Hello,

I am not really sure how to correct the fact that the chain rubs against the bottom of the jockey cage. This is only a problem when the chain is on the smaller sprockets and does not occur when the biggest sprocket is engaged.

I would be grateful if someone could point me in the right direction to fix it!

Thanks,
Adi

Looks like the stop that keeps the cage from rotating back to far has broke. The derailleur needs to be replaced.

Judging from what I can see of the stays and dropout, this photo appears to be upside down and the derailleur is in the right positon. What chainring is it on in the front? If this bike has a triple and you have it in the small front ring and small back cog, then there is just too much slack for the derailleur to take up and you need to be on the middle ring.

I would like to see a better pic maybe with a bit more of the bike in but I agree it loks like the derailleur may be broke.

The derailleur is not "broke" (unless it's wallet is missing).

Seriously, just like every other modern derailleur that derailluer rests against a stop when the chain pulls it forward. There is not stop to keep it from moving back too far, as it will not do so on its own.

The chain is too long, even if you are in the small-small on a triple (though that gear should indeed be avoided). Go to Sheldon's or Park tool site and follow carefully the instructions on how to size a chain.

Those two sites are generally the first place you should go. Once you have thoroughly studied and followed correct procedures that relate to the item you are working on then you should come here. To do otherwise robs you of fully learning about how bike components and systems work and wastes time giving you information already available.

Thanks for the info.

I did take a look on those sites but i wasn't really sure what i needed to focus my attention on, not having worked on a bike before.

Indeed the picture was upside down and on the small-small combination of gears. But i don't understand why this gear combination should be avoided? Surely the chain should not rub against the brackets in any combination?

I have attached a few more images.

Would i be right to conclude that: the derailleur is not broken but i need to adjust the chain? And i should avoid this gear combination?

If the the bike has a triple ring crank, in "small-small" then the problem is mostly operator error. You could shorten the chain by one link to improve the function of a gearing combo that you shouldn't use, but a better solution would be to find an identical gear ratio in a different spot on your drivetrain. Using a gear that involves more teeth helps spread the wear around, keeps the chain from slapping on the frame and makes you look like you know how to operate a geared bicycle. Try matching shifts more often: simultaneously shift both derailleurs to a bigger ring.

This video should help:

https://www.youtube.com/watch?v=NMYGTc5bzNY

Skip the first 60 seconds of the video, as that part may be unnecessary.

The derailleur is not broken, period; you need to adjust the chain length; three people have said not to use the combo.

The small-small combination is an extreme angle for the chain, which is noisy and can produce more wear. Because you are engaging the minimum amount of teeth front and rear it wears faster from that also. All multiple geared bikes have overlap, so there is a combination with the next largest chainwheel in front and a larger cog in the rear that is essentially the same gear ratio.

As for the sites, your problem was with the chain and derailleur, so you go to the pages for each of those and go through the procedure for every adjustment until you find one that applies and fixes it. Do not just shorten the chain by one link - follow the procedure on one of the sites for sizing the chain - you will learn something that way.

+1


As for why you wouldn't run the small-small combination, this is called cross-chaining. You will notice that in the front, the chain is all the way to the left, but in the rear it is all the way to the right. While this will theoretically work, it puts the chain in an awkward position, angled between the two gears. If you think about it, it also doesn't make sense for riding a bike: It gives you the lowest possible gearing in the front, but the highest possible gearing in the rear; this is not a commonly used combination. If you went to the middle ring in the front and one of the middle ones in the rear, you would get similar gearing but the chain would be better aligned.

+1,

The chain is too long for use with the small/small combinations.

Pull the chaiin's lower loop forward and see how much you'd need to shorten t to solve the problem.

However before you cut it, shift (off the bike) to the big/big combination and see how much chain you have to spare. Test by pulling the lower loop forward until it's almost straight with the RD's lower pulley above it. Leave some margin for additional movement, and count how many links you could safely pull forward, and this is the maximum number of links you can cut off.

If the number of links you want to cut off is more than the big/big combination would allow, the RD has insufficient take capacity for your gear combination. You have two choices, replace the RD with one of greater capacity (longer cage), or cut the chain based on the big/big combination, and live with some limitations with the small chainring.

It's absolutely critical, that the chain can safely loop the big/big pair with an inch to spare, because if you were to (accidentally) shift into a combination for which it's too short, the chain will cause serious to the RD, hub, and/or crank set.

Perhaps ideally it would not, but there are limits to any mechanical device. The derailleur has a tension spring to pull it back and keep tension on the chain, but there is too much slack here, so it is all the way back with the chain slack. I doubt the chain is too long unless you just installed it. If it was fine before and all of a sudden it isn't, then something we can't see is out of place or broken. Like the chain going around the front chainwheel.

Here's how to ride those gears:

Leave it in the middle ring, unless you're struggling up a hill or into a headwind, or you're hammering along with a tailwind and/or downhill.

If you shift to one of the larger cogs on the rear before you stop, it's easy to take off in the middle ring. In an area as flat as mine, you'd be in it 98% of the time.

Yeah, you might accidentally* the whole thing!

Boomer-- There's a missing clue here.

Normally all new bikes are set up with an RD which has enough capacity to take up ALL the chain from the big/big combination, to the small/small combination. While most people don't ride these because the high chain angle coming outer to inner or the opposite cause higher friction and wear, the bikes are set up to allow it just in case.

So what's missing is what happened since the bike left the factory.

Did someone put on a new chain which might be too long, change the RD to one with less capacity, or change the sprockets to ones requiring more capacity?

If you bought the bike used, you might not know the history, so your best bet is to use the method I suggested earlier to determine the minimum and maximum chain length, and size the chain accordingly (if possible). Remember, that if it's a capacity issue, that longer than minimum (big/big +1 inch) chain length is critical, and you might have to accept limitations on the small/small side. (you don't use this combination anyway).

Great catch, FB - i was thinking it could not have always been that way but never addressed it directly. The chain could indeed be the right size if the wrong derailleur was installed, which is why I refused to come to the conclusion that it was too long. I should have told him to get a new derailleur if the chain sizing was correct. The freewheel is not a mega, so the chain would not have needed to be sized too large, and the chainwheels look to be OE. That Shimano Tourney style SIS was a very common low end replacement at a lot of shops and online. It actually work passably - I had one on a bike when I was in a low income period, but I believe that model was at best 6 speed compatible - note the op's bike has a 5 sp freewheel.

It wouldn't be unheard-of for an LBS to fail to check for proper chain length. Ask me how I know.

Yeah, somebody's obviously thrown this thing together from spares, or just replaced the RD with the wrong one.

BROMERS:

If you find the chain is the right size, then the fix is still not terribly expensive. There is a Shimano derailleur that is 15 speed compatible that is similar to the one you have but is 15 speed compatible. It will work fine and can be ordered from a local shop if they do not have it in stock or from:
Amazon - SHIMANO SIS RD-TY15 (or from eBay)

HOWEVER,

Do not install it yourself without in-person help unless you are confident that you can properly follow the instructions from online resources. It only takes one mistake to blow far more than the $15 or $20 a shop will charge you to install and adjust it. If you do so make sure the size the front and rear sections of cable housing properly. That rear section is longer than it needs to be, which makes shifting less precise.

It seems to be the most recent incarnation of that model, which formerly had a bracket like th one on your current derailleur. I will admit I do not have 1st hand experience with this model, but it says it is an "axle mount" and that seems to be consistent with the bracket attached to it. That is OK as you have bolt-on rear wheel, but it may be tricky to get a good solid, centered mounting of the wheel along with the derailleur in the proper position.