Originally Posted by
base2
You don't say what kind of bike. But on some level it doesn't matter. My guess is you have one of those ginormous 11-50 cassettes &/or a reasonably long cage derailleur.
What makes me think this is the sudden stop of drivetrain input after a hard sprint exposes the rotational inertia of the giant cogs & the decreased leverage the long lever (derailleur cage) has on the system.
If this is true, then your derailleur may have a clutch mechanism to help the weak lever component of your problem. Engage it.
The other option is to get a short cage derailleur to fight a high friction drivetrain like would be found on an IGH hub.
Another option is to not sprint, spin up all the heavy giant cogs, then suddenly stop the input.
I am pretty sure before every sprint on a ride I tell myself I am not going to sprint, but it just happens. So I gladly accept this advice, but say I wont sprint anymore until I fgure this out but doubt that will hold true.