Chain tension on a fixopholus fixed-gear fixie?

[Boris Bajic]

I believe the time is coming when I'll have to fork out for a new chain.

Pah! So much for fixed-gear being low-maintenance.... But I digress.

The chainring and sprocket look OK and the chain is still not in 'replace' territory on my wear gauge (the little stick that looks like a squashed tuning fork).

But... It's that age-old thing with chains not running through a derailleur.... It's got tight spots and 'floppy' spots.

Here's the question: Assuming the tight spot is as tight as I'd like it to be, how floppy can the floppy bit be?

In otherwords, when I rotate the chain so that I'm getting maximum floppiness between chainring and sprocket, what is the consensus on how much up-down travel (inches or centimetres) there should be.

I have a feeling that I'm going to need to get a new chain, but I have a medical condition that makes spending money extremely painful and emotionally distressing.

Any clever words on maximum chain floppiness?

All advice welcome.

 

[GrumpyGregry]

at its slackest point it must never be more than a bit slack. Up to a bit is fine but anything equal or exceeding a bit is unacceptable and all who see it will intone...

'chain's a bit slack, mate.'

a bit = 5 - 10 mm approximately. imo. ymmv.

 

[fossyant]

More likely your chain ring is slightly out of round or possible not centred correctly, slacken it off, jiggle it, and retighten.

You shouldn't really have that noticeable amount of slack.

 

[totallyfixed]

The problem, if you can call it that, as Fossy says is that chain rings are rarely perfectly round, no idea why, not exactly rocket science is it? Your chain is fine, rotate the cranks until you find the position that gives the tightest chain then pull the wheel back at that point, once done the slackest part will probably move up and down a centimetre or so in either direction. Don't sweat it, I have never derailed one on my fixed even when it could probably do with tightening and that's hitting the odd bump at 40mph and I run a 3/32, cheaper and lighter As long as your chain line is good, no problems.

 

[Deleted member 1258]

The problem, if you can call it that, as Fossy says is that chain rings are rarely perfectly round, no idea why, not exactly rocket science is it? Your chain is fine, rotate the cranks until you find the position that gives the tightest chain then pull the wheel back at that point, once done the slackest part will probably move up and down a centimetre or so in either direction. Don't sweat it, I have never derailed one on my fixed even when it could probably do with tightening and that's hitting the odd bump at 40mph and I run a 3/32, cheaper and lighter As long as your chain line is good, no problems.

I've only just replaced the chain, cog and chainring on mine and I've got major tight and loose spots on the chain, something is definitely not round, I run 1/8, as totally fixed said find the tight spot and adjust there, I normally turn the cranks a quarter of a turn at a time checking the chain as I go, once I've gone right the way round the chain I go back to the tightest spot and adjust there.

 

[totallyfixed]

I've only just replaced the chain, cog and chainring on mine and I've got major tight and loose spots on the chain, something is definitely not round, I run 1/8, as totally fixed said find the tight spot and adjust there, I normally turn the cranks a quarter of a turn at a time checking the chain as I go, once I've gone right the way round the chain I go back to the tightest spot and adjust there.

Exactly so Dave, only you said it better [think I may have sunstroke].

 

[Theseus]

As in all things, Sheldon has the answer.

 

[Boris Bajic]

Good Lord! You chaps were spot on in your diagnosis.

I popped the bike on a stand today and rotated the pedals with a metal blade flush with the chainstay and touching the extremity of the teeth on the chainring. The gap was not constant. Not a bit of it.

Guess what? It's pissed.

I would never have come up with that possible cause in a billion years.

I now have to centre it, which will be big fun and games.

But HUGE thanks to all who spotted the possible cause and took the truble to post about it.

I'm too tight to do so in real life, but please imagine I've bought you all a drink.