Just move from a Charge Duster SS to the Cooker SS and am loving it. That is apart from it throwing the chain (always towards the spokes) when crossing rough surfaces whilst pedalling.
Chain line is perfect (easy to adjust as it has the eccentric BB) and has a new 16T rear sprocket and ordered a new chain although I don’t think that is the issue either.
This may be far fetched but could there be too much “spring” in the frame resulting in the chain line becoming slack enough to climb off the sprocket?

Seems unlikely.
I’d be looking at other causes. Chain – is it a 1/8″ on a 3/32″ or narrower sprocket? Try a narrower chain. I used to find that sram PC1 in 1/8″ would throw whilst a kmc 3/32″ wouldn’t on the same sprocket/chainring combo.

Also is the chainline right, not just the tension? Not sure how an ebb can help with lateral chainline, unless the whole thing is sticking out or in a bit. Usually need spacers somewhere to get this right.

If you have enough chain tension and you are losing the chain (always to the same side) it means that your chainline is off.

Move the chainring out or the cog in.

What they said, EBB’s shouldn’t be adjusting chainline, only tension?

Can’t help other than that, I’ve never had a problem, and have often run a mish mash of stuff, just always set the chainline up perfectly with spacers on the cassette body.

Chain line is perfect (easy to adjust as it has the eccentric BB)

not sure the difference having an eccentric BB makes to the chainline . Chain tension yes, but line, no.

As BillOddie says, sounds like the chainline off. Either the chainring needs a bit of shimming or BB spacers need moving around a bit

not sure the difference having an eccentric BB makes to the chainline

Most of them can be adjusted side to side by a few mm as well as rotated. Niner Biocentric and Sanderson are the only 2 I can think of now that don’t.

OP, chain may be the issue if it’s a 9-10s rather than SS chain, they do come off a lot easier ime.

as above, it shouldn’t happen but I posted about this in repsonse to a similar question a year or so ago.

If chainline definitely OK, wheel not moving, and everything tensioned correctly then it *shouldn’t* be able to come off, however having spent a good 3 months trying to diagnose a dropping chain on a friends frame (Singular Hummingbird) we finally got to the bottom of it when I was following him and saw him stomp on the pedals to put some power down and I watched the frame physically flex and twist enough for me to see the bottom run of his chain go slack and pop right off as he pedalled the crank round, and that was with the chain at a tension that I considered to be silly tight.

Not saying that’s what’s happening to you but just my experience and worth ruling in/out.

Check all the obvious things first though, make sure your chainline is absolutely 100% bang on, tensioned properly and that you are using correct width chain for your cog and sprocket (and make sure they all match!).

FWIW, the most reliable combos I’ve used are KCM 610HX (3/32) chain with Surly 3/32 SS sprocket and a similar decent SS 3/32 chainring. (If you already have a 1/8th cog and ring then use 510HX)

It is possible for flex to be an issue, but it’s much more likely that there’s something else causing it that you can tune out with a few adjustments.

As a last resort belt-and-braces approach you could always try two spacer-plates, one on each side of the rear sprocket and bigger diameter than the sprocket to sandwich it so that the chain can’t come off at the back end. Agin, shouldn’t be necessary but I’ve resorted to it in the past for extra security, especially on trials bikes where you really don’t want the chain to come off mid gap.

If the line looks good, and it’s not too loose, try putting the chain in the opposite direction. Then, if it comes off to the right…

I’d say it was possible if your a big guy on a cheap steel frame. I had a dmr that would auto brake for me when cornering hard. Frame flexed enough to drag the disc.

Haven’t had issues on better quality frames though.

A chain will always go slack at the bottom when putting power down however if the tension is correct it will never be slack enough for the chain to come off (I can’t get my chain off without removing the rear wheel, i.e. I cannot push it off to the side)

If a frame is flexing enough for a properly tensioned chain to come off then I would not use that frame as it something must be wrong with it.

I had an MTB that was so flexy that if I pedalled hard out of the saddle it’d shift chainring.

It was aluminium.

Its not simply a stiff link or twisted link in the chain is it?

