Sometimes when I start pedalling again after bumpy downhill sections there is a loud ‘crunch’ noise. I’m pretty sure it’s coming from the chainrings somewhere as if the chain is getting caught or maybe skipped onto the wrong ring or something. It wouldn’t bother me too much but it made my chain snap recently.

Does any one know what this might be and how I can stop it happening?

Thanks.

i use the big ring on the downhill sections find it stops the chain jumping around too much

I removed the big ring and replaced it with a chainring protector and the chain is always on the biggest ring when I go downhill. I’m pretty sure this used to happen when I had all three rings too.

The crunch I hear pedalling after a downhill is my knee. Check your knee.

Ha ha! Probably my back actually!

Me eating tortillas

nom nom crunch crunch! 🙂

Probably the sound of my gonads smashing the stem on The Wall at Afan today on the final day of my MIAS Lev 2. How I laughed…

Except I didn’t.

😀

Might be badly aligned tyres/ Valves?

Anyone else got any ideas?

When you stop pedalling over bumpy ground, the intertial loading on the chain may cause dynamic excitations and spacial misalignment. This, coupled with the isotropic materials used in the funicular chain-sprocket can produce undesirable effects in the presence of silica crystals and large masses of stone. I suggest that the inherent weaknesses in this design should be mitigated by combining the loading characteristics of the handicapped mainstay assembly with the self-meshing properties of the flux-energy alignment array. For even better performance use a hydrocarbon based (NOT water based solvent!!!) lube.

If all else fails, find your local machine shop and get them to machine you a snub-dongle, which will be useful in maintaining the haphazard hysteresis due the uneven wave-function of the loading and also prevent sudden and catastrophic loss of pedal-resistance.

TL:DR: It could be a child’s face next time.

erm

It might always have been the rotating eccentric expangulator. Check that.

What size rear mech do you have? Did you change when dropping the outer ring?

Consider a smaller one for more chain tension, maybe a few links out first before shelling out on a mech.

It sounds like a slack chain and its jumped onto bottom ring then the crunch is when its working its way back on to the middle cog.

Is it a credit crunch? 😕