HDQG wheel adaptors can also be used in conjunction with Self Centering Adaptors. Since there is no way to raise or lower the sensor shaft in the front wheel adaptor, they are unsuitable for some low bumpers or air dams. Attempting the front HDQG adaptor for a middle sensor application will cause the middle sensor to block line of sight to the rear sensor, so a Self Centering Adaptor will need to be used for this application. The front adaptor CAN be used for a rear tag axle on a bus. These adaptors are for rolling compensation only.