Identifying and Correcting Disc Brake Judder

Update: 10,500 miles now on the HP+ pads and front Royalty rotors. Rear Brembo rotors have 35,500 miles. Brake judder is completely gone; I will consider this issue solved. For the first time I can say the brakes are the strongest and most confident system on the car - they used to be the weakest link (not too bad at stopping, but the judder was a reoccurring problem). It will be interesting to see what happens after another 20k miles.

AA wrote:

Brake judder is completely gone; I will consider this issue solved.

Do you consider the problem is solved because of the products used or the technique of braking late.?
Or Both..???
I'm still running the EBC rotors and pads and have noticed I can eliminated the minor brake judder that occur re's by scrubbing the brakes, meaning - performing much more aggressive braking from higher speeds.
I also did my annual inspection which involves removing calipers and pads, cleaning all components and re-lubing the necessary parts. This also helped the low speed judder I was experiencing. From a high speed recently, over 120mph +, I experienced no brake judder while braking it down to legal speeds.
Racing a new Challenger- that was fun.

Everything I've learned and experienced so far suggests "cold" scrubbing of the brakes is key to removing uneven compound deposition. The Hawk HP+ compound is ideal for this purpose (at least for me) because it stays cold (abrasive friction mode) longer than some other pad compounds, which tend to heat up more quickly. The Hawk HPS compound I used previously resulted in judder, but I think my driving style may have contributed to the condition. Many others have seen good results with HPS, and some EBC pads. The key is to use a pad compound that works into a higher temperature range - they won't liquefy until you really get on them (a heavy car like the Riviera can push the pads into adherent mode pretty fast), so it helps you accomplish your mission.

I also think it's very important not to come to a dead stop after heating up the pads a lot. I have been switching into neutral and letting the car slow naturally (hitting the brakes in short bursts) on it's own. This prevents uneven smearing or imprinting of hot pad compound to the rotor.

Your idea to lube the brake hardware is a good one. Going a step further to replace or polish the metal clips helps ensure they are smooth - so will keep the pads paired with the calipers and floating pieces, not rubbing the rotors when the brakes are "off".

alright, so i keep warping rotors. i tried the cheap-o ones from autozone ($35 each). I had them so bad i couldnt hold the steering wheel still while breaking from speed, took all of 2 months to get like that. then i figured i'd go for something a bit higher quality in hopes they would last longer. i ordered some raybestos "made in USA" AT rotors from rockauto ($55ea). these were fine for a few months, but they are starting to get bad. i got on them hard from 120mph yesterday and i think that did them in.
i am using HAWK HPS pads and will need new ones soon. i plan on getting the same pads again despite the serious dusting b/c they work well under track conditions.
I also have the f-body calipers w/12" rotors.

what do track cars use? i cant afford $300 brembo rotors only to have them warp too.

I realize there is debate on whether or not you can actally warp a rotor by use, but i made sure to do proper break in when i got them, i dont sit on them when the pads are hot, and my fluid is bleed every 6mo w/DOT4 full sys.

please advise! i cant keep spending $100 for rotors every oil change.

Remove the wheels, put a few nut on the studs and torque them down to hold the rotors.
Place a dial indicator on them using either a magnetic mount attached to the strut or a vise grip type mount, either one with a flex shaft for the dial indicator and check runout of the rotors near the outside edge of the rotor. Shouldn't have more than .003 .004" max runout.
If you have more than that try removing the nuts, rotating the rotors one bolt hole and reinstall nuts and torqu them down again. Re-check runout, and continue to do this until you find the spot with the least runout. If that smallest number exceeds .003", then you can buy shims from Raybestos that go between the rotor and hub to eliminate the excess runout.
An inexpensive dial indicator and magnetic mount can be had from some the tool vendors that sell stuff Made In China, that will be OK for what you want to do for less than $50.00.
I've even seen them on sale for around $30.00 sometimes.

like this?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=623

also,rotors are not guaranteed to be true straight out the box. cast iron rotors can warp on the shelf if not stored flat. the best way to buy is to have them checked before installing. this could help avoid more work for you in the future.

there were perfect for the few month when i first got them, but i drive really hard on the street. the vibration has been slowly getting worse and i do see small stress cracks on the rotors surface.
i may try changing pads out to a set of ceramics and stomping on them while cold to try and clean the surface good. then re-bed the hawk pads.

