noahsmonark

Any thoughts on what could be a likely cause for a slightly bumpy first/lowest gear?

1950's Monark - Maillard Atom 66 (5-speed) freewheel - Huret Allvit derailleur

The chain is less than two years old (tension looks good to me) and the cogs look to be in nice shape visually - the first gear is the most commonly used one though.

The chainline is dead straight and the chain isn't hitting the spokes - switching gears is crisp and effortless and there is never any skipping. Changing to the second gear and then onward, everything is operating smoothly - the slightly bumpy/uneven feel only affects the first gear and only while pedaling; when just turning it by hand it feels smooth.

Two years ago I completely serviced the Huret Allvit, cleaned/re-packed the bearings etc. I'm not sure whether the distance from the upper derailleur pulley to the largest freewheel cog is perfect, but it looks ok to me. If I'm not mistaken there's no way to change that distance with this particular derailleur.

Any ideas?

masi61

I’ve never set up a Huret Allvit but from the photo, I was also thinking that the distance from the upper pulley to the bottom of the cog seems to be too much. I was fiddling with my semi-modern road bike last month thinking that my B tension screw didn’t have the upper pulley tracking my cassette tightly enough. Turned out that I had an incompatible chain (Taya) and when I went back to my SRAM chain it was fine again.

so... #1 I would suggest trying a different chain - you never know, a new one might do the trick.

but before you do the chain, I looked again @ your housing loop. It appears to be too short. If you use a piece of housing about 2.5” longer, the added length could just goose that cage forward to make the upper pulley track better with the “grindies”.

I’m curious if this will help....good luck!

noahsmonark

Thanks for the tip! I actually had no idea the length of the housing loop might have something to do with this - I'll have to try that out asap.

Kuromori

Allvit does not have a sprung B-pivot so housing loop will have little effect unless it is holding it back from hitting the stop on the hanger nor does it have a B-adjust screw. Not only that but the guide pulley is concentric with the A-pivot, so chain length has no effect on it. Since it's a claw hanger, you can't move the wheel axle in the dropout. Basically there's no normal way to adjust the gap. There are several potential issues, but it is hard to tell without being able to actually diagnose it. Check limit screws and check how the chain is engaging with the cogs, pulleys and if it touches the cage.

John E

Check the length of your chain -- 24 half-links, from center of first pin to center of twenty-fifth, should measure no more than 12-1/16", which would indicate 1/2 percent of elongation due to internal pivot wear (so-called "chain stretch"). If the chain is too long, replace it.

Since you (understandably) use low gear all the time, and since that 22-tooth cog looks much more worn than the others, it may be time for a new low-gear cog. Consider replacing the 22 (assuming you have a 14-16-18-20-22 freewheel, which was very common back then and which I eyeball guess yours to be) with a 23 or a 24.

ThermionicScott 

Sometimes used stuff feels a little rough or bumpy. If it doesn't skip or have shifting issues, I'd leave it alone.

dddd

Could be the angle that the chain is making as it feeds onto the lower pulley. If this is the case then this should be much more of an issue when the big chainring is in use and the chain is crossing more sharply.

The big cog is also suspect here as was mentioned.

The Allvit has no problem with your gearing, but will shift faster/crisper if a bigger freewheel is used.

One can slightly adjust the body angle and improve shifting response by grinding away at the stop on the claw bracket (I've used a thin round file for this), but remove too much metal there and the protrusion may break off.
Remember that old derailers were designed with stiff, bushed chains in mind, so modern chain does not transmit cage motion into pushing the chain around very effectively unless the chain gap is kept small. The Allvit works best with today's chains over a 14-28t, 5s freewheel.

The cable housing length looks to be exactly as I would cut it, you want the loop to be minimal for the cable to have a smoothest path and for the housing to flex as little as possible as the lever is moved!

Reynolds 531 

excellent advice
I appreciate 'been there, done that" info from y'all

Salamandrine 

That chain looks too short.

Is this a 5 speed? IOW is there only one chainwheel in the front? Or is it a ten speed? If it's a 5 speed there's no need to have the chain that short. How's your chain deflection angle? That can be an issue. Also, check alignment of the hanger, pulley cage, etc.

