Brake pulsate... I'm stumped!

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Originally Posted by roodoo2

we need to remain open minded to others shared experiences (real life) and not try to preach something that was written by someone else and then tell people they don't know what they are talking about when they share non-fictional recollections of factual events to back it up.

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You dare to question the mighty brake lord? You shall be shot for heresy.:lol:

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Originally Posted by sunofogun

Yeah the pads I put on are ceramic, front and rear. Theyre like 2 weeks old on new cheap rotors. Im wondering if that week or so I drove with the new pads and the old rotors if that was enough to wear the new pads unevenly and ruin them? Oh yeah and I fixed the rear brake problem . I had to loosen the shoes the whole way just to get the drum on and then I adjusted it tight from the back access hole. Now theyre almost too tight! One click on my parking brake! Oh well theyre pep boys brakes so theyll wear down soon enough lol!

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Whats was the brands ? make of the rears. Some compunds might be real noisy and make the "Mack" truck sound when braking.

Also make sure the shoes are on the correct sides I believe one shoe is longer then the other atleast on most drum setups. its been a long time since I done my rear.

wp

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Originally Posted by Ls1-Inside

Yeah - I agree... it is possible to have vibrations from unevenly deposited pad material w/o creating cementite... Especially considering most braking conditions don't heat the rotor up so much as to chemically change the molecular composition of the rotor...

When i bought my car, i had slight vibrations when braking from higher speeds... I posted about it on CorvetteForum. It was recommended that I do a series of long hard braking then drive around to cool the rotors. Sure enough - after that, the shuddering went away... The reason was the previous owner never used the brakes that hard, and never followed in a proper bed-in procedure for the pads/rotors. So over time a gradual build up of unevenly deposited pad material was on the rotor. That Doesn't mean it was BAKED IN, just deposited...

Kelvin - do YOU understand how brakes work? A properly functioning rotor should have a layer of PAD material deposited on it, bedded into the rotor. During proper operating temperature that material uses adhesive friction against the pad... almost sticking to the pad, then breaking away... creating a good bite. When you have an even layer of pad material you get optimal braking performance. That Pad material is SUPPOSED to be on the rotor, and will NOT turn into cementite. If your pads bedded in unevenly, then you will have an uneven layer of pad material on the rotor causing a slight vibration. You can correct this by heating up the brakes and rebedding them in with the correct procedure. Extreme overheating of the rotor however, will create the cementite and 'temper' the metal...

I've done it, it works, people i know have done it... people on corvette forum do it all the time... it is possible... the Pad Material on the rotor doesn't automatically mean you're fucked... unless you get the rotors heated up to an obscene temperature which is highly unlikely on daily driver applications.
In addition Rotors can and DO warp... just ask the people who have washed their cars right after some "Spirited Driving/Braking" or rally cars who hit puddles when at extreme braking temperatures. Anytime tremendous temperature changes happen, the metals in a rotor can and will warp... 2ndGenGuy is right... i'm sorry - rotors warp... and improperly bedded in rotors can be corrected...

-Dan

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Part 1: Yes. I explained this a few days ago.

Part 2: Oh I forgot! You know MORE than Carroll Smith. Silly me. :bs:

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Originally Posted by Ls1-Inside

Rotors warp, it's physics... metal cools at different rates and changes shape. Obviously this guy has never washed his car... because People have ruined their rotors with water on a very hot rotor...

-Dan

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Oh yeah! ANOTHER guy on these forums with more automotive knowledge and experience than Carroll Smith! Holy cow! This place is amazing! :bs:

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Originally Posted by roodoo2

.... when they share non-fictional recollections of factual events to back it up.

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Maybe I should buy a Tornado Gas saver. I've read some people who said they saved like 20mpg since they started using it! And maybe I should buy some of that spray on hair, I hear that works! Or maybe some of those dick enlarger pills too! I mean, after all, if people are sharing their 'non fictional recollections' of 'factual events' then it MUST be true.

Wait. Hold on a sec. One problem:

50% of the population is of below average intelligence. ie, Half of whatever you see is probably written by a MORON.