I had a 1/8″ chain that kept trying to come off, SRAM PC-1 possibly. Moved back to simple 3/32″ 8 speed (and KMC) and not (touch wood) had similar problems.

As above – EBB will check tension (check for flat spots with loads of movement in chain spacing) but won’t really change chainlink – though can be moved laterally a bit.

Hi all, thanks for all the suggestions.
I realised I didn’t work my initial post correctly and meant chain tension not chain line. The BB can move sideways as well as rotating, allowing for minor line up issues.
The write up for this frame is pretty good with no remarks about it and it’s the 4th Charge frame I’ve had and they’ve always been excellent.
Set up is standard for the Charge Cooker SS 2014 apart from me swapping the 18T for a 16T rear cog. The supplied chain is a YBN S410 which I’m swapping for a KMC Z510-HX and the front is still the Truvative E400 32T ring.
I’m tempted to go with the above comment from “amedias”
the frame physically flex and twist enough for me to see the bottom run of his chain go slack and pop right off as he pedalled the crank round, and that was with the chain at a tension that I considered to be silly tight.
I’m 15 stone and the torque through the 16t setup will be higher than expected I suppose. It is also worth noting that I have a 2 x 10 Cooker (2015) and this frame has an additional brace in the frame near the rear drop outs on the non drive side (I thought this was to counter the brake potentially twisting the frame under heavy braking).
I’ll see what the new chain brings and get a pal to ride behind whilst I “try” to make it happen.
Thank again.

molgrips – Member
I had an MTB that was so flexy that if I pedalled hard out of the saddle it’d shift chainring.

Perhaps the bike was sub-consciously preparing to overtake?

Also worth considering if you’re a big powerful guy with a single speed is that the more teeth engaged the better, ie: 40:20 is a much better* than 32:16, same ratio but the load is spread over a lot more teeth so you get less chain wear, less sprocket/chainring wear, less chance of skipping, lower chain tension and as the cogs are physically bigger there’s more wrap and its harder to derail the chain, obvious drawback being slightly hevier (who cares) and a sidge less ground clearance.

maybe not worth doing right now but when you come to replace drive train it’s always better to have more teeth engaged if you can.

* a 16tooth cog only ever has 8 teeth engaged, (with less taking the actual load**), bump that up to 20t cog and its 10/more, a 25% increase and corresponding reduction in load, same thing at the other end, over the lifetime of the drivetrain it does make a difference

** why I also recommend odd numbered rings/sprockets if possible to extend working life, unless you use even number and then advance one tooth to even out wear

Narrow /wide chairing?

** why I also recommend odd numbered rings/sprockets if possible to extend working life, unless you use even number and then advance one tooth to even out wear

I might be having a brain fail here but how does that make any difference?

I might be having a brain fail here but how does that make any difference?

When the chain engages on the sprocket it is actually ever other roller/tooth taking load*, so with an even number of teeth you’ll only ever wear half of them.

With an odd number of teeth you’re rotating the sprocket through as well so the other teeth get engaged and it spreads the wear out over the whole sprocket, it also means if you go for many many miles without derailing the chain (as you would hope on a SS) you don’t have to pay attention to put the chain back on ‘in phase’ with the already worn teeth.

There is the converse school of thought that says stick with even, grind it to dust and then pay attention to the phase and then rotate/advance one tooth when you put a new chain on, but you need to pay attention more with this method and I’ve had noticeably better sprocket and chainring wear with odd numbered and replacing comparatively cheap chains.

* it’s not even that simple as due to the way things wear the bulk of the load can end up on comparatively few teeth or even just the last one as it goes round, but the bulk of the wear is on alternate teeth when using even numbers due to it only being the links between outer plates that change apparent pitch.

** obviously some combos are worse, ie: integer ratios with and equally divisble number of chainlinks or even numbers of teeth, so do the maths to work out where to add some oddness in to make sure it spreads well.

Well I never knew this…

chain engages on the sprocket it is actually ever other roller/tooth taking load

…but if that’s the case I get the rest.

When the chain engages on the sprocket it is actually ever other roller/tooth taking load

Sorry, but that sounds like complete bobbins to me!

