A brake proportioning valve is typically located in the rear brake line and enables you to adjust the rate of pressure increase to the rear brakes. It changes the proportion of brake fluid. You can slow down the pressure increase that happens when you apply the brakes with a brake proportioning valve. After continued use, the proportioning valve can become out of alignment and it may need to be reset. It is helpful to have some knowledge of vehicle mechanics to complete this task, but it is unnecessary.
Locate the brake proportioning valve near the rear brake line. It will have one or two buttons located on it. The reset button usually has a rubber cap on it. It is an “L”-shaped metal valve.