Left crank/pedal "clunk" at top of stroke, advice please

[Wynne71]

Hello all, first post for me following my introduction in ten tea room section.
I'm about to get onto a road bike in early Sept, Merida Rode 300, but in the next few weeks I will be continuing to use my Giant Seek 2 hybrid.
I'm finding an odd problem though, my left foot feels a clunk/vibration at the top of the stroke. I can't re-create this on the turbo, just on the road and pretty much always when under load on a higher gear. Occasionally I can feel this if I'm out of the saddle going up hill, but mainly in the saddle on the flat.
I've recently fitted SPDs thought maybe the cleats in the shoes were worn, maybe slipping slightly under pressure. So I change them for the ones that came with the pedals, new. Still the same on the ride this morning.

Although this isn't the end of the world, and I'm really looking froward to the new bike, it is annoying, and want to get to the bottom of it.

Does anyone have advice as to where to start looking? I can't feel any movement on the crank, or the pedal itself. But then I don't think I would be able to recreate the loads it experiences on the road.

All help appreciated.

[Wynne71]

A few pics of the pedal crank in case anyone can see something obvious I am missing.

[Brucey]

there's only a few likely possibilities

- BB moving in the frame, or in the cups
- crank moving on the square taper
- pedal moving in the crank arm
- pedal bearings bad
- pedal to cleat or cleat to shoe interface bad.

BTW the BB might be loose on the Rh side or the left, although the left is more likely. I would suggest that you manhandle the pedals with as much strength as you can muster with your arms and see if you can get any clunks. If necessary, get a helper to help you.

hth

cheers

[Wynne71]

Thanks for the thoughts.
I was thinking pedal to cleat issue as it feels as though the foot moves/jumps slightly against the pedal at the point of clunk. Hence me swapping to new Shimano cleats.
Oddly if I try cycling slightly toe in, it goes away. But this feels odd. Have I possibly set the cleat in a position that is against my pedalling style?

Tried moving the crank, put the bike of the turbo and yanked with everything I've got, not a murmur.

Apologies for all the questions, as you can tell, I'm trying to learn.

[thirdcrank]

Try sitting on the bike where you can support yourself against a fence or similar then with the cranks horizontal stand on the pedals with all your weight. Sit down again to remove the weight from the pedals and move them through 180 degs to horizontal the other way and stand on the pedals again. If what you are experiencing is looseness of one crank, this should reveal it to the extent that you'll feel it in your feet.

[Wynne71]

Just been into the garage to try that, have found a use for the Work Mate at least, makes for a good leaning point...
I'd already taken the left pedal off, checked ten thread and the fitting, refitted carefully and properly torqued up.
Having just tried you test Thirdcrank it seems there is no movement in the crank end of things, firm on both sides.
Possible try the bike on its original flat pedals on a run and see if it does it then?


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[Brucey]

...Oddly if I try cycling slightly toe in, it goes away. But this feels odd. Have I possibly set the cleat in a position that is against my pedalling style? ...

possibly; is your normal position in the middle of the 'float' range or not?

is the shoe slightly worn, so that there is a little bit of vertical movement possible? IIRC if the front claw has worn a small depression in the sole, this could happen...?

cheers

[Eyebrox]

I tend to think it could be a fault at the cassette end with the clunk sensation being transferred along the chain. Try pedalling with the chain removed. If no clunk I suggest you service the bearings and refit the chain to check the chain line and cassette movement on the hub.

[thirdcrank]

Ever since the so-called Yorkshire Ripper murders, detectives have been keeping open minds. Don't discount anything until you have eliminated it. All my standing-on-the-cranks test does is eliminate the possibility of a crank being loose on the spindle. We've had a lot of threads on mysterious noises and many had a cause which was not originally suspected.

[Airsporter1st]

I had this exact same problem - clunking at the top of the left hand crank stroke.

In my case, it was the pedal bearings, in an almost new Shimano A530. I stripped and regreased several times and each time the problem would go away, then recur after around 30 miles. I inspected the races under magnification and by touch and could see/feel absolutely nothing.

Finally resolved by returning the pedals under warranty. The replacements have been fine for more than a year, so I am absolutely confident that it was a microscopic fault in the pedal race.

[Wynne71]

Thank you for the response. I bought the Shimano pedals "as new" from eBay. They have never been fitted or used, obvious from the packaging and pedal. Maybe I have a faulty one.
Will strip and grease to see if this removes the fault, as well as a trip with the flat pedals to see if this is a crank/cassette issue.

Great guidance from you all so far, much appreciated.
Can't wait to get the new bike, another learning curve I imagine!

[Brucey]

the way SPD pedal bearings are configured, the LH pedal bearing is (under precession forces, when the locknut is not tight enough) liable to start to bind, but in such a way (loose cone) that it may also start to clunk. Also note that the 'sleeve' part of the bearing is a press-fit into the pedal body. It is possible for a tiny change in manufacturing tolerances to make this fit bad; I have seen this once or twice.

cheers

[Wynne71]

I've done 45 mins on the turbo, trying to replicate the feeling.
Either the refitting of the pedal has sorted it, or the turbo won't generate enough of a real road load to the crank/pedal.

[Wynne71]

Good news, after re-greasing, re-fitting the left pedal it seems
all fixed.
Have done a 28 mile round trip today and not a single clunk or groan. Hopefully this will be good for a while now.

Many thanks for all the advice and suggestions. Hugely appreciated.

[Captainmorgan]

Good news, after re-greasing, re-fitting the left pedal it seems
all fixed.
Have done a 28 mile round trip today and not a single clunk or groan. Hopefully this will be good for a while now.

Many thanks for all the advice and suggestions. Hugely appreciated.

Thanks, this was the solution for my identical issue too. New to road cycling and as an ex-BMX rider I was jumping straight to the cranks/BB.