Rust on the other side of the rotor?
Sounds like a rust spot.
Sounds like a rust spot.
Warped Rotor got better by itself?
Weird. I don't drive the car a lot, sometimes go a week or so without driving it. Earlier this year, after the car had been parked for better than two weeks, when I drove it I had a pulsing in the steering when I applied the brakes. Classic warped rotor feel. Left front, since the steering wheel got tugged lightly to the left with each pulse. Couldn't figure out how a rotor had warped since the previous drive when it wasn't warped was not in the least bit abusive. Did a couple of high speed "stand on it" braking maneuvers on the off chance I had a rough/rust spot from where the pad had been sitting against the rotor while the car wasn't being driven. This did not change the issue at all. So I've been living with it all summer because I don't really drive it a lot and I am too lazy to do the work to fix it. But. Last week I took the car out for a drive and the pulsing was almost nonexistent. Drove it again today and laid on the brakes hard and I can barely feel the problem anymore. It was best characterized as "severe" and now it's "hardly noticeable".
WTF? Warped rotors don't get better by themselves. At least, not in my 40+ years of automotive experience. The outside face of the rotor looks fine.
Anyone have any suggestions as to what's going on?
WTF? Warped rotors don't get better by themselves. At least, not in my 40+ years of automotive experience. The outside face of the rotor looks fine.
Anyone have any suggestions as to what's going on?
1 - 20 of 26 Posts
Sounds more like you had a deposit of pad material on the rotor and it wore off with your "spirited" braking.
Agree.Sounds more like you had a deposit of pad material on the rotor and it wore off with your "spirited" braking.
Wife pulled the rotors and had them turned for you.
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
In my experience, 'warped rotor' is an over-used indictment that seems accurate in many cases because the path to fixing the rotor likely will incidentally repair the actual cause of the issue...none the wiser. Rusty, sticking pad retaining pins, contaminated or loose-fitting pads, rusty, sticky, jammed pad shims, misaligned or loose parts, bushing or bearing wear...various other things that go unnoticed under the warped rotor umbrella.
I hear what you're all saying, but this was really grabby. And no noise to suggest something was loose anywhere. Given that bent metal isn't going to unbend, and loose stuff isn't going to retighten itself, but the problem has definitely gone away, I have to think it was something on the rotor, like a spot of grease or something, and sufficient time and maybe a few nights of heavy rain (car lives outside) managed to clean it off. I should probably crawl under the car and look at the back side...
In a previous life I was a rotor manufacturing engineer with Bosch. I got to participate in a lot of FMEA's and learned way more than I ever wanted to know about rotors. Like MrSurly said, warped is an overused term. It's too generic. If a rotor was "warped" like a pringles chip like most people imagine, you'd never feel it. With a floating caliper, the caliper would shift back and forth on the pins and the piston would never move. With a fixed caliper and opposing pistons, the pistons would shift back and forth so that one is going in while one is coming out. Effectively you'd never feel that.
What you feel in the pedal is "thickness variation". If you put a mic on the caliper you'd have a thicker spot in one area than the rest. TV will make the piston retract in a floating caliper and make an opposing piston caliper push both pistons in. Both of those you'll feel in the pedal. There are three common causes of TV.
1. Manufacturing problems. The Bosch OEM rotors were held to TV of less than 10 microns (.0004") if I remember correctly. We could do this with turning in a lathe, but mostly used a double disc grinder. How you hold the rotor as it's turned has the biggest impact on it's TV. The double disc grinding is what you get with a high end rotor vs the chinese or indian made autozone special that usually just turned with no thought to how it's chucked in the lathe.
2. The other issue is inherent with rotors. Usually, when the blanks are cast, they are standing up due to the continuous mold press. The hot cast iron is poured in the top of the mold into a runner. Once the mold is full, that runner cools fastest because it has the least sand as an insulator. The faster cast iron cools the harder it becomes. That hard spot never goes away and as your rotors wear, it wears the least. So you get a spot where the rotor is slightly thicker, ie TV. The plant we used for castings (Thyssenkrupp Waupaca in Tell City, IN) has a specific spru/riser design to minimize this hard spot or actually make more of them, but it was still there.
