Anybody thats ever turned a rotor on a lathe has seen 1\2 the rotor cut on one side and the opposite cut on the other side
Brakes Rotors DON'T WARP - Article
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Sure, its common enough. IMO they are leaving something out, if everything is true when its assembled the warpage, distortion or whatever you want to call it probably doesn't occur to any great extent.
If the run out is too great or the braking force is uneven for some reason then i can certainly see the hot disc becoming distorted.
If the run out is too great or the braking force is uneven for some reason then i can certainly see the hot disc becoming distorted.
Initial runout and pad imprinting are the primary causes. Overtorqued lugs do warp some vehicles/types of rotors.
Uneven wear is a symptom not a cause.
Uneven wear is a symptom not a cause.
I will say that if one is driving in the mountains and HAS to use the brakes a lot then at minimum the rotors get super HOT and feel warped. My 08 Ford Fusion had a transmission that did not allow one to use nothing but Drive. Only other option was D1 in which the maximum speed was 25 mph @ 6000 rpm. No other option. Therefore the rotors got VERY hot going from 6,054 ft of elevation down to 3600 ft. This phenomenon may well have been due to pad build up on the rotors. . but totally ruling out IF enough heat applied that rotors can't warp could be questionable to a degree. That's how blacksmiths shape metal and change its shape by applying high temperature to them. Watch a Richmond NASCAR race and see the cars that aren't driving the best... Rotors burning/ glowing with heat even on the straightaways. But hey, may well be just pad build up or rotor was jacked up beforehand that causes pulsations instead of warped rotors. Just glad that I have a transmission now that I can downshift in so this hasn't been a problem anymore
I don't know anybody outside racing who has done it but further deep cryo treating the rotors is said to alleviate the "warping" which would lead me to think that warping is real and at least partially caused by heat. Cryo is relatively cheap ($25-50) as well but slows down any brake job for a day or so even with good scheduling so it becomes an annoyance that people wouldn't likely be willing to take on.
JHZR2
Staff member
It strikes me that under the right conditions, temperature gradients could be created in a rotor that would cause various stresses, and perhaps warpage would be an outcome. But it sure seems that there are so many other possible causes associated with poor practices and cost cutting by the OE or a shop, that anything is plausible.
The only time I've encountered pulsation of any kind was on a car with four wheel solid discs.
The only time I've encountered pulsation of any kind was on a car with four wheel solid discs.
Kestas
Staff member
I know OEM bearing hub unit manufacturers go through great lengths to make sure the rotor mount surface runout is as tightly controlled as can be. Some then put a bead of grease on these mounting points, and cover with a plastic shield before shipping to the assembly plants.
Originally Posted By: DeepFriar
I don't know anybody outside racing who has done it but further deep cryo treating the rotors is said to alleviate the "warping" which would lead me to think that warping is real and at least partially caused by heat. Cryo is relatively cheap ($25-50) as well but slows down any brake job for a day or so even with good scheduling so it becomes an annoyance that people wouldn't likely be willing to take on.
I'm not convinced cryotreating works on brake rotors. I've read LOTS of testimonials where people claim it helps with rotor performance, but I have yet to read about its efficacy it in any peer-reviewed journal that publishes experimental data. Nor has anyone explained to me the mechanism of how it works on a microstructural level, which - humbleness aside - I am an expert in.
The fact that NASCAR uses it does not impress me. They do lots of crazy stuff and throw incredible amounts of money on any hare-brained idea where they perceive an incremental benefit.
Originally Posted By: DeepFriar
I don't know anybody outside racing who has done it but further deep cryo treating the rotors is said to alleviate the "warping" which would lead me to think that warping is real and at least partially caused by heat. Cryo is relatively cheap ($25-50) as well but slows down any brake job for a day or so even with good scheduling so it becomes an annoyance that people wouldn't likely be willing to take on.
I'm not convinced cryotreating works on brake rotors. I've read LOTS of testimonials where people claim it helps with rotor performance, but I have yet to read about its efficacy it in any peer-reviewed journal that publishes experimental data. Nor has anyone explained to me the mechanism of how it works on a microstructural level, which - humbleness aside - I am an expert in.
The fact that NASCAR uses it does not impress me. They do lots of crazy stuff and throw incredible amounts of money on any hare-brained idea where they perceive an incremental benefit.
Originally Posted By: Vikas
Is it OK if we just invent a new word for "WARP"? Why not just say the rotors have "foobared" and need to be cut or replaced to make the brake pulsation go away? Does that technically change *anything* ?
Bingo. 99 times out of 100 the symptom means machine or replace your rotors. Call the cause whatever one wants.
Is it OK if we just invent a new word for "WARP"? Why not just say the rotors have "foobared" and need to be cut or replaced to make the brake pulsation go away? Does that technically change *anything* ?
Bingo. 99 times out of 100 the symptom means machine or replace your rotors. Call the cause whatever one wants.
Turned plenty of rotors, some cut all the way around from the moment the bit touched, others cut on one side and then the other, and yet others cut sporadically but at the same point on the rotor.
Material transfer can cause problems.
Uneven wear can cause problems.
And yes, WARPING can cause problems.
Material transfer can cause problems.
Uneven wear can cause problems.
And yes, WARPING can cause problems.
Originally Posted By: cat843
People just say the rotors are warped. They are just not of uniform thickness anymore. Could be wear or pad transfer material. Replacing the rotors almost always fixes the problem (for awhile).
How many shops use a dial gauge on brake rotors?
