Maxy91

hey guys ive been noticing for a month now that when im coming to a stop while braking the steering wheel begins to shake also the brake pedal itself shakes a bit too now ive been told this is what is called "warped rotors" and i can have them "refinished" Does anyone have any solutions as to what i can do or is it true that i must have them refinished? would the rotors themselves have to be replaced? Thanks in advancefor your anticipated advice/help!

Rochester

iTrader: (3)

Try bedding in the brakes before you commit to replacing or servicing them.

Also, read this: http://www.stoptech.com/tech_info/wp...rakedisk.shtml

Scottwax

iTrader: (8)

Technically, the rotors aren't actually warped but pad material has stuck to them in an uneven pattern. If the discs have enough metal on them, they can usually be resurfaced. Then as Rochester recommended, bed them in properly.

Rods03Max619

iTrader: (5)

I usually get mine resurfaced at a machine shop for 8 bucks a rotor since shop's rob you out here on brakes and all!

dragonle87

Lift your car, put it on jack stands, remove wheel, remove calipers, & remove rotors

Take your rotors to PepBoys or O'Reilly & let them resurface your rotors for you. Should be $10-$15 per rotor.

Then properly break-in your pads

CMax03

iTrader: (3)

Problem solver:
Throw your 5.5th gen brakes in the thrash and @ least upgrade to 6th gen rotors/calipers/torque members.....Hawk, EBC, Raybestos just anything better than OEM sissy a$$ factory pads

Rochester

iTrader: (3)

Research wheel fitment considerations first. 6th gen swap isn't feasible for everyone.

So true.

trooplewis

iTrader: (1)

Huh? I've seen a lot of warped rotors (especially with Toyota) but I have never seen brake pad material "stuck" on a rotor. If that was the case you could clean it off yourself with some crocus cloth.

Warped rotors get that way from overheating, I have no idea what you are talking about regarding brake pad material stuck on their surface.

ghostrider17

iTrader: (6)

Time for you to read-up TROOP!!

Scottwax is dead-nuts ON.

"Warping" a 1" thick cast iron rotor, is damn near impossible under daily driving conditions.
Yes - pad material transfer it is....those who doubt me: suck ballz by CHOICE!!

gr

trooplewis

iTrader: (1)

LOL, ok, so what happens, my brake dust builds up on the rotors, does not get scrubbed off by the pads, and petrifies on the surface?

ghostrider17

iTrader: (6)

It's at the microscopic level -- but typically happens when hot brake pads get clamped to HOT rotors while sitting in traffic or at a stop light.

This is why so many people who do lots of stop and go driving have this issue.
Living in Atlanta for many years, I rarely got more than 10-15k miles on a set of rotors before I'd have to have them "turned" or lathed.

Yep - I've been thru three sets of rotors in 80k miles -- and each one of those rotors has been lathed at least ONCE in between.

Thanks Nissan!!!

gr


***Oh yeah - and to the OP: take 'em off yerself and get 'em lathed at a shop....WAAAAAY Cheaper!!!**

nelledge

iTrader: (6)

Troop, check out that link Rochester posted. I've read it a few times. Very technical.

CMax03

iTrader: (3)

Where they get that from is unknown but it's kinda funny! Heat warps tiny **** that can't dissipate the heat fast enough cause they're too small or puny!

trooplewis

iTrader: (1)

Ok, I did some Internet research, and I checked out the StopTech info on rotor warping. Theirs is the only site I could find that did not attribute warping to heat and related conditions.

So maybe I'm just out of touch, I checked with my primary Service guy here at BMW and shared the Stop-Tech theory on "material transfer" between the rotor and brake pads. He got a good laugh out of that. (BTW, we are the largest BMW service center in San Diego county, there is a small mountain of discarded rotors out back at any particular time).

You may all be drinking the same koolaid off that website, but I have to call bull$hit.

When brake pads lose material, I clean it off my wheels.If you can figure out a way to reconfigure that and melt it to the brake rotor, you have a heck of a thesis to write.

BTW, pads aren't the only thing that lose material during braking, rotors do as well. How your iron rotors are gonna do what that one site says they do is, IMO, outside the realm of reality. Sorry guys, but I don't buy it.

Rotors warp from heat, and most commonly when they heat up, and the driver stops and keeps the pads clamped on one spot on the rotor surface. That spot stays hot while the rest of the rotor cools, and voila', you have a warped rotor. No magic chemistry involved, just heat expanding and contracting the base metal.

Let the games begin...

Note, I did find another site or two that talk about "pad material transfer", notably wikipedia, so I'm not adverse to the idea, but the physics of such a process baffle me.