3. Last is material stuck to the rotor, rust, pad material etc. This is the only one that will go away.
What you feel in the pedal is "thickness variation". If you put a mic on the caliper you'd have a thicker spot in one area than the rest. TV will make the piston retract in a floating caliper and make an opposing piston caliper push both pistons in. Both of those you'll feel in the pedal. There are three common causes of TV.
1. Manufacturing problems. The Bosch OEM rotors were held to TV of less than 10 microns (.0004") if I remember correctly. We could do this with turning in a lathe, but mostly used a double disc grinder. How you hold the rotor as it's turned has the biggest impact on it's TV. The double disc grinding is what you get with a high end rotor vs the chinese or indian made autozone special that usually just turned with no thought to how it's chucked in the lathe.
2. The other issue is inherent with rotors. Usually, when the blanks are cast, they are standing up due to the continuous mold press. The hot cast iron is poured in the top of the mold into a runner. Once the mold is full, that runner cools fastest because it has the least sand as an insulator. The faster cast iron cools the harder it becomes. That hard spot never goes away and as your rotors wear, it wears the least. So you get a spot where the rotor is slightly thicker, ie TV. The plant we used for castings (Thyssenkrupp Waupaca in Tell City, IN) has a specific spru/riser design to minimize this hard spot or actually make more of them, but it was still there.
3. Last is material stuck to the rotor, rust, pad material etc. This is the only one that will go away.
Yeah. #3 for the win, I guess.
Appreciate everyone's feedback. Thanks!
Appreciate everyone's feedback. Thanks!
Mike
Can't remember where, but I remember reading or being told that hard braking to a complete stop on warm brakes and remaining stationary -- almost running through a red light and sitting still waiting for it to change -- was the largest cause of warped rotors. Bullshit or no?
Can't remember where, but I remember reading or being told that hard braking to a complete stop on warm brakes and remaining stationary -- almost running through a red light and sitting still waiting for it to change -- was the largest cause of warped rotors. Bullshit or no?
Probably not true. More likely would be to have extremely hot brakes and get a huge dump of water on part of the rotor. You probably couldn't get enough water without running through a puddle deep enough to be up to the rotor.
Think about drag racing. I can slow my car from 140 and stop at the ticket booth and nothing happens.
Think about drag racing. I can slow my car from 140 and stop at the ticket booth and nothing happens.
Rotors don't warp. They get "pad transfer" problems, which creates high spots on the rotor. I tried sanding them off in place, to no avail. You can swap pads to an aggressive pad, and remove the material buildup that way, or run the shiiit out of the brakes like you did. and you re-bedded the pads.
I changed my rotors because of pad transfer. The factory pads seem to have a problem with material transfer.
I changed my rotors because of pad transfer. The factory pads seem to have a problem with material transfer.
Years ago I read an article from a NASCAR pit mgr (don’t remember who) he said he rarely if ever saw warped rotors, despite drivers telling him otherwise. Problem almost always was pad relatedIn my experience, 'warped rotor' is an over-used indictment that seems accurate in many cases because the path to fixing the rotor likely will incidentally repair the actual cause of the issue...none the wiser. Rusty, sticking pad retaining pins, contaminated or loose-fitting pads, rusty, sticky, jammed pad shims, misaligned or loose parts, bushing or bearing wear...various other things that go unnoticed under the warped rotor umbrella.
Good explanation from Mean Mike on this topic. I always wondered if the cheap rotors are ever “normalized” metalurgically after being cast and before they are machined, to stop them from warping the first time they heat cycle during normal operation.
I have had new rotors warp .002”-.004” when new, and you could feel it in the brake pedal.
Fortunately, my family had a machine shop and I could turn the rotors to .0005”-.001” runout.
This is why you don’t buy cheap rotors.
I have had new rotors warp .002”-.004” when new, and you could feel it in the brake pedal.
Fortunately, my family had a machine shop and I could turn the rotors to .0005”-.001” runout.
This is why you don’t buy cheap rotors.
