need help diagnosing a rear derailleur problem
 

I need some help diagnosing some derailleur problems if you can. I’m posting this in the mechanics area as well as classic and vintage.

I recently changed out the rear derailleur on my 25 year old Cannondale racing frame. I’ve had a 13-24 Suntour New Winner Freewheel on there with a Suntour Suberbe derailleur since the bike was built. (The front has been a Sakae triple with a 34-42-52 since about 1990). I recently decided to throw a bigger freewheel on the back in a concession to age and weight, (59 and 230 respectively) :) I’m hoping to shed the extra pounds by next year, at which time I’ll go back to the old setup.

I have a pretty good parts bin, and had no trouble locating a 13-32 New Winner Freewheel in good shape, along with a Cyclone MK-II long cage derailleur. I also managed to find a brand new, NOS Sedisport chain in the original packaging. I put the whole thing together, taking three links out of the chain to fit the new drivetrain. Everything sounds perfect, doesn’t it?

Unfortunately, my first test ride the other day was a dismal failure. The derailleur shifted like crap and was noisy as hell. I was really surprised at this, since I’ve done this kind of modification many times. The chain often overshot the sprocket I was looking for, (I remember this being a not unusual problem with New Winners, since the spacing is fairly narrow), and I even managed to throw the chain to the inside of the freewheel once or twice. (Yes, I do know about the adjusting screws)! :)

I put the bike back on the workstand today, and took a good hard look at the new setup. I realized that the pulleys on the old Cyclone MK-II were fairly worn, and the brand new chain wasn’t seating correctly. The jockey pulley seemed worse off then the tension pulley, and it appeared that the chain was coming off the jockey pulley and clattering like hell.

Back to the parts bin, and there I find a mint condition Cyclone MK-II short cage derailleur with perfectly new pulleys. I remember taking this particular derailleur off my wife’s new Nishiki International in1983, when I changed out her freewheel for a bigger one. I took the pulleys off the short cage derailleur and swapped them for the worn out pulleys on the long cage derailleur. Now I have a good condition long cage Cyclone II derailleur, with brand new pulleys, a brand new Sedisport chain, and a good condition 13-32 New Winner freewheel.

Back out for a test ride, and I’m still getting a lot of clattering. Back on the rack, and it seems that now it’s the tension pulley that’s making a lot of noise .The chain and pulley are having trouble staying synchronized, and the chain is jumping off the pulley a little.

I have two theories, but I’d appreciate some expert help if I can get it. My first theory is that I need to take another link or two out of the chain. My second theory is that the derailleur long cage might be bent after two and a half decades in the parts bin.

What do you guys think?

Thanks, in advance, for your help

You may well have other things going on there, but I don't understand taking out links. Changing freewheels to a large freewheel cog that is eight teeth larger means adding the equivalent number of chain links, not subtracting.

Are you friction or indexed shifting? If friction, I don't know what the problem might be. However, if you are swapping freewheels and derailleurs, it is possible that the index of the shifters does not match the derailleur, or more likely, the freewheel cog spacing. Other than that, I am not sure.

If you can switch your shifter from indexed to friction and then try the bicycle, the problem might reveal itself.

I do wish you good luck with your problem.

The chains usually came longer than you need, and even with a big freewheel some needed to be removed to prevent chain slack. I think I'm going to try removing one more.

Thanks for your response.

Friction. Suntour didn't develop indexed shifting until a year or two after the Cyclone MK-IIs.

Thanks for your response.

Sounds to me like you are over shifting. I have a Mk II on my 620 also. In order to shift to a lower gear, I have to over shift then move the shifter back a bit, otherwise a lot of noise. I think it has to do with the gear ratio on the freewheel. Closer gear ratio requires less overshifting. For wide ratio freewheel, try the newer Shimano 6 speed freewheel with ramps, much easier to shift.

I'd check the vertical alignment of the 2 jockey wheels and a freewheel cog. Cage might be out of alignment.

It sounds like you know your stuff, but since you haven't mentioned the following I will.

