I have recently replaced the chain and the cassette. Previous chain never slipped. I never had any problems with it at all. But I have made about 10 000 km on it and the wear was beyound any limits, so friends and guys in the bike service recommended replacing both chain and the cassette. I did a lot of reading and I know that chain and the cassette wear together.
So I got chain and the cassette replaced. It is a 9 speed cassette. I have asked to replace it with a little lower gear ratio. Guys in the workshop also indexed the derailleur for me.
Since I collected my bike the chain slips terribly every time I stand up on the pedals. Sometimes it also slips when I apply enough pressure even while seated. But standing up is a definite slip. I already have few bruises from falling down on the frame.
I had assumption about chain being too long, but is seems to be just about ok.
I have also figured out that the chain never slips if it is on the lowest or the highest chainring. It only happens with the middle chainring. As I have said before - it never happened before with the old chain/cassette. Now I have tried to stand up and pedal very hard in all gears on low and high chainrings. Never got a single slip in about half an hour of trying. Changed back to the middle chainring - it slips in every gear from 1 to 9 when enough torque is applied.
So the question is: can it be that chain is slipping at the chainring? Do chains ever slip at the chainring at all? I have never heard of anything like that. Is there a simple way to test it in order to be sure that the chainring is the root cause?
I really don't want to blame it on the chainring and get it replaced just to figure out that the problem never went away.