how often do you need to turn your rotors before getting new ones?

[Zenmervolt]

Originally posted by: Wingznut

Originally posted by: Zenmervolt

Originally posted by: Wingznut

Originally posted by: Delleet
Turning rotors = tax on the stupid.

Do you understand what turning the rotors means? Definitely NOT a useless proceedure.

andylawcc, the mechanic you talked to is very correct.

Yes it is useless. Turning rotors reduces mass and therefor reduces heat dissipation. If a rotor needs to be turned, it should be replaced. Turning rotors is a half-assed way of temporarily ignoring the problem while guaranteeing that it will happen again and faster.

And I should point out that turning rotors is _not_ the same as re-surfacing rotors, which is done when pads are replaced to help them bed-in a little better. Turning rotors is done after warpage.

ZV

I guess I'm not understanding the semantics here... What I define as "turning" involves putting the rotor on a lathe and taking off the least amount of metal necessary to get the job done. But then again, "re-surfacing" means the same to me.

You must be talking about using a disc grinder (or drill) to hone a cross-hatch pattern on the rotor. I guess I never really had a term for that, but did it with every brake job... Even with new rotors.


When doing brakes, the rotor never wears perfectly even. Even with normal wear, there are pretty much always grooves and always some semblence of warpage. It is incredibly rare that you could take .001" off of a rotor on a lathe and have the job be done. There are always spots still left unfinished.

Besides, how would you measure warpage to determine if they needed to be turned or not? Mount a dial gauge caliper on the vehicle and actually measure it every time you do a brake job???

Doesn't take that long to check with a dial guage, though I usually only bother with that if I'm getting a pulsing back through the brakes. There's a spec for maximum warpage and as long as it's under that, I don't worry about it.

And yeah, I was using "re-surfacing" to refer to honing the rotors and "turning" to refer to actually putting the rotor on a lathe.

I just have a bit of a phobia about putting a rotor on a lathe to bring it back to true. If it warped with the original mass, it'll warp that much faster with the mass taken off by the lathe. Would rather just replace it if it's too warped and be done with it. But I'm anal-retentive.

ZV

 

[zoiks]

It all depends. My rotors cost about 80 dollars each and the entire brake job cost about 125 for the front axle. Your mechanic should have a book that shows how thin the rotor plate can be for any type of car. I think the values differ from car to car too.

 

[OS]

Originally posted by: CadetLee

Originally posted by: OS
Supposedly $25 autozone rotors are pretty good.

The only time they've given me trouble is when I've had stuck calipers..but I'm replacing them with Brembo next time -- it's only $16 more for the pair..

Dunno, depending on who you ask, the brembo blanks are no better or worse.

 

[virtueixi]

Originally posted by: Delleet

Originally posted by: Wingznut

Originally posted by: Delleet
Turning rotors = tax on the stupid.

Do you understand what turning the rotors means? Definitely NOT a useless proceedure.

andylawcc, the mechanic you talked to is very correct.

Yes, I know what it means. I didn't say it was useless, I come to my conclusion because a) new rotors are often cheaper to buy and install than having old ones turned (and thus shortening their effective life anyways), b) getting your rotors turned is very often in line with getting your brake light fluid replaced, and c) if your rotors ARE actually in need of turning it's probably because you're stupid and don't drive well (you brake poorly).

So, does turning rotors serve a purpose? Sure. Whether or not it actually needs to be done depends on how stupid you are

While it definitely shortens your rotor life (Any shorter than replacing them?), I don't think turning your rotors is as stupid as you suggest. Especially since most OEM rotors are great quality and cost around $80- $100 each in many cases. So your saying that if you need your rotors turned you are stupid? Even though you are supposed to turn or replace them with new brake pads? Also, some metallic brake pads can wear out rotors pretty quick, so I would not neccessarly relate that to driving style/stupidity.

 

[Delleet]

Originally posted by: virtueixi

Originally posted by: Delleet

Originally posted by: Wingznut

Originally posted by: Delleet
Turning rotors = tax on the stupid.

Do you understand what turning the rotors means? Definitely NOT a useless proceedure.

andylawcc, the mechanic you talked to is very correct.

