Just fitted an On One ‘Doofer’ (I think?) chain tensioner thats been in my cupboard for years, a singelspeed cog and spacers on a 9 spd hub etc. Using a normal 9spd chain cos the front ring is a 9spd middle ring and it seems to fit the rear cog ok.

Under any sort of load I get a slipping ‘clank/crack’ noise and loss of power at the pedals as though the freehub is slipping. I’m running 32:14.

I’ve tried 3 different back wheels from fancy to bog standard Shimano and it still does it. Which leads me to think its not the freehub? Or are geared freehubs not up to the load? I’ve got the sprocket 2/3rds the way across the freehub body, probably about where it would be on a normal cassette even.

So I can only think its the Doofer losing tension? It pushes out and down like a rear mech, rather than up towards the chainstay.

Anyone else had problems running this sort of kit? I have interchangeable drop outs so could get the dedicated singlespeed ones if this would fix the problem.

Pushing up is better because more of the chain is engaged on the teeth of the cog. But it is more likely your chain is stretched and is skipping on the new sprocket.

Pretty much got the same setup as you, 9 speed chain ring, single speed cog with spacers and on one tensioner, however the 9 speed chain slipped under load. changed chain to a single speed chain and problem solved no more slipping 😀

i would say you have a SS rear Sprocket. i would get a new chain.

14 teeth ain’t very many. if you can get the tensioner to push up as suggested you’ll have a better chance with it – more chain wrap that way.

It is a new chain but it is a 9 spd I had in the toolbox. The sprocket is a dedicated singlespeed sprocket.

This was meant to be a cheap conversion! What kind of chain do I need then that will work with the 9spd middle ring?

I can also swap to singlespeed drop outs – presume this would be better than a tensioner but would I also need chain tugs to run with a quick release wheel???

if you get a ss/bmx chain it will work with your 9 speed chain ring.

the problem (by the sound of it) is the sprocket is a ss specific which is too wide to take a std 9 Speed chain.

the chain should cost about £15 from your LBS.

Ah, ok.

Quite like the idea of a tensioner that pushes up too. Can anyone recommend a good one?

surly

http://surlybikes.com/parts/singleator/

it comes with 2 springs one to push up and one to pull down.

have you tried to shorten the chain a little more to give more contact?.

Made that ‘mistake’….tried to get more contact and shortened the chain by one link too much and it was so taught it virtually jammed the drivetrain.

I’ll have a look at Surly

I had that when I converted my Overbury, sorted by shortening the chain.

half link?

Some singlespeed sprockets are 1/8″ So an 8 0r 9spd chain won’t work at all.

I had this same problem, but changed to a proper On-One singlespeed “full size” chainring and a KMC half link 1/8 inch chain.
You have to get the chain as tight as possible first though. I tied my on-one doofer to the chainring to hold it as close to the chainstay as possible.

Take a ling out and fit a half-link.

Take a ling out

yes, a fish in your chain will cause no end of problems.

I run Sram 8spd chains on mine, & they are fine.

For £70 you could buy my Inbred frame & do away with this tensioner mullarkey. 🙂

See? wwaswas knows too. Alternatively you could try removing a link 😀

What size is the Inbred?

If you’re going to go the tensioner route VeloSolo do a push up tensioner – cheaper than the Singleator but not as nice. The Singleator does have a draw back in that it may foul on the chainstays if you’re running the front ring in the outer position – it does on my Scandal anyway. Other than that try a half link.

14T is small i’d run a 16 or 18 and us a bigger c ring.

This is all very familiar… you have picked my mastermind specialist subject.

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