[Closed] Chain drop.. help needed

You may be knackered.

About the only thing you can do is depressurise or remove the rear shock and run the backbend through its arc to find the longest point between axle and crank axle, tie the frame there with s bit of string between axle and round the seatpost and then do your chain sizing again in case it's too long.

If it's the right length then your options are basically altering the chainline which may lead to other problems or running a smaller back tyre.

I was thinking maybe it's something to do with the long cage rear mech but maybe not. For normal trail riding it ok but anything slightly rutty or rock garden I can hear the chain flapping about all over the shop

A sharksfin?
https://www.bike-discount.de/en/buy/radon-chainstay-protector-shark-fin-443876

I have never properly measured the chain so maybe going through the proper directions like you said may help. So remove shock and fully compress and tie up in that position? Then move to large cog on rear and see if there is slack? Is this also still running through the dereilleur or not? Cheers

swingarm in the position where the dropout is furthest from the BB, big to big not thru mech, add two links

I've just done it using the equation on park tool website and says I was one link out. Taken a link out so fingers crossed will improve but can't see if with only removing one link.....

Smaller tyre or bigger chainline.

What will a smaller tyre do? Other than increase chance of jamming because will be bigger gap? What do you mean by a bigger chainline?

It's not (usually) quite as simple as compress shock and tie in that position. The longest point between axles is usually somewhere in the middle of the stroke. You only let the air out so you can easily move it and see what's going on. The straightforward number of links and cog difference sum doesn't account for chaingrowth (swingarm arc) - it's for hardtails.

You probably can use a shorter RD but that's not going to affect chain length as you shouldn't have chain through RD when checking length. Longer RDs are needed to control longer chains (take up slack) and if this was a double or triple and is now a single there should be a few links too many and a good chance of using a GS not SGS mech if you want - this is more about keeping the mech clear of rockstrikes etc though.

If the chain is loose enough at any point to get jammed between tyre and frame you pretty much have to be somewhere in 'too much chain/too much tyre' so sorting out your tension is the first thing.

Smaller tyre will give a bigger gap between tyre and chainstay so chain can't get trapped although it shouldn't really be there. It would give you more mud clearance if that's ever a problem.

Altering chainline is literally about moving the crank further out or in to the BB - you do this by adding and subtracting spacers on the BB. It's unlikely to be the answer here though and could lead to other issues. Swapping to a proper 1x crank will automatically alter your chainline and may help but it's a drastic option.

If it'll fit, a larger front ring might help - if the tension is improved and the chain is higher it may become impossible to jam it - but as already said, if it's jamming like this while riding but not in the stand then you need to make sure there isn't too much chain first, and if the chain is right you need to decide what you're going to compromise on as that'll mean that your current setup just won't work together whatever you do.

Can you fit the front ring in the outer position on the spider?

What does the chainline measure? (Centre of seat tube to centre of chain)

Can't tell what the crank is but it looks like you may be able to remove the spider and mount a direct mount chain ring which could improve the chain line.

A sharksfin?
https://www.bike-discount.de/en/buy/radon-chainstay-protector-shark-fin-443876

It makes me happy that this is still a product, 25 years or so since I last had one on a bike.

😀

Thank you for detailed responses. The bike did originally come with a triple on the front and converted to single. So I pretty much guessed chain length. Chain line should be ok because one up components supposed to keep chainline same as original. I have taken a link out so have to see how get on with that. Not sure if my swing arm arc work differently to other bike as got fox dyad shock that works opposite to normal shocks

I am also running a maxxis high roller 2 2.3 width so not a huge tyre but might have to change to ardent which is slightly thinner and try that

The sharksfin should stop the chain hitting the tyre and getting pulled down into the swingarm

When you say "chain drop" does the chain actually come off first or does it just jam?

You can pissibly just move the chainring to the outside of the crank, it'll give a fairly ugly chainline but probably still within usable range (people still obsess about chainline but with 1x it's not as big a deal as it was). And yep smaller tyre should sort it too, the problem isn't so much where the chain is going as the fact that it doesn't have enough room to go there

The chain doesn't actually come off because it can't the chain guide stops it completely coming off it just jams in between the frame and tyre. Might try and sharksfin will it fit on my frame though as I presume it's designed for radon frames?????

Is it possible the free hub isn't running freely allowing excess slack?
Failing that I'd be cleaning the whole back end of the bike and checking for cracks or play in the rear end.

jamesoz - Member

Is it possible the free hub isn't running freely allowing excess slack?

That is an actual excellent point

^I was going to suggest pedal more, then the chain wouldn't be slack enough to get in there but freehub is a good suggestion.

Great point haven't checked freehub. What should I be looking for??? If I rotate crank arms anti-clockwise they spin freely if this make sense regarding the free hub? Don't say cracks that's the last thing I want hahahah

Get the bike in a workstand and pedal forward normally. Then stop pedalling. Does the momentum of the wheel cause the top side of the chain to sag?

will the chain ring fit to the "outside" of the cranks ? should move the chain line enough not to jam

When this started happening on my hardtail it was because the axle had snapped so the freehub was binding when freewheeling, causing slack in the top run of chain.

Is the derailleur clutch working?

It should be a lot harder to move the derailleur cage to the rear when "on."

^ Sorry, I mean forward, not to the rear! Cage moving forward slackens the chain.

I'm tired...

How new is the chain?
If it's got some stretch that will add lateral movement...

Worn chain

Chain length too long

Mech clutch faulty or slackened (I get this with older SRAM clutch mechs after a while, but this is Shimano. Clutch is on?)

Chainline is driving chain into tyre which is going to grab it and jam.

Try a larger front chainring?

Thanks for all the responses guys. The whole set up is fairly new so have minimal chain wear or any other wear. Oldest component is the clutch mech. Checking last night it definately works but there is a slight bit of movement if press which does drop slack to the top of the chain. Think it may just be that the 30t chainring is too small because when I'm in 11t on the rear the chain is actually running on the chainstay protector. Feeling a little tender this morning but will have a look later see if freehub is sticking to start with

Think it may just be that the 30t chainring is too small because when I'm in 11t on the rear

I can lend you a Superstar 34T if you pay postage and you want to try it ?

Thanks for the offer Steve but I hazard a guess that yours is 104bcd and mine is 96?????

if the chain is running along the chainstay protector then the setup is not suitable for that frame

Spacers on drive side of BB perhaps to shift it out, or if you can fit one, a direct mount chainring which might have less offset than the spider you've got, or mount other side of spider or get different spider. In short, move the chainline out.

Though, does this only happen when in biggest cog(s), or does it happen on any gear regardless? If the latter, then it's something else than chainline I'd have thought.

Thanks for the offer Steve but I hazard a guess that yours is 104bcd and mine is 96?????

Thanks for the offer though Steve greatly appreciated

I think wolftooth were quoting a need for 6mm clearance between the inner face of the chain and the outer edge of the tyre. Do you have that when on the largest sprocket?

Update guys. Doing a little research the one up components chainring is supposed to convert to 1 upfront keeping correct chainline. I have slightly tightened clutch mech, taken and link out and rode today and had the same problem don't know if it's slightly better but it only happened once ahaha. Checked frame for cracks nothing checked over everything, slightly tightened up rear wheel. Don't know what else to do really. All I know is the top of the chain is so slack it just flops around