)? How does the chainline look? Is the derailleur hanger straight?