:\

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Originally Posted by Kelvin

That's because they were never warped. What happened, was that your wife maybe braked really hard, and let the pads cook onto the rotor. This uneven pad deposit will cause CEMENTITE. Cementite.
"Regardless of pad composition, if both disc and pad are not properly broken in, material transfer between the two materials can take place in a random fashion - resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken, if, when they are very hot or following a single long stop from high speed, the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a telltale deposit behind that looks like the outline of a pad. This kind of deposit is called pad imprinting and looks like the pad was inked for printing like a stamp and then set on the disc face. It is possible to see the perfect outline of the pad on the disc. (FIGURE 5)
It gets worse. Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake disk, any uneven deposits - standing proud of the disc surface - become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad, the local temperature increases. When this local temperature reaches around 1200 or 1300 degrees F. the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral - the amount and depth of the cementite increases with increasing temperature and so does the brake roughness. Drat!"
Yes, but only for a short time period. You've effectively sliced off some of the rotor's surface, making it 'true' again, but the problem is you have sections of 'cementite' would still exist on that rotor, and after a short time period, the 'pulsating brake pedal' would reappear again, like you said it did.
Basically, everything you've said concides perfectly what Mr. Smith's braking article. I have had ZERO pedal pulsation on all three of my cars for the past 3-4 years, after switching to fresh, cheap rotors and high quality pads with a high maximum operating temperature.

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apparantlly that article is a good read. i'll have to get the time to read it sometime.

i still wouldnt suggest cheapo rotors though poor casting, poor materialls, and subpar heat disapation. something a little better with a lifetime warranty like someone else suggested.

I have also experienced rotor warpage from rapid cooling bis flash tstorm several times in my life.


but everyones gotten off topic here. good discussion but wrong place. answer the poor guys question

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Originally Posted by guaynabo89

i still wouldnt suggest cheapo rotors though poor casting, poor materialls, and subpar heat disapation.

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Poor casting? Who cares. They're machined. That means they'll fit fine. As for 'heat dissapation.... I dunno, I really don't think it's something you're going to notice. In fact, if I had the money I'd use my gtech and do a 'rotor test' just to prove this once and for all, but again, pads are far, FAR more important than rotors.

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Originally Posted by LX-incredible

You dare to question the mighty brake lord?

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Brake lord - :lol:

The brake lord must have been mad at me when I took my ASE test.

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Originally Posted by Kelvin

Poor casting? Who cares. They're machined. That means they'll fit fine. As for 'heat dissapation.... I dunno, I really don't think it's something you're going to notice. In fact, if I had the money I'd use my gtech and do a 'rotor test' just to prove this once and for all, but again, pads are far, FAR more important than rotors.

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well most people dont want to have to swap out rotors to get them machined. To you and I it might not be a big deal, but there are most people who want their moneys worth without having to pay a mechanic to resurface the rotors. theyd rather just put em on an expect to get like 2-5 years of no problems.


it all comes back to the old saying "you get what you pay for" and sometimes when you pay cheap you get cheap. (not for every single case though) youd have to ask the original poster how he feels and what he expects out of his money.

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Originally Posted by Kelvin

Of course you do, you didn't understand what he was talking about. Basically uneven pad deposits from crap pads or overheated good pads can alter the cast iron rotor's surface, chemically. It will change the cast iron into 'cementite', which then spreads basically like rust, somewhat, through the rotor. Cementite is harder and more brittle than cast iron, so if you have UNEVEN pad deposits, this cementite forms UENVENLY, and thus the rotor WEARS unevenly.

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Aha I just saw this, and I've read this article several months ago. I also understand the metallurgy behind iron and steel and know that temperatures below the Lower Critical Temperature (930 deg C) WILL NOT cause any more cementite to form. All of the cementite present in the material has already formed from the above Upper Critical Austenitic solution of Iron and Carbon, as the material cooled directly after the pour. Also, pad material will not influence the chemical make up of the cast iron rotor's surface. Also, Cementite WILL form evenly from Austenite (material heated above LCT) because it is coalescing directly from a solid solution.

In fact, heating below the LCT (like how brakes heat up) is commonly known as a process anneal, and when done evenly and cooled properly, is done to improve machinability, ductility and to remove stresses and strains.

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Originally Posted by guyhatesmycar

Aha I just saw this, and I've read this article several months ago. I also understand the metallurgy behind iron and steel and know that temperatures below the Lower Critical Temperature (930 deg C) WILL NOT cause any more cementite to form. All of the cementite present in the material has already formed from the above Upper Critical Austenitic solution of Iron and Carbon, as the material cooled directly after the pour. Also, pad material will not influence the chemical make up of the cast iron rotor's surface. Also, Cementite WILL form evenly from Austenite (material heated above LCT) because it is coalescing directly from a solid solution.
In fact, heating below the LCT (like how brakes heat up) is commonly known as a process anneal, and when done evenly and cooled properly, is done to improve machinability, ductility and to remove stresses and strains.

