Brake travel?

I thought that brake travel meant measuring the play in the brake pedal. Not sure though.

 

It's how far the push rod has to travel into the brake chamber when the brakes are pressed. It is supposed to be under 2" or 2.5" depending on the type of brakes you have, 2.5" is for "long throw" (think that's the correct term.) If you have automatic slack adjusters, and 99.9% of brakes today do, then you shouldn't have to worry about it to much however they do fail so it's a good idea to check them now and then. If your rod travel is out of adjustment it means the auto slack adjuster needs some work. You can still do manual adjustments but that won't stop it from going out again and eventually you'll have to fix the slack adjuster.

Here is a good writeup on air brakes. And they have a good diagram on another page so you can see what it looks like:

 

The above is a full and completely correct answer. So, Alex, lets take Movies that would be better with a nude scene for 1000.

 

What is Kramer vs. Kramer?

 

Everything said above is correct. I have been pulled over by the DOT and had them crawl under my truck and mark pushrods with a marker and have me press the brakes so they could measure travel. They allowable amount depends on which brake chamber you have but generally speaking when you check you brakes you want the travel to be about an inch. 2" is the out of service limit for most brake chambers though long strokes are 2.5" I think.

 

You need two to check it. Usually what I have seen it's 2 inches or less.

There is a way to work around the travel problem. Let's see before you get into the scales or walk into the scalehouse coop mash your service brakes 8 times to the floor waiting a moment to build your air. This will tighten your automatic slack adjusters a little bit. Maybe enough to pass the inspection.

Another fast and dirty way to find out if you got a weak brake application when parked is to get under there with a chalk (The kind used in elementry school blackboards) as a single person.. Chock your tractor wheels. Set your trailer brake only but not the tractor ones. Get under tractor and mark your push rod where it enters the chamber on all of them. (6 total under your tractor) get up and set your tractor brakes, climb back under with a measuring tape and measure from the chalk mark to your brake chamber. You should have a set of numbers in a range when done.

Do the same with your trailer.

It's really hard to type and describe just how to do it here, Easier just to show you.

 

If you're hooked to a trailer, it's easy to check it yourself. Set tractor parking brakes and release trailer brakes. Mark pushrods. Use hand valve to apply trailer brakes. Measure. Set trailer spring brakes and release tractor brakes. Mark pushrods. Use a board cut to length wedged between the seat and pedal to push the brake pedal. Measure.