CMax03

iTrader: (3)

Good writeup! If the material was sticking to the rotor then a high speed wire wheel would be able to fix it not a lathe......Or you could simply wash it off.....Bigger beefier rotors can take the heat and maintain their structural integrity and those puny little rotors on most cars today (built for economy/MPG) can't handle the heat cycle of one basic high speed panic stop without warping......

trooplewis

iTrader: (1)

Leave your car in the rain or wash it and let it sit for a couple days, you will get a light coating of surface rust on your rotors. Drive it for 5 minutes, and *bam* the surface rust is gone, scrubbed off by the pads. Why would any other material on the rotors be different?

nelledge

iTrader: (6)

Here's the thing. Physics is easy, but it's complicated. Talk about convoluted. Multiple courses on thermodynamics and materials are offered within engineering degrees for a reason. There is a copious amount of information needed to fully understand the underlying concepts. The local BMW tech isn't always the source most appropriate for these kind of questions. (No offense to your guy.) I worked with a friend I believe to be the most intelligent BMW tech (I've known quite a few) I have ever had the pleasure of knowing. He will be the first to tell you that there are some concepts that cannot be fully ascertained by a couple posts in an automotive forum.

I can offer an analogy to the superficial complications this subject involves. We all know that a flywheel with hot spots will begin slipping or 'chattering'. Yet, the disc has plenty of friction material and the flywheel is not warped. The reason for this is those areas of material we call 'hot spots' are actually the same original material with its properties physically altered by heat and stress. This alteration causes differing temperature fluctuations in the flywheel which in turn alters the coefficient of friction in these spots. In other words, it's time for some new material. Either a new flywheel or machining to completely remove the transformed material. Brake rotors have very similar thermal properties to a flywheel.

I'll stop there. Very intense subject for so late in the evening. I also want to add that I have spec'd and turned many 'warped' rotors. I can't say that I've ever mic'ed one that was warped. Run-out? Yes. Warped? No.

I do like these discussions, though. Hearing different, intelligent perspectives from everyone is very refreshing.

[/My $.02]

Scottwax

iTrader: (8)

Rust isn't nearly as hard and it isn't baked on by the heat build up between the pads and the rotors.

I'd take what ANYONE at any dealership says with a huge grain of salt. I detail cars for a living and I can tell you that dealerships don't know squat about detailing. I could make a good living fixing the screw-ups from the local BMW dealership.

CMax03

iTrader: (3)

Your $.02 is worth just that....LOL! I guess warped headed are cause by brake dust ingested into the air intake and causing hot spots between the head and block and wedging the head away from the block and causing the head gasket to fail but the head isn't warped at all just wipe it down with a rag and some dishwashing liquid and reinstall it and you're good to go.....machine shop and techs that measure excessive run out and lack of flatness call this condition warpage.

CMax03

iTrader: (3)

Next time yall have a warped brake rotor tell the machine shop about this material tranfer situation.....They'll laugh yall out of their shop!!!!!LOL! Maybe this tranfer of this break pad material was actually not the pad @ all!!!!! Maybe it was the brake pad backing plate instead and the backing plate transfered it's material to the rotor...we call this galling.... Main/rod bearings do this when there's no lubrication is present during operation....with today's loud audio systems alot of things will be missed such as hearing those brakes dragging metal to metal with the backing plate and the rotor!!!!!!

P. Samson

Considering that years ago I remember reading an engineering paper presented at an SAE automotive industry conference on the problem of brake issues related to "warped rotors" where the "warped rotors" were mostly found to be an issue related to rotor runout issues and/or rotor thickness variation. One cause of rotor thickness variation was "non-uniform lining transfer" according to the author of the paper. There have also been TSBs issued by more than one auto manufacturer that have mentioned pad/lining material transfer. There is no doubt that it is real. Every manufacturer has had to deal with customer compaints related to brake judder/brake pulsing etc.......it's not just a Nissan issue.

Rochester

iTrader: (3)

Over the last few years (prior to my last rotor/pad upgrade), there were a few times where my brakes were experiencing judder, pulsation, call it what you will. This was obviously a problem that gradually got worse and worse.

I bed-in the brakes, and the problem almost entirely diminished, and was resolved for about a year the first time, and about a half-year the second time. This cycle occurred twice before buying my current hardware.

My point is, if the rotors were physically "warped", this wouldn't have done a damn thing.

BlackMacks

iTrader: (3)

Couple of items to note:

The flywheel reference almost works with the brake rotor/pad one, but I think you guys are overlooking something. First, let me say I agree with Troop- I've spent waaaaay too many hours following road racing, and participating in it myself, I've seen and driven very basic brake setups, and full carbon on carbon pads/rotors. It is indeed possible to warp a rotor, given enough heat and exposure, and "material transfer" is not contributing to it.

But I'll counter with this: I think the phenomenon you guys are arguing over boils down to basically the same problem: the pads, the material they're made of, and the rotors, or even the flywheel and clutch disk, WEAR at different rates, due to variations in the make-up of the material. It's impossible to achieve 100% conformity in any given rotor or brake pad, or flywheel or clutch disk.

These variations in the "mohs/rockwell", if you will, rating of those materials, leads to gaps created by peaks and valleys of harder materials wearing away slower than the softer ones. That non-uniform application of friction causes differing degrees of "slip and grip", which causes clutch chatter, for one, and contributes to that pulsing pedal and shimmying steering wheel.

