2011 Silverado braking vibrates during downhill

[whosgreg]

Hi fellow RVers,

For the 3rd time, going downhill in the mountains, the brakes vibrate. I had to manually use the BC instead of the truck brakes. Tires are brand new. Brake pads are good.

Without the trailer, the brakes don't vibrate downhill. Wonder if I'm setting up the BC wrong because when I manually apply the BC and truck brakes the same time, the brakes didn't seem to be vibrating as much.

Any help would be appreciated.

[97chevor]

I always run downhill in a lower gear. Low enough that truck doesn't speed up off throttle.

[marspec]

My F450 did the same thing. Heavy braking downhill or sometimes level ground caused vibration. Not towing no vibration. Took to dealer. Problem was in front end, not the brakes.

[whosgreg]

Campfire Time wrote:
It is not warped rotors. True rotor warp is very rare. If it was warped rotors you'd get the pulsation all the time at all speeds.

It's hardened pad material stuck to the rotors. And yes it's caused from heat. Moreover it's caused from improper bedding of the pads, or lack of, after installation. Especially with ceramic pads. After it happens pull over and look at the rotors. You'll see little comet like deposits. It's more prevalent with ceramic pads but can happen with any type of pad. Thickness of pads is not an indicator that this will or will not happen.

I'd put new pads on before doing anything else. And readjusting the BC would not hurt either.

When I push the BC button, the trailer slows down and I know it's working. The number on the BC shows 18. However, I am suspecting that when I apply the truck brakes, I don't feel the trailer brakes being applied. I would assume that the trailer brakes and truck brakes would be applied equally??

[hawkeye-08]

Campfire Time wrote:
It is not warped rotors. True rotor warp is very rare. If it was warped rotors you'd get the pulsation all the time at all speeds.

It's hardened pad material stuck to the rotors. And yes it's caused from heat. Moreover it's caused from improper bedding of the pads, or lack of, after installation. Especially with ceramic pads. After it happens pull over and look at the rotors. You'll see little comet like deposits. It's more prevalent with ceramic pads but can happen with any type of pad. Thickness of pads is not an indicator that this will or will not happen.

I'd put new pads on before doing anything else. And readjusting the BC would not hurt either.

Some more reading can be found at Not warped rotors

[Campfire_Time]

JustLabs wrote:
As inexpensive as new rotors are, people are still getting old rotors turned?

I've been told places like AutoZone do turn them. I usually don't have them turned so long as the surface is fairly smooth and isn't gouged. Once they start really wearing down I just get new ones.

As far as cost, it's like $12 bucks to turn them. The set of rotors I just put on my Sierra in spring were $45 each. So there is a bit of savings to turn them, mine are usually to far gone to turn them.

[whosgreg]

Thank you all for your advises. I will check them out and see what I can find.

When I push the BC button, the trailer slows down and I know it's working. The number on the BC shows 18. However, I am suspecting that when I apply the truck brakes, I don't feel the trailer brakes being applied. I would assume that the trailer brakes and truck brakes would be applied equally??

[JustLabs]

As inexpensive as new rotors are, people are still getting old rotors turned?

[Community Alumni]

Campfire Time wrote:
It is not warped rotors. True rotor warp is very rare. If it was warped rotors you'd get the pulsation all the time at all speeds.

It's hardened pad material stuck to the rotors. And yes it's caused from heat. Moreover it's caused from improper bedding of the pads, or lack of, after installation. Especially with ceramic pads. After it happens pull over and look at the rotors. You'll see little comet like deposits. It's more prevalent with ceramic pads but can happen with any type of pad. Thickness of pads is not an indicator that this will or will not happen.

I'd put new pads on before doing anything else. And readjusting the BC would not hurt either.

x3. I would get the rotors turned to remove the deposits, some new pads, and bed them in correctly. Also don't depend so much on the trucks brakes when descending. Let the transmission and the trailer do the majority of the job for you. Also, watch your speed at the top of the hill so that you can more easily control your speed on the way down.

[larry_barnhart]

no issues using our GM brakes. Really don't use the truck brakes going down a mountain. Our 2001 8.1 going North on the I-5 grapevine did over heat the brakes and caused the steering wheel to shake but it was drive error on my part starting too fast at the top. Just not thinking. The allison was new to me.

chevman

[Shadow_Catcher]

My experience and research I did is that rotors seldom warp, however certain pads will deposit bits and pieces of themselves. It was a matter of finding the right pads.

[FrankShore]

Campfire Time wrote:
It is not warped rotors. True rotor warp is very rare. If it was warped rotors you'd get the pulsation all the time at all speeds.

It's hardened pad material stuck to the rotors. And yes it's caused from heat. Moreover it's caused from improper bedding of the pads, or lack of, after installation. Especially with ceramic pads. After it happens pull over and look at the rotors. You'll see little comet like deposits. It's more prevalent with ceramic pads but can happen with any type of pad. Thickness of pads is not an indicator that this will or will not happen.

I'd put new pads on before doing anything else. And readjusting the BC would not hurt either.

This is what's happening, exactly!

[BenK]

Sounds like high spots from stopping while the friction material is hot and still
out-gassing...to bake a high spot on the rotor surface(s)

Take it out on the freeway up to 65MPH...NAIL the brakes several times and DO NOT STOP

Keep rolling so that the out-gassing will NOT bake a high spot, but leave an
even coating on the rotor surfacce

Or, change friction material to higher performance. The point at which it will
out-gas will be higher and most likely not bake on a high spot...though they will
too...if you get them hot enough

[LIKE2BUILD]

whosgreg wrote:
Hi fellow RVers,

For the 3rd time, going downhill in the mountains, the brakes vibrate. I had to manually use the BC instead of the truck brakes. Tires are brand new. Brake pads are good.

Yep, brakes have been too hot and caused glazing on the pads and/or rotors.

Is the truck diesel or gas? If diesel, do you have an exhaust break or does your transmission have and engine braking feature? If gas, are you leaving the transmission in 'D' or are you shifting to lower gears?

When descending a hill, you really need to let the driveline work for you to scrub off speed. A general rule of thumb is to descend in the same gear you ascended the hill. We have a long steep climb in eastern KY that was always 2nd gear @ 40MPH. I would leave it in 2nd gear on the downhill side and let the engine backpessure scrub speed so I only needed to tap the brakes occasionally to maintain control. If I don't, I'd be on the brakes the entire descent and they would cook in a hurry.

[azdryheat]

Sounds like you're overworking the truck brakes. Check the adjustment of the brakes on your trailer. Trailer brakes need to be adjusted often as they are not self adjusting. Dexter says every 3,000 miles, as I recall.

Do you manually downshift your transmission? Most all hills I go down are done in 4th gear and sometimes 3rd if it's really steep. It helps keep the speed down. I also have the exhaust brake which works well.

Also, could you be towing too much trailer or not have enough truck?