[FrankJ]

Here are two examples of frame perimeters of a west coast style frame. The not legal one has a wheel defining the frame perimeter. The wheel moves relative to the frame so is not legal. To be legal the bumper would have to be attached to and be supported by the wheel. Not useful. On the legal frame, the upper frame defines the frame perimeter because it is in the bumper zone. If was not there the robot would still be legal because the front rail would define the frame perimeter, not the wheel. Bumper support rules would still have to be met.

While probably not as heavy defense year as beach ball bot, Good practice says you want to keep the bumpers from being driven into the wheels.