i had a p-10 with steel rims and mafac brakes.. and it would not stop... period.. so there is that... and if you buy 25 or 50 dollar wheel sets... then you get 25-50 dollar hubs... hubs are kinda important.. its where you really dont want to go cheap.. free wheel mech and bearings on a 25 buck wheel are kinda of a gamble.. if you are talking just the rim... still breaking surface is kinda important.. if you are going 20mph... and reach for a handfull of break and its just skates on the pad with that awfull sound an no slowing of down.. then even at 5 bucks the rim is just not worth the price... nope.. not a fan of carbon wheels at all but alum rims are really a sweet spot on technology.. will never go back to steel..