2004 xc70 brake shudder

[norski]

I really need to get to the bottom of this. Please tell me where I went wrong.

First time around I replaced front and rear pads only. Eventually they wore into the rotors and when you stepped on the brakes it caused a severe vibration that was revolution in character, the vibration slowed as the car slowed down, almost like the rotors were out of round. So, I replaced all the pads again with the best (choice of three) quality the parts store offered and I ordered all new Zimmerman rotors. I was pretty sure they were quality, not drilled or anything but came with a zinc coating, at any rate brand new.

Within a month I was back to an ever increasing shudder and vibration upon braking. Another year and 15,000 miles has gone by and they are as bad as ever. I can't ignore it anymore and need to address the problem but I don't want to just repeat the same, inadequate job.

Any advice appreciated.
Thanks,
Arne Boveng

[Franxc06]

Hi norski, sorry to hear about your brake drama I have changed my front brakes a few months ago the discs looked good and never machined them, braking is very good and no vibration the only thing I paid attention to were the callipers runners/ guides I made sure that these were dirt free and free to slide and I even lightly greased them and made sure that the dust boot over them sealed properly .
The only think I could think of is just may be your callipers guides are binding and not square to the actual discs .
(If it was your brake booster your brake pedal would feel harder then normal and braking action would be delayed)
I hope this helped.
Cheers
franxc06

[kain]

+1 to franxc, not as a guarantee but a possibility

[billr99]

+1 to franxc, not as a guarantee but a possibility

I also agree that it is something to check first. Since I live in salt air, I typically pull my calipers every spring, clean up everything and re-grease the pins.

Also because I get a lot of overnight rotor rusting (the view is great but the salt air is a killer), I occasionally get brake pulsation due to the contact area between the pad and rotor getting a buildup from the car sitting. I just go out on our fairly deserted road and give the brakes a good fairly high-speed slam to clean up the rotor surface. I wouldn't think you would have a rust problem in MT but maybe you still have some kind of uneven buildup on the rotor surface?

Cheers,

Bill

[MacNoob]

That was my first thought, that the brakes were never properly bedded in and there is an uneven pad material buildup on the rotors.

[norski]

That was my first thought, that the brakes were never properly bedded in and there is an uneven pad material buildup on the rotors.

Talk to me more about bedding in the brakes. I remember reading about it when I did the job but either didn't understand it or felt it was unnecessary, at any rate I ignored it.

We actually have the worst rust I think, now in the nation. Not due to salt air but salted roads in the form of magnesium chloride. They are just dumping it on the roads all winter long. When they dry the roads are pure white and it's no longer tire tracks through the snow but tire tracks through the salt. It is causing lots of brake problems.

Arne

[MacNoob]

Below from Tire Rack. The "Hawk pads" process is the most extreme but it gives you the best idea of a specific process. Won't hurt to follow that kind of regime and see if it helps.


Brake Pad and Rotor Bed-In Procedures

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All brake pads must be bedded-in with the rotor they will be used against to maximize brake performance. The bedding-in process involves a gradual build up of heat in the rotors and pad compound. This process will lay down a thin layer of transfer film on to the rotor surface. Following the bed-in procedures provided by the manufacturer will assure a smooth, even layer of transfer film on the rotor and will minimize brake judder. Here are a few things to keep in mind when installing new rotors and pads:

When installing new pads, the rotors should be new or at least resurfaced to remove any transfer film from the previous set of brake pads.

It is critical that the installer clean any rust, scale, or debris from the hub mounting surface thoroughly and check it for excessive run-out with a dial indicator gauge before installing the rotor.

The new rotor should also be checked for excessive run-out using a dial indicator gauge before the caliper and pads are installed. If a rotor has excessive run-out of over .004" (.10mm) it should be replaced.

If your new rotor has excessive run-out, please contact our customer service department for a replacement rotor. Do not install and drive using the rotor! Rotor manufacturers will not warranty a used rotor for excessive run-out. Running with excessive run-out on the hub or rotor will cause vibration issues.

Failure to follow these procedures may result in brake judder, excessive noise, or other difficulties in bedding-in the new brake pads. The pads need a fresh surface to lay down an even transfer film. Residue from the previous pad compound on the surface or an irregular surface on a used rotor will cause the pads to grip-slip-grip-slip as they pass over the rotor surface under pressure. The resulting vibration will cause noise and telegraph vibrations through the suspension and steering wheel. This vibration is known as brake judder or brake shimmy. This is typically caused by an uneven transfer film on the rotor surface or an uneven surface on the rotor not allowing that transfer film to develop evenly. This is often misdiagnosed as a warped rotor.

Bedding-in new pads and rotors should be done carefully and slowly. Rapid heat build up in the brake system can lead to warped rotors and or glazed brake pads. Most brake pad compounds will take up to 300-400 miles to fully develop an even transfer film on the rotors. Following are the recommended bed-in procedures from each manufacturer:

AKEBONO

400 to 500 miles of moderate driving is recommended. Consumer should avoid heavy braking during this period.

ATE

400 to 500 miles of moderate driving is recommended. Consumer should avoid heavy braking during this period.

BREMBO Gran Turismo

In a safe area, apply brakes moderately from 60mph to 30mph and then drive approximately 1/2 mile to allow the brakes to cool. Repeat this procedure approximately 30 times.

HAWK

After installing new pads make 6 to 10 stops from approximately 35 mph with moderate pressure. Make an additional two to three hard stops from approximately 40 to 45 mph. Do not allow the vehicle to come to a complete stop.When completed with this process, park the vehicle and allow the brakes to cool completely before driving on them again. Do not engage the parking brake until after this cooling process is compete.

NOTE: Hawk racing pads (Blue, Black, HT-10, HT-12) may require a different bed-in procedure. Contact your sales specialists at the Tire Rack for racing application information.

POWER SLOT

Follow the brake pad manufacturer's recommended break-in procedure taking care not to produce excessive heat in the system. Avoid heavy braking for the first 400-500 miles

[norski]

Wow, super helpful! I wonder how many people simply drive out of the brake shop without using these techniques?

Anyway, one question I have here is what is "runout"? Both in regards to the hub and the rotor? I don't understand how to measure for runout or what that means?

Thanks some more.

[MacNoob]

Measuring brake runout

http://www.youtube.com/watch?v=Pmb9MlWvCD8


http://www.youtube.com/watch?v=Pmb9MlWvCD8