This comes up surprisingly often. I still contend the most common cause of pulsation is pad transfer. Most pulsation concerns can be fixed with a roloc disk and an angle die grinder. Machining those "warped" rotors on a lathe does nothing more than clean the garbage from the surface.
Dial indicators- Used them constantly for brakes. The big secret......ck the runout on a set of rotors not causing vibration concerns. Sort of eye opening. Have seen rotors out .020"+ and stop smoothly (ruins your caliper slides and/or whatever your pads rub on). Actual rotor thickness variation is rare but really causes a problem when it happens.
One of our helpers managed to bend the pilot shaft on our brake lathe......visibly bent if you looked close enough. We turned a fair number of rotors on that lathe before the problem was corrected. No rechecks on them.
People just say the rotors are warped. They are just not of uniform thickness anymore. Could be wear or pad transfer material. Replacing the rotors almost always fixes the problem (for awhile).
How many shops use a dial gauge on brake rotors?
This comes up surprisingly often. I still contend the most common cause of pulsation is pad transfer. Most pulsation concerns can be fixed with a roloc disk and an angle die grinder. Machining those "warped" rotors on a lathe does nothing more than clean the garbage from the surface.
Dial indicators- Used them constantly for brakes. The big secret......ck the runout on a set of rotors not causing vibration concerns. Sort of eye opening. Have seen rotors out .020"+ and stop smoothly (ruins your caliper slides and/or whatever your pads rub on). Actual rotor thickness variation is rare but really causes a problem when it happens.
One of our helpers managed to bend the pilot shaft on our brake lathe......visibly bent if you looked close enough. We turned a fair number of rotors on that lathe before the problem was corrected. No rechecks on them.
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Originally Posted By: The_Eric
Originally Posted By: cat843
How many shops use a dial gauge on brake rotors?
Mine. I start off by cleaning the bearing hub surface, washing the (new) rotor in hot, soapy water with a Scotch Brite and finishing with a rag. Rinse and blow them dry. Then I apply a layer of anti-seize to the inside of the rotor hat and tighten them down using cone washers in between the rotor and lug nut. I typically shoot for .002" or less run out, and it's not uncommon to need to re-index them on the bearing hub to achieve it. Every now and again I'll get one that simply won't go in spec and the bearing hub is to blame. It's not often it happens, so I don't typically check them.
Originally Posted By: ford46guy
Some parts of the article are correct but you have to realize it is written or endorsed by a company who sells many millions of imported rotors! With today's rotors you need to be ultra vigilant that torque specs and patterns are observed and runout is minimized. Old rotors were much heavier and newer cars try to minimize material to save gas.
That's not my experience. Rotors seem to be getting bigger and beefier. Look at a rotor from an 80's or early 90's car of truck and compare it to the same model car or truck from a much later year. BIG difference! Bigger in diameter and thicker braking surfaces too.
Pablum. Off the top of my head, the front rotors on my Caddy (same as a 9C1 Caprice) are BIG. Though only 12" diameter (had to fit in a 15" wheel), they are about an inch thick and, more to the point, they are probably 25lbs of cast iron, which makes for a nice heat sink!
My Magnum's rotors, though a bit bigger (320mm, about 12.5"), were lighter...and warped very easily! (I put a caliper on them: they were WARPED.)
Originally Posted By: cat843
How many shops use a dial gauge on brake rotors?
Mine. I start off by cleaning the bearing hub surface, washing the (new) rotor in hot, soapy water with a Scotch Brite and finishing with a rag. Rinse and blow them dry. Then I apply a layer of anti-seize to the inside of the rotor hat and tighten them down using cone washers in between the rotor and lug nut. I typically shoot for .002" or less run out, and it's not uncommon to need to re-index them on the bearing hub to achieve it. Every now and again I'll get one that simply won't go in spec and the bearing hub is to blame. It's not often it happens, so I don't typically check them.
Originally Posted By: ford46guy
Some parts of the article are correct but you have to realize it is written or endorsed by a company who sells many millions of imported rotors! With today's rotors you need to be ultra vigilant that torque specs and patterns are observed and runout is minimized. Old rotors were much heavier and newer cars try to minimize material to save gas.
That's not my experience. Rotors seem to be getting bigger and beefier. Look at a rotor from an 80's or early 90's car of truck and compare it to the same model car or truck from a much later year. BIG difference! Bigger in diameter and thicker braking surfaces too.
Pablum. Off the top of my head, the front rotors on my Caddy (same as a 9C1 Caprice) are BIG. Though only 12" diameter (had to fit in a 15" wheel), they are about an inch thick and, more to the point, they are probably 25lbs of cast iron, which makes for a nice heat sink!
My Magnum's rotors, though a bit bigger (320mm, about 12.5"), were lighter...and warped very easily! (I put a caliper on them: they were WARPED.)
I'm so sick of this topic, I can't believe it still comes up.
I have experienced so many scenarios that cause brake vibration with properly torqued and indexed parts, on so many vehicles (including sportbikes). The common thread is the rotors turn blue or gold and then starts to shake mid race. shaking never goes away. Replace rotors, problems are gone.
I will adopt whatever word is a suitable replacement for warped, but it won't change what happens.
I have experienced so many scenarios that cause brake vibration with properly torqued and indexed parts, on so many vehicles (including sportbikes). The common thread is the rotors turn blue or gold and then starts to shake mid race. shaking never goes away. Replace rotors, problems are gone.
I will adopt whatever word is a suitable replacement for warped, but it won't change what happens.
industry needs to provide better brakes or teach the service industry about how to fix this problem.
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