Today’s ride with a new (and apparently badly chainlined by me) frame got me thinking – bigger diameter than the sprocket and spaced so that they can hold the chain on

do these exist ?

if not, why not ?

Alfine sprockets come with a chain guide attached (on one side only). I don’t know if it would be possible to convert such a thing.

Never seen any or seen the need tbh.
But could you not find somthing to use each side of the cog to act as a guide
Maybe some of the larger rear cogs from an old rear cassette

yes they exist but totally pointless, just learn to set your bike up.

They dont need to exist if you get
the chainline right !

I have a bodge in mind, yeah, but would have thought it’d be a useful thing for somebody to make – almost, “why would you not have them ?”

Or do other riders never lose the chain ?

Lost a few chains on ss over the years but always at the front end
And always due to eithe lack of tension , busted chain ring or just poor build

They dont need to exist if you get
the chainline right !

[quote]just learn to set your bike up[/quote]Thanks 🙄
It was a bit of rushed build with a brand new chain & cogs before going out this morning and the main issue was tension (lost once inside and once outside off the back) but yes, oh masters, the chainline also wasn’t bang on either as I said above

Then again, I CBA correcting tension all the time (ever) and I’m almost def going to bodge this up as a result

With proper chainrings front and rear you can get off with quite a lot of slack in your chain.

Just look at the pics of any overloaded singlespeed bike in a 3rd world country.

Chainline needs to be right though.

The trek 69’r of 6/7 years ago wi upside down maverick forks used to come wi such a device/setup.

just measured up, out by 1 or maybe 2mm at the max at the moment

chain was pretty slack though – maybe 2-3 inches of play from up to down – and the route was bloody rough dried hoofchurn

Sort both tomorrow and bodge in a couple of keepers, I think

This, perhaps? Bit pricey though.

Good spot, thanks, but bloody hell !

could buy 2 20t sprockets for half that and just use them as spacers

You really shouldn’t be able to lose the chain. I’ve never dropped the chain whilst SSing.

I’d add a little more tension if I were you.

Proper cog/ring/chainline the chain won’t come off, even surprisingly slack.

Even if you had those things sat ready in your toolbox, it’d be as much faff to fit them as to sort your chainline properly so you didn’t need them!

you just need a couple of Nylon or delrin discs 35mm ID ~90mm OD should cover you up to about a 20t sprocket or so…

canibalise a cassette of two for spacers an a lock-ring,

but it’s probably wiser to simply aim for better alignment, have you got the chainring mounted in the ‘middle’ or ‘outer’ position?

Sometimes you can improve alingnment from the other end of the drivetrain if you need to…