seems like youre asking 2 things,
do i need same length cranks?--- the difference between cadence on different length cranks might be something MDCC tester would know but I doubt it makes much odds.
what length cranks on velodromes?, depends which one really, most coaches advise 165's for garunteed clearance. although you can use 167/ 170 on HH easily,
dont try it at Calshot though
what if youve got 7 bikes?
seems like youre asking 2 things,
do i need same length cranks?--- the difference between cadence on different length cranks might be something MDCC tester would know but I doubt it makes much odds.
what length cranks on velodromes?, depends which one really, most coaches advise 165's for garunteed clearance. although you can use 167/ 170 on HH easily,
dont try it at Calshot though