Hot Brakes

Cause of smoking flaming brakes? My guess is a malfunctioning spring brake chamber. With the torque and pulling power these trucks have, you would never feel one trailer brake hanging up. But you could sure see it in your mirrors!

Smoking brakes going down a hill? Not in a low enough gear and keeping constant pressure on the brake pedal. That steady friction will create lots of heat very quickly. You should apply adequate pressure to slow 5 mph below your safe speed, then completely release the brakes to let them cool. Rinse and Repeat. Never ride the brakes going downhill.

Smoking brakes going down a hill? Not in a low enough gear and keeping constant pressure on the brake pedal. That steady friction will create lots of heat very quickly. You should apply adequate pressure to slow 5 mph below your safe speed, then completely release the brakes to let them cool. Rinse and Repeat. Never ride the brakes going downhill.

You can keep 5-10 lbs pressure on (properly working) brakes indefinitely and they won't burn up, but that's not enough braking pressure for any significant grade unless you are in a very low gear or using jakes. If weather and roads are good, I run every 6+% grade with jakes and constant feathered brakes, beginning to end. Haven't smelled burning brake since my first time down a slope with my first trainer.

Farmerbob, I would suggest that you read this:

Downhill Braking

Snub don't ride!

•Some drivers don't understand the severe demands put on the brakes by long downhill runs. Suppose your doing 6 miles with an average 6% downgrade. Runs like this are common out west. (In the east too?) This is a 1900' change in elevation. A free fall from 1900' results in a terminal velocity of 238 mph- neglecting air resistance. This would be the velocity of your rig -neglecting air and rolling resistance- if you didn't brake. •Negotiating this grade is the same as slowing down from 238 mph. This is like 16 stops from 60 mph (not 4, kinetic energy varies with the square of the speed: (238 x 238) / (60 x 60) = 15.74 ) Suppose you average 30 mph coming down, the run will then last for 12 minutes. Sixteen stops from 60 mph in 12 minutes is a lot of stopping. Obviously your brakes had better be right and you had better use the right braking technique if you want to make it safely to the bottom. •In recent years there has been some erroneous information going around about how to brake on long downhills. It was suggested not too long ago that a continuous application of the brakes as opposed to intermittent application or snubbing was the preferred method. THIS IDEA IS COMPLETELY WRONG! •The proponents of the old theory have rescinded it, there is now (almost) universal agreement that the proper way to brake on a downgrade is to intermittently apply all your service brakes in a way that will reduce the speed of a fully loaded vehicle by about 5 or 6 mph during each application. What is key here is not the speed drop, this will depend on weight, grade and other factors, but air pressure, you have got to get the application pressure high enough to get all your brakes working. •In theory, it doesn't make any difference whether you ride or snub the brakes on the way down. The problem is that you don't drive a theory, you drive a truck. In theory, the same amount of heat is put into the braking system regardless of how you apply the brakes. In practice, unless your brakes are in good condition, tractor-trailer balance is right and the load is ideally located, the continuous application of the brakes is likely to result in uneven drum and lining temperatures and problems before you get to the bottom of the hill. •Steady, low pressure application of the brakes may not cause all the brakes on the vehicle to apply and may result in some brakes -those with the lower activation pressures- doing more work than others. Specifically, in many cases the tractor brakes will do too much of the work while the trailer brakes loaf and you might then get fade at the tractor axles.. Other brake problems can be aggravated by the low and steady braking technique. What you want is all the brakes working some of the time, not some of the brakes working all the time. The application pressure must be high enough to ensure that all brake chambers apply and that all linings make solid contact with the drums - about 20 psi or higher.

One last thing. You probably won't smell the burning of your own brakes because your are driving away from it. The guy behind you will though!

I pulled out of a truck stop once not realizing the brakes hadn't released on one side of my trailer. Unfortunately, it was raining out and the smoke was blending in with the mist being kicked up. Fortunately, another driver radioed me and let me know I was smoking. Ended up with flat spots on the toes, but that was about it.

This was one of my biggest fears going solo. Every time I smelled something I pulled over to check the brakes!

I was once stopped in Memphis rush hour and saw what I thought was smoke, jumped out the truck with the extinguisher and was ready to tackle the problem. Then I realized it was fog. People were looking at me but I didn't care. get back in truck and wait to move. Then a truck comes by me with only one trailer door and the broken one inside the trailer. Made me feel good that wasnt me. Mean of me, but even of I scared other cars over fog...at least o didn't rip a door off.

One last thing. You probably won't smell the burning of your own brakes because your are driving away from it. The guy behind you will though!

You can smell your own burnt brakes for days when you do PTI's. I did, the one time I burnt brakes with my trainer. For three days I smelled it clearly. On the fourth day I wasn't sure.

As I said, constant brake pressure is only reasonable when you only need to feather 5-10 lbs pressure on the pads to control your speed. When your transmission, Jakes, or some combination of both is already doing a large part of what is needed to control your speed.

Your quote does not mention jakes at all, nor does it mention feathering.

If you need more than a constant 5-10 lbs pressure to slow the truck, THEN, yes, you stab brake, and allow the brakes to cool between applications. Constant high pressure application of brakes is BAD.

Brakes generate heat based on how much work they are doing. Brakes at 5-10 lbs pressure are doing a lot less work than brakes at 20-50 lbs pressure, so they generate less heat over time.

The brakes do not only cool when unused. They cool constantly, but a little faster when unused. They overheat when work performed by the brakes generates more heat than ambient cooling.

At 5-10 lbs pressure, a braking system will heat up to a point that is not dangerous, and maintain that heat level. This is basic physics, and is not addressed by your article.

Farmerbob, You obviously did not read the article. Or you are lacking in reading comprehension.

Speaking of friction, I saw this a couple years ago, thought it was pretty cool. Friction welding.

https://youtu.be/5JbnDXw-0pM