Bicycle Mechanics - Clank in hub while coasting (helicomatic)

I have a 1985 Peugeot PH501 and have started to notice a clank noise that I can feel in the pedals while coasting (once per wheel turn).

The bike has a helicomatic hub which I know have a tendency to wear out quickly in the cones. I took them apart, cleaned and repacked with new grease and bearings but I still have the clank. There is definitely some wear on the cones, but I don't know if that is enough to feel a pretty solid "clank". I would think cone wear would come across more like a grinding? The front cones had similar wear patterns but I don't hear anything coming from there.

Could this be something in the freewheel mechanism? Cleaning/repacking is the extent of my experience with hub maintenance. I'm hoping someone here might have a better idea what this noise could be and hopefully point me to some information that could get me started.

they are orphaned, company long gone, so all you can do is find another used one.
save long term continuing problems, time for another wheel.. different hub.

the French attempt at a freehub.. back then..

Yeah, thats what I'm thinking is just replace it.. but I only spent 250 on the bike and would like to try to get it working without that if possible. I guess I'll try to flush some oil through the freewheel, maybe there's something solidified in there. I found some used and NOS helicomatic hubs on bikeville for $25-50. I don't know how to build up a wheel but my LBS will do them for $25. With the used hub I could keep the bike a bit more original and still come out cheaper than buying a decent new 126mm wheel from the prices I've found so far.

I found some used and NOS helicomatic hubs on bikeville for $25-50. I don't know how to build up a wheel but my LBS will do them for $25.

If the problem is in the freewheel, as you seem to suspect, then a new hub will not help unless it includes a new freewheel as well.

Good point. I'm going to take the freewheel off today and flush it out, try to take a closer look at the wheel while it's off and see if I can hear it in either the hub or the freewheel to pinpoint further.

Would you expect a periodic clank could be something with the races/bearings/cones or would that be more of a gritty grinding like I'm thinking?

Would you expect a periodic clank could be something with the races/bearings/cones or would that be more of a gritty grinding like I'm thinking?

Just a guess, but perhaps it's a pawl skipping?

Well after removing the wheel I confirmed the noise only happens when it is coasting. I took the freewheel off and have been flushing it with some liquid wrench. A lot of grime is coming out but it so far is only making the noise more pronounced. I'm going to try to open it up and see what happens using these instructions: http://www.borgercompagnie.com/helicomatic/technical.html

Unfortunately it doesn't look like the freewheels are any easier to come by than the hubs.

As with any diagnostic task one must first understand how parts interact as a system, and then apply logic and isolation to determine the source of a problem. Otherwise you will just thrash around in trial and error mode, which not only takes longer but which may make things worse, or at least even more complicated to figure out.

If you can hear and feel something pronounced enough to be called a "clank," and there is no sign of it during pedaling, then it simply cannot be anything but the freewheel. However, as the freewheel "mechanism" consists of 2 pawls that each operate multiple times per wheel revolution, and ball bearings that operate continuously, it would not be the mechanism. The only thing in the rear moving in relation to another part once per wheel revolution, and that is not doing so when you pedal, is the outer part of the freewheel in relation to the body that is attached to the wheel. Whether pedaling or coasting the cups, ball bearings and cones are moving in relation to each other in exactly the same manner. If anything there are some hub related problems that would show up when pedaling and not when coasting.

I would conclude that the noise is caused by some defect (crack or similar) in either the outer or inner freewheel body.

As always I may have overlooked something - I'm always willing to acknowledge oversights and acquire new information. I'm going into detail to show the process rather than to exhibit my knowledge.


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thanks cny, that makes sense and I think I have to agree with you. Something with the pawls would either make sound many more times than once per revolution, or twice if it was the pawls hitting something. Unfortunately will have to put this bike to rest until I can find a new freewheel :(. Although if it's just the freewheel I suppose the worst that could happen is I can't pedal, or suddenly can't coast. It wouldn't seize the wheel up and cause a catastrophic crash.. I'd just have to take the bus the rest of the way home.

I noticed this morning I didn't hear the sound when spinning the freewheel, I thought the oil had a chance to settle in and fix whatever the problem was. When I added more oil, the noise was back. It seems strange that I would only hear a noise due to a defect/crack when there is an excess of oil.