Do you know of engineering papers for what people call brake rotor 'warp'?

An interesting aside is that we all have seen grooved rotors, and we all know the "fingernail test" (i.e., if it catches your fingernail, it's too deep) - but - if you LOOK UP the specs for grooves, they have to be absolutely huuuuuuge (like the thickness of a dime!) to fail a rotor.

At least in my experience.

If anyone actually has a bona-fide "groove" specification for their rotor - please share!

I should clearly state that I too believe rotors CAN warp!

However, what MOST people "call" warp, isn't warp at all. It's merely brake judder. Which, as we've seen from the dozen papers, can be caused by a LOT of things. And, as shown by the industry advertising anyway, most of the time it's NOT warp.

Plus, how would anyone know it's warp if they didn't measure the rotors on the bench, as that's the ONLY way to tell a warped rotor (as far as I can tell).

I haven't seen rotors cut in decades, I'll have to make a call.

As I recall the lathe was "marked" in .001 increments (and a "standard" cut was .003) but "infinitely" variable. My buddy set it up once then left me to finish the job, so I played with it.

Being cautious, since it was my rotor, I set the bit to barely touch and dialed it in slowly and could see it hit high spots, small and large, short and tall.

Whether that was the result of warp, even wear or molecular deposits, I couldn't guess. -----

- gpsman

my caravan carries a lot of weight, and the pads wear out fast.........

Used to be garages demanded we turn the rotors, in my application they would warp fast.

so now i just buy new rotors any time the pads get replaced.

my neighbor a highly skilled guy does lots of my vehicle repairs, sadly i must find someone new.

he is a smoker and has lung cancer stage 4......

he is a good hard working guy i will miss him:(

It can happen but not as often as those selling "rotor turning" say so.

In every car that I've had, shaking was caused by the calipers not being properly lubricated. The viscosity is important to prevent sticking and produce motion dampening.

The odd thing is that the one car I've had (actually a company car) that had chronic "warping" issues was nearly new, so you wouldn't think that this would be the issue?

OTOH I have had all sorts of cars that go years without any brake maintenance other than every two years fluid flushes and never had any brake oddness... Last really long term car I think I did repack the front wheel bearings once for insurance but just put the brakes back together, I suppose I must have cleaned and lubed the sliders because it would make sense to do so... Others just stopped fine until I had to address the brakes for whatever reason (usually the pads wearing out eventually) and continued stopping fine afterwards.

Now I do make sure that if the rotor sits on a hub and is not a one piece that the interface is clean, but you'd think that that would be a best shop practice as well.

nate

there's lots of ways, but that's not the point. the point is that runout only a few molecules thick has absolutely no effect - surface roughness alone of the disk is many orders of magnitude larger.

which is what most people do. it "works" because the new disks are clean and thus seat properly. if old disks were properly cleaned, they would too, but since time is money for shops, and disks relatively cheap, replacement is in fact an economic option.

he has very little time according to his doctor.

its sad people get addicted to smoking then spend horrendous amounts of money to get sick and die

If there's lots of ways, please name one of those ways. Just one. My point is that I'm not talking about surface roughness. Just the mechanical plating of pad material onto the cast iron surface.

The rotors are cut from the center to the edge. There's a slight bevel on the outside edge that should be left on. My assumption is that if there's no bevel on the edge, the rotor is too thin.

The worst lathe job that I ever had was done at one of those big Auto Parts chain. There was grooving on the surface. Come to think of it, I should have tried to get them to comp me a new set of rotors. That would have been cool.

The best job of machining a rotor was done of some holiday and the machinist at the parts store was a home with his family or drinking it up with his buddies. The shop recommended a guy that had a machine shop in a shack nearby. It was kind of scary going back to his shop. I was expecting to get jumped by crackheads and have my rotors stolen and sold for some crack. The shop was dirty and stuff was crammed into the small space and this big hairy guy in dirty overall emerged from the mess. I handed over rotors and came back a couple of hours later. My rotors were beautifully machined. It was so smooth that you could see the surface glint with points of refracted light. It was the work of a master. I'm never gonna see work like that again!

I've had the cheap Chinese rotors hold up better then the factory OEM that were new. I've had "warp" that disappeared with more miles and "warp" that got much less when the tires were rotated, and that's with Discount doing it and using torque wrenches. When I do it at home I just use the air impact at the same setting (around medium) for all the lugs - seems to be just as consistent as using the torque wrench.

are you serious? i hope not.

dude, seriously, how do you think adding a "molecular layer" to a disk surface makes the slightest difference? surface roughness is in the order of 10 microns. that's at least 10,000 times bigger than even a huge "molecular layer".

oh, and oem runout tolerance is ~10 times greater than that.

excuse me, but any machining of this mature is going to leave "grooving on the surface". slotted disks have /really/ big "grooving on the surface".

and that surface got all tore up inside the first few degrees of pad friction...

which is, as i've said many times, simply a function of getting the disks seated correctly. because disks don't actually "warp".

which is what it says to do in the manual...

it would be better yet if you cleaned/antiseized the hub faces and torqued with a torque wrench in a two/more stage process.

Oh yeah, "there's lots of ways" - none of them are serious. Nothing personal, but you're the dude that full of bs. You don't even know what the heck I'm talking about. Have a nice life dude.

As I asked before - does anyone have a pointer to a real specification that shows how deep grooving must be to fail a rotor?

you need to be careful how you define the question. brand new slotted rotors would fail any spec that didn't recognize their "grooves" as legitimate.

i'm glad i didn't bother! i spent years of my life measuring stuff to microns and below, so if you think i'm going to try to educate a guy who's clutching at "molecular layer" straws and being hostile about it because he can't be bothered to pay attention to fact or can't be bothered to google, you need to think again.

just as i suspected, the relevant stuff is way over your head.