32 is too small for 650b conversion on a bike designed to accept 40 700c tires. 38 would be a good minimum with 42 recommended as the best size.

650b is for when you want bigger tires with wheel diameter close to the same of the larger 700c wheels with smaller tires so the rotational inertia and "feel" of the wheels stays about the same but comfort and capability increase. There's no point in running 650bx32 on a normal sized bike.