Hi there,
I installed a new cassette and rear derailleur (both Deore M5100) and new chain. Even with the the b-gap screw fully backed out, the b-gap is several mm too big (first picture). Second picture is what I’m aiming for, from the Shimano installation guide.
Pictures 3 and 4 are the drive train while in the biggest and smallest cogs.
Any idea what is wrong? Is the chain too short / would that cause this?
Thanks very much.
by tabbys_star
5 Comments
P.S. Derailleur hanger is integrated into the frame, so I don’t believe it’s bent.
Correct me if I’m wrong but I think that derailleur is meant to be run with a shimano direct mount hanger. You would need to buy an adapter link to make your hanger position correct
I think the issue is that the frame has slotted dropouts for running a single speed. Generally you will have to add a stop in the bottom of the dropout slot to stop the wheel going in so deep. With a derailleur, the position of the axle should be slightly forward, but because you don’t have a stop they look directly above each other.
We’ve seen some frames be a nightmare to get to the exact b gap, you could certainly try a longer chain with 1 extra link, as it will move the mech back around to where it needs to go to improve the b gap.
It looks to me like your wheel needs to be further forward in the dropouts, as for that to work properly, the axle needs to be ahead of the derailleur mount (as it is on thru axle or vertical dropout frames)