Thanks Howmet ! Yes please Don go for it ! You are right Don , I have many 16D motors , and some rev very hard , then you place them in a chassis , and do the laps , and just no go ! Then you can place a motor which don't rev as hard , and it goes like a scalded cat ! You would think that higher revs would propel more , but magnetic pull of armature , wire used , contacts -- the list goes on - play a huge part in overall performance ! Even two motors ( say we use 2 new Classic 16D motors for argument sake ) , they will have differing performance ---- each may have been constructed out of the same materials --- yet performance will differ . So , are we to assume that each motor out there is unique -- and like a human fingerprint ? Zig