SS Losing chain tension, help please

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  • SS Losing chain tension, help please
  • Premier Icon woody2000
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    I have a RoadRat that I’m using for mud busting duties. It’s set up singlespeed, I’m using the Cotic “chaintug” and bolt up skewers but I keep losing tension and shipping the chain. Any suggestions? Can I use a different (better?) chain tug?

    TIA

    jackthedog
    Member

    You can use another kind of chain tug, but I’m not sure what issue you’re having with the standard part (do they call it “mech tug”?)

    Is it due to braking effects rather than pedalling effects?

    My SS Rat with the standard setup is fine with a Shimano QR, albeit I tend to do it up pretty tightly. It certainly prevents the axle being pulled forward on the drive side.

    Premier Icon shortcut
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    Is it definitely the wheel moving? Or is it simply that the chain is becoming worn and therefore longer?

    I’ve had this issue with a chain that proved unsuitable; it was one of the BMX type half-link chains, which just continued to stretch almost infinitely. I was adjusting the chain before each ride, and taking a half link out every 10 rides or so for quite a while before it stopped getting worse.

    Then I ran the chain and both chain rings until they were absolutely destroyed without touching anything, so it wasn’t all bad. It made some awful noises by the end!

    Premier Icon woody2000
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    I hope it’s not the chain, it’s only about 100 miles old if that. It’s a SS chain so should be pretty tough? (SRAM PC1 I think)

    JTD – you might be right, maybe I need to look at some kind of tug on the NDS

    thomthumb
    Member

    SRAM PC1

    it’s that. they’re awful.

    buy a decent chain

    http://www.charliethebikemonger.com/kmc-z610-hx-chain-332-41-p.asp

    it’ll stop.

    Premier Icon kelvin
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    100 miles…. but was it a new chain on old worn in teeth?

    Thrustyjust
    Member

    As thomthumb.Last PC1 I had was just crap. Use KMC chains now and happy days. Previous PC1’s were great. The last one lasted 2 months before being stretched to death.

    SRAM PC1

    There’s your problem, worst, chain, ever!

    KMC do singlespeed chains in various sizes, 1/8″ is BMX which some people find falls off or snaps on narrower MTB gears as it’s not suppourted properly on the teeth (imagine it can twist), I’ve not had trouble though, and they can be cheeper or more bling, 3/32″ is the same size as old 6/7/8 speed chain, but with less play in it and no shifting ramps. X1, 510 and 610 have all been good IME.

    Premier Icon D0NK
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    Is it definitely the wheel moving? Or is it simply that the chain is becoming worn and therefore longer?

    +1 when I ran horizontal dropouts I had to adjust my rear wheel atleast once a week (~100miles) in shitty conditions, admittedly on pre-worn ring/sprocket so that will have speeded wear up.

    Run vert drops and tensioner now, less hassle

    I concur on PC1, I run kmc 510 1/8″

    Premier Icon woody2000
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    Actually, it turns out it’s a KMC S1 chain, not a SRAM PC1. The drive train is all the same age @ ~100miles or so (sprocket, chain & chainring).

    Premier Icon woody2000
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    Right, it’s p*ssing me off now! Dumped the chain again on Saturday, sending me off the bike and down like a sack of spuds. Chainline looks good, tension seems ok (tight enough to not have a lot of movement in the chain and reasonably even). It does seem to come off under load rather than when it’s bumpy, so when I’m grinding up a hill mainly.

    Shimano DX 18T sprocket, KMC S1 chain and on-one 33T SS chain ring. I think, but I’m not 100% sure obviously, that it’s coming off the rear. Wheel does not seem to have moved – I’ve got a 1.8″ tyre in the back which gives me 7 or 8mm or so of clearance so it’d be pretty obvious if it had moved.

    Help! 🙂

    binno
    Member

    Are you sure it’s not your chain line then?
    If the chain line is not straight, then the chain can get puled off to the side easily enough.
    There is a chain line measurement method, google to be sure – i thin this is the culprit, you can’t check your chain line by eye!

    When the chain pops off, has the wheel moved?
    If so, try a shimano steel QR nice and tight (as prior post states).

    Also check that:
    You’re using single speed specific rings – not ramped ones?
    Your chain the same width as your cogs / rings i.e.: single speed vmx width vs mtg narrow 9/10spd width?
    The rear cog mounted to the rear hub securely, with no movement or slack?

    + Post back your solution if you find one for future problem solvers to know.

    fuzzhead
    Member

    Dropping chain under load is probably tension. I used to drop my chain a lot until I got a proper tensioner on the case (On-One Doofer).

    Does it skip at all or just drop the chain?

    cfinnimore
    Member

    3/32 On One Groove Armada with 3/32 Gusset Slinky & Renthal 32t plus On One chaintug and Hope QR.

    Perfect, all the time, tighter than a gnats bumbits. Only chain i’ve used for 4 years. About to convert pro 2 QR to bolt through though.

    Premier Icon woody2000
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    binno – I’ve checked my chainline by eye before, worked ok for me then! Everything is SS specific, frame has horizontal dropouts and I’m using a tug on the drive side. Rear sprocket is nice and secure. I’m not using a QR, I’m using an hex key skewer.

    It doesn’t seem to skip fuzzhead, I’ll be riding and then I get a “ping!” and I’m pedalling fresh air!

