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-   -   Chain skipping, rear derailleur adjustment problem. (https://www.bikeforums.net/classic-vintage/1109086-chain-skipping-rear-derailleur-adjustment-problem.html)

Yoyo2012 05-25-17 12:35 PM

Chain skipping, rear derailleur adjustment problem.
 
[IMG]http://i1380.photobucket.com/albums/...pswy9udimb.jpg[/IMG][IMG]http://i1380.photobucket.com/albums/...pskjlrv4ha.jpg[/IMG]Hi. I have installed a new chain and a very good condition freewheel on my bike. Both Regina and 5 -speed. The drivetrain system shifts well.
The problem is when the chain is on the smallest sprocket of the freewheel. it keeps skipping.
A mechanic in LBS, who is not very familiar with vintage bikes, assumed it's because of the inappropriate angle of the rear derailleur, caused by the lack of tension of the spring in it. and there is no tension adjusting screw available on this models of RD. so I was suggested the RD should be replaced.
What do you think? Is this vintage rear derailleur really in a wrong angle? and if this is the case of the chain skipping?
Thanks in advance for sharing your ideas.

The Golden Boy 05-25-17 12:47 PM

This is a Shimano 600 Arabesque derailleur?

It does look like the pulleys are not even with the last sprocket- It's possible your derailleur hanger is mis-aligned.

Have your mechanic check for a bent derailleur hanger.


noobinsf 05-25-17 12:52 PM

I notice your high limit screw is all the way in. Is it possible you just need to let that out a turn or two to bring the cage just a smidge farther to the right?

randyjawa 05-25-17 01:02 PM


It does look like the pulleys are not even with the last sprocket- It's possible your derailleur hanger is mis-aligned.
That is the first thing that I noticed, also.

In addition to that, it appears that your chain wrap on the small sprocket, contacts less than half of the cog teeth. Moving the wheel back, fully, might correct that situation and solve the problem.

More often, than not, however, any chain skip I have experienced is a result of a worn chain and/or sprocket. Significant wear in the chain will not allow for the chain to contact all teeth the same amount, allowing it(the chain) to climb up over the teeth and skip.

Yoyo2012 05-25-17 01:04 PM


Originally Posted by The Golden Boy (Post 19609656)
This is a Shimano 600 Arabesque derailleur?

It does look like the pulleys are not even with the last sprocket- It's possible your derailleur hanger is mis-aligned.

Have your mechanic check for a bent derailleur hanger.

https://www.youtube.com/watch?v=TpsG8eDF53U

Yes. It's shimano 600 arabesque RD. we haven't though about this problem yet,and did't check the rear derailleur hanger.thank you very much for the reply. Will do some research and check.

The Golden Boy 05-25-17 01:08 PM


Originally Posted by Yoyo2012 (Post 19609694)
Yes. It's shimano 600 arabesque RD. we haven't though about this problem yet,and did't check the rear derailleur hanger.thank you very much for the reply. Will do some research and check.

Ah- you added the other picture! I thought I was being really slick recognizing it! :D

Yoyo2012 05-25-17 03:16 PM


Originally Posted by randyjawa (Post 19609692)
That is the first thing that I noticed, also.

In addition to that, it appears that your chain wrap on the small sprocket, contacts less than half of the cog teeth. Moving the wheel back, fully, might correct that situation and solve the problem.

More often, than not, however, any chain skip I have experienced is a result of a worn chain and/or sprocket. Significant wear in the chain will not allow for the chain to contact all teeth the same amount, allowing it(the chain) to climb up over the teeth and skip.

the LBS mechanic actually told me that to replace a rear derailleur with higher spring tension was to change rear derailleur angle, then add chain wrap. Clearly your suggestion is a much better method to get the result.
Very helpful suggestion. Thank you very much.
By the way.will it have a significant impact on riding experience by adjusting dropout screw about 1 cm back?

Yoyo2012 05-25-17 03:18 PM


Originally Posted by noobinsf (Post 19609670)
I notice your high limit screw is all the way in. Is it possible you just need to let that out a turn or two to bring the cage just a smidge farther to the right?