The only normalizing even our US cast rotors had was time. If the foundry wasn't keeping up, we'd be cutting freshly cast rotors as soon as they hit our floor and they were hell on tooling. If we could let them sit 2 weeks, they cut much better. I don't think anyone ever figured out what was going on there, but it could be seen in tool life. How that plays out long term for the end user is anyones guess.
It was more likely an ABS glitch, I went through this on my 2012 Vagon, had high speed braking pulsation, had the rotors check, even had them turned. I suspect you are experiencing something similar.Weird. I don't drive the car a lot, sometimes go a week or so without driving it. Earlier this year, after the car had been parked for better than two weeks, when I drove it I had a pulsing in the steering when I applied the brakes. Classic warped rotor feel. Left front, since the steering wheel got tugged lightly to the left with each pulse. Couldn't figure out how a rotor had warped since the previous drive when it wasn't warped was not in the least bit abusive. Did a couple of high speed "stand on it" braking maneuvers on the off chance I had a rough/rust spot from where the pad had been sitting against the rotor while the car wasn't being driven. This did not change the issue at all. So I've been living with it all summer because I don't really drive it a lot and I am too lazy to do the work to fix it. But. Last week I took the car out for a drive and the pulsing was almost nonexistent. Drove it again today and laid on the brakes hard and I can barely feel the problem anymore. It was best characterized as "severe" and now it's "hardly noticeable".
WTF? Warped rotors don't get better by themselves. At least, not in my 40+ years of automotive experience. The outside face of the rotor looks fine.
Anyone have any suggestions as to what's going on?
Ages ago I owned and ran an import auto parts store. Our biggest supplier for rotors and pads was REPCO (ITM) out of OZ. I really miss their Metal Master pads...
Anyway, we sold a LOT of rotors for Euro cars. At the time, the typical rotor for MB or Volvo was unvented and cheap. So cheap that it made sense to just buy new rotors rather than paying to get old rotors turned. And then REPCO told us to tell the customer that there would be no warranty on the new rotors... unless the customer had them TURNED before use. Why did they do this? I never figured it out,. Warranty comebacks on rotors were few. Well as you might guess, rotor sales took a hit. They claimed that the rotors would 'warp' because they were stacked flat on the shelves and over time this would cause them to warp. I called BS, but no matter.
So, I would inform the customer about the warranty requirement (it was printed on a notice in the box as well) but a large percentage didn't bother with turning. And at the same time, other customers would tell me that AutoShack had no such policy.
Anyway, we sold a LOT of rotors for Euro cars. At the time, the typical rotor for MB or Volvo was unvented and cheap. So cheap that it made sense to just buy new rotors rather than paying to get old rotors turned. And then REPCO told us to tell the customer that there would be no warranty on the new rotors... unless the customer had them TURNED before use. Why did they do this? I never figured it out,. Warranty comebacks on rotors were few. Well as you might guess, rotor sales took a hit. They claimed that the rotors would 'warp' because they were stacked flat on the shelves and over time this would cause them to warp. I called BS, but no matter.
So, I would inform the customer about the warranty requirement (it was printed on a notice in the box as well) but a large percentage didn't bother with turning. And at the same time, other customers would tell me that AutoShack had no such policy.
I recently replaced by pads and rotors on my 2016 CTS V and paid premium for GM replacement rotors. After reading Mean Mike response I am glad that I did!
I still have the original rotors and wanted to know if they could be TURNED?
If yes, where could I find someone that has the proper equipment to do this properly?
I still have the original rotors and wanted to know if they could be TURNED?
If yes, where could I find someone that has the proper equipment to do this properly?
There is a minimum thickness number indicated on each rotor. As long as you can clean them up and they're not thinner than that, they're good to go.I recently replaced by pads and rotors on my 2016 CTS V and paid premium for GM replacement rotors. After reading Mean Mike response I am glad that I did!
I still have the original rotors and wanted to know if they could be TURNED?
If yes, where could I find someone that has the proper equipment to do this properly?
thanks!There is a minimum thickness number indicated on each rotor. As long as you can clean them up and they're not thinner than that, they're good to go.
1 - 20 of 26 Posts
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