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What dost thy say to this me lord?

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Originally Posted by LX-incredible

What dost thy say to this me lord?

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Thy says that technobabble sounds impressive, but ultimately one must have faith in way more experience/knowledgeable Carroll Smith. Though must remember that disbelievers are not famous for racing in lemans, or on first name basis with Carroll Shelby. Have faith in thy never-warped discs.

:bow:

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Originally Posted by Kelvin

Thy says that technobabble sounds impressive, but ultimately one must have faith in way more experience/knowledgeable Carroll Smith. Though must remember that disbelievers are not famous for racing in lemans, or on first name basis with Carroll Shelby. Have faith in thy never-warped discs.

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This is not technobabble, it is the reality of basic metallurgy. I tried to put it in the simplest terms possible, in order to convey the fact that what they are saying is WRONG. The most basic properties of iron and carbon forbid it.

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Originally Posted by Kelvin

Maybe I should buy a Tornado Gas saver. I've read some people who said they saved like 20mpg since they started using it! And maybe I should buy some of that spray on hair, I hear that works! Or maybe some of those dick enlarger pills too! I mean, after all, if people are sharing their 'non fictional recollections' of 'factual events' then it MUST be true.
Wait. Hold on a sec. One problem:
50% of the population is of below average intelligence. ie, Half of whatever you see is probably written by a MORON.
:\

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I decided not to pick apart the above statement like you have done to everyone who has responded to your posts. I read it and found that over half of it was , nevermind.
You have a lot to learn amigo, true you have brought to our attention a very interesting read, not written by you, and already posted here previously. But your communication style really does not reflect on you positively and frankly is a textbook demonstration of blissfull ignorance. If you can't see that by the responses you got then... well maybe you just read the half that quotes you.
Kelvin a lot of us here do enjoy a good debate so when you can come up with a stong enough pitchnet, bring it on. Leave the insulting tone and name calling in your shorts though. I am sure you more smarter than you appear to be, you enjoy bringing some compeling arguements to the table, but be advised you are addressing a diverse crowd here, some are just owners who do not even do their own work they are entheusists, some of us though have many years of experience in all areas...imports, domestic, fabrication, performance, paint and body, business, non automotive, duh brakes., education, medical, military, geez who do you think you are.talking to these people like you do.....I apologize for going off topic.

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Originally Posted by sunofogun

Okay here's an update: Today I took all the tires off and notice some weird movement on the balance machine. I put 4 new tires on and theyre still acting weird. The rims dont look bent, maybe they do have some lateral runout though. I also noticed my front upper ball joints have some play. They dont make any noises yet or really affect the steering. I doubt that they are causing the brake shudder, they primarily would affect my steering and handling on a regular basis.

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A few other things to check according to those symptoms. If you are using low profile tires make sure the beads got seated properly. Make sure the caliper mounting bracket is put on correctly, clean mating surfaces and slowly run down the bolts a little at a time so it goes on exactley straight and DO NOT BEND it, or the caliper will never hang streight again. On the rear , excessive clunking could the be backing plate worn out where the shoes slide, grease those places where the shoes contact the backing plate with a very very light dab of brake safe grease. You may need to replace holddown springs too. If you can get your hands on a infrared thermometer, you can make a few stops and measure the temps, if you have an excessive amount on one side you may have brake line or caliper sitcking issue.

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Originally Posted by guyhatesmycar

This is not technobabble, it is the reality of basic metallurgy. I tried to put it in the simplest terms possible, in order to convey the fact that what they are saying is WRONG. The most basic properties of iron and carbon forbid it.

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See other thread.

Well I talked to the best mechanic at my shop and he is pretty sure im start ing to get play in my front hubs. This would explain why a complete brake job did not solve anything. First I will clean and scrub all mating surfaces and sliders, and machine the rotors off the car. I wish I had a dial indicator so I could check the hub runout, ohwell . If after this the problem is still there, I will go to the dealership to have the rotors cut on the car.( Because I do not feel like buying new hubs or pressing the bearings out!

you didnt replace your akels recently did you?

check the tourque on the hub nuts just in case. you never know could be something simplelike that.

Nope never taken the axle nuts off

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Originally Posted by sunofogun

Well I talked to the best mechanic at my shop and he is pretty sure im start ing to get play in my front hubs. This would explain why a complete brake job did not solve anything. First I will clean and scrub all mating surfaces and sliders, and machine the rotors off the car. I wish I had a dial indicator so I could check the hub runout, ohwell . If after this the problem is still there, I will go to the dealership to have the rotors cut on the car.( Because I do not feel like buying new hubs or pressing the bearings out!

