I was just trying to find the lowest cost main wheels( 3.5 inch wheel) pneumatic brake system for my turbine trainer. So far when I add up the various fittings , valves etc to go with a brake sytem , its not very cost effective versus a complete package from say Trim . The lowest cost alternative seem to be the electric systems from Kavan but I am not sure how good and maintenance free these are. Any comments ? Tks