Funktopus

I've been having trouble with one of my bike's chains recently. Over the weekend I went for a ride and found the chain kept slipping off the front cogs unless I kept it in a low gear. I decided this was chain wear and bought a new one. When changing the chain I found that the old chain was indeed very stretched in comparison to the new one, so thought the case was closed.

I just went out on my first ride with the new chain and it was horrible. It *feels* like chain suck, but I don't know for sure as I can't watch it happen while I'm cycling and I can't replicate the problem with the wheels off the ground The problem goes away if I shift into the big ring and a larger sprocket, which again makes me think of chain suck.

I had a similar problem on another bike which was resolved my taking a few links out of the chain. I just tried the same with this one and it hasn't fixed anything. In fact I'm now wondering if this could be a symptom of the chain being too short? I definitely couldn't get this one any tighter. Photos of chain in big/big and small/small below:




​​​​​​

Advice appreciated! Thanks
​​​​
​​

bitpuddle

It is difficult to say without seeing it happen, but:

1. that chain looks too short
2. if the chain was that worn, there is a good chance that the cassette and possibly the chainrings are also worn. Chains and cassettes wear together, so putting. New chain on a badly worn cassette can make the performance worse.

dsaul

It sounds like its new cassette time. If a new chain skips on a old cassette, the cassette is worn and needs to be replaced. The problem goes away on the bigger cogs, because there are more teeth in contact with the chain.

ARider2

+1 what dsual said and you most likely need to replace the cassette, but in addition to this, and you probably already know this, riding in the large chainring in front while using the larger cogs in the back (crosschaining) can cause the issues you mentioned. You also seemed unsure about the length of the chain. One way to take the guesswork out is (assuming the old chain was the correct length) is to hang the new chain next to the old chain and use it as a guide to cut the new one to proper length. See Shimano notice about avoiding crosschaining below, this is for one of their newer systems but the same likely applies here:



[edit - strike smaller cogs, replace with larger cogs!]

mitchmellow62

+1 for worn cassette and possibly chain rings. I'm assuming you experienced the symptoms in the most used gear combinations. They would be the most worn. Shifting to less used/worn combinations should alleviate symptoms (as it did). I'd start with a new cassette/freewheel. If the symptoms persist I'd change the most used chainring.

Greiselman

Is this right? Big chainring up front and small cog in the back should be fine... big up front and BIG cog in rear is what would be crosschaining.

andrewclaus

I'd start here.

The good news is it looks like the chain is a 7 speed and you should be able to easily press a link or two back in.

Iride01 

Is the chain falling off the front chain wheels still an issue after the changing chains? Or is it just the perception of chain suck in your second paragraph?

It does look like your chain is one link too short when on the big big combo. But some DR's just look that way. When I'm putting a chain on a bike for the first time, I'll either size it by the mfrs recommendation for that particular groupset and number of chain wheels or by the chain I took off and then go one set of links longer. Then see if I have too much slack in the smalls for the DR to take up and how well it shifts. If I think it's too much slack then I'll go for the original chain length or mfr sizing, which for me usually winds up being what I finally end up with for chain length.

But if it's still coming off the front chain wheels then something else is up. Did or does that happen in all front rings when you are in the small sprocket on the back?

Funktopus

Thanks guys, there's a new freewheel on the way. I definitely shouldn't have shortened the chain this morning, it was the right size beforehand. That was a decision made in frustration, and before I'd had my coffee! The chain on this bike has always been sized by me, its my vintage gravel monster that I threw together with spare parts. But I evidently got the length right the first time. I'll try and press the link back in, or if that doesn't play ball I'll just use my spare master link.

ARider2

Woops, you're right! I corrected my post above.

RandomLetters98

Um, what you do is count the number of links in the old chain and then use the chainbreaker tool to break off at the right number of links in the new one. Its pretty unlikely a new chain will fit snugly in the old sprockets, but after a few months it should wear in okay. Probaly wouldn't be using it for a Triathlon or anything though.

RandomLetters98

I just looked the second picture, that chain is WAY too short !

You'll need to get the bit of the new chain you didn't use and link it back on. Count the number of links in the old chain.