Thanks for correcting.Will also try to readjust H screw later

Wildwood 05-25-17 03:43 PM

Was it a new chain? Maybe too long?

davester 05-25-17 03:55 PM

As noted, this can be caused by a worn chain or a worn sprocket. I'd pull the wheel and look very carefully at the small cog to determine if the teeth are hooked or assymetrical due to excessive wear. A worn chain can change the spacing between the leading edges of the cog teeth and then when a new chain comes along it will only engage completely with one tooth at a time, causing skipping.

sdn40 05-25-17 04:01 PM

I just watched a video where he talks a lot about chain skipping causes due to adjustments. Being relatively new myself, I can only say it's worth your time to watch.


carbomb 05-25-17 04:19 PM

If the derailleur hanger is straight, the limits adjusted correctly, and if sliding the wheel back another centimeter doesn't help I suggest going out on a limb and getting a fresh shimano compatible 6-speed and slapping it on there, one of the ugly, shiny chrome deals that are sold for like 10 bucks. (or a 5 speed, but the 6's are common and should fit)

I had a similar problem and I tried everything and it just still skip. Someone at my LBS recommended trying a new type one and sure enough, no more skipping. Same damn small tooth count and for the life of us and the mechanic that recommended it we could swear my existing freewheel looked like it had no wear. Still, the new freewheel fixed it. I bought a darker metal one to not be visually upsetting on my vintage bike and it's all been sunshine and roses since.

I miss the click of the suntour that was on there, but not having it skip is worth it.

corrado33 05-25-17 04:24 PM

A few things things.
  1. Check for wear on the small sprocket, they wear quicker than larger sprockets.
  2. Wear on the chain as well.
  3. Chain may be a tiny bit too long. On that style freewheel there is little danger of running out of "wrap" room for the derailleur. Try taking a set of links out.
  4. Remove the axle positioners and pull the wheel all of the way back.
  5. Is it just the smallest cog? Try letting out the H limit screw.

Some of these have been mentioned. Try them all.

Yoyo2012 05-25-17 04:29 PM

[IMG]http://i1380.photobucket.com/albums/...ps5bpfel2a.jpg[/IMG][IMG]http://i1380.photobucket.com/albums/...psyujtgoj3.jpg[/IMG]
Yes I bought it as NOS chain,though it's rusty on surface. And the freewheel teeth are also in very good condition.

Mtbnomore 05-25-17 09:32 PM

Aside from the derailleur hanger, it's possible that the derailleur cage itself could be tweaked. I had a Deore DX derailleur that had this issue a while ago. Acts just like a bent hanger, though that's where I'd start first.

Lazyass 05-26-17 04:51 AM

The hanger looks bent to me. Even being off by a millimeter can cause the chain to skip, I know from experience. Unbolt the derailleur and clamp an adjustable wrench on the dropout and straighten it out. If you have a spare wheel with a threaded axle you can screw it into the bolt hole for the rear derailleur, then measure the distance between the two wheels at different points.

Kabuki12 05-26-17 06:14 AM

Also check cog on freewheel sometimes they are bent but usually on the larger cogs. They can be straightened by using an indicator with a soft brass punch and hammer. I have saved a few Regina Freewheels this way. Once you get it right , it shifts and stays in gear - no skipping

John E 05-26-17 06:37 AM

Great responses to this thread, which covers about all of the possible causes I can think of. In my experience working at a bike shop and on friends' and my own bikes, by far the most common causes of high gear skip are an elongated chain and -- sometimes resultant -- wear of the teeth of the smallest cog. Measure a span of 24 half-links, from rivet center to rivet center. This length was exactly 12" when that chain was new, and anything beyond 12-1/16" (a mere 1/2 percent elongation) is ripe for replacement.

One more thing to check -- with the torn-off end of a match or paper towel, see if every chain roller spins freely. If any are stuck, they need to be de-gunked or otherwise freed. Turn the cranks backward while watching the chain as it comes off the bottom derailleur wheel. Does it play out smoothly, or do you see any link-to-link bends that are reluctant to straighten out?

Yoyo2012 05-30-17 12:22 PM

Many thanks to all the replies for the great contribution. I spent a whole afternoon at a LBS with a professional mechanic to have all the possibilities mentioned above carefully checked and tried all the methods suggested. Pity the problem in my situation hasn't been solved.
Chain is NOS stuff. we checked every link and roller, they are in great working condition, also tried to have it shortened, twice; The smallest sprocket teeth are also in very great shape,no bent,only little wear,(judged by eye and limited experience). they bite very well with the chain;Derailleur hanger was checked, it's aligned, sorry for the poor pictures I provided, the flash of camera seems to make this part misleading;The rear derailleur looks not tweaked,and shifts very well,but is in a low spring tension because of aging, a condition that the mechanic had thought was the reason to cause chain skipping in my situation.we tested it with a method of tying the RD cage with a string to the ring of quick release nut in order to fix it in a tightened angle.but it didn't work neither.
It seems in a situation beyond my ability to solve the problem for the moment, I may have a double check this week, or swap for a rear derailleur with higher spring tension to give a try. Not considering abandoning the chain and freewheel yet. They are really beautiful on my bike. Thanks again for all the help offered. Really appreciate.