But, in the interests of science, please can you expand on your theory and explain why you think this is so…

Sorry, but that sounds like complete bobbins to me!

But, in the interests of science, please can you expand on your theory and explain why you think this is so…

Sure, it’s not my theory, its fairly well documented ‘feature’ of roller chain driven sprocket systems but I have a meeting to go to now but if nobody else has popped in with references I’ll update later this evening when I get back from my ride.

In the mean time some google fu for “Sheldon Brown chain wear”, “Jobst Brandt” and the less bike specific “tooth engagement chain sprocket alternate every other” will probably get you some reading material

quick pre-meeting EDIT – eg chapter 5 in here is relevant

https://books.google.co.uk/books?id=hnYZBwAAQBAJ&pg=PA130&lpg=PA130&dq=tooth+engagement+chain+sprocket+%22alternate+teeth%22&source=bl&ots=2VD9XzT8N9&sig=mmPxYCdY1EmTr3g28mVz6IrOOdw&hl=en&sa=X&ved=0ahUKEwik6u6mhpPKAhXEfxoKHTsFBcEQ6AEIJjAB#v=onepage&q=tooth%20engagement%20chain%20sprocket%20%22alternate%20teeth%22&f=false

the “Chain and Sprocket Wear” section down here:

http://www.sheldonbrown.com/chains.html

and Sheldon also describing what I’m on about here.

http://www.sheldonbrown.com/chain-life.html

Obviously only matters on SS drivechains as with gears you’re constantly moving between ratios and sprockets anyway so you don’t get the repeated same-position wear you do on an d SS drivechain.

only being the links between outer plates that change apparent pitch.

Why?

Why?

see above links

with diagrams here:

http://pardo.net/bike/pic/fail-004/000.html

which also references the book in the google link above.

chain roller and sprocket engagement and load is actually pretty complex and not a case of each link meshing with each tooth beyond the ideal non-worn, zero-friction situation

I assess chain wear by counting how many teeth are touching rollers on the rear…

EDIT D’oh, of course, because the outer pins are fixed, obvs…

Love the idea of “upping the teeth” but maintaining the ratio. I have a gazillion “big” rings (that rarely got used) from a couple of old triple mtb sets, not correct I know but a short term trial may help to prove things. I have 18 and 20 tooth SS rear cogs so if I can find a 36 or 40 I’m sorted.
I’ll read the suggested articles too as I can’t fathom the “wear of every other roller” bit either.
Thanks again.

I had this on my Kona Unit when I rebuilt it.Which was weird as I’d never had it before in 6 years of riding it!! You can see the shadow of the chain going slack when I pedal hard.NW ring solved it.

OP: Not much to add after all the good advise from other folks, I’ve had the same issue and found that one of the links was slightly bent. After replacing the chain – no issues!

I always thought that using 1/8″ chain on 3/32″ sprockets would mean that there’s a little bit of play for the chain to deal with, for example, frame flex or non-perfect chainline…

@amedias: many thanks for interesting links, definitely an eye-opener!
I was just wondering regarding the teeth wear – would that be the case with a half-link chain being used instead of a normal outer/inner plate chain?

Cheers!
T

Run a wide narrow ring… I’ve never dropped my chain on a single speed running them, and I don’t even run a single specific chain. I use a 10 speed or whatever is cheap and light.

I use a Hope Front wide narrow ring….brill

duffyc – Member
Run a wide narrow ring… I’ve never dropped my chain on a single speed running them, and I don’t even run a single specific chain. I use a 10 speed or whatever is cheap and light.

Shouldn’t need to – I’ve never dropped a chain on a single speed during ten years of riding them – if your chainline is good, you’re using proper full tooth sprockets and a singlespeed specific chain you don’t even need to bother that much about perfect tension.
All in my opinion, of course.

I’d rather have NarrowWide cog – whenever I’ve dropped the chain it was at the back, not on the chainring 😉

Nothing much to add that hasn’t already been said, but I had similar problems with a Genesis Day 0, changing from an SRAM PC-1 chain to a KMC something or other sorted it immediately. I think the plates are deeper on the KMC so they need more slack to completely climb over the teeth on the sprocket (or something). Either way, it worked.