Glazed rotors or warped rotors or uneven pad deposits?

[ChrisW]

Under moderate braking from say 60-45 in my mother's 97 accord EX sedan (car has abs), the steering wheel shimmies or vibrates a little, I'm not sure if there is pulsation in the pedal.

Brembo blank rotors with akebono ProACT pads in the front. These are less than 10k miles old.

Driver's front (front left) rotor surface appears to have some glazing (but no glazing spots or dots) on the outside face, but none on the inside face.

The ProACT pads worked great but now this?

I'm going to try and re-bed the pads in tonight when there is less cars on the road and see if it ain't uneven pad deposits or glazing of the pads or rotors. If I cannot fix this myself I'll have my mom take it to our indie honda mech. Maybe the ProACT pads aren't all that great, though I do know the OEM pads are ceramic based like the ProACT.

I doubt its warped rotors because my mom doesn't drive that aggressively. I don't think its sticking caliper pistons. I have flushed the brakes myself using gravity and the pedal feel is good.

 

[Chris142]

Were the lugnuts torqued properly?

 

[ChrisW]

Yes.

It did this shaking both before and after I rotated the tires today. I used a torque wrench to tighten the lug nuts to 80 ft.lbs.

The steering wheel does not shake/vibrate at any other time; only when braking from 60+ with moderate pedal effort.

Car brakes fine and within anticipated distances.

I just though of this, could it be the tie-rod ends? But wouldn't it [steerwheel] vibrate all the time then?

I am going to try and re-bed the pads tonight and perhaps I'll snap a photo of the LeftFront rotor so you can see the suface condition. I am going to pay attention to see if the shake/vibration is felt through the brake pedal.

 

[Gary Allan]

We can assume that these are single piston "floating" calipers?? If so, you should check and see if they are rusted on the sliding surfaces. You'll still have to turn them to get a pristine surface, but you shouldn't have the same condition return.

 

[shortyb]

Pro-ACTs are great pads, I've used them with excellent results on a few vehicles. They are suseptable to glazing though if the brakes are used very gingerly or the brake pedal is ridden. My mom used to do this and it drove me crazy. If the pads are in fact glazed, they need to be removed and the glaze broken, either with a stone or emery paper. Trying to re-bed a glazed pad will not work without doing this first. If you have noticable "blotchiness" on the rotor surface, they will need to be skimmed. They will probably have uneven deposits if they look this way and will need a fresh surface. Like Gary Allan mentioned, check the caliper pins. Hondas are notorious for having sticky pins that could result in the braking performance you're observing. How old are the pads? Did you install them? What bedding procedures did you use? Were the pads and rotors installed at the same time? If so, were they heat cycled at all? One final item to check that is quite overlooked is the tires. Uneven pressure, uneven wear, tire damage etc. can contribute to abnormal braking performance since it is the tires that stop the car.

 

[ChrisW]

Pressures are checked and are ok. 32psi all around.

I regreased the slide pins today, even though they were already free sliding when I took them apart. I sanded the pads with garnet paper and also scuffed the rotor faces, followed with brake cleaner.

When I took 'er round in the backroads, the steering wheel still vibrates when braking over 60mph, but it stops just when it reaches 45-50mph. Whether the brakes are hot or cold make not difference.

The brake pedal does not vibrate/pulsate.

I'm starting to think its something suspension related, like when all the weight of the car gets transfered foward while braking, some suspension piece or part is making the steering wheel vibrate. My first guess would be tie-rod ends, but I chekced those and there is no play; they are not loose, unless I am checking them wrong.

Pads and rotors are definately less than 10k miles old, more around 8000 miles im sure. The pads and rotors were put in together at the same time and they were brand new. They were installed by my mothers indie honda mecahnic.

As for bedding procedures, when they were first installed, I did some moderate stops, about 5 from 45-10. These ProACT pads are not high-performance race pads IMO, so no need for several 60+ to 5 stops.

Looks like I will have to tell my mother to take it into the shop. I am at a loss of what it could be.

Thanks everyone.

