Shaking above 50mph

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Jay R Lawson

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my 2005 Yukon started to have a shake in my steering wheel and a pulse on my brake. Any suggestions?
 

iamdub

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Turn or replace the rotors. You should replace the pads as well when you do this. Don't cheap out on the pads or it'll happen again and sooner.
 

HiHoeSilver

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Thanks man. I just got her. Dealer "said" new brakes. Ceramic you think?

They probably just slapped some new pads on there and said "new brakes." I had symptoms like that on my old one. When I cut the rotors, it would be fine for a bit, then come back. When rotors heat unevenly, the steel hardens unevenly, and won't ever want to wear at a uniform rate again. Cutting them will fix it for a bit, but I vote to just change them. Go ahead and do the NNBS brake upgrade while you're at it!
:happy107:
 

iamdub

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I used to always think that rotors warped from uneven heating/cooling, primarily from getting the brakes hot then hitting a water puddle. After further research, it seems that this is a common misconception. The temperatures needed to heat rotors to the point where the metal is able to be deformed is much higher than they will ever reach when braking. It's said that the "warping" is not warping at all and that it's actually deposits left from the pads. The pad material is softer than the rotor and the high heat causes a layer to delaminate and adhere to the rotor surface. This mainly happens when the car comes to a stop after hard braking and the pads sit in one spot on the rotor. A thin layer of pad material is left on the rotor, then this spot collects more during subsequent brakings, the rotor is slightly wider at this point, causing the pedal pulsating and eventually shaking, and the cycle continues downward. Not all people resurface the rotors during a brake job like they should and I don't see a dealership investing in quality pads. Get the rotors turned and invest in some good pads or do nothing at all because it will happen again. The ONLY time I've ever not had "rotors warp" was when I used cryogenically-tempered Power Slot rotors and Hawk HPS pads on my S10. I could stand on the pedal from 100+MPH repeatedly and it would stop just as smooth as ever. No brake fade, either. I ran that setup for over 12 years with no issues. I replaced the pads once or twice but couldn't turn the rotors because they were slotted. I thought I was getting the same setup (or close enough) for my Tahoe when I got cryo-tempered PowerStop (different brand that Power Slot) and Hawk LTS pads. But, they developed a minor shake when braking in less than 1,000 miles (yes, I followed the bed-in procedure in accordance with the manufacturer's instructions). My guess is the Hawk LTS pads are a much different composition than the HPS pads. My original rotors were bad enough to cause shaking at highway speeds when not braking. At least the shaking now is only noticeable at low speed braking.
 

HiHoeSilver

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I used to always think that rotors warped from uneven heating/cooling, primarily from getting the brakes hot then hitting a water puddle. After further research, it seems that this is a common misconception. The temperatures needed to heat rotors to the point where the metal is able to be deformed is much higher than they will ever reach when braking. It's said that the "warping" is not warping at all and that it's actually deposits left from the pads. The pad material is softer than the rotor and the high heat causes a layer to delaminate and adhere to the rotor surface. This mainly happens when the car comes to a stop after hard braking and the pads sit in one spot on the rotor. A thin layer of pad material is left on the rotor, then this spot collects more during subsequent brakings, the rotor is slightly wider at this point, causing the pedal pulsating and eventually shaking, and the cycle continues downward. Not all people resurface the rotors during a brake job like they should and I don't see a dealership investing in quality pads. Get the rotors turned and invest in some good pads or do nothing at all because it will happen again. The ONLY time I've ever not had "rotors warp" was when I used cryogenically-tempered Power Slot rotors and Hawk HPS pads on my S10. I could stand on the pedal from 100+MPH repeatedly and it would stop just as smooth as ever. No brake fade, either. I ran that setup for over 12 years with no issues. I replaced the pads once or twice but couldn't turn the rotors because they were slotted. I thought I was getting the same setup (or close enough) for my Tahoe when I got cryo-tempered PowerStop (different brand that Power Slot) and Hawk LTS pads. But, they developed a minor shake when braking in less than 1,000 miles (yes, I followed the bed-in procedure in accordance with the manufacturer's instructions). My guess is the Hawk LTS pads are a much different composition than the HPS pads. My original rotors were bad enough to cause shaking at highway speeds when not braking. At least the shaking now is only noticeable at low speed braking.

This is correct. I am not talking about deformities or warping of the rotor. I talking about uneven wear. And yes, pads deposit material on (and into) the rotor. But it's not just the pads that wear. The rotor does, too, obviously, but not necessarily evenly. Like you said, it's dependent on the hardness of the steel vs. the pad. And how do we harden, or temper, steel? You guessed it, we heat it up and cool it down again. The point to which we heat it combined with the rate at which we cool it determine the characteristics of the steel, hardness, brittleness, etc. This is a molecular change in the steel, and, like it or not, some parts of your rotor are harder than others.
 

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