Wednesday, September 19, 2012

Brake Shoes

The following discovery is the result of a pre-trip, walk around inspection. 

A bad brake shoe.  Normally I don't have any issues with brakes because I don't really use them.  Most of the time we do highway driving, and to slow down, we just use the engine brake.  The engine brake is a compression brake, also called a "Jake Brake", named after the Jacobs Brake which is an air driven cylinder that increases the air compression in an engine cylinder, that when released, causes the engine to slow the truck down.

The brake shoes look brand new.  Here is a picture of the old brake shoes next to the new ones - the old ones are on top:

As you can see, the thickness of the brake shoe is almost identical.  These old shoes have 475,000 miles on them.  Hard to believe, but it's true.  The drive axle brakes were replaced last year and were in the same condition; barely used.  The trailer also has these brakes, and they too are in very good condition.  The fact is, that if you use your engine brake correctly, you can get one million plus miles out of a set of brakes. 

So why am I replacing them?  At first glance they look fine, and one of them IS fine.  But here's a closer look:
Can you see it?  Here's an even closer look:


If you click on the picture and make it larger, you'll be able to see a crack in the pad.  This is an automatic fail on a DOT roadside inspection.  If that happens, you'd have to get a certified mechanic to come out and change the brake shoe at the inspection site, which means unnecessary down time, and is one of the reasons why routine inspections are so important.  Even though the shoes have hardly any wear on them, they still get old and sometimes the just start to break down. 

Brake shoes don't like heat.  Neither do wheel seals.  Typically, new drivers will drive their trucks as they would their cars.  This is a tell-tale sign that a newbie driver is behind the wheel.  Trucks require greater stopping distances, and slow travel when going up and down hills, which I'll get into in a later post.  The point is, when drivers use their brakes constantly, they generate tons of heat which causes the wheel seals to prematurely wear out and leak.  Often, they even catch on fire. 

So when you see a truck or trailer with billowing smoke coming out of the wheel areas, it's almost always brake related.  This isn't always the driver's fault, as sometimes the brakes will come out of adjustment while driving, as the result of a bad slack adjuster.  I'll cover that  topic in another post also.   

After the cracks were found, the brake drum was then removed.  It took a while to do this because this brake drum was installed at the factory in August 2006, and has never been taken off the truck before.  Because of that, the mechanic had to beat on the drum with a mallet to loosen it up.  Eventually, it came off  and the brakes were replaced.




The drum was in new condition, so they just slid it back on the hub, followed it with the wheel, and in no time at all I had new brakes. 

As a result of taking 15 to 20 minutes to do a proper pre-trip inspection, I not only saved myself from getting a possible DOT violation and points on my CSA, but I also knew that the safety of my vehicle was intact before I got back on the road. 

2 comments:

mom said...

Wow...You sure have an "eagle eye" to catch that.Good job.

Belledog said...

Good eye, Ed.