Rickw wrote:

Would you say the EBC's were more abrasive on the Rotor's than the Raybestos pads.???

Yep.

Albertj

Mr.Riviera wrote:

there were perfect for the few month when i first got them, but i drive really hard on the street. the vibration has been slowly getting worse and i do see small stress cracks on the rotors surface.
i may try changing pads out to a set of ceramics and stomping on them while cold to try and clean the surface good. then re-bed the hawk pads.

Thinking about it, there ar e a few things that come to mind. You probably already do these but people reading this may find it a useful reminder:

One - do your hubs have runout? You really might want to check. Usually not BUT it can happen. Sometimes, kind of rarely actually, a judder problem results from hub runout. You can replace with a high quality hub or use a Raybestos shim.

Two - when you install the rotors, do you clean the face of the hubs? If you don't then you are going to have some runout. If you have runout, you will warp the rotors fairly soon. You ought to clean the hub faces down to shiny metal. A thin and uneven layer of rust *will* cause runout.

Three - In my experience you'll save money using the more expensive (Raybestos, Bendix, Ate, ACDelco (actually Raybestos usually for our cars), EBC, or other rotor made of a good cast iron alloy. The cheaper ones meet specs upon installation but heat/cool unevenly because of how they are manufactured--and so will warp after a good hard (some call it "panic") stop and stay warped. If you are a 'spirited' driver, don't use economy rotors.

Four - I've found it's always a good idea to break down and inspect the calipers with every pad change. On new calipers use a file to make sure the castings are shaped right. Reassemble the calipers and lube properly, or one pad or the other will drag and cause various problems.

Hope this helps

Albertj

Mr.Riviera wrote:

like this?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=623

Yes that is the dial indicator gauge, now you need to look for the magnetic base with the arms and attachment for the gauge.
That is what I use on the Riv and it works good.
The magnetic base just goes onto the strut and the misc rods that come with it will position the gauge so it will contact the outer edge of the Rotor to give you the most accurate run-out reading. Meaning, by placing the tip of the gauge on the OD of the Rotor you will be able to record the maximum run-out.
As Albert mentioned, the hubs run-out will be included in this measurement. So if it is excessive you can remove the rotor, clean the hub and measure hub run-out as well.
There are two measurements to take. One is to rotate the Rotor or Hub and measure the surface run-out and then just hold the Rotor or hub in place and pull it in and out to measure the amount of end play.

Matt, in replacing rotors probably 6 or more times, I have found only one solution that has worked "kinda sorta" over 14,000+ miles of hard stopping. The solution is to use abrasive pads with quality iron rotors, and changing my stopping habits in a way that might surprise you.

The more abrasive HP+ pads I use keep the rotors cleaner, preventing uneven compound deposition, which can eventually lead to warping. So far, it's worked. No judder after more than 14k miles. In addition, the HP+ are the fastest stopping pad I've ever used. We put them on our LeMons race car, and got rave reviews from all the drivers - car stops insanely quick.

To get the most abrasive effect from pads, use the brakes in an "on-off" fashion, so the pads shave off any uneven deposits before they heat up and liquefy. The result is more very hard, short-term stopping events (the opposite of dragging the brakes). This works particularly well at high speeds; abrasive pads with higher operating temp limits work better for this purpose, because they clean the rotors longer while heating up.

Unfortunately, abrasive pads with higher operating temps come at a price: more dust, noisy metallic squeal, and increased rotor surface wear. To eliminate judder, I've had to put up with that stuff, but it's worth it because I HATE judder! This is why I said "kinda sorta" before, as there is a give & take to everything.

I also agree with RickW about measuring run-out with a gauge and rotating the rotors to fix the issue. This usually works for new rotors, and is important to give them a fighting chance by mounting them with least amount of run-out. I don't know about rotors that have warped on the hub, but it can't hurt to try (see earlier in this thread for instructions).

