: 2008 STS brakes pulsating (?)



Grunder
06-30-13, 09:15 PM
So it started about a month ago. A slight "pulsating" in the front during braking. Now it's every time I try to stop, and a lot harsher. It's not the ABS, it's no where near as fast as that. It doesn't feel like a warped rotor, because it's not 'quite' the same each time you decelerate, and it's straight ahead pulsating, no side-to-side whatsoever. It seems to be the front only.

I haven't looked at the pads, or anything else yet. 69,000 miles, 20,000 of which are mine. I have no other history on the vehicle. The brakes are JE5.

Opinions, please...

John

MoistCabbage
06-30-13, 09:44 PM
No such thing as "warped" rotors. Excessive runout is caused by uneven wear.

The problem may be pad material buildup on the rotors. Try braking hard from highway speeds to ~10/20 MPH or so. Repeat several times in a row, then drive a few miles to allow the brakes to cool.

dannyquest
06-30-13, 10:14 PM
Grunder, Sound like it's time for new brakes & rotors. Danny

Guy.Seminerio
06-30-13, 10:15 PM
I still vote rotors. But it wouldn't hurt to check the brake fluid since you have an issue with braking. Not that I think that's the issue.
What do you mean no such thing as warped rotors? Are you saying that terminology is flawed?? It seems pretty widely accepted that rotors eventually can become "warped."

Ludacrisvp
06-30-13, 10:22 PM
Might you have thin 'hairline' vertical cracks in the rotors?

MoistCabbage
06-30-13, 10:25 PM
What do you mean no such thing as warped rotors? Are you saying that terminology is flawed?? It seems pretty widely accepted that rotors eventually can become "warped."

"Warped" rotors, as in their shape has changed/they're bent, is flawed terminology. Rotors are made of cast iron, they don't warp. Ask a brake manufacturer. Thickness variation due to wear, is what is usually referred to as "warped".

Guy.Seminerio
06-30-13, 10:29 PM
ok i got what you're saying.

EChas3
06-30-13, 10:57 PM
Use the term you like. It's your rotors: residue build up, surface imperfections caused by quick temperature change, over-torqued lugs or other imperfecdtions, or uneven wear.

The reason most shops recommend new pads & new rotors is because it leads to higher customer satisfaction. Many people will accept the higher cost but most will be very dissatisified if a return visit is necessary.

MoistCabbage
07-01-13, 12:09 AM
Still worth a few FREE hard brake applications, it may very well remove any pad residue.

Guy.Seminerio
07-01-13, 12:14 AM
hahaha that post gave me a good laugh. ohhh just noticed.. Boston. I'm originally from NY so I was pretty butt hurt over the Bruins Rangers series. So I was rooting for the Blackhawks for the Cup. Hockey fan here.

EChas3
07-02-13, 12:19 AM
Still worth a few FREE hard brake applications, it may very well remove any pad residue.

No argument hre. Too many STS owners think these cars are fragile. Drive it like you stole it.

Grunder
07-02-13, 09:16 AM
Still worth a few FREE hard brake applications, it may very well remove any pad residue.

Well, that didn't work. Tried four hard stops from 60 down to rolling, let them cool, and the same thing. Tried to see the pad thickness w/o taking off the wheel - no dice. I'll pull the front wheels this week to do a better inspection.
The rotors "look", from what I can see through the wheel, to be in fine shape - no visible cracks, smooth wear area, no "grooving", etc. Got to be the pads, he says.
Thanks for all the opinions, that's what I wanted.

John

Submariner409
07-02-13, 09:24 AM
Study time ..................

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

And get into the EBC Brakes site, U.S. Automotive, and read the slew of links on brakes and rotor problems. EBC is pretty informative and doesn't resort to a lot of "ours is better" advertising in their info pages.

turnne
07-02-13, 11:04 AM
Use the term you like. It's your rotors: residue build up, surface imperfections caused by quick temperature change, over-torqued lugs or other imperfecdtions, or uneven wear.

The reason most shops recommend new pads & new rotors is because it leads to higher customer satisfaction. Many people will accept the higher cost but most will be very dissatisified if a return visit is necessary.

that and the fact that rotors can be bought cheaply

Many manufacturers( the german ones) dont recommend turning rotors


Warren

malatu
07-02-13, 05:53 PM
This is a cut n paste from a website called Powerstop. They sell rotors and brake pads. I don't endorse the company, I just happen to be looking up some info when I cam across this post. This info was from their "Frequently Asked Questions" section. I thought it was worth posting.

What causes rotor warping (a.k.a. pulsating brakes)?The term “warped rotors” is commonly used to describe brake pulsation, but the rotor is not actually warping at high temperature so the term “warped rotors” is not accurate. The primary cause of brake pulsation is from uneven friction deposits on the rotor. As the brakes get hot, friction material from the pad is deposited as a very thin layer on the rotor. If you come to a hot stop and clamp your brakes down, the pad continues to deposit material on one spot. As you continue to use the brakes, this high spot on the rotor will get hotter than other parts of the rotor. When the temperature starts to exceed 1150 F, the crystal lattice structure of the iron can change into a very hard, brittle material called cementite. Your brakes can hit 1100 F or higher coming off a highway ramp with severe deceleration. Hard spots start to form, and it doesn’t wear down like the rest of the rotor. The hot spot nodules will not dissipate heat as well as the neighboring material, so it gets hotter than the rest of the rotor and causes the spot to grow. The result is a permanent high spot that you feel as pulsating brakes. You can try to turn down the rotor, but chances are the nodule is bigger than the cut depth on the lathe. So it is just a matter of time before the pulsation will come back. However, you can prevent brake pulsation two ways: 1) use a high quality, properly drilled rotor to keep the temperature low, and 2) don't clamp down on your brakes after a hot stop!

Guy.Seminerio
07-02-13, 06:21 PM
Good to know.