I’ve noticed that I seem to have tight spots on the chain tension on my Malvern Star. It’s very noticable when pedalling. I recently swapped out the BB and cranks for Ofmega track cranks and I have swapped the chain ring twice and I still seem to get it.
I tried the Sheldon Brown method with loosening the bolts and retightening them in the correct order, but it doesn’t seem to do anything.
Could it have anything to do with the chain? It’s one of these KMC chains.
Highly likely its the chain. I had the same problem and swapped the chain and now there are no dramas.
To be sure, take the chain off and spin the cranks around as if you life depended on it.
Look at it from behind, and see if there any “Jumps” in the chainring. If there are, then the chainring is not round and you should get another one or try making it sit better on the spiders. If not, its most probably that your chain has just worn unevenly thus producing tight and loose spots.
you can also try doing the chainring studs up to about 80% tight, pausing the drivetrain in the ‘tight spot’ and then giving the chainring some taps with a block of wood from the front end of the bike(while the chain is still on). Give it a spin, and see if the chainring is more concentric on the crank.
I’m guessing Sheldons method would be quite similar in trying to achieve ultimate concentricity in the chainrings fit on the crank.
p.s. it could be an issue at the hub, where the rear cog/hub isn’t centered but highly unlikely.
If your chain was ‘kinda loose’ you wouldn’t have a problem tight spots.
If the chainring doesn’t fit snuggly on the spider - and it is a good quality chainring, i.e. round, slip pieces of paper into the gaps between the chainring and spider, evenly until you can’t fit any more pieces in. Then tighten your bolts - that’ll help centre the ring.
To check that your chain is not too loose (and yours isn’t if you are feeling tight spots) pick the back wheel up, crank the pedals up to speed, then pick up the whole bike so that it’s horizontal and shake the shit out of it. This is a pretty standard way to check that your chain won’t fall off.