Hi,

I've got this old Bates road bike and recently I've noticed that if I'm in the highest gear and back pedal when at traffic lights to get my foot in the right place to set off, the chain sticks and gets stuck in the mechanism of the derailleur.

Now I'm still at the early stages of learning about such mechanicals and am stuck as to what to do to fix this. It certainly didn't do this a month ago I can say that much.

The back derailleur is a Suntour Cyclone and the three photos I've attached show how the two little cogs seem to be almost touching which I think is the cause of this jamming.

Can anyone identify this problem and how to sort it? I'm not completely hopeless at fixing things if I get some instruction but I couldn't find the right words to describe the problem and do a google search for the fix.

Cheers,

Joe

Looks like you have too much chain!
Shorten it up a bit and you should be fine.
Shift to the large sprocket and the largest cog and allow just enough chain to have maybe one extra link.
Or, check online for chain length calculators.
That should do the trick.

• Not necessarily too many links, could also be so worn that it's too long. If it's not worn you badly need to remove and clean it. Then, whether the same chain or you replace it (and likely freewheel as well) rest of the drive train needs to be cleaned. Check https://sheldonbrown.com/chains.html for info on maintenance, measuring wear and sizing. Just about all you need to know is there.
• Backpedaling is a poor practice - the rear derailleur only has to be a little bit out of line with the cogs to jam, and doing so does not always indicate a problem, especially with friction shifting.
• Finally, though the chain should not rub on the pulley cage in small-small that combo should also not be used.

Before doing anything, would be giving that chain / gears a real good clean, as they are covered in oil/grime, doing this along may alleviate the issue you are having.

Would also look at the dropout adjustor screws, the drive side one is fully to the rear, is the NDS one in the same position, centering the wheel?

I'm wondering if perhaps the OP did that in an attempt to tighten the chain.

I suspect the photos are of the chain when in the front small ring. To have this much chain wrap going on and the chain on the large ring is odd, WAY too long a chain. So if the shot is when the chain's on the small ring you have another issue not yet mentioned. This being that you're in "cross over". Meaning that the chain is spanning from the outer end of the rear cog set to the inside of the crankset. This amount of chain angle can often cause, when back pedaling, the chain to want to derail. The best solution is not to use this combo and also not to backpedal if in it.

If you are using the cross over combos you will find a very similar combo, ratio wise, where the chain is FAR less crossed. Often a couple or three cogs larger in the rear with the larger ring will be a near perfect match to the cross over's effort (ratio). If you're good with math you can simply count the teeth on each cog and on the rings and run the ratios to see where the overlap combos sit.

Some chain and cogs are more susceptible to this derailing, some less. A cog set's ratchet's ability to freely spin (the freewheel or cassette's body) as well as the der's pulley wheels ability to freely spin also come into play. But the best way to insure minimal back pedaling derailing is to keep the chain angles straighter.

BTW- two more points. Why aren't you down shifting to an easier gear when stopping? Do you like rolling off in a high effort gear? Second- the chain and gear set really needs to be cleaned! It's like changing your undies when going to see your Dr. or brushing your teeth before the dental visit. Andy.

Many thanks for the responses - the chain is about 18-24 months old and gets about 2 miles a day for 5 days a week on it.

Are there any particular chain cleaner tools/liquids and chain chopping/joining tools you'd recommend? I see plenty of stuff from China on Ebay but you never can tell if they're all much of a muchness or if there's a particular one that is best to use.

And thanks for the Sheldon link - I looked at most but not that page which explains a lot :-)

And also yes I'm on the smaller ring up front - crossing over, which as a temporary measure whilst I get it sorted I will cease to do and take your advice about using other combos but maybe this needs to be a permanent change to my riding practice for the reasons mentioned which make sense. When I come to a stop at the lights I have just tended to stay in the high gear as I'm in a small village with very little traffic so my slow start is rarely a problem. I do take your point though - I used to change down and will start again.

Cheers,

Joe

For chain tools, Park or Shimano, have used cheap ones, pay a bit more, andy you won't be replacing any time soon.

For chain cleaners, plenty of threads on BF, also, try your LBS for cleaners, Finish Line,Pedros and others make chain cleaning solution.

Since it's the smaller front chainring and the smallest back cog, then your chain is a bit too long, but I wouldn't shorten it just yet. It works reasonably OK as it shows in the photos. And you don't normally use this combination, anyway. (Since I have the chain tool, if it was my bike, I'd probably shorten it, though)

I would first clean the chain and cogs.

Most critically, wipe all the road grime off the derailleur and oil all the derailleur pivots including where it says "Suntour" and where it says "patented". Use chain oil. Shift it up and down to work the oil in, then wipe off all the excess oil. This may help to keep more chain tension when it's in the small-small combination, and will help with shifting in general.

That's a close ratio freewheel, for flat ground riding. Each cog is only 1 or 2 teeth more than the one next to it. Other freewheels have much bigger cogs for riding hills. Perhaps the chain was sized for a larger freewheel.

For example, close ratio:


Wide ratio:

Quick update to let you all know how awesome your help has been - I put it on the big cog at the front and all is well and also on reflection, given my ride length is so short these days (I have a 3 year old son) then making the ride harder going is a good thing really . My LBS will be getting a visit so I can get him to teach me about the points raised in the replies about chains and cleaning (he's an old school enthusiast).

Thanks everyone

It was already suggested that you shift to a lower gear for starting, and you've already said you'll start doing it again. I'd like to second that. Over the long run it will be easier on your knees, and it will get you in the habit of shifting down so that some day in the future you may avoid an unexpected problem in starting in heavy traffic or on a steep uphill.

As mentioned, it's best to make use of the lower gears as well as the higher. Surprisingly, even though you are on the large chainring now, most of the gears on it are not higher than the ratio you had on the small-small. So it's not so bad using the large chainring, as long as you stay away from the smallest rear cogs. Also, contrary to popular belief, pedaling harder (more pedal pressure but slower pedaling) will not do much for either fitness or strength. Have your LBS person talk to you about gear use as well. And again, the first order of business is to measure the chain for wear - there's no sense at all in cleaning a worn chain.

Wouldn't be a bad idea to clean out the derailleur pulley bearings/bushings while you're at it. Yuck!

A brief word on gear combinations.
Most casual or "rec" riders think that using the small chainring and the smallest cog amounts to "5th gear" on an old 10 speed setup.
(or 6th of 12, or 7th of 14,etc.) This is why you find so many garage sale bikes with rusty chains frozen in this combination.
(That is also the resulting combination of broken cables in most setups.)
As pointed out earlier, this combo does not represent the middle of the available gear ratios, but rather, much closer to
the higher end of the range.
There are usually several large ring and larger cog combinations available that are easier to pedal than the small/small combo.
BUT, large/large is just as much taboo as small/small, as both induce more lateral chain deflection than should be used,
which results in premature chain wear. In fact, in the this day of narrow chains necessitated for more cassettes, I always avoid cross-gearing
to the 2 cogs at either extreme of the cassette. But, that's just me.........

While I am pretty anal about keeping my drive train clean, but I have read several well thought out arguments that an oily black drivetrain really has no effect on shifting and as a matter of fact keeps everything thoroughly coated with lube and will last longer than a cleaner drivetrain that can dry out of not continually maintained..