Clank every pedal rotation?

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toontra
Posts: 1182
Joined: 21 Dec 2007, 11:01am
Location: London

Clank every pedal rotation?

Post by toontra »

Trying to narrow down an annoyance. Once every pedal rotation there is quite a loud clanking noise, BUT only when in the small ring (compact 50-34). Louder the heavier the load.

It's a BBright pressfit bottom bracket (Cervelo S2) with Sram Force 22 crankset. As it's synced to the pedal rotation I assume that it's the bottom bracket bearings or the crankset, but can't understand why it only happens in the small ring (irrespective of load on either ring).

Nothing as simple as components hitting each other unfortunately ;)

Any suggestions much appreciated.
Jdsk
Posts: 24478
Joined: 5 Mar 2019, 5:42pm

Re: Clank every pedal rotation?

Post by Jdsk »

There's a useful recent thread: viewtopic.php?f=5&t=146300

One of the major themes is that there are many places from where it could be coming...

Can you reproduce it with the bike on a stand?

Jonathan
PT1029
Posts: 1742
Joined: 16 Apr 2012, 9:20pm

Re: Clank every pedal rotation?

Post by PT1029 »

If only on the small ring, might only "clank" due to pushing harder(?) ....
.... or the protruding end of the gear cable catches on the RH crank (or LH crank if a top swing F mech).

Previous "BB/chainset" noises have included laces knocking on toe clips, jacket draw string draw cord ends dangling on top tube, so quite a few options to investigate!
gregoryoftours
Posts: 2234
Joined: 22 May 2011, 7:14pm

Re: Clank every pedal rotation?

Post by gregoryoftours »

Does it make the clank in small ring regardless of which sprocket you're on at the back? Can you make it clank at a different point in the rotation? Say for example if it's in the right crank power stroke can you ease off of the right and push harder on the left crank stroke to make the clank? Check for damaged teeth on small ring, chainring bolts for small ring amongst other stuff.
Last edited by gregoryoftours on 15 Jun 2021, 9:02pm, edited 2 times in total.
toontra
Posts: 1182
Joined: 21 Dec 2007, 11:01am
Location: London

Re: Clank every pedal rotation?

Post by toontra »

PT1029 wrote: 15 Jun 2021, 7:53pm If only on the small ring, might only "clank" due to pushing harder(?) ....
.... or the protruding end of the gear cable catches on the RH crank (or LH crank if a top swing F mech).

Previous "BB/chainset" noises have included laces knocking on toe clips, jacket draw string draw cord ends dangling on top tube, so quite a few options to investigate!
No, as I say I've ruled out all types of "stuff hitting other stuff"-type noises. Whatever it is it's not visible.
toontra
Posts: 1182
Joined: 21 Dec 2007, 11:01am
Location: London

Re: Clank every pedal rotation?

Post by toontra »

gregoryoftours wrote: 15 Jun 2021, 8:56pm Does it make the clank in small ring regardless of which sprocket you're on at the back? Check for damaged teeth on small ring, chainring bolts for small ring amongst other stuff.
Yes - all cassette cogs on the small ring, although I tend to push harder on the lower rings (bigger cogs) so that may have some bearing.

I've taken the crankset off, cleaned and greased everything and tightened the chainring bolts. Will test tomorrow.
NickJP
Posts: 793
Joined: 24 Sep 2018, 7:11pm
Location: Canberra, OZ

Re: Clank every pedal rotation?

Post by NickJP »

Yeah, I was about to suggest the chainring bolts. I had a creak in my drivetrain that I thought was either pedals or bottom bracket, but in fact it turned out to be that the chainring bolts had come slightly loose.
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