That's why, as Roch noted, your manufacturers advise "break-in" procedures for new pads/rotors or clutch kits. They're attempting to minimize that "soft/hard" material make-up affect on wear.

nelledge

iTrader: (6)

This makes me sad. My analogy was at least analogous. A header has a great tendency to warp with excessive because of the gross disparity in material thickness; multiple angles, rounds and fillets; and shape. No comparison. Next.
Not really. I have machined brake rotors and flywheels for compact cars up to heavy duty trucks. 'Run out' and 'warpage' are not interchangeable terms.

I think some people are taking this too far. Yes, any metal can be warped at some given pressure/heat value. However, you almost have to intentionally try to warp a brake rotor. Some exaggerated bedding procedure followed by a prolonged stop in a deep puddle while the rotor is still cherry could probably do it. But c'mon. 'Warped' brake rotors are not as prevalent as you are being led to believe. Next time you think you have warped rotors with normal driving, ask the machine shop to measure deflection of the cooling vanes. It will be within specs almost every time.

trooplewis

iTrader: (1)

Think about the "bedding in" process, that is supposed to "evenly distribute" the brake pad material across the surface of the disc. If you have normal iron discs (not zinc-coated, not stainless) and ceramic or organic pads, there is a nice experiment you can do.

Hose down your brake discs in the morning and don't drive the car all day. Take a look at them the next morning. Iron rusts, ceramic and organic materials do not. If your rotor is rusty, there is no brake pad material on its surface. Experiment over.

I've done the "bedding in" process for years, in fact anyone who knows anything about brakes does it. But I do it for the pads, not for the rotors...

Scott-Max, I respect the detailing work you do, but to compare our 100% Hispanic detailing dept to the pretty technologically advanced Penske service center is fairly ludicrous. I've taken the classes that those guys have to take, and they are way ahead of your average mechanic's tech level. And the guy I spoke to was their supervisor who is the 'problem solver' on tough issues.

Rochester

iTrader: (3)

Fall of 2008, I went to Midas Muffler for an inspection sticker. They told me my rear rotors were warped and needed replacement.

They were 4 month old Brembo blanks.

Obviously, someone else finished the inspection, because I couldn't get my car out of there fast enough. I'm just saying... "warped rotors" is a great way to rip off the general public. Sounds very scary.

ghostrider17

iTrader: (6)

And back to what Blackmax said:

Yes of course you can literally WARP a rotor in a racing or heavy duty commercial application....but again: Not on THESE CARS and NOT in day to day driving conditions.

Why do people constantly try to refute the obvious?!?!

Read the Stoptech article that Rochester posted, and stop wasting space on the forum debating this.
Sheesh!

gr

vinco

iTrader: (3)

I think that "run-out" and "warpage" are really referring to the same idea. The "warpage" in question is not really warpage in the traditional sense, which would be more like the rotor being twisted or curled. It is actually more like bumps forming in the metal itself, due to variances in heat transfer on different parts of the rotor. If you've ever actually watched a rotor being turned, you will see every time that on the first pass or two, the milling tooth will hit only certain spots on the rotor, leaving the rest of the rotor completely untouched. These spots are where the heating and cooling variations have led to different expansion and contraction rates in the base metal. This process is undoubtedly heavily influenced by friction material transfer from the pads to the rotor (think of the pad material as either a heat sink or a heat conduit.) The pad material gets distributed across the face of the rotor in varying amounts in different places around the rotor. This distribution variation is minimized by using better pads, which tend to have more consistency in composition throughout the friction material. So, while the friction material transfer does have a direct correlation to the occurrence of runout, "warpage", bumps, or however you wish to describe the phenomenon, at the end of the day you're cutting metal off the rotor when you true it up. Bedding the pads does help, but the reason it helps is that it forces a more even distribution of heat around the rotor.

trooplewis

iTrader: (1)

GR, that is way beyond normal to have to turn rotors that often. My 2007 Camry needed the rotors and pads replaced (under warranty) at 38,000 miles. 14,000 miles later they warped again, this time out of warranty. I replaced them with a set of Raybestos rotors, kept the same pads since they only had 14,000 miles on them, and have not had an issue since. I'm now at 65,000 miles on that same set of pads and Raybestos rotors, no judder.

You must push the car pretty hard to have issues like that; my Maxima at 85,000 miles still had the original rotors AND pads on it, and the previous owner did 50% stop and go driving. He did torch 2 clutches, but no brakes.

And I agree about clamping the pads in stop and go driving, a big contributor to the problem. The spot under the hot pads stays hot while the rest of the rotor cools down, and when a big metal disc cools at different rates, you have a good chance of warping it.

And to the OP, sorry about the total hijack of the thread. Yours is a common problem and easy to fix.

BlackMacks

iTrader: (3)

Troop- the phenomenon you've described is more than likely attributed to current car makers' practice of shaving every single ounce of weight they can off of any given car before selling, for two obvious reasons: the less material they sell you, the cheaper they can price the car, and less weight to move around= better fuel economy.

That's why your "old" '02 rotors are still chugging along, when the '07's needed replacing already. I don't know precisely when any given auto manufacturer started pushing that practice, but you get my drift.....