 

[mechtech]

Rims could be bent, tires out of round or internally compromised, wheel bearings loose, tie rods, ball joints, upper strut bearings suspect.
You may also have vibration from the rear brakes, and are attributing it to the fronts.

 

[ebaker]

See http://www.stoptech.com/faq/data/faq25.htm

 

[Lumberg]

Wow!

I have the exact same problem with a '00 Camry my mom recently gave me.

One thing to note: the higher the air pressure in the front tires, the lesser the vibration.

So I guess the fisrt thing to try is a quick turn of the rotors and re-bedding?

 

[BlazerLT]

Warped Rotors.

 

[ChrisW]

quote:

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Originally posted by Lumberg:
Wow!

I have the exact same problem with a '00 Camry my mom recently gave me.

One thing to note: the higher the air pressure in the front tires, the lesser the vibration.

So I guess the fisrt thing to try is a quick turn of the rotors and re-bedding?

---

Hmm...this leads me to some correlation, I know that toyota specs ceramic pads for their newer cars, as does honda, on certain models. Maybe its somethig inherent in the ceramic pads (more subseptible to uneven pad deposits)? I seriously doubt the rotors are warped; the brakes are used by my mother, who does not brake or drive aggresively. I would lean more towards uneven pad deposits than warped rotors. Plus, warped rotors are often felt through the brake pedal, there is NO vibration of the brake pedal. There is only of the steering wheel, and the steering wheel stops vibrating by the time the car slows to 45-50.

I have known about the "Stoptech warped rotors myth" for over a year.

 

[Lumberg]

well whether it's warped rotors or not the first step is to get the turned, and inspect the pads amd if they're glazed give them a once over with the emery cloth.

List I said the more pressure in teh front tires, the less the vibration, and just like you, absolutely nothing in the brake pedal, steering wheel only.

 

[kenw]

It does not take aggressive driving to warp rotors, a few trips down the block with a foot on the brakes, leaving the e-brake on, etc can cause warped rotors. Ask me how I know....

My experience is that front rotor warp is noticed immediately with only the slightest braking effort. Have you checked the rears? (i4 Camry have rear drums, v6 have rear disk, not sure on Accords).

Others have mentioned bearings, I've seen a bad wheel bearing do something like this.

 

[ChrisW]

kenw, you may want to read this: Stoptech Myths of Braking Systems

 

[kenw]

wow, it's posted on the www so it must be fact!!!

racing rotors are a lot different than the average consumer rotor. Mass is good. I've seen them warped, and I've seen the TIR while on the lathe that proves it.

Never had a warped rotor myself until I started driving Toyotas and Hondas. My experience with my older GM stuff was with glaze only, but these Toyota and Honda rotors warp.

btw, as an intro, I'm a mechanical engineer with about 30 years of experience.

 

[jsharp]

The Stoptech link posted above is a reprint of an article by Carrol Smith. He's knowledgeable but not right 100% of the time for sure.

Check out myth #6 - The brake fluid reservoir should be topped up during routine service.

In most modern passenger cars, the brake fluid reservoir is designed with a specific volume and is equipped with an internal float. The volume corresponds to the amount of fluid that will be displaced when the pads have worn to the point of replacement plus a generous reserve.

Wrong. Totally wrong. If this were true, how can he explain how different cars from the same manufacturer with substantially different sized brake components can end up with the same brake reservoir and low level sensor...

 

[kevm14]

quote:

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Originally posted by kenw:
It does not take aggressive driving to warp rotors, a few trips down the block with a foot on the brakes, leaving the e-brake on, etc can cause warped rotors. Ask me how I know....

---

I was able to bring at least one of the 4 rotors on my Camaro to a red glow with repeated 90mph ABS stops and riding the pedal in 3rd gear, gas floored (I was bedding my new performance friction pads...). These are presumably the OEM rotors and the car has 148k on it. They are not warped even after this abuse. The most important thing is to let the rotors cool evenly after bringing them to such high temps. Not stopping is ideal, and if you have to stop, put the car in neutral and let your foot off the brake...