Shop Talk

On the steering axle of a semi truck, the minimum required thickness for brake shoe lining is 4.8 mm (3/16 inch) at the shoe center for a shoe with a continuous strip of lining, 6.4 mm (1/4 inch) at the shoe center for a shoe with two pads, or worn to the wear indicator if the lining is so marked, for air drum brakes. For air disc brakes, the minimum required thickness is 3.2 mm (1/8 inch). On non-steering axles (also known as drive axles or tag / additional axles) of a semi truck, the minimum required thickness for brake shoe lining is 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). For disc brakes, the minimum required thickness is 3.2 mm (1/8 inch). If your measurement is less than the minimum required thickness, the brake shoe lining may need to be replaced.

Gather the necessary tools and equipment: You will need a variety of tools to complete this task, including a hydraulic jack, jack stands, a wrench, ratcheting wrench and correct sockets, a torque wrench, a pry bar, and a hammer. You may also need special tools to remove the cab bushings, such as a hydraulic bench press stand or a mobile hydraulic press tool. Raise and support the cab: Use the hydraulic jack and jack stands to raise the cab of the truck and secure it in place. Make sure the cab is stable and secure before proceeding. Remove the cab mounting bolts: Using the lug wrench or a socket set, remove the bolts that secure the cab to the frame. Be sure to keep track of which bolts go where, as they may be different sizes. Remove the old cab bushings: Once the mounting bolts are removed, you can press the old cab bushings out of their mounting points using a hydraulic press or a special press tool. Install the new cab bushings: Once the old bushings are removed, you can install the new bushings in their place by using the hydraulic press or special press tool. Make sure the new bushings are seated properly and aligned with the mounting points on the frame. Reinstall the cab mounting bolts: Using the torque wrench, tighten the cab mounting bolts to the manufacturer's specified torque. Be sure to tighten the bolts in a crisscross pattern to ensure an even load on the bushings. Lower the cab: Once the new bushings are installed and the mounting bolts are tightened, you can lower the cab back down to the frame using the hydraulic jack. Make sure the cab is seated properly and aligned with the frame before removing the jack stands. Test the cab: Once the cab is back in place, it is a good idea to test the movement of the cab to make sure the new bushings are functioning properly.

Takeaways from the Haldex guide are: 4515 style brake shoes have a hump on the web (the web is the center rails that hold the roller pins and hardware), but 4707 style brake shoes DO NOT have a hump on the web (BE ADVISED THIS IS NOT ALWAYS THE CASE, USE THE OTHER FOLLOWING METHODS TO VERIFY) 4515 style brake shoes have 4 holes on one side the brake shoe table (the table is just a fancy word for the brake shoe metal base that holes the brake shoe lining with rivets), while 4707 style brake shoes have 3 holes on one side of the brake shoe table 4515 style brake shoes have the rivet holes in the 4 hole groups starting at 3/8 in. from the web (again the web is just a fancy word for the center rails that contain the roller pins and hardware), while 4707 style brake shoes 3 rivet hole groups are spaced 5/8 in. away from the web Takeaways from the Meritor guide are: 4707 style brake shoes MAY OR MAY NOT have a hump, do not be deceived Some 4515 brake shoes may have a cast iron brake shoe table aka base (this will be an obvious difference) 4515 has a few variations of length between the larger roller pin slot and the nears spring pin hole (view pictures on pg. 12) 4515 looks visually different, for example; some 4515 have contained holes for the roller pins instead of slots on the ends for the roller pins like the rest of the brake shoes (view pictures on pg. 11-12)