I had the same problem coz I bought a cheap ring (TA from Condor) and I got the tight/loose/tight thing happening.
Changed my ring for a Miche one (2nd hand and well used) and the problem disappeared completely.
I tried two different rings from condor, and the gy tried to convince me it was my chain . . . .duh!
So, to sum up. Get the best track ring you can afford, slapp it on the best track cranks you can afford, and enjoy perfect chain tension on your bike.
There! YOU said it! TRACK chainring!!
I had the same problem coz I bought a cheap ring (TA from Condor) and I got the tight/loose/tight thing happening.
Changed my ring for a Miche one (2nd hand and well used) and the problem disappeared completely.
I tried two different rings from condor, and the gy tried to convince me it was my chain . . . .duh!
So, to sum up. Get the best track ring you can afford, slapp it on the best track cranks you can afford, and enjoy perfect chain tension on your bike.