Like albertj said, the cheaper Chinese iron is a bad idea. It doesn't stand up to heat generated by serious stopping. I've had this happen as well - no more Chinese iron for me.

So there are actually three reasons for having judder, imo:

1) cheap iron rotors
2) stopping technique
3) pad composition

You can fix the rotor problem by upgrading to a quality brand like EBC. However, I managed to warp a pair of $150 EBCs, probably because I didn't use the right stopping technique. I was using the HPS pads you have, but I don't blame it all on the pads.

The "on-off" stopping technique works to eliminate uneven pad compound build-up. If you can keep this from happening, a quality rotor should never warp, or at least not for a long time. You will find that hard stops from high speeds actually will reduce judder rather than increase it, if the rotors are up to the extreme cleaning. Cheaper rotors often aren't.

Pad composition of HPS is pretty good, imo. I wouldn't change them if you like their performance. Just put on some new quality rotors and try out the new stopping technique. Or, for added assurance, get a more abrasive pad and you'll see even better results (at the expense of noise, dust, and increased rotor wear).

I wouldn't recommend ceramic pads for spirited driving. They won't clean the rotor surfaces, but an abrasive metallic sport, club, or race pad will do this.

The things that AA mentions above are all factors. I feel that pad composition may be a part of your problem. Try a high quality pad.

Matthew was using Hawk HPS pads, which are very high quality.

thanks for the advice guys. so i will try a few of the things mentioned. hopefully my brakes are not so far gone a good scrub down with cold pads cant fix.

Mr.Riviera wrote:

thanks for the advice guys. so i will try a few of the things mentioned. hopefully my brakes are not so far gone a good scrub down with cold pads cant fix.

IMHO the first thing you need to do is chuck (as in replace) your current rotors, the ones you said had cracks. No good can come of that.

Albertj

Good call Albert.
I forgot that he had mentioned noticeable heat cracks in the surface of the Rotors.
I agree, replace them soon. Before doing any additional high speed bed in procedure.

every rotor i have ever had on this car has had heat cracks...
these rotors literally have 4,960miles on them. at $100+ a set i cant just chuck them.

the look similar to these, only the cracks are not quite that long.


that is actually a flywheel off a vette, but it's the only pic i could find that shows what i mean by cracks

You are hard on her!

Cracks are cracks, you are a rotor killer, you may not be in danger of the rotor breaking up but you will most likely always have judder.

How are your rear brakes? Are they working strong?

You may need a size upgrade to keep up.

He's already gone up one size on the front by installing the F-body kit.
But good point about the rears, if they are not doing their job you are putting more strain on the fronts.
When is the last time you pulled your rear calipers, cleaned everything, inspected the shims, sliding pins and lubed them to make sure they are sliding easily, etc.
If the rears aren't working 100% then the fronts are doing overtime.

You may have already mentioned it, but what make are the front rotors.?
5,000 miles and heat cracks already doesn't say much for the rotors, unless the front pads have been dragging as well.

yes i am a very "spirited" driver. there is a strech of road before turning into my neighborhood and i regularly do 15mph-90mph-15mph runs. i also make full use of my suspension mods and brake late going into corners.

Then get the best rotors you can, make sure you periodically remove the calipers and lube everything and inspect everything.
You need to do maintenance that would be equivalent if you were racing a car on the track every month or so.
And if you want to play, you gotta pay.

thanks, that's what i figured. so what rotors do you recommend then? something slotted to reduce heat and help prevent future cracks?
I am already using pads that come close to track only, i bleed the system every few month and the F-bodys (ones you sold me) with SS lines are checked of pretty regularly.
new hubs up front, all new front suspension w/poly links/bushings and HD parts too.

15-90-15 regularly , its the driver!

Most likely even bigger brakes are the only cure.

I have had to pay more attention to certain cars about wheel nut torque to avoid causing judder, is the riv one to be especially worried about? I am starting to suspect so.