Creaking Aluminium Frame

[Jim77]

Hi all,

I have notice that my aluminium frame flexes slightly when under load, around the bottom bracket area, and there is a creak on each pedal revolution.

Are the two things related?

Thanks

Jim

[Jdsk]

Usual warning: these can be very hard to locate.

Creaks that match the pedal movement might be caused by the drivetrain or where it connects to the frame. But they might also be caused by the weight of your body and how it moves around as you pedal... seat post, saddle, bars...

Can you reproduce the sound with the bike on a stand?

Jonathan

[Brucey]

if you can make the sound at a standstill, you may be able to better trace it's true point of origin using a mechanic's stethoscope.

[Nearholmer]

Are the two things related?

They might not be, but they might be.

If I were you, I’d try to devise some way to load the pedals to represent pedal force, with the bike static, and then examine the BB area, and the rest of the frame too, very closely, looking for signs of incipient cracks.

Easier said than done, but if you can get a mate to help it might be practical. Have him/her sit on the bike while leaning against a wall, then bounce up and down on the seat. Then stand up taking all weight through one foot while bouncing up and down on one pedal.

Hopefully, it won’t be crack-related, but even if it isn’t, this might (or might not!) help you pin down the source of noise.

[Barrowman]

Try standing alongside the bike, grip the saddle and the bars then put your foot on the crank and push with your leg .
You will see how much the frame flexes and you might reproduce the noise.
If you don't it's probably not the frame but as previously mentioned noises can come from anywhere and can be quite difficult to source. One of our CTC group had a random noise on a Tandem, it was a stripped thread on a spoke nipple.

[cyclop]

what type of bottom bracket have you got?Screw in or one thats pressed in?

[rareposter]

If you don't it's probably not the frame but as previously mentioned noises can come from anywhere and can be quite difficult to source.

Very much this ^^.

Could be anything from an improperly tightened QR to the pedal threads, crank/chainring bolts, any of the seatpost/saddle bolts...
If you can isolate the rough area of the noise and any kind of factors (eg, does it happen while freewheeling, pedalling or both; does it happen seated or standing or both, does it happen in all gears or just some, are any parts like BB, cranks etc loose or stiff...) it makes it easier but really you just have to go through with a fine tooth comb in a methodical manner, checking everything and making a note of what you've done and what (if any) effect it's had.

[SprokenBroke]

Remove the cranks and put a bit of grease on the taper flats. If the creak stops then that's what it was.

[Jim77]

Usual warning: these can be very hard to locate.

Creaks that match the pedal movement might be caused by the drivetrain or where it connects to the frame. But they might also be caused by the weight of your body and how it moves around as you pedal... seat post, saddle, bars...

Can you reproduce the sound with the bike on a stand?

Jonathan

I can replicate it at a stand still just put pressure on the pedal/crank without putting weight on the handlebars or saddle.

[Jim77]

what type of bottom bracket have you got?Screw in or one thats pressed in?

Threaded bb - hollowtech.

[Barrowman]

I have no direct Hollotech Experience but sounds like the bolt that holds the crank on isn't at the right torque setting ( ' too loose ')

[Brucey]

if you can make the sound at a standstill, you may be able to better trace it's true point of origin using a mechanic's stethoscope.

further to this if you don't have access to a mechanic's stethoscope, pretty much anything with a microphone might do. All such devices are susceptible to knocks and bangs because the microphone will respond almost equally well if 'the tail is wagging the dog' as it were. You can exploit this by simply pressing the device against the possible source of the sound. Whatever part manifests the loudest/clearest sound (for the same contact) is probably the source.

From what you have said, I am suspicious of the chainring bolts and the pedal threads. It certainly won't hurt to disassemble/clean/regrease these parts (preferably one at a time, so you know what the cause was). NB the only part of the chainring bolt assembly which should be greased is the screw threads. Everything else should be clean and dry, in particular, remove every trace of black <i>[inappropriate word removed]</i> from under the chainrings..

[Jim77]

if you can make the sound at a standstill, you may be able to better trace it's true point of origin using a mechanic's stethoscope.

further to this if you don't have access to a mechanic's stethoscope, pretty much anything with a microphone might do. All such devices are susceptible to knocks and bangs because the microphone will respond almost equally well if 'the tail is wagging the dog' as it were. You can exploit this by simply pressing the device against the possible source of the sound. Whatever part manifests the loudest/clearest sound (for the same contact) is probably the source.

From what you have said, I am suspicious of the chainring bolts and the pedal threads. It certainly won't hurt to disassemble/clean/regrease these parts (preferably one at a time, so you know what the cause was). NB the only part of the chainring bolt assembly which should be greased is the screw threads. Everything else should be clean and dry, in particular, remove every trace of black <i>[inappropriate word removed]</i> from under the chainrings..

Ok thanks I will give the cleaning process a go and report back. I know it isn’t the pedals as I took them off and tried on another bike (same with the cleats) and no noise. So as you say could be where the pedals screw into the crank arms or the chainrings etc.

[Jim77]

if you can make the sound at a standstill, you may be able to better trace it's true point of origin using a mechanic's stethoscope.

further to this if you don't have access to a mechanic's stethoscope, pretty much anything with a microphone might do. All such devices are susceptible to knocks and bangs because the microphone will respond almost equally well if 'the tail is wagging the dog' as it were. You can exploit this by simply pressing the device against the possible source of the sound. Whatever part manifests the loudest/clearest sound (for the same contact) is probably the source.

From what you have said, I am suspicious of the chainring bolts and the pedal threads. It certainly won't hurt to disassemble/clean/regrease these parts (preferably one at a time, so you know what the cause was). NB the only part of the chainring bolt assembly which should be greased is the screw threads. Everything else should be clean and dry, in particular, remove every trace of black <i>[inappropriate word removed]</i> from under the chainrings..

Ok thanks I will give the cleaning process a go and report back. I know it isn’t the pedals as I took them off and tried on another bike (same with the cleats) and no noise. So as you say could be where the pedals screw into the crank arms or the chainrings etc.