What is the minimum thickness for brake drums?
3.2 mm
Most car mechanics also agree that the bare minimum brake pad thickness is 3.2 mm (⅛ inches). Any thinner than this, and you’ll need an immediate brake pad replacement to avoid brake failure.
What is the minimum brake thickness allowed by DOT?
An air braked commercial motor vehicle shall not be operated with brake lining/pad thickness less than 6.4 mm (1⁄4 inch) or to the wear indicator if the lining is so marked (measured at the shoe center for drum brakes); or less than 3.2 mm (1⁄8 inch) for disc brakes.
What is the minimum thickness for brake shoes?
Shoes with bonded lining should, for safety, be replaced when the lining is worn to & 1/10 in. (3 mm) thick, even if a minimum thickness of 1/16 in. (1.5 mm) is quoted in the car handbook. Always renew brake shoes on both wheels on an axle , even if the lining on one wheel is less worn than on the other.
What is the maximum brake drum diameter?
Brake drums have a wear limit which is the maximum inside diameter the brake drum is allowed to be. This number is often cast on the outside of the drum it’s allowed to be 422.1 millimeters or sixteen point six two inches. This is for your standard American trailer brake drum or drive axle drum.
Do new brake drums need to be turned?
Just truing them when replacing the brakes helps a lot. However, check for smooth contact surface, and if there is a lip on the edge, turn them so the surface is even with the edge, that allows the drum to come off without adjusting the shoes in, or forcing them off.
How do you measure brake drum thickness?
Always measure the inside of the brake drum before deciding to discard or machine on a lathe. Use a drum micrometer or an equivalent tool to retrieve these measurements. Compare them to the diameter stamped on the outside of the drum. If the drum is scored or grooved, place the tool into the deepest part of the groove.
How do you tell what size brakes you have?
Call your local OEM dealer and ask for the original rotor sizes or OEM rotor/pads part numbers based on your vehicle’s VIN number (VIN# is referenced in your ownership papers). The dealership may not tell you the rotor size, but they will give you the genuine part numbers for your vehicle.