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Should show up if your rock the tire off the ground at 12 and 6 position.

I dont think our cars need the rotors turned on the car but you can give it a shot.

You can rig up a pointer to try and see if you have run out. A fine tip marker works if you can find a way to hold it steady.

wp

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Originally Posted by Kelvin

Part 1: Yes. I explained this a few days ago.
Part 2: Oh I forgot! You know MORE than Carroll Smith. Silly me. :bs:

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:wtf: are you talking about?

Between this thread, your attitude, and the other thread, you've completely lost any and all credibility to me...

I honestly hope that others don't "Keep the Faith" and listen to what you preach because it is simply wrong, dated, misunderstood, and misrepresented by you. Carol Smith - were he still alive - would most certainly agree with the modern sciences on braking rotor and pad technology, and would undoubtedly accept breakthroughs in physics and metallurgy research as fact. You represent 30 year old material as if it were modern day fact. I'm sorry, but what Racers knew in the 70's is different from what they know today.

-Dan

Yep. That's why nobody other than accord enthusiasts refute his articles. His books are still sold, and not updated, because you weekend warriors know more than the thousands of engineers and racecar builders who've read his books.

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Originally Posted by Kelvin

Yep. That's why nobody other than accord enthusiasts refute his articles. His books are still sold, and not updated, because you weekend warriors know more than the thousands of engineers and racecar builders who've read his books.

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Nope Kelvin - we just know more than you.

You're the only one misinterpreting the data.

Read 'em and weep.



-Dan

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Originally Posted by 86AccordLxi

Honestly, I have to agree. My autozone blanks on both of my 240s (coupe had axxis metal masters, fastback has hawk hps), have held up with 0 problems.

I put brembo blanks on my accord with some performance friction carbon metallic pads (higher end autozone pads) and after one long spirited drive (and probably turning the car off with my foot on the brake haha) I managed to leave uneven pad deposits and had shuddery BRAND NEW brakes (honda calipers, new fluid, p.f. pads).

Alex

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He agrees with me. So does Carroll Smith, and the following brake company websites:

http://www.raceshopper.com/tech.shtml#warped_rotors

"Warped rotors (in most instances) are caused by the brake pads being operated at temperatures outside of their specified range. When the pads get too hot the pad material actually melts and 'fuses' itself to the rotor surface and creates a 'bump' on the surface of the rotor. In most cases this is not noticeable to the naked eye. This creates an annoying vibration when the brakes are applied"

http://www.performanceoiltechnology....ingsystems.htm

"The problem with this diagnosis and repair procedure is that first of all is that brake rotors do not warp. The second problem is that replacing a brake rotor with a new brake rotor or machining the rotor on a bench lathe will only fix the problem temporary. The problem will almost always re-occur after a period of time, thus necessitating further repairs. Brake rotor disc thickness variation or excessive lateral runout, as well as drums that are out of round can cause vibrations and pulsations in the brake pedal and/or steering wheel. Brake lining material transfer onto the rotor can also have an effect on this as well. "


http://www.powerbrake.co.za/download..._01_judder.pdf

"Even the best quality discs money could buy would have developed the same brake judder. Here’s why.... As explained above, the disc was continually coming into contact with the pads at the point of maximum run-out first. If abrasive pads were being used this area of the disc would wear down quicker than the rest of the disc surface causing DTV, which is felt as an intrusive judder. If adhesive pads were being run then the pads would have deposited more material on the initial contact point (the area of max. run-out) than on the rest of the disc surface. Again this leads to DTV and brake judder.

"It gets worse! Once you have the development of DTV the surface of the disc will begin to heat unevenly. The high spots will get extremely hot compared to the rest of the disc. When the temperature around these high spots reaches 650 – 700°C. the cast iron in that area will change structurally and transform into a material called Cementite. Cementite is far harder than the cast iron of the unaffected parts of the disc and will therefore wear considerably less as the disc wears down with use.
Cementite also has very poor heat sink properties and will therefore continue to run extremely hot resulting in the rapid spread of the Cementite formation deeper and deeper into the disc. As a result the DTV will get progressively worse with time until it becomes literally unbearable to use the brakes. Depending on the pads used and the driving style of the vehicle owner this process could take 1000 – 6000 kilometers to develop and, NO, the initial run-out will not necessarily be felt by the driver. Hence the confusion and clinging to the concept of brake discs “warping”



Other than that, yep, nobody agrees with me. I'm okay with that. It seperates the cream from the curds.