so last week i posted about my SS set up and was advised all sorts of things to try.
tried all of these (inc fitting a new bb cos the other one seemed a bit graunchy (is that a word?)) to no avail, still jumping and clunking.
so to recap; new chain, new 17t sprocket, vvgc 34t ring, superstar tensioner nad now a new bb.
fitted an old 16t sprocket, just as a last resort what else to check... and its fine!
wtf?? advice please!!! PLEASE!!!!!
Freehub slipping? Poor chainline?
hmm this a tough one then, can you put some pics up so we can take a look?
at gee. works sound with a 16t sprocket, but the new 17t doesn't work at this point i'm guessing everything is fine with chainline, tension, length etc.
will try and get a pic up.
are you using a spring loaded tensioner or a two bolt type?
spring loaded
two bolt type
the reason i ask is i've used both types and under high loads the spring loaded type can allow slippage as it is able to move but the two bolt type can't as it bolted down.
superstar spring loaded, but it works fine with a 16t sprocket but not a 17t so again, i guess no issues with tensioner.
its an issue happening all the time straight out of the door under mild load but not on a stand.
Is the 17t sprocket machined/stamped off centre, so eccentric on the hub? I've had 2 cogs like this.
ok just looked at the superstar type and it's a spring loaded one?
now then what i found with mine was that
1.under high loads(uphill and sprinting etc) the spring was not strong enough to stop the chain from slipping over the sprocket.
2.the little cage under jockey wheel would move out of position causing it to make contact with the chain and thus sounding rough
have a look at the cage position and make sure you've got it in the right place and make it's good and tight. as for slippage well you may have to change to the two bolt type to eliminate that.
we really need a pic though slippage nearly always comes from poor tension or a mix of worn and new parts.
pic of the set up... soz, dunno how to upload pics.
is the 17t sprocket for a different chain width to the 16t sprocket?
This is rank speculation (plus I didn't read the last thread so may have already been suggested) but if its under load then perhaps the chainstays are bending/flexing, reducing the distance between chainring and rear sprocket, allowing the chain more slack, and so to get caught up. Alternatively are there tight/loose spots in the rotation of the chainring? This could be quite severe, enough to move the chain across. Perhaps try remounting the chainring if there are tight/loose spots, and try to make sure it is central if you can (spin and check visually for radial movement). Of course all of this doesn't explain why on 17T and not 16T. HTH
Shorten the chain for starters 
Actually (after properly reading everything 
) I had a similar problem after playing about with ratios. The chain I was using was just too worn, despite being quite 'young', to play nice with a new cog. New chain sorted everything. My setup was virtually identical; 34t Blackspire ring, 15,16,17t cheapo pressed cogs, SRAM 8spd chain (the 'weak link') and a spring loaded tensioner.
crikey that's a long chain length! i would certainly recommend losing some links from that chain as it'll give more contact with the sprocket and more tension to the chain.
wait a minute i'll see if i can find a pic of mine.
the chain length is fine... the pic is with the 17t set up, doesn't work. with a 16t set up (effectivly lengthening chain) its fine.
since this pic was taken the chain has had a couple of links removed to give better contact. and notice the tensioner type it's fixed so can't move.
That type of Superstar tensioner is worse than useless. I had one and it is the biggest waste of money ever. Get a fixed type and your problem will go away.
are you swapping between sprockets from time to time? is the 16t getting more use than the 17t if so the chain and 16t are probably more suited to each other now? chains stretch a fair bit when new then settle down.
i'd bet the tensioner is out of alignment with the sprocket. when you switch to the 16, the tensioner is moving away from the sprocket, therefore giving a greater distance to loose the misalignment over.
I have the same type of sprung tensioner but changed the spring inside for a push up version off a Surley one - can get them for around £4. Make sure you get the chain length as short as possible (use a half link if needed) to stop it getting too close to the chainstay.
I also removed the pin so I could rotate the pivot to get the tension I wanted.
I had slipping problems on 14t sprocket but not on a 16t (the other way round to your problem). The sprung tensioner was essentially pushing the chain off the sprocket and there wasn't enough teeth engaged with 14t sprocket.
But looking at your photo...Sprung tensioners are to take up the slack using vertical drop outs.....not to be run in the same position as a rear mech would. i.e. run it more like mmb's photo or shorter. Could be a combination of this and badly shaped teeth on the 17t?
I bet a fixed type, possibly set up to push upwards would help the problem go away.
I would agree with "mmb"
I had a single speed setup with a singulator tentioner springing down which work ok for a while. But when I swapped out the rear cog to a different size it would slip under any decent load.
Changed over to the same fixed bolted tensioner shown above with the same, chain & chainring etc.
I've had no problems since.
I use the two bolt with the chain on the top of the roller.
chains too long for that tensioner, though a push up wont help as chains too long...
make sure your chain alignment is perfect, and check for stiff links in your chain.
also big cogs tend to slip less and wear less than small ones
push up tensioners tend to wrap the chain around more to help chain slip.
you could also try flipping the cog around to see if it works ok, good tip for worn cogs though may require realigning the spacers.
check your chainring bolts arnt loose..
fwiw i have a tensioner like that, that works fine
I bet your new 17t sprocket is 1/8" instead of 3/32". Does your chain whip grip it properly?
sorry to be a poacher and vulture and a hijacker *but* can you sell me the 17t cog if you give up!?
Another reason could be the position of your chainring and that it is not truly centred.
To test spin the cranks slowly and every eighth turn of the crank grab the chain and see how much it wiggles. If the chainring is not centred you will find that the chain is loose at one point and tighter in another.
To fix tension the chain so the chain is tight, spin the cranks till it is tightest, then loosen the bols though best to do in pairs. Then tighten up the chainbolts then retest. The chain should be an even tension for a full revolution of the crank.
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exact same issue this morning - every time i went up a hill lots of horrible banging and jumping. new surly rear cog, newish 9 speed sram chain, old as the hills singulator. i couldnt wind on any more tension so i added an additional tensioning device (ie i bodged it with a stick) and it worked perfectly. no more jumping at all whatsoever..
so - best wood for bodging singulators?
Sorry if this is a dumb q. But why are you all tensioning by pulling a long chain down, instead of having a shorter, nearly tight chain w/o the tensioner and then pushing it up? Is it the type of tensioner you are using?
the chain length is fine..
No it's not. Chain is too long. You could get a couple of links out of that and achieve a better chain wrap and probably better tension as well.
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