Brake Vibration Not Caused By Warped Rotors

[Zephyrefi]

Hi all! I've been trying to track down a brake vibration my '04 Aviator has always had. I bought it last year with 95,000 miles on it, and really this is the only mark on its record. I love the truck otherwise. First thing I did was pull all 4 rotors and have them turned. No change.

I had it in to the dealer when my used car warranty was about to expire and they gave me an estimate on new brake pads all around and new rear rotors. It was really spendy, (not to mention what self-respecting shade tree mechanic worth his salt can't do a brake job?) so I decided to do the job myself. New Motorcraft pads all the way around and new rear rotors. The old pads were all far from in need of replacement. The vibration has improved slightly, but is definitely still there.

I was talking to a guy I trust about it and he suggested I take a look at the rear suspension and it's many "ball"-type joints. I tend to agree that may be the issue, since if it needed tie rod ends, I would think the dealer would have caught that on their inspection. So, I defer to you, the experts. I've tried wiggling the rear wheels horizontally for the toe link and vertically for the ball joint. It seems tight to me. Could it be the shocks? The ride isn't bouncy though... What are your thoughts?

 

[Dave8338]

You say brake vibration. Does it increase with speed and do you feel anything in the brake pedal?

 

[Zephyrefi]

It acts just like the rotors are warped. Light pressure on the pedal produces the most vibration in both the brake pedal and steering wheel. As you increase pressure on the brake pedal, the vibration diminishes. Vehicle speed doesn't really affect it.

 

[Number4]

They make rotor shims. The rotors as they set against the hub may not be true. You can keep putting on new rotors but that won't fix it because it's the mating surface. A shop would have to spec them mounted. May just be one side.

Edit: don't see shims for this one. May have to replace the hub assembly if it's found to be offset.

 

[Zephyrefi]

Interesting, thanks. I'll have to check that out!

 

[icepickjazz]

Any pulling to the side if you slam on the brakes? Any pulling when you apply the brakes at all?

 

[03 Explorer XLT]

It could be sticking caliper pins. Clean and lube, or just replace them.

 

[Zephyrefi]

No, it doesn't pull. And I've lubed the crap out of the pins and slides, haha.

 

[icepickjazz]

Only reason I asked about pulling is I had similar problem with hard braking and turned out to be a bad wheel bearing.

 

[partsman48210]

vibration

you should start by checking the runout on both your rotors and hubs to see whats really going on. You would think if you buy new parts or have rotors turned that everything should run true but thats not always the case. Get yourself a cheap dial indicator with a clamp. harbor freight has them for about $30. This will tell you exactly what is going on.

heres a video that will explain what I'm talking about

http://youtu.be/t0lgZcELTn0

just something to think about:

when you have a vibration on braking, the majority of the time it will be an issue in the front end of your vehicle. this can be caused by any issue in the front end(brakes, suspension, steering)

 

[Zephyrefi]

Yeah, I know you can't always trust new parts. I will definitely check those things. I do have a dial indicator.

I was kind of hoping this was a common problem, and there was something I could go straight to and replace, haha. I haven't ruled out the tie rod ends either. Kind of makes sense it would be in the front end, if I'm feeling the vibration in the steering wheel, now that I'm thinking about it.

Thanks to everyone so far for your thoughts!

 

[Sedition]

What your describing is called "run out" search in that direction.

 

[Sedition]

This will help explain.

http://rdabrakes.com.au/page/TB01.aspx

Sorry it's in Australian.

 

[pet575]

If that doesn't work, has the master cylinder been bled recently to make sure it isn't air in the brake lines?

 

[Dave8338]

Also check for loose / worn suspension parts. Tie rod ends like to cause "shimmy" when braking. Wheel bearings is another.

 

[Sedition]

I found some more information on 'Run out' in a box of disc rotors while I was changing some brakes today.

Enjoy...

 

[cross6]

Most of the time, if runout is found, simple reindexing the rotor to the hub will eliminate or minimize it.

You're supposed to check and find the least runout position when you replace a rotor. One reason why I always do my own brake work. You think the guy at the tire place is taking the time to ensure least runout?

The problem with shims for the DIY is that individual high quality shims can cost close to what a new rotor costs. Tire/Brake shops buy them in huge kits, napa sells one, so they get them much cheaper.

Also, don't confuse runout with rotor warping.

 

[cross6]

I found some more information on 'Run out' in a box of disc rotors while I was changing some brakes today.

Enjoy...

YES!

Always clean the rotor and hubcentric ring with steel wool or wire brush or something.

And if you use an impact you need to use a torque limiting extension or "torque stick."

But it's best to snug by hand, put the car down and then torque with a torque wrench. Even a cheap harbor freight torque wrench would be better than blindly using an impact.

 

[cross6]

Also check for loose / worn suspension parts. Tie rod ends like to cause "shimmy" when braking. Wheel bearings is another.

A blown shock will give that sensation, too. When you brake the wheel will hop up and down skipping over the road. So it *feels* like the brakes are pulsing, but really the wheel hopping is what's causing the wheel+brakes to catch/release quickly.

 

[cross6]

Here's a good video by NAPA that goes through measuring runout and correcting.

https://www.youtube.com/watch?v=I5Mj_G5LIz8