fritz1255

I recently bought a bike training stand where the back axle clamps in and you pedal against resistance. The bike I use on this is my 1960's French ten speed that I got in junior high school. This bike has not had a wrench on it in over 40 years, so I have discovered numerous problems that needed attention. Doesn't help that back in high school, all I had to work with was my parents' sparse collection of tools, so lots of stuff is having to be done right this time.

One problem that I have not been able to solve yet is a "clunk" that is felt rather than heard under my left foot. It is when the crank is parallel to the ground, and the left foot is coming up. I first assumed that the crank was hitting the kickstand, and eliminated this possibility by moving the kickstand. The left pedal did not spin smoothly, so I took it apart and regreased the bearings (inside bearings were dry) and readjusted the bearing cone so it now spins freely. The "clunk" is still there, however. I have narrowed it down to three possible causes, two mechanical, one not:

1) Something wrong in the bottom bracket
2) Something in the pedal is bent, and is making contact at that point
3) I am doing something with my feet - letting up in pressure as the foot comes up maybe, that is causing a "hitch" in the chain movement that manifiests itself in the left foot

Any ideas on how to isolate the cause? The bike itself is an off-brand entry level machine with cottered cranks.

Zef

Start easy and move on to the harder stuff:

1. Make sure the crank arms are torqued down sufficiently.

2. borrow some pedals off another bike and see if that causes the problem to go away. If so, then buy a new set and you're good to go.

3. Overhaul the bottom bracket. Check to see if the bottom bracket axel is bent...if so, replace.

4. Take the pedal apart again and and check whether or not the spindle is bent....replace pedals if necessary.

-j

jolly_ross

Swap pedals, as suggested by Greenfieldja is the cheapest first step. If the noise goes away try putting one of the old pedals back (each side in turn).

Somehow I''m doubting the bike has clipless pedals, however if it did you can avoid pedal swapping by pedaling along a flat road with one foot only - for a while on each side - try to apply force around the whole circle ... noise with both pedals means a BB problem ... noise on one pedal only points to that pedal (not 100% definite, but strong indication)

cny-bikeman

It's not the pedal (unless it's not tight on the crank arm) nor is it likely a problem with the BB bearing itself (wear, etc). Of course you can just go straight to overhaul, which would be advisable anyway, and would eliminate both of the more likely issues, but be aware you may well need to replace parts, which could be a challenge. I'm including the procedures below so that you and others can understand how to isolate the problem and address it when overhaul is not necessary.

The most likely candidate would be cotter pin that is not properly tightened or that has a notch in it. Put the cranks level and then stand on them. Turn 180 degrees so the other crank arm is forward and stand on them again. If the cotters need attention you will probably feel a clunk. See https://sheldonbrown.com/cotters.html for information on proper removal, sizing and installation. DO NOT just crank down on the cotter pin nuts.

The second likely cause is a loose lockring or fixed cup. Move one crank parallel with the down tube and pull it hard toward the down tube, then repeat with the other crank. If you feel a shift then a bottom bracket cup is loose. Even if you don't that could still be the problem. Tightening the lockring is fairly straightforward - part of BB adjustment, but a loose fixed cup will require removal of the right crank arm at a minimum, but likely will require a crank overhaul to properly tighten it, and it may of course need replacement.

ksisler

OP; You are wasting a lot of your time chasing potential ghosts. A bike that has sat neglected for 40 years... Well, fully service it end to end and then see if it has any additional issues.

Doohickie

5. Make sure your chain ring bolts are tight.

Doohickie

Well, he's using it on a trainer, so no harm in taking a little time and trying different things. It might be something simple.

ksisler

Doo; Well if the bike had only been sitting neglected for a decade, then maybe. But 4 decades; no. That would be irresponsible/dangerous. A bike so neglected should not be ridden until it has been fully gone through and serviced. During that effort, most all things needing attention will be discovered. Riding it otherwise can come to considerable grief; running the end of a sheared off pedal spindle up the inside of his calf; Going down head in from the steerer breaking off right above the fork crown bearing; being deprived of a good wallhanger when an internally rusted out frame tube collapses mid-ride while training.
So I will stick with my first recommendation! /Kerry

Doohickie

Dangerous? Really?

ericzamora

I had something similar happening with my daughter's new (old) 1972 10-speed motobecane mixte bike i just bought off of CL last month. i saw one of the cotter pins had been sheared off by a probably past repair attempt. cluNcking sound and feel while pedaling. when i took it into a shop which specializes in old bikes (they actually stock french sized cotter pins) the left crank arm fell out into his hand. very embarrassing, it hadn't been that loose when we test rode it. $40 later it had new pins and regreased BB. it works like new now. good luck. hopefully it's something that easy.

eric
fresno, ca.

fritz1255

And the winner is: cny-bikeman, the first to recommend looking at the cotter pins. The left crank has a slight, but perceptible movement. Unfortunately, the cotter pin is all the way in, so there is no way to tighten it. This is the result of an amateurish rebuild done by a friend of mine and me in about 1968 or so. Too much filing to make it fit, apparently. Possible that it can be tightened a little by adding washers under the nut. I have a replacement set of cotter pins of the correct size (9mm) bought several years ago. I was able to find them in my messy basement inside of 30 minutes, which I take to be a sign from God. Other things have gone missing down there for as long as a couple of years before being found.

As for the bike being neglected, it has not had 40 years of hard riding. It has spend nearly all that time hanging on the wall of my basement or storage room. Hopefully the grease won't dry out or bearing cones loosen themselves while the bike sits, but who knows? I found the bike abandoned in about 1967. My best buddy's parents had just bought him a new Peugeot, and I HAD to have a 10-speed. My parents could not understand why the massive Schwinn single speed that they had "just" bought me a couple of years before was not good enough any more, and it would have taken me at least a year to save up the $100 that a new bike would have cost. Another friend of mine and I did a rebuild on it, and that's the last time it was serviced extensively.

cny-bikeman

Right the first time - it cannot be tightened. As I mentioned before the nut is NEVER used to tighten the cotter, only to secure it after tightening. The reason is that the cotter, in order to facilitate conforming to the spindle, is relatively soft. It's very easy to shear the threaded stud off the pin by overtightening the nut. In an emergency you might be able to move the cotter a bit more with a punch, but the nut/washer may just bottom out on the other end, and you still will not have the problem solved.