I have been running a single speed for a good while now but in the last month or so I get a right clonking noise from the drive system (like chain dropping back on to sprocket) when i put a bit of tension on the cranks. It's fine when spinning along or under constant pressure but if i coast and put pressure back into the drive i get the a sharp snap from the drive system. I have checked the sprockets which are steel and they seem fine , I also have a fairly new chain (only about 4 months old)one of them fancy KNC gold track jobs so all i can think is that the line is wrong and the chain is picking up on the sprockets and snapping back down. Also have the chain pretty tightly tensioned as well. The chain line was fine a few months back though. Any thoughts??

new chain old sprockets?

Also have the chain pretty tightly tensioned as well

loosen it slightly.

pawl slipping?

Mine does this a fair bit – old shimano hubs.

could be the freehub – shimano can make a bit of a clonk if they're worn – runnign the chain too tight will make it worse.

if you spin the wheel off the ground do the cranks go round? If they do the chains too tight/the freehubs a bit sticky.

used to do this on mine. Stripped my hope freehub, re-greased and it sorted it. If its a shimano then your ****

or you could do what i did last night, pedal really hard into a jump, slip your slack singlespeed chain and let your knee shave some weight on the ground 🙁

I'll give the wheel a spin after work then and see…but i have a feeling they do rotate so maybe i'll slacken the chain. I bloody hope it's not the free hub or I'll have two to get as my spare rear wheel needs one as well..

If its a shimano then your **** need a new freehub

There we go!

and of course a shimano freehub is cheap as chips.

i had a similar noise, it was the wheel bearings

well the cranks dont move when the wheel is spun which is something but the freehub being the problem is quite plausable…anyone know the cheapest place for shimano freehubs?

i have not long had the rear axle and bearing changed..

what hub is it – complete hub from crc is often cheaper than just a freehub.

Shimano XT wheelset XT775.