(I've moved the thread to the Tech Section.)

I'm not sure your vibration sounds like cush drive. That's more or a stutter/jurk when you are changing speed or gear.

Cush rubbers lifespan is a little hit and miss, some have seen them go after 3 or 4k miles, my first set lasted 13K miles, but the second set has been packed out (with inner tube rubber) after 4000 miles.

It's all a matter of 'how much' they have gone I suspect.

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