Slack and stiff chain on my track bike

[ianf]

Recently my track bike that I use at the Chiang Mai velodrome has developed a problem in that as I rotate the pedals, the chain is very taut at one point and incredibly slack at another. I've checked the chain (1/8th) for wear and that's ok; The chainring is a newish Campagnolo Pista 52-tooth and seems perfectly ok; the frame is inline (check in a decent bike shop) so I am at a loss ..... The main problem it causes is when really winding it up, I get harsh noises and the fear that the chain will jump off. Any help available?

[stella-azzurra]

Check bottom bracket it's possibly loose or worn.

[crohnsy]

Your chainring could be out of round. try another chainring and see if you still have that issue..

[CarlosFerreiro]

Sheldon has advice on centering chainwheels on fixed gears....
http://sheldonbrown.com/fixed.html

[Tapeworm]

In addition to the above, check the cogs at rear and every single link in the chain to see if one has binded.

[ianf]

Thanks for your help. I had a new 50-tooth Stronglight chainring and that seems to have been the problem. After flaffing about for an hour I changed the chainring for an old-style Campagnolo 51 -tooth and what do you know? Perfection. Thanks for your help guys.

[horse]

Your problem is sorted.
Chain wear is usually uneven and is also the culprit. Possibly the worst thing about track bikes is the drivetrain and having it remain correct.