Look at the derailleur from the rear. Is the cage perfectly vertical? That is, do both pulleys spin on perfectly horizontal axes in all gears? And do the two pulley wheels align correctly with one another? If not, something is bent. If that's the case, bend it back. It may e the dropout or derailleur claw; it may be some part of the derailleur body; or it may be the cage. If I had to guess, I'd say the cage is bent; and that's a very easy fix.

edit:
Ack! what a debacle! While I'm typing, dakl beat me to it!

Well, its the most common problem I run into!

I know this is basic, but did you check the interference fit of the derailer? I just had the identical problem with two mountain bikes and both times it was the set screw in the back of the derailer that sits against the back of the frame at the drop out. In both of my instances, that screw was set too low so the derailer jockey wheels were hitting the cassette/freewheel.
If none of the suggestions here work, I'd put the old chain back on the bike to see if the problem remains.
Hope you get it fixed.

what about the B-screw? I've run into problems where the derailleurs are incorrectly spec'd for the frame and the B-screw won't engage the drop out.

Just a thought...

Two good suggestions! I'll try putting the old chain on as a last resort, since it would probably be too short.

Could be bent, since it was in the parts bin for a couple of decades. To be honest, I didn't even know that I had it until I went snooping. I'll check it with a straight edge today.

It's definitely over shifting! That was always a big problem with the New Winners, as I remember it. I had quite a few in those days, and they all over-shifted!

Thanks, all, for your suggestions. I'm going to work on it today, and I'll let you know how it works out.

There are 2 ways to size a chain.....small/small or big/big. Depending on you setup either has the potential for causing issues. There is absolutely on reason why you should be taking out links. ZERO. NONE.

Chain shortness: Primarily determined by your small/small gearing. Since you 34/13 low/low hasnt changed you need to add back all of those links.
Chain length: It needs to be long enough to wrap the big/big gearing. You've added 8 teeth to the back which means you need to add about 4 links to your original chain length.

Have you ecked the derailleur hanger alignment? I know this is C&V but do yourself a favor and buy a full Shimano indexing system.

Thanks for your analysis. However, I would never run my chain little-to-little or big-to-big. I don't know many people who would. Maybe I'm misunderstanding your point, but I would never switch up to the big cog while riding if I was on the big chainring. Likewise, I would never switch down to the smallest cog if I was on the inner chainring.

That said, please understand that I did not take the links out of the chain that I had been running on this bike. That chain was put away in storage, along with the freewheel and derailleur that I took off the bike. This is a brand new chain. If I am on the middle chainring, and smallest cog, and the derailleur doesn't swing back far enough to take up all the slack, then I take a few links out. Likewise, I make sure that I can get up to the largest cog while on the middle chainring. Perhaps this isn't the correct way to do it, but it's always worked for me in the past.

BTW....I prefer my downtube levers and friction shifting. I'm not changing! :)

Thanks for your input!

UPDATE!

I did all the things we were talking about. I switched back to the original chain to see if the problem persisted, which it did. I took another link out of the new chain, which helped with the shifting, but didn't solve the rattling problem. Upon close inspection, (which means I took my bifocals off and stuck my face down right next to the derailleur), I determined that the two pulleys were not in alignment. I bent the derailleur cage by hand, and that seemed to do away with most of the noise. My hunch is that the poor derailleur got slowly bent after sitting in the parts bin for twenty years. I don't think that it's the derailleur hanger, since I didn't have any problems with the previous derailleur, a Suntour Superbe.

Thanks all for your help. I'll update again if the situation warrants.

Unlikely. More likely is it was bent in a single event, while mounted or not.

Could be. Perhaps I was a little rough on it while I was changing the pulleys out. I don't remember having trouble with it in the old days. On the other hand, maybe that's how it ended up in my parts bin in the first place! :lol:

UPDATE! Took it into the LBS for an expert opinion. The RD cage was definitely bent. Easiest fix was to replace it with a new Deore RD. It shifts great now. Thanks all for your advice. I'm going to watch for an old Cyclone MK-II for good measure, just so it matches the rest of the drivetrain. Thanks all for your input.