RWKW = FWKW - DRIVETRAIN LOSS A dynometer is an accelerometer, the inertia of the steel drum is a known fact and this means that calculating the power from this spinning drum is pretty easy to do. Wheels, driveshafts flywheels clutches and pretty much anything else that makes up your drivetrain* will effect the DRIVETRAIN LOSS this in effect increases your RWKW it does not increase the FWKW (as this is measured without a drivetrain) if you want examples here are some Light weight flywheel = more power Light weight wheels = more power carbon fibre driveshafts = more power weight requires inertia to move, reduce the weight of your drivetrain and you reduce the inertia it takes to spin your drivetrain meaning more power ends up on the rollers If you really want to see this taken to the extreme take a look at the Jap JTC race cars, they may be rice but they have extreme amounts of power being made reliably out of little engines and they incorporate all the lightweight parts I listed as examples above. p.s pashen I would be interested to see the weight difference between your 17's and your 19's