warped rotors

cneary812 · 01-04-2007, 05:27 PM

As my sig says i have an 05 CC and just turned 3100 miles on it. A few months ago i noticed that I was getting some shaking in the steering wheel when braking (thought brake judder was starting). So I took it into the dealer Tuesday (day off) and had it looked at. They came back and said that they replaced the front rotors cause they were warped. They then advised me that the brakes had already been upgraded prior to me buying the truck in September. Truck rides great now. The mechanic said to me that the rotors probabally warped from sitting for so long, I agree with this, however, why do you think it took over 2000 miles for me to notice it? Just seems strange.

helomech · 01-04-2007, 06:17 PM

Man brakes don't warp from sitting to long. Think the mech is trying to blow smoke up your ***.

SoBeGraphics · 01-04-2007, 07:38 PM

something doesn't sound right - warped from sitting and they did the TSB a second time? hmm sounds fishy.

**chunko** · 01-04-2007, 07:55 PM

My guess is that they did not do the full upgrade before.

That's about how many miles it took for my crappy brakes to warp.

cneary812 · 01-05-2007, 05:16 AM

Thanks guys,

I believe that you may be right about them not doing the full upgrade before but I have heard of rotors warping from sitting before. I used to do all my own maintenance on all my other cars up to the titan so I do know a little about cars and brakes, dont get me wrong im no ASE certified mechanic but I can find my way around the underside.

I did take it to a different dealer than I bought it from. They said the parts were all the upgraded parts that were there and it was just the rotors. Time will tell...

adamsrk · 01-05-2007, 08:04 AM

I thought (and so did the dealer) that I was having judder on my 06 but they turned my rotors and said the front left was warped.

helomech · 01-05-2007, 09:44 AM

Quote:

Originally Posted by cneary812

Thanks guys,

I believe that you may be right about them not doing the full upgrade before but I have heard of rotors warping from sitting before. I used to do all my own maintenance on all my other cars up to the titan so I do know a little about cars and brakes, dont get me wrong im no ASE certified mechanic but I can find my way around the underside.

I did take it to a different dealer than I bought it from. They said the parts were all the upgraded parts that were there and it was just the rotors. Time will tell...

Rotors warp from getting to hot, not from sitting on a shelf. The old rotors warped bad because one side was thicker than the other.

cneary812 · 01-06-2007, 11:52 AM

Quote:

Originally Posted by helomech

Rotors warp from getting to hot, not from sitting on a shelf. The old rotors warped bad because one side was thicker than the other.

Acutally I bought a set of rotors once for my Maxima and they were warped out of the box, if they are not stored flat they can warp.

The rotors that were on my truck were the ones on the truck from when i purchased it. Dont know how exactly they warped but they did.

helomech · 01-07-2007, 07:25 AM

Quote:

Originally Posted by cneary812

Acutally I bought a set of rotors once for my Maxima and they were warped out of the box, if they are not stored flat they can warp.

The rotors that were on my truck were the ones on the truck from when i purchased it. Dont know how exactly they warped but they did.

I don't doubt that you got some warped out of the box, but they were probably not cut to specs. A peice of steel that thick and that small won't bend under its own weight. It would take lots of weight being placed on it to bend it. They may have even been reconditioned rotors sold as new. It happens a lot.

cneary812 · 01-07-2007, 09:35 AM

well at any rate, the truck is running and stopping fine now, hope it continues to do so for a very long time.

Steve Tarring · 01-27-2007, 06:16 PM

Warped rotor? You must be thinking of a condition know as "Brake Judder"

Judder is a phenomenon where the steering starts to shake when applying the brakes. Many think this shaking is due to the disc having been warped. This is a tale to in need of mythbusting...

Let say that if a rotor could warp just for argument. If a disc was un-true or had some sort of "run-out" the brake calibers are mounted on the suspension in such a way as to allow them to float and would simply follow the run-out of the disc under braking. No, classic brake judder is the cause of two types of problems associated with friction systems use on brake systems today. This condition is caused when the friction faces are no longer parallel to each other.

Judder is caused when adherent friction mechanism, used in street application, get to hot during braking. Abrasive friction is altogether different and is used in racing systems. However, the adherent system uses a thin layer of brake pad material transfered to the faces of the discs and sticks (adheres) to the friction faces. This layer of pad material, once evenly established on the rotor, is what actually rubs on the brake pad. The bonds that are broken, for the conversion of kinetic to thermal energy are formed instantaneously before being broken again. It is this brake pad-on-transferred brake pad material interaction at the molecular level that yields the conversion process. This is the mechanism used in a street applications of modern street vehicles today. But, this is were an unwary owner can get in trouble too.

Consider the following. You’re driving your vehicle a little too aggressively and the light changes on you. You start applying heavy pressure to stop, right? We’ve all been there before…

Now that the hard part is finished, what's do you think a unwary owners might do while waiting on the light?
1) Roll down the window;
2) Change the radio station;
3) Ease up on the brakes and let the vehicle move slowly so as to avoid the brakes pads from resting in one place on these "hotter the hell rotors".
If an owner fails to do the later he risks a phenomenal called "Pad imprinting" This is where most adherent friction or street brake problems start. What happens is the pad faces can bond to the friction faces of the rotors after this type of stop and when driven off, an uneven deposit of pad martial can results. What's worse under braking now when the pad(s) encounter this uneven build-up of pad martial, local temperatures can reach 1200F to 1300F degrees. If this continues, iron which contains inclusions of silicon-iron carbides and high percentages of carbon can develop deposits of "Cementite" (Fe3C) in the rotor's iron matrix.

