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Chain issues on French bike- freewheel or derailleur?

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Chain issues on French bike- freewheel or derailleur?

Old 06-04-20, 02:18 PM
  #1  
morganmarie19
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Chain issues on French bike- freewheel or derailleur?

I've got a vintage French tandem that has some consistent issues with the chain. If we pedal backwards, the chain slacks and will then skip gears when pedaling forwards again. The chain also skips gears occasionally when pedaling uphill. We've tried adjusting the current derailleur but it has not changed anything. I think it could be due to two possibilities:

1. The ~40 year old freewheel might not be moving freely enough (we've done our best with cleaning it)
2. The derailleur is not working properly due to the hacked Simplex dropout (previous owners threaded the mounting hole and cut a notch to act as a b-screw tab to fit standard derailleurs)

Or I could be wrong about both possibilities! I would love to hear anyone's opinions on what the problem could be.

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Old 06-04-20, 02:39 PM
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Just from the pic, it seems like the derailleur should be more clockwise rotated than it is?
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Old 06-04-20, 02:58 PM
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There are probably multiple issues. Chain skipping under power generally indicates worn out freewheel cog teeth. It can also indicate misalignment of the derailleur. Pedaling backward slacking the chain can be caused by misaligned derailleur hanger, or a gunked up freewheel that needs to be cleaned and lubed. Also, as mentioned above, the RD angle is incorrect.

As a start, chain and freewheel should be cleaned with solvent and relubed. The derailleur alignment should be checked with an alignment tool. You will probably need to replace the chain and freewheel. 3 speed freewheel? That's going to be hard to find.
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Old 06-04-20, 03:14 PM
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Looks like the chain is too long for the current setup. But I would first change the freewheel to a newer one. If the hub threads are standard (not french), most any new (Sunrace, Shimano) or used (Suntour) freewheel will work with friction shifting. If the rear spacing is 120mm, stick with a 5-speed. If it's 126mm, you should go with 6- or 7-speed. A new 5- or 8-speed chain might also help when changing the freewheel.
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Old 06-04-20, 05:59 PM
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A couple other thoughts.

That's a 4 speed freewheel, not 3 speed. I'm sure you know that... I mistook the skip tooth big cog for a spoke guard. Most likely French. If you can read a brand name there may be a small chance some forum member has a cog. At this point though, 4 speed stuff is more antique than vintage. They do still show up on ebay. If after cleaning it it is still not spinning freely, it may need to be taken apart and overhauled manually. It's a pain, but doable. You may want to try soaking it overnight in kerosene or naphtha or something first.

WRT the derailleur angle, when you modify those simplex hangers, there should be a stop at ~7 o'clock, and they typically function like a standard hanger if it's done correctly. Not sure what's happening there, but it's probably fixable. If the derailleur has a b-screw, adjust it, or put in a longer one as needed, or figure out some other way to make the stop actually stop the RD from rotating. Solder some metal on there if you have to. The main body should be roughly parallel to the chainstay.
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Old 06-04-20, 09:08 PM
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I thought that looked like a Schwinn/Shimano 5s freewheel (with the 14t cog hidden by the retention ring?).

Check derailer alignment by eye, it should appear to be parallel to the wheel. The chain and freewheel should remain or be replaced as a pair imo. Might be worn out.

If the top pulley is perhaps contacting the larger sprocket's teeth, then the shift position sensitivity could be extreme, leading to skipping. I agree with others here who mentioned that perhaps the derailer body position needs to be adjusted "clock-wise" as viewed.

As also mentioned, check for free rotation of the freewheel, also of the pulleys. Check the chain for any tight links!
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Old 06-05-20, 06:04 AM
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If it was mine, I would disassemble the drivetrain. Soak the freewheel & RD in a plastic tub of diesel fuel. Use elbow length nitrile gloves to manipulate the freewheel and RD and continue soaking until they move freely. Get a new chain. Reassemble everything. Use a few drops of lightweight sewing machine oil or automatic transmission fluid on the drivetrain for lubrication.
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Old 06-12-20, 09:39 AM
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Turns out the hacked Simplex dropout was the big issue- the b screw wasn't hitting the notch. We found this website that shows different options to deal with upgrading a Simplex dropout Derailleur Hangers Demystified - Red Clover Components. We decided to try the "Hermaphrodite Approach" and mounted a derailleur claw on the dropout. With a bit of modifications, we got the derailleur working properly again!


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