If everything else checks out, try a different chain. Measure it first, as suggested. Might be worn out. I rarely use the same chain for more than a year. Depends on your mileage of course.

+1 on using a longer piece of housing. It's ok as is, but my preference would be to add about 3/4". Try to use ferrules also. It will help.

ridelikeaturtle

Also double-check the limit of the derailleur, I've found (usually on the smallest cog of a cassette, but it could happen at either end of the cassette) if it's aligned even a little off it can mean the outer plate of a chain link can bump the next cog in the cassette, when they all come together the odd time in the revolution.

fietsbob

chain 2 years, old freewheel out of production for. maybe, 40 years , so cannot be new, or 2 years old bought with chain..

so chain & freewheel not engaging smoothly,,, your chain will wear in , over time ,
then get replaced, then the process repeats..

noahsmonark

Amazingly helpful responses, thanks.

@Salamandrine - no it has two chainwheels up front, 10 speeds total.

What I've tried so far is check the limit screws and do test drives with different settings - and I also managed to change the angle and distance of the chain (between large cog and pulley) just a little bit by moving the axle back in the dropouts some 1 cm / 0.4 inches - there was still some room for that, as the axle was currently set very close to the forward-most position.

It made no difference, not even slight.

The issue could be either the freewheel or the chain, even though neither appeared worn to the naked eye - I haven't measured the chain just yet. Over the course of these 2 years I have ridden - very very rough estimate - about 400+ km / 250+ miles on the bike, but 90% of that has been light city cruising and I would say I'm way more gentle to the drivetrain/chain than a lot of pedalers while shifting etc, just a gut feeling of course but I always like to treat this bike with extra care and avoid rough pedaling etc.

I'll see if I can think of more ways to reduce the gap between the large cog and pulley a little. Grinding the stop on the claw bracket as suggested by @dddd is an option, although I think I got the distance changed about that amount when pulling the axle back a bit - and nothing changed.

I think it doesn't have to do with the chain hitting anything sideways (cage) because the uneven feel is more 'heavy and thumpy' (instead of 'clanking and rattly') with almost no sound, just more of a feeling while pedaling.

Easiest next step would probably be to change the chain, I also know a bike shop in my city who has a replacement Maillard Atom 66 freewheel if needed. I think I've sometimes noticed that the freewheel can move the drivetrain/pedals a little bit (momentarily) when just walking with the bike next to me, I don't know if that indicates the freewheel might need replacing at some point anyway.

Salamandrine 

OK. If the picture shows the chain tension when the bike is in lowest gear (small chainring/biggest cog), then IMO the chain is most likely too short. I'm sticking with that...

The whole rule of measuring chain length according to BIG/big + one link is only a rule of thumb. It works OK with typical gearing modern road bikes, but it can be downright wrong. An alternate method of determing length is to put the bike in highest gear, and set chain length so that the jockey wheel is vertical. In this case you may be better off making it as long as possible. Put it in SMALL/small (5th), and make the chain as long as you can. Should be just short enough that the jockey wheel doesn't hit itself. There is often a range of chain lengths that technically are OK, but often one particular length will shift best and feel smoothest.

Besides double checking in your limit screws, also check for stiff links. I don't think that's the issue here, but it should always be checked.

blamester

Chain looks short. Cable housing the same.
Has it always or just recently started feeling rough?
If recent it is likely a wear item.
Chain or sprocket.
400kms shouldn't wear out a chain.

noahsmonark

Ok. This is good material. Noted. When I did the chain I just went by the general rule of thumb, and if I recall correctly I figured a little too tight will be better than a little too loose.




Yep, recent. Well, there may have been some -very- slight unevenness but I've only started noticing it recently (my bb had gotten slightly loose a while ago, and after adjusting it, I started paying more attention to the general feel of the gears).

To be honest, I may be a little too pedantic with it, seeing as the bike rides pretty well (with worn/uneven asphalt it's barely noticeable) but I'm pretty sure I'll be swapping the chain sometime soon and then if nothing changes, have the freewheel upgraded.