Let’s use a metaphor here and say that the inclusion of silicon iron-carbides and the high content of carbon (30%-40%) in cast-iron is simply a recipe for the development of cementite. All we have to do for its development is locating a heat source and when working with brakes, this will not be a problem...

Cementite deposits are very hard and even a poorer heat conductor and if allowed to continue to develop the softer iron where cementite is not developing will begin to ware more causing a greater problem. It is at this stage where an owner will normally bring their vehicle to a shop or dealer and they will turn the discs. But, all this does is knock off the high points and after continued driving the disc will start to exhibit judder again sometimes as little at 7K miles depending on the owners driving habits.

So, what is the cause of judder with the above in mind? We need to revisit our school science classes. Remember when we learned fluids could not be compressed? Sure. This is a fundamental law in hydraulics and brakes systems used are based on hydraulics principles. When your foot depresses the pedal, it forced brake fluid thru to the brake calipers causing the pads to grab the discs. It is here where the judder is felt under foot on the brake pedal. Since fluids can not be compressed, and if the rotors are not parallel as they rotate into the caliper(s) this caused the pads to try and fight back the pressure against your foot on the brake pedal. Or, classic brake judder.

I'm not sure where you got the idea about slotted rotors but, I have been running them for years on my vehicles. The slots cause the vehicle to stop much better with good quality brake pads. However, the type I use are cyro-treated. After using them I noticed that the dealer never told me that the brakes discs needed replacement. From time to time they would only indicated that the pads needed replacing. I asked them to check the thickness of the disc to make user and they told me the the discs were fine. Now I thought this was very strange because I when thru the first set of brake discs at 15k miles or so, and there were close to 56k on the vehicle then. When I asked the service manager to double check the records he confirmed replacing brakes near 15k miles. When I asked how could he explain the milage on the rotors now any why they didn't need replacement he had no answer other they to say his service personal check the discs and they indicated they were OK.

Well, to make a long story short, I have been using these types of brakes ever since. I have sold three vehicles now using these brakes and never replaced a one. When the dealer informs me I'm nearing replacement of the stock rotors, I order a new set and I have the dealer installed them. Well, I have them on my Titan now... What a relief.

Yahooligan · 01-27-2007, 06:32 PM

My '05 Titan developed brake judder right around 3000 miles, the dealer replaced the front and rear pads and the front rotors. He may have said the pads had already been updated but they replaced them anyway along with the updated rotors.

Anyhoo, brakes are good now!

Steamguy · 01-28-2007, 10:04 AM

Quote:

Originally Posted by Steve Tarring

<SNIP>
3) Ease up on the brakes and let the vehicle move slowly so as to avoid the brakes pads from resting in one place on these "hotter the hell rotors".
If an owner fails to do the later he risks a phenomenal called "Pad imprinting" This is where most adherent friction or street brake problems start. What happens is the pad faces can bond to the friction faces of the rotors after this type of stop and when driven off, an uneven deposit of pad martial can results. What's worse under braking now when the pad(s) encounter this uneven build-up of pad martial, local temperatures can reach 1200F to 1300F degrees. If this continues, iron which contains inclusions of silicon-iron carbides and high percentages of carbon can develop deposits of "Cementite" (Fe3C) in the rotor's iron matrix.
<SNIP>

Good explanation of pad imprinting. We drivers of Titans are not alone in this. My old Dodge Dakota, my 1500, and a buddy's Chevy were also subject to this. I learned to do exactly as you say: stop short, then allow the truck to slowly roll forward when stopping really hard from highway speeds.

You CAN reverse pad imprinting to some degree by making a panic stop, then rolling forward slowly to redistribute the heat. You have to do this at least three times. It used to work really well to do that in my old Dakota. That sucker would get pad imprints just too easily.

Our Titans are also subject to rotor warp through incorrect installation of tires and wheels. I got my snows swapped onto the truck a few years ago, and the idiot kid used a 'torque stick' - a real no-no. Ye gods, did I have pedal feedback. I went back to the shop and asked them if they used torque sticks to install tires... and of course the answer was yes. I told the manager to get into the truck with me and I took him for a ride around the block.

Long story short: After completely loosening and precisely (two-step method) re-torquing the wheels, the problem went away. You might give that a try, see if it works for you. Maybe us old wrenches do still know a thing or two.

BKW · 01-28-2007, 10:44 AM

Steve...This is the most informative post I've read here or elsewhere. This explains the cause and effect of all the Titans brake issues.

Your statement about turning rotors really should hit home with all the owners of 2004's and some 2005's.

When the judder issues began, many Nissan dealers had none of the new brake parts, so they turned the warped rotors (A No No under any circumstance), and replaced the pads. The brake judder then re-appeared within a few days.

The Titan got a bad rap...still unresolved among the many 2004 owners, because the dealers were unprepared to handle the issues.

cneary812 · 01-29-2007, 05:09 AM

Wow nice to see that my post became the most infromative post ever

Steve thanks for the engineering perspective, very nice.

Now Judder or not the rotors were bad and the dealer replaced them with new ones. Its been about 1000 miles since and they are still true (for now)

I would have to think that todays materials are a little better than in the past and that the hard emergency braking would not cause imprinting as much, if that were the case then we would all be in the shop every week getting our brakes checked.