Yoyo2012 05-30-17 12:24 PM

Any possibility that Shimano rear derailleur is not compatible with Regina freewheel and chain?

Mechanicjay 05-30-17 12:48 PM


Originally Posted by John E (Post 19611310)
...by far the most common causes of high gear skip are an elongated chain and -- sometimes resultant -- wear of the teeth of the smallest cog.

I hate to advocate for mere parts swapping -- but a new freewheel is cheap and a quick test could have saved a 1/2 day of messing about ( I mean it's your time, so if you enjoyed it, that's really all that matters!)

I had high-gear skip after installing a new chain on one of my bikes. I screwed around with it for days as the cogs "looked good". Shortened the chain, fiddled with tension on the derailleur, etc, etc, etc. Finally broke down and just got a new Shimano 6-speed freewheel and BOOM, no more issues.

jeirvine 05-30-17 12:55 PM

Swap out one part at a time to isolate the cause. I'd start with the derailleur. Or with whatever you have on hand - chain, freewheel, derailleur. It's always something.

Dboyle 05-30-17 02:49 PM


Originally Posted by Yoyo2012 (Post 19620158)
Many thanks to all the replies for the great contribution. I spent a whole afternoon at a LBS with a professional mechanic to have all the possibilities mentioned above carefully checked and tried all the methods suggested. Pity the problem in my situation hasn't been solved.
Chain is NOS stuff. we checked every link and roller, they are in great working condition, also tried to have it shortened, twice; The smallest sprocket teeth are also in very great shape,no bent,only little wear,(judged by eye and limited experience). they bite very well with the chain;Derailleur hanger was checked, it's aligned, sorry for the poor pictures I provided, the flash of camera seems to make this part misleading;The rear derailleur looks not tweaked,and shifts very well,but is in a low spring tension because of aging, a condition that the mechanic had thought was the reason to cause chain skipping in my situation.we tested it with a method of tying the RD cage with a string to the ring of quick release nut in order to fix it in a tightened angle.but it didn't work neither.
It seems in a situation beyond my ability to solve the problem for the moment, I may have a double check this week, or swap for a rear derailleur with higher spring tension to give a try. Not considering abandoning the chain and freewheel yet. They are really beautiful on my bike. Thanks again for all the help offered. Really appreciate.

I am not familiar with the construction of the Shimano derailleur, however: I had the same problem with a Raleigh Grand Prix with a Simplex Prestige rear derailleur. Yes the plastic one. The problem did not manifest itself until a couple years after I bought the bike new. When I would crank down hard on the pedals the chain would slip over the lower freewheel cog. It took several visits to the LBS and eventually we nailed it to the upper pivot spring not providing enough tension. Replaced the Prestige with another Prestige and it solved the problem (later, like nearly everyone else I came to my senses and put on a SunTour).

repechage 05-30-17 03:21 PM

The chain may be NOS, but the freewheel is just old looking, possibly worn cog, especially if it ONLY skips in that one cog, if it does not skip in others- make more and carefully inspect / compare the problem to the no problem cogs.

Small chance there are worn derailleur pulleys, can't tell.

Assuming that the rear derailleur was removed and the pro mechanic checked the derailleur tab alignment with a proper tool. A jaundice eyed view, but not all that get paid should be playing that role.

Get the bike in a stand, remove the rear wheel and with a gloved hand, let the chain pass through your fingers while you "backpedal" guide the chain to take some pivot not under any load, if any are stiff, chain tool time with a dose of lateral manual effort.


As mentioned earlier, chain / freewheel wear are the top two suspects. Way back, for casual riders the small cog would wear out first, for us who trained in the early season, it was the 17t cog, all those early season miles in a 42x17 spinning up PCH. Back then, individual cogs were easy to get, not today.

speedy25 05-30-17 03:45 PM


Originally Posted by Yoyo2012 (Post 19620158)
The smallest sprocket teeth are also in very great shape,no bent,only little wear,(judged by eye and limited experience).

Sorry but I disagree about the condition of the freewheel. I see some major wear between the teeth. Compare the tooth valley on the trailing edge vs the leading edge. The leading edge is missing metal when I look at the pics.

Compare your freewheel to a new one and you will see what I think I'm seeing.

-SP


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