2006 Chevrolet Equinox brakes/rotors

Tiny
THEBUICK
  • MEMBER
  • 2006 CHEVROLET EQUINOX
  • 3.4L
  • V6
  • FWD
  • AUTOMATIC
  • 87,323 MILES
Steering wheel shakes like crazy when brakes are applied. Tirod and hub assembly seems fine, no movement in the wheels when lifted. Brake pads are all good, plenty of meat. Rotors are clean, no scratches or gouges. They look straight but I can't think of any other reason for this other than warped rotors. The wear in the pads is even. I'm not sure if this will help but tires are aligned and vehicle doesn't pull in any direction. Steering wheel shakes BAD, like my whole dash. Help me. Please
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Thursday, April 9th, 2015 AT 4:01 PM

6 Replies

Tiny
CARADIODOC
  • EXPERT
Yup, you have a warped rotor. If you have dentures, you can estimate how bad the rotor is warped by how far your dentures fly! Hahahaha. Sorry, ... Couldn't help myself.

Rotors can warp two ways. Most commonly the friction surface turns at an angle relative to the mounting surface. That causes the caliper to slide back and forth once each way once per wheel revolution. If it's bad enough, it can cause the brake pedal to pulsate up and down too, but to be that bad it is almost always caused by improper setup on the brake lathe, then the warp is actually machined into it. It's more common for the warpage to occur from unevenly-tightened lug nuts and repeated heat-up / cool-down cycles. Most people can't put up with that for long and they get it fixed before it gets bad enough to be felt in the brake pedal. You'll feel it in the steering wheel because the mass of the calipers causes the spindle and steering arm to tug back and forth on the steering linkage.

Always use a click-type torque wrench when tightening the lug nuts. That insures, 1) the nuts wont work loose, 2) the threads wont be pulled or "peeled", 3) a 90-pound weakling can get them loose to change a flat tire, and 4) the rotor will have even clamping forces all the way around to reduce the chance of this happening. Every repair shop and especially every tire and alignment shop will have a wall chart listing the torque values for almost every car and light truck. They'll be happy to tell you what to set your nuts to! A common value for front-wheel-drive cars with steel wheels is 95 foot pounds. Cast wheels usually call for around 80 foot pounds. Light trucks can be a little higher, like perhaps 110 foot pounds. By the way, number 2, peeled threads is always blamed on the mechanic who is trying to remove the nuts to take the wheel off, but the damage was actually caused by the previous mechanic who severely over-tightened them.

I should also point out that a lot of people run into problems with Chinese rotors warping. There actually isn't anything wrong with them, and getting them replaced under warranty wont help either. When we cast parts out of iron, we set them aside for 90 days to "age" before they get their final machining. The Chinese cast 'em, pack 'em, and ship 'em, then they age on your vehicle. Warping is a common result, typically after one to three months, but all that's needed is a light machining on the brake lathe. Machining does reduce the life of the rotor a little, but they're all so inexpensive now compared to 20 or 30 years ago, that it isn't worth sniveling over.

You may also notice that the two "plates" of a rotor aren't the same thickness. That's the plate on either side of the cooling fins. You might think that would lead to warping due to the thinner plate heating up faster, but that doesn't seem to occur. All that's important is the overall thickness. There is a published legal limit a rotor can be machined to, and a slightly thinner limit it can be allowed to wear to on the vehicle.

This type of warpage is called "lateral runout". It is identified by using a dial indicator with the probe resting on the friction surface of the rotor while it is spun slowly by hand. Most mechanics just place it on the brake lathe and watch where the cutting bit hits and misses to verify it's warped. The only time we're interested in how much it's warped is when we're reporting it to the vehicle manufacturer for a warranty repair. When you're paying for the repair, time is money and we don't have time to waste measuring the parts. The amount of warpage is irrelevant. We just want it gone.

The second type of warpage is called "thickness variation". This is found with a micrometer and taking a number of measurements at various places around the rotor. Since the rotor is thicker in one area, it pushes the piston back into the brake caliper. That pushes brake fluid back up to the master cylinder where it pushes on the brake pedal. You often won't feel thickness variation in the steering wheel but you definitely will in the pedal.

As a final point to this wondrous story, there is a new problem that has been showing up mostly on light trucks, starting in the mid '90s. That is an extremely hard brake pull that doesn't show up until the pads have reached a specific temperature, typically from five or six rather hard stops in close succession, as in when coming down a steep hill. There will be absolutely no hint of a pull one pedal application, then the next time you press it, you end up on the sidewalk or in oncoming traffic! This is caused by the pads and two rotors reaching different temperatures which alters the coefficient of friction unequally. The uneven heating is caused by a difference in thickness of the two rotors. We never used to see this or even consider it. In fact, I had an old '70s Chrysler with one front rotor that was.125" thinner than the other one, (and below the legal limit, but I'll never admit to it), and never had a problem. Now, I've run into two trucks with this problem and I've read about others. These were fairly heavy pickup trucks with rotors that were almost 1 1/2" thick. One had 0.020" thickness difference between them, and the second one had 0.007" difference. That's the thickness of two sheets of paper but it was enough to cause the brake-pull-when-hot. Standard procedure now is to machine both rotors just enough to clean and true them up, then continue machining the thicker one until it matches the thinner one. The common clue to this problem is it is always noticed for the first time shortly after a normal maintenance brake job was done. A lot of mechanics still haven't run into this or even heard of it. If this happens to you, simply return and explain this and have them machine the thicker rotor again to match the other one.

