Weird rumble, silent pop when pedaling - Solved

[Mark McM]

Another thought comes to mind:

If the momentary 'rumbling' appears to be periodic, but at a different rate between different chainrings, that suggests a stuck link in the chain.

A typical chain has about twice as many links as the number or teeth on a (standard road) outer chainring, so a stuck link passing through the drive train will be felt roughly every two crank revolutions. A typical chain has about 3 times the number of teeth on a (standard road ) inner chainring, so a stuck link passing through the drivetrain will be felt roughly every three crank revolutions.

[R3awak3n]

/\ very interesting and good point. will investigate tonight and see if any link is stuck.

Will also take the crank out and check bearings when I can (in a week or so). But when the crank went in, and this was maybe a couple months ago, the bearings felt great. I do have an extra set of ceramic bearings I can throw on it if its the case but I thought ceramic bearings lasted a looooooong time

[oldpotatoe]

Originally Posted by R3awak3n

/\ very interesting and good point. will investigate tonight and see if any link is stuck.

Will also take the crank out and check bearings when I can (in a week or so). But when the crank went in, and this was maybe a couple months ago, the bearings felt great. I do have an extra set of ceramic bearings I can throw on it if its the case but I thought ceramic bearings lasted a looooooong time

The ball bearings themselves do last forever but even on hardened races/cups, a little grit in there and the very hard balls can kill the steel races. Grease into cups, around bearings..great seal. Can't use too much.

[yashcha]

Had something similiar. One of the paws in the hub mechanism was cracked and needed replacing.

[thwart]

Originally Posted by yashcha

Had something similiar. One of the paws in the hub mechanism was cracked and needed replacing.

That (failure in a generic hub) would seem to be more likely than the other higher quality components in the drivetrain...

[cmbicycles]

I had this be the cause of noise on my small chainring recently...

A few tiny pieces broke off where the chainring bolts go, but made an audible grinding noise rather than being able to feel it.

[IFRider]

I had a weird noise on a new to me frame I built up. Campy ten speed. I could not isolate and the noise only occurs pedaling. This was Campy 10 13-29 with a compact 11 crank. I finally isolated to the cassette every so slightly tight fit against the dropout. Coincidently, that is where some touch-up paint was needed. Careful adjustment of the wheel in the dropout fixed it. It was not a problem on the previous install (steel frame also). I am guessing the 13 is the issue.

I have it on my list to reach out to the builder privately and ask advice but for now, the noise is gone and all is right with the world.

[oldpotatoe]

Originally Posted by IFRider

I had a weird noise on a new to me frame I built up. Campy ten speed. I could not isolate and the noise only occurs pedaling. This was Campy 10 13-29 with a compact 11 crank. I finally isolated to the cassette every so slightly tight fit against the dropout. Coincidently, that is where some touch-up paint was needed. Careful adjustment of the wheel in the dropout fixed it. It was not a problem on the previous install (steel frame also). I am guessing the 13 is the issue.

I have it on my list to reach out to the builder privately and ask advice but for now, the noise is gone and all is right with the world.

Had the same issue with a few Waterfords/Gunnar's...little cutout of plug for seatstay/dropout a little too low, an issue with the 'taller' 13t only...easy production fix.

[keevon]

My guess is the freehub. Can you take it apart to see if any pawls are sticking or cracked?

[R3awak3n]

unfortunetely been working weekends and havent had time to figure this one out hope I can take a look this saturday.

[11.4]

Sometimes those sensations can be deceptive. If it's bearings, chain, or anything else drivetrain related, it should be reasonably consistent and reproducible. If they're gone, they're gone.

I'm actually wondering if it's a saddle or saddle/seatpost problem. Pedaling cadence can cause cadence-associated noises and feelings in the saddle. They can transmit down the leg and you actually feel them more where your feet have a harder contact with the carbon fiber sole of your shoes. It can also be a problem with the seat post or seat lug/seat post clamp that you feel each time you go through a pedal revolution and alter your weighting somewhat on the saddle, and the seat post transmits it to the frame, at which point it goes everywhere. Anyone who's had to track down a spurious noise on a bike is familiar with this problem.

If the saddle is even rocking slightly because a frame rail is loose in the plastic shell, it can create this kind of problem but feel like it's pedaling related. Ditto for a failing rail, not enough clamping pressure from the seat post, too much pressure, and so on.

[IFRider]

Originally Posted by oldpotatoe

Had the same issue with a few Waterfords/Gunnar's...little cutout of plug for seatstay/dropout a little too low, an issue with the 'taller' 13t only...easy production fix.

As it would happen, I pulled the groupset off a Waterford RS-22, against which I compared. Thanks for posting, I thought I was going crazy with this one ...

[R3awak3n]

thanks for everyone for helping me out here.

finally had time to work on the bike this weeked and on a quick ride last night problem seems to be gone.

I put the bike on the stand and it shifted fine but I noticed that when pedaling backwards really fast on the stand the chain would get caught btw the RD and the cassette. It was weird and obviously would not ever happen on the road but meant something was strange.

I then looked where it was happening and was on the quick link, well I then remember that I needed this chain to be longer so I used 2 quick links with 3 extra chain links btw them. Was immediately like, oh maybe this is the problem. Looked at the quick links and one seemed a bit looser than I like it so I put a new one there (I should just buy a new chain I know I know).

I then also cleaned the chain, removed the cassette and cleaned. Check the freehub because maybe stuck pawn but it was fine. Then I also checked derailleur alignment and it was a bit out of wack. Fixed that as well.

Now it all seems to be working fine. Pretty sure it was the quick link but I guess we will never know.

[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.