light duty truck brake
light duty truck brake
(OP)
For a light duty pickup truck, what is the brake duty cycle?
Going down a long 6% grade, with the brake pedal lightly held with a constant light pedal force only to maintain freeway speed, no load in truck except driver, my 1/2 ton 2005 Chev Silverado truck brakes begin to chatter slightly with increasing excitation, then after about 1/4 mile distance they shudder increasingly more and are audibly louder as heard in the cab. Note that ABS is not engaged (pedal has no ABS pulsation) and the roadway is smooth. No other automobile we have owned nor does our other vehicle (2006 SUV) exhibit this symptom. Brakes are front disc and rear drum (Bosch, I believe) and have been replaced, remachined, etc. under warranty but the problem remains.
Dealer now advises to downshift to 3rd gear to use engine braking, but I believe trucks, meant to be loaded, should have sufficient brakes to enable light pedal force-downhill braking, especially unloaded!
Brake design/test engineer suggestions are most welcome!! Thanks.
Going down a long 6% grade, with the brake pedal lightly held with a constant light pedal force only to maintain freeway speed, no load in truck except driver, my 1/2 ton 2005 Chev Silverado truck brakes begin to chatter slightly with increasing excitation, then after about 1/4 mile distance they shudder increasingly more and are audibly louder as heard in the cab. Note that ABS is not engaged (pedal has no ABS pulsation) and the roadway is smooth. No other automobile we have owned nor does our other vehicle (2006 SUV) exhibit this symptom. Brakes are front disc and rear drum (Bosch, I believe) and have been replaced, remachined, etc. under warranty but the problem remains.
Dealer now advises to downshift to 3rd gear to use engine braking, but I believe trucks, meant to be loaded, should have sufficient brakes to enable light pedal force-downhill braking, especially unloaded!
Brake design/test engineer suggestions are most welcome!! Thanks.





RE: light duty truck brake
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: light duty truck brake
Your rotors either have hot spots or are warped. Hot spots are not permanantly removed by re-machining. What is the history of those front brakes?
RE: light duty truck brake
Mike Halloran
Pembroke Pines, FL, USA
RE: light duty truck brake
Answers to several questions I received are: 1. Length of downhill 6% grade is >1 mile, but I only keep the brakes on for approximately 1/4 mile at a time, in order to let them cool a bit before re-applying. 2. Re: Rotor hot spots: Problem existed when truck was new. Dealer has installed new front rotors and machined the rear drums, then re-machined the front rotors under warranty, and replaced rear drum brake adjusters. 3. Have not tried ABS system fuse removal, which is a good idea.... am applying only light pedal force; feel no ABS pedal pulsation as ABS should produce if ABS is in effect. Any follow-up ideas are appreciated. Thanks again, all.
RE: light duty truck brake
Was the re-machining done for the problem described? That again points straight to messed up rotors. This condition is not always felt in the steering wheel and you can't machine the problem away. You need new rotors.
It happens to many kinds of cars and trucks. You just have to deal with it. If the problem comes back someday after installing new rotors, you may have to try a different brand of rotors and/or pads.
RE: light duty truck brake
I have a situation where I drive down a mountain to catch a ferry. I always stop short and move forward a foot or two every few seconds so as to even out the cool down rate and the deposit of sublimated resins from the hot pads.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: light duty truck brake
Incidentally, I doubt it is the rotors themselves. I'd look at the pads.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: light duty truck brake
RE: light duty truck brake
I will digest the tips/tech info you have given me, and work on this using your input. I will re-post separately later if I resolve this brake problem, as it may shed some light on this topic for you responders + anyone who has a similar brake issue. I really appreciate your time and effort and hope I can do the same for eng-tips members!! Again, my sincere thanks! LAL2004
RE: light duty truck brake
http://ww
http:/
RE: light duty truck brake
What you're doing, riding the brakes down a long grade, is putting enough heat into them to stress-relieve them: initial stresses, when relieved, distort the rotor surface. Hence the need for re-machining them.
And no, distorted rotors do not always produce a steering wheel vibration; rotor thickness variations too small to be measured with an ordinary micrometer - e.g., less than .001" - will produce bad pedal pulsation, and no steering wheel motion.
RE: light duty truck brake
I would try a different set of frictions since there has been no improvment with OEMs. The factory is not always best on everything.
The heat vs friction ramp rate is importent as well as the material.
I have replaced my frictions with aftermarket and would not go back to OEM now with such good brakeing. Some of the reason is towing nearly 12,000 lbs gross combined weight pulling a trailer with it's own electric brakes and a controller in the cab.
I use just enough braking on long hills to keep the truck at a reasonable speed as well as consideration to traffic ahead and behind.
OBTW it's a Ford.
RE: light duty truck brake
You might call Dearborn and ask for Sandy Moody; she's the manager of brake development, and she might direct you to someone who could answer your questions and solve your problem.
Or not.
regards,
- R