Minimum Brake shoe thickness

They never quite wear the exact same, though close. When one of the hub's brakes get close, they all get done. I have 341,000 miles on the original brakes on the truck and steers are getting close, though still well within limits. So, all the brakes are getting done on all hubs along with new drums at the first of the year.

 

Don't just check for minum brake thickness. Any cracks on the pads is cause for concern.

 

Because a crack on a brake shoe is an out of service.

 

When you look on brand new brake pad ,you can see one side is thinner than the other one.
So,where exactly do you measure for that 1/4 inch? Right in the middle?

 

There's no certain spot. The entire brake has to be above 4/32. If you find ANYWHERE in that brake that is less then. It's time to replace.

 

393.47
(d) Linings and pads. The thickness of the brake linings or pads shall meet the applicable requirements of this paragraph— (1) Steering axle brakes. The brake lining/pad thickness on the steering axle of a truck, truck-tractor or bus shall not be less than 4.8 mm (3/16 inch) at the shoe center for a shoe with a continuous strip of lining; less than 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. The steering axle brake lining/pad thickness shall not be less than 3.2 mm (1/8 inch) for air disc brakes, or 1.6 mm (1/16 inch) or less for hydraulic disc, drum and electric brakes. (2) Non-steering axle brakes. 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. Hydraulic or electric braked commercial motor vehicles shall not be operated with a lining/pad thickness less than 1.6 mm (1/16 inch) (measured at the shoe center) for disc or drum brakes.

 

It's your brakes. If you have to ask, it's time to get them done.

 

Been driving a CMV for a year and 3 months now, in that time I have experienced 2, level one inspections. Both times brake linings and stroke were measured.

 

Keitht has been good enough to post the actual regulations in post #26. It is impossible to accurately measure the thickness of a brake shoe while it is installed on the axle. the same with drums. I haven't seen a brake shoe in years that didn't have wear indicators built into them.
Brakes are cheap by truck parts standards, as are drums. I replace both well before any question, which is my point.

 

Here are the Out Of Service regs for brake linings. You have to keep in mind that when a brake lining meets the OOS criteria on a steer it is included in the 20% rule AND OOS by itself. It is also included in the percentage equation if other linings are also under thickness. So a lining that is too thin on a steer axle is out of service. If you had one more thin lining on the trailer, it would also be out. On axles other than the steer, you would have to meet the 20% rule. So on a standard 5 axle TT, one thin lining would not place you OOS unless it is on the steer. Two thin linings anywhere meet the 20% rule on a 5 axle vehicle.

Lining violations are in the category of those violations that have to meet the OOS Criteria ,
before they are considered a violation.




Steer Axles

Lining with a thickness less than 3/16 inch (4.8 mm) for a

shoe with a continuous strip of lining or 1/4 inch (6.4 mm)

for a shoe with two lining blocks for drum brakes or worn

into the wear indicator if lining is so marked. (393.47(d

All Other brakes
Lining thickness less than 1/4 inch (6.4 mm) or worn into

the wear indicator if lining is so marked, measured at the

shoe center. (393.47(d)(2))

Inspection Bulletin 2007-01 – Express Brake

International, Inc. – Segmented Brake Linings