What is brake glazing? How do you prevent it?
In a recent thread, we were discussing brake glazing and I was surprised to see that the term was not widely understood or defined so I looked it up. Here's what I found: What causes brake pad gla...
Forum Discussion
rgatijnet1 wrote:
When the brake pad material, that has overheated and glazed, gets deposited on the rotor, it makes the rotor look like it is glazed. This can usually be removed from the rotor by turning them.
Pad glazing occurs whenever the pads are overheated. This can be because the wrong pad material was used for the brakes on a certain vehicle. OEM pad material is usually the best choice and will dissipate heat better than some ceramic pads which may transfer more heat to the rotors. Basically all of the same thing apply to shoes and drums. Drum brakes were still used on some vehicles. My Chevy HHR toad has drum brakes on the rear.
The brake glazing shown in this picture is the brake material heated to the temperatures required to melt sand and turn it to glass.
Getting the brakes up to the 1,400F mark will glaze them and cause them to make a lot more noise.
Jake brake, or other engine braking will prevent this to some extent. Sometimes it requires the driver to downshift from 4 to 3 on some roads that have more curves, and might be steeper than average. Monitor your engine RPM as you descend the hills, and you will get an idea of how much RPM you can handle, and how much braking the engine can provide.
When I was leaving Sequoia National Park, I was in 3 and 4 gears, going down the hill, marked as about 45 MPH, with 35 MPH curves every 1/4 mile or so. I think it was a 6% downgrade as well. IN areas where it leveled out for a bit, I would shift to 5th gear, and turn off the engine brake for a bit. Then as I picked up speed, I could shift back to 4, and turn on the engine brake, slowing the RV even further.
If I had just left the transmission in 'drive' it would have been in 6 speed, then shift to 4 when the brake is applied, and as I shut it off, it would go back to 6, giving a slight jerk to the RV, as well as letting it coast up to a higher speed fairly quickly.
Overall, I did not need to use the service brakes very much, until I was going to make a left turn at the bottom of the hill. I think I used the service brakes a bit before each tight curve in the road, but had the engine brake on at the same time, most of the way down that 5-8 mile long 4,000' descent on highway 180.
Of course when you are descending a long hill like this, be aware that you might collect about 10 cars behind you, wanting to drive the speed limit, and pass you. Pull off if there is a turn out.
Good luck,
Fred.