    DrP
    Member

    I was having to do this with the KMC510 chains… rubbish, and was stretching them after about 1-200 miles.
    I’ve stuck a 510hx on there now, and not had to adjust at all.

    Buy cheap, buy twice etc etc…

    DrP

    Premier Icon amedias
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    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.

    Premier Icon woody2000
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    amedias – that could be a very good point. The frame is very flexy, and I’m not exactly subtle in my power delivery. I bet that’s it, it only drops under power so it makes some sense. I’ll double check everything else though.

    Cheers 🙂

    fuzzhead
    Member

    If it’s not skipping then it’ll be your chain tension – as mentioned above, it may feel OK in a static position, but under load and over bumpy ground you’ll get enough flex/movement to drop the chain.

    I had this self same problem, fixed with a sprung tensioner.

    Premier Icon wwaswas
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    maybe add a sprung tensioner to allow for a bit of frame flex but keep the chain tight on the cog?

    binno
    Member

    Options:
    If it’s flex, you could try dropping your gearing a little, so less power stomp required for those hills.

    If you buy some callipers it’s easy to measure your chain line correctly:

    1. Measure outer width of seat tube (i.e.: 30mm)
    2. Measure outer edge of seat tube to centre of front chain ring teeth. (i.e.: 55mm)
    3. Minus 1/2 the seat tube width from the above measurement (i.e.: 40mm)

    4. Measure your rear frame spacing (i.e.: 120mm) divide by half (i.e.: 60mm)
    5. Measure from the inside drive side dropout to the centre of your rear cog (i.e.: 15mm).
    6. Minus the 15mm from the 60mm = 45mm in this instance.

    This indicates the above chain line is off by 5mm. So, an adjustment is required at either / both chain rings till you get the same number and incredibly smooth, fast and efficient pedal action that makes single speeds so great.

    If you’re new to callipers, measure things you know the width of until you get accurate readings before trying the above tried and true method.

    Premier Icon woody2000
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    I’ve got a Blackspire stinger lying around that I’m not using – would that be any good as a tensioner or do I need the tension at the rear to keep the chain on the sprocket?

    Premier Icon woody2000
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    Where are you cut and pasting that stuff from binno? 😉

    I’ve already dropped from 36/18 to 33/18, don’t want to go any lower TBH or it’ll be spin city. I’ve got some callipers as it happens so I’ll do some geeking later 🙂

    Premier Icon amedias
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    If it is flex on yours too allowing enough give for it to drop then one thing we did try with the Singular flexorama incident that almost fixed it was using two alu plates either side of the rear cog, just used 2 or 3mm thick alu with an hole punched out of the middle same diameter as freehub and roughly same outer diameter as a 20t cog (he was running a 16t) to sandwich the chain.

    It prevented a few drops but then on one particularly nasty one it managed to mangle and bend one of the plates and drop between the cog and plate, thicker plates probably would have sorted it but he ended up putting gears back on after that.

    binno
    Member

    From my experience the rear wheel would slip if the skewer was not up to the job.

    I’m thinking you’ve checked the front chains are round.

    You can loosen the allen key bolts (a little) and knock out any tight spots in the chain as you back pedal. I use a fat handled screwdriver to do this. Also, if you get it set, I don’t think you want to run your chain too tight, not stretch tight but with a little bit of wiggle in it. with clean lubed chain you’ll be able to tell if it’s too tight / too loose easily enough.

    Plus:

    Is you spoke tension and dishing sound on the back wheel?
    Freewheel / Freehub not slipping under pressure?
    Botom bracket smooth and tight?
    Crank arms not working loose / moving under load – can happen with square taper style ones under load.
    No teeth are bent, chipped, missing worn on the front ring. check to see if it always pops off in the same position.
    + check your split link is not an issue / chain links are not tight from fitting.

    john_l
    Member

    Switch to a 9spd chain – much lighter & more able to hold the sprocket teeth. It doesn’t take much to de-rail a chain & a heavy SS chain that’s a bit baggy is much more likely to make a break for freedom.

    trail_rat
    Member

    Will eat hat if its anything to do with flex.

    Road rat here

    Those hex skewers are all terrible at holding wheels imo.

    A real shimano enclosed cam skewar exerts far more clamping pressure.

    fuzzhead
    Member

    @woody2000 – I’d use a sprung tensioner at rear sprocket

    Premier Icon amedias
    Subscriber

    Will eat hat if its anything to do with flex

    I was of the same opinion for years, thinking anyone who dropped a SS chain was either running it too loose or had a diagonal chain line, until I watched him put down a couple of hard pedal strokes coming out of a bermed corner and saw the chain go visibly slack on the bottom run* before popping off, when back on the chain was tight enough for there to be noticeable drag/tightness when turning the cranks by hand.

    It’s rare but it can happen!

    * then replicated in car park with standing start sprints.
    ** thats on a bike with vertical dropouts and an EBB, rear wheel definitely not slipping/moving, and using a big howitzer external BB and DH cranks so no movement there either

    Premier Icon woody2000
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    Actually remembered I had a sprung tensioner so been out with that on tonight, no drops. Will give it a few more rides but hopefully that is the end of it. Trail_rat – I’m using the rat as a MTB, I reckon it’s getting a bit more stick than riding it on the road.

    trail_rat
    Member

    Ive used mine for touring with the panniers on and throwing it up hills , it shakes its tail feathers alright but its never thrown a chain- infact the chain has to be silly silly slack for it to be thrown.

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