SS Losing chain tension, help please
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.Posted 4 years agopaulrockliffeMember
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!Posted 4 years agothomthumbMember
it’s that. they’re awful.
buy a decent chain
it’ll stop.Posted 4 years agothisisnotaspoonMember
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.Posted 4 years agoD0NKSubscriber
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″Posted 4 years ago
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! 🙂Posted 3 years ago
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.Posted 3 years ago
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!Posted 3 years 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.Posted 3 years ago
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.Posted 3 years ago
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.Posted 3 years ago
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.
Is you spoke tension and dishing sound on the back wheel?Posted 3 years ago
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.
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.Posted 3 years ago
** 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
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.Posted 3 years ago
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