I need to convert my bike to singlespeed for a race.I am going to get a chain tensioner,i have a new 11 speed chain and some old cassette spacers.I am already running 1×11 so the front ring should be fine.Can i use an 11 speed cog from my cassette or do i need to buy something specific.Any help appreciated.Ben

I would get something specific, otherwise you’ll be dropping the chain a fair bit. I’m guessing a normal 3/32″ singlespeed sprocket will work, but I’ve not actually used 11sp…

Problem Solvers dual-pulley tensioner is far more effective than a single-pulley IME.

The problem with regular cassette sprockets is they have ramped/shaped teeth to aid shifting so don’t hold the chain quite as securely – cheapo SS sprockets are available that’ll hold your chain more securely

Go SS specific with the sprocket, they last a lot longer and are far more tolerant of the chain bouncing around. Cassette sprockets are designed to chuck the chain off the moment it goes out of alignment (i.e. the mech moves), so has the potential to do that when the bikes bouncing around too.

Front chainring will be fine, if a bit expensive to wear out a nice one for no reason.

3/32 SS chain is far stiffer than 10s/11s chain, it won’t twist and jump around and get itself pulled off the sprocket.

You might get away with 11s chain and an old sprocket just to give it a go, but it’s not perfect. Especially with a new chain on an old sprocket which can slip if the sprocket isn’t in perfect condition still.

KMC Z610 is the dogs bollocks of SS chain and costs <£10
On-One Groove armada sprockets are £13 at the moment.

After a lot of trial and error I’ve found the single armed tensioners to be just fine, if the chain comes off it’s always been something else’s fault (they still put a lot more chain wrap on the sprocket than a rear mech). The only thing better is a proper SS frame, a setup worn enough to jump the sprocket on a tensioned setup will last hundreds/thousands of miles longer on a proper frame (you can go until there’s barely and teeth left on the sprocket!)

Buy TWO Surly cogs, space them in the middle of the freehub. Change gear manually. With a tensioner, you may never go back! My SS has a 15T and 17T cogs, and I have to slide the back wheel back to tension.

Another with no issue with single roller tensioner.

The only tensioners that ever gave me any issue at all were the sprung ones regardless of which way I turned the tension.

I find the fixed ones to be far superior.

Thanks for the help,keep it coming.

Get a proper sprocket.I’ve got a nice big scar from a using a geared sprocket and it coming off.It was on a horizontal dropout with the chain VERY tight too!

I’d get a proper SS cog for the back, you will drop a chain off a cassette cog (especially if it’s muddy!) and that’d be a PITA in a race.

For the minimal cost of an SS specific cog and spacers it’s a no brainer really. As many have said, cogs from a cassette are designed to allow easy shifting which is exactly what you don’t want.

I picked up a SS chain for £7 from my LBS so that isn’t exorbitant either. If you want to go the whole hog then CTBM does complete kits