Forget looking at the rotors to identify a problem. You'll feel thickness variation as little as 0.002", similar to one sheet of paper. If lateral runout is real bad, you might see the brake caliper walking back and forth when you run the vehicle in gear with the wheel off, but I've had many where that happened but there was no noticeable pulsation or vibration.
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Thursday, April 9th, 2015 AT 5:10 PM
Tiny
CJ MEDEVAC
  • EXPERT
REALLY SOUNDING LIKE WARPED ROTORS

WITHOUT A DIAL INDICATOR (GAUGE) YOU MIGHT BE ABLE TO DETECT A WARP-AGE LIKE THIS

IT'S CRUDE AND MAY ONLY SHOW SOMETHING SEVERE

SNATCH THE WHEEL OFF

DEPENDING ON THE WAY YOURS WORKS

YOU MIGHT RUN THE LUG NUTS BACK ON TO HOLD THE ROTOR FLAT

NOW

SCOOT A CONCRETE BLOCK OVER THERE CLOSE TO IT

ADD BRICKS OR WOOD TO GET THE HEIGHT JUST RIGHT

NEXT FIND A SCREWDRIVER/ CHISEL/ PENCIL

LAY IT ON TOP ON THE BLOCK AND TOUCH THE POINT ONTO THE ROTOR'S PAD SURFACE

ROTATE THE ROTOR

DOES IT PUSH THE TOOL AWAY? DOES IT LEAVE A GAP AS YOU ROTATE?

CHECK THE OTHER ONE

EVEN A TEENY GAP IS A WARP AND WILL MAKE THINGS SHUDDER, EVEN MIGHT MAKE THE BRAKE PEDAL PULSATE

AS FAR AS THE STEERING LINKAGES

BACK ON THE GROUND

HAVE SOMEONE TURN THE STEERING WHEEL CW AND CCW, BUT ONLY FOR AN 1/8th OF A TURN. SORTA LIKE "CORRECTING" AS YOU DRIVE DOWN THE ROAD, BUT MAYBE A LITTLE BEYOND THAT (NOT HARD LEFT AND RIGHT TURNING)

WE SORTA WANT TO BARELY MAKE THE TIRES MOVE THE AS WE JIGGLE THE STEERING WHEEL SLOWLY BACK AND FORTH

WHILE YOUR HELPER DOES THIS

GET IN THERE AND LOOK FOR LOST MOTION IN THE STEERING PARTS

THE "JIGGLE" MIGHT HELP YOU SPOT ONE PART MOVING (THE ADJOINING PART SHOULD MOVE AT EXACTLY THE SAME MOMENT) IF ONE MOVES A LITTLE AND THE OTHER SORTA HAS TO "CATCH UP" BEFORE IT MOVES, YOU MAY HAVE FOUND A PROBLEM

ALSO, AFTER THIS TEST, TURN IT MORE AND MORE (FURTHER AND FURTHER TO MAYBE IDENTIFY OTHER POSSIBILITIES

FAST BACK AND FORTHS (GOING WILD) AND MAJOR TURNING OF THE WHEELS MAY MAKE YOU MISS THE SMALLEST OF LOST MOTION, AS THINGS WILL HAPPEN TOO FAST FOR YOU TO SEE

LET US KNOW WHAT YOU FIND

THE MEDIC
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Thursday, April 9th, 2015 AT 5:28 PM
Tiny
THEBUICK
  • MEMBER
Thanks for the quick and detailed response. And the humor was much appreciated since I've been ready to pull my hair out over this. Thankfully no dentures yet. I'm changing rotors tomorrow. Dura last golds is the best rotor autozone carries in my area. $60 buck a piece. Any thoughts? And one more question. Wouldn't the pads be unevenly worn if the rotor is warped?
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Thursday, April 9th, 2015 AT 5:41 PM
Tiny
CJ MEDEVAC
  • EXPERT
NICE AND HOT AND A NICE SPLASH OF WATER COULD DO IT

DOC MAY HAVE OTHER EXPLANATIONS- HE'S ONE OF THEM (OR NOW RETIRED) SCHOOL AUTO SHOP INSTRUCTORS

THIS MAY AID YOU IN SOME WAY TOO

http://www.2carpros.com/questions/2001-dodge-neon-milage-just-want-put-fliuds-their-locations

LET US KNOW HOW IT GOES

THE MEDIC
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Thursday, April 9th, 2015 AT 5:52 PM
Tiny
CARADIODOC
  • EXPERT
The pads don't have any idea the rotor is warped. They just move left and right a little as the high spot on the rotor pushes them back and forth.

There ARE some things that will cause pads to wear unevenly. Most commonly that's a caliper that was installed without being lubricated with special high-temperature brake grease. Ford trucks used to have a real big problem with this due to their very poor design. It was common to find the outer pad worn down in less than 10,000 miles because the caliper couldn't slide freely to release its pressure on it, and the inner pad looked like brand new because it was able to push the piston in to release its pressure. You actually need a hammer to move the caliper to either side. On most other vehicles the mounting system commonly consists of a pair of chrome-plated bolts the caliper can slide freely on. You can move those calipers very easily with one hand.

More expensive rotors doesn't mean they're better so don't fall into that trap. Before replacing what you have, your mechanic will measure them to see if they'll still be above the legal minimum thickness after they're machined. If they will be, they can be reused and the chance of this happening again is exactly the same as with new rotors.
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Thursday, April 9th, 2015 AT 6:55 PM
Tiny
THEBUICK
  • MEMBER
Changed the rotors and threw on some new ceramic pads. Car runs smoother than ever. Thanks a lot for the help guys. Much appreciated
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Wednesday, April 15th, 2015 AT 1:38 PM

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