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I too have turned houndreds of rotors and have never seen pad material come off when the brake lathe was cutting, only metal. The brake material building up to cause warped rotors is a urban legend. The metal warps and the only way to make them true again is to remove metal. It has been my experience that when a rotors is badly warped the only good solution is replacement. You my be able to turn the back true but they will work again in short order. Buy a good quality heavy-duty fleet grade rotor. Slotted rotors are good, but drilled ones will crack under high heat. Also buy a good fleet grade pad.
Mark
Sorry to burst many bubbles but slotted rotors do not have any benefit except more income for the manufacturer. Not gas escaping is a marketing gimmick. Ask any mechanical engineer that deals with friction and knows his metallurgy.
Best rotors have higher carbon content but you will be hard-pressed to find anyone advertising that except Autozone, which their ‘Gold’ line of rotors do offer this. These are the rotors we ran on our SCCA race car.
just like chrome muffler bearings... and blinker fluid.. some ideas just will NOT die.....
then there is the 3,000 mile oil changes... that came from the era... when engines did NOT have oil filters....
and the oil bath air filters.. I so hated them....
I have Powerslot Cryo rotors with Hawk pads up front and have been using Permatex brake lube for the last 20k without an issue. I've towed trailers, stopped hard and generally drive hard.
The brake material building up to cause warped rotors is a urban legend. The metal warps and the only way to make them true again is to remove metal.
Nope. Do you know how hot rotors have to get to warp? There are two ways to have uneven rotors. Pad deposition and uneven hardness. A lot of cheaper rotors have uneven hardness throughout the running face. This means different wear rates, leaving the harder sections proud of the softer sections. That would be the metal you're chipping away.
If you don't think pad material can be deposited on rotors, I can't help you. That's just chemistry and the side effect of brakes doing braking.
I don't care if they're warped, deposited, uneven, unparallel, or unhinged (like this argument is starting to become).
OP has brake pulsation. He can either 1) keep swapping rotors when it starts happening, or 2) get some measuring tools and get actual, factual data to try to solve the real problem here, be it rotors, pads, bearings, lug nuts, etc. Arguing over how the 0.001" runout happened doesn't help the guy, it's a fact that it's there and he needs a solution. It sounds like new rotors was his solution and he's sick of changing them out, so if ya'll don't like the recommendation of actually measure the parts he's swaping to find a root cause, come up with a new idea that actually helps the guy. Spend money on big name parts could be an equally valid start, so long as we advise him to correctly install them which includes maintenance on the pads, calipers, and slide pins, and measuring runout.
Anyone else have anything practical to offer? Or is intelligence turning into an internet myth also?
I don't care if they're warped, deposited, uneven, unparallel, or unhinged (like this argument is starting to become).
OP has brake pulsation. He can either 1) keep swapping rotors when it starts happening, or 2) get some measuring tools and get actual, factual data to try to solve the real problem here, be it rotors, pads, bearings, lug nuts, etc. Arguing over how the 0.001" runout happened doesn't help the guy, it's a fact that it's there and he needs a solution. It sounds like new rotors was his solution and he's sick of changing them out, so if ya'll don't like the recommendation of actually measure the parts he's swaping to find a root cause, come up with a new idea that actually helps the guy. Spend money on big name parts could be an equally valid start, so long as we advise him to correctly install them which includes maintenance on the pads, calipers, and slide pins, and measuring runout.
Anyone else have anything practical to offer? Or is intelligence turning into an internet myth also?
I think no matter which side of this argument you are on, you probably want to take precautions to prevent both possible causes.
So:
1) buy "quality" pads and rotors.
2) lube, assemble and torque everything carefully
3) use a bed-in procedure
4) do your best to reduce heat and not hold the brakes in one spot when you've created high heat.
No worries, if you don't want to just throw parts at it next time you do a brake job, take measurements when you pull stuff off. Or just get a shop to cut the rotors on the truck and see how long they last for this time, not really any worse than putting in a new pair.
Some of the basic measurements would be to check runout of the rotor, then take it off and measure the the hub face. Measure the rotor thickness in several places with a micrometer, same with the pads. If those measurements bear out that the rotor has high and low spots, then we figure out what's causing that. If your hub has 0.003" runout, it's could not be the brakes fault at all. If one pad is thinner than the other, it's not the rotor necessarily and could be slide pins. You don't have to sweat the entire decision tree right now, just get the readings when you can, and if you throw in new parts one last time you're another year down to road before you have to do it again and have time to think about it.
How the runout happens is the best way to determine a solution.
That there's runout at all has yet to be established, ya'll're arguing based on him just saying the rotors were warped, there's nothing of diagnostic value to support that yet. I believe him that he has brake pulsation, but what that IS hasn't been established yet.
Wow this is quite a thread. There is some bad advice, some wrong information, and a lot of misunderstanding about what is going on.
First, the chemisty... it's irrefutable that a compound called cementite is formed on the brake rotor due to the intense heat and pressure of braking. This article explains it well: -Warped- Brake Disc and Other Myths
If you want to solve the problem, stop using cheap pads and rotors. I use Hawk brake pads and Powerslot slotted brake rotors (do not listen to the guy above that thinks that slotted rotors are nothing but marketing hype). I have no brake pulsation at all and it was pretty bad before. To Bryan's credit, yes it's possible that the hub runout is out of spec but it's not that common. Most of the time it's the pad and rotors that are at fault.
Sorry to burst many bubbles but slotted rotors do not have any benefit except more income for the manufacturer. Not gas escaping is a marketing gimmick. Ask any mechanical engineer that deals with friction and knows his metallurgy.
I would love to have a conversation with one - by sear volume alone there is less surface area on a slotted rotor.
Originally Posted by seventyseven250
I think no matter which side of this argument you are on, you probably want to take precautions to prevent both possible causes.
So:
1) buy "quality" pads and rotors.
2) lube, assemble and torque everything carefully
3) use a bed-in procedure
4) do your best to reduce heat and not hold the brakes in one spot when you've created high heat.
To Bryan's credit, yes it's possible that the hub runout is out of spec but it's not that common. Most of the time it's the pad and rotors that are at fault.
Hub runout is not normal (unless you can already hear the bearings), but sometimes it gets people thinking "hey I should clean the rust off this flange since my dial gauge is bouncing like a pogo stick". But sometimes just reindexing the rotor can get a better reading on install due to variations between the hub and rotor, that's a reason to check even absent a current concern. He's probably seeing low spotting on the rotor from (pick an argument ^^^), I still think mic'ing the rotors and getting them cut on the truck this go round wouldn't hurt him at this point. I have Cryoslots and Hawk LTS pads waiting to go in just sitting on a shelf, but Autozone Gold pads have worked (albeit been very very dirty) for about 60k so far.
I would love to have a conversation with one - by sear volume alone there is less surface area on a slotted rotor.
5) be sure to properly torque the lugnuts
agreed on the lug torque. I've lost several sets of rotors on my wife's Audi from the dealership morons not using torque sticks when they zip the lug bolts back in.
I believe the reason for the slots is that they allow the heat and gas build-up from the friction material wear to to escape without pushing out against the pad. I guess they're useful for racing or maybe long down grade runs. Regardless, any sort of 'texture' on your rotors whether it's slots or dimples or holes is going to wear your pads out faster from all the sharp edges that get created. maybe that helps the stopping power, too.
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