Yes, I know what it means. I didn't say it was useless, I come to my conclusion because a) new rotors are often cheaper to buy and install than having old ones turned (and thus shortening their effective life anyways), b) getting your rotors turned is very often in line with getting your brake light fluid replaced, and c) if your rotors ARE actually in need of turning it's probably because you're stupid and don't drive well (you brake poorly).

So, does turning rotors serve a purpose? Sure. Whether or not it actually needs to be done depends on how stupid you are

While it definitely shortens your rotor life (Any shorter than replacing them?), I don't think turning your rotors is as stupid as you suggest. Especially since most OEM rotors are great quality and cost around $80- $100 each in many cases. So your saying that if you need your rotors turned you are stupid? Even though you are supposed to turn or replace them with new brake pads? Also, some metallic brake pads can wear out rotors pretty quick, so I would not neccessarly relate that to driving style/stupidity.

What honest person told you that you need to turn or replace your rotors with every pad change? That's a load of BS right there, which just goes to show you've fallen for the ploy (do you also get a transmission "flush" when servicing your transmission?). What does pad composition wearing out rotors quickly have *anything* to do with turning your rotors? I didn't say wear = stupidity. You don't turn rotors because they're worn, you turn them because you've warped them.

 

[Wingznut]

Originally posted by: Delleet
What does pad composition wearing out rotors quickly have *anything* to do with turning your rotors? I didn't say wear = stupidity. You don't turn rotors because they're worn, you turn them because you've warped them.

Quite a bit, actually... Rotors do wear, and they wear uneven. Not only that, but they glaze also.

Turning the rotors gives the new pads a perfectly flat surface to seat into. No, you don't "have" to turn them, as is proven every day. But to NOT machine them is so much more "half-ass" than not doing anything with them.


In short... Machining the rotors and honing them with a cross-hatch pattern will result in a much better performing brake system than not doing anything at all.

 

[TechnoKid]

If you have thickness variation in the rotor, and excessive runout, this could cause what would be perceived as rotor warpage. Of course, if you have thickness variation, you likely do not have parallel rotor faces. TIR, total index runout, has much to do with what is percieved as rotor warpage/steering wheel shimmy.

Rotor warpage could be something as simple [and complicated at the same time] as uneven pad-to-rotor surface deposits. If you have uneven pad deposits, you will have high and low spots on the rotor suraface, it only takes as little as .005" of thickness variation to feel it throught the pedal. Uneven pad deposits can be caused by many factors, but the pad and its composistion is the most likely cause, with how the brakes are used a second.

I usually get brembo blanks instead of turning when i do my own brake jobs, cheap enough ($30ea for hondas, $50ea for german cars) because I don't alwyas have access to my school auto shop's brake lathe. Bits/tips can get expensive too for the lathe.

Slotted/drilled/dimpled and what have you; the thing these really do is reduce rotor mass, and therefore reduce the heatsink ability of the rotor, likely leading to increased heat related rotor failures.

i may have mistated some stuff, im really tired. i prob forgot some stuff i've learned in class. i will correct and update tomorrow.

 

[QuitBanningMe]

Originally posted by: Wingznut

Originally posted by: Delleet
What does pad composition wearing out rotors quickly have *anything* to do with turning your rotors? I didn't say wear = stupidity. You don't turn rotors because they're worn, you turn them because you've warped them.

Quite a bit, actually... Rotors do wear, and they wear uneven. Not only that, but they glaze also.

Turning the rotors gives the new pads a perfectly flat surface to seat into. No, you don't "have" to turn them, as is proven every day. But to NOT machine them is so much more "half-ass" than not doing anything with them.


In short... Machining the rotors and honing them with a cross-hatch pattern will result in a much better performing brake system than not doing anything at all.

With all due respect and being aware of your past occupation I have never seen glazed rotors. I have seen glazed pads and a couple passes on flat concrete fixes that. I have also not seen any significant wear to the rotaors through normal use. If you let the brake pad dwindle to nothing you will score them, if they are substandard metal or they change temperatures quickly you will warp them. Then theywill need to be turned. However turning them or honing them is not going to give you any noticable performance difference.

 

[Delleet]

Originally posted by: QuitBanningMe

Originally posted by: Wingznut

Originally posted by: Delleet
What does pad composition wearing out rotors quickly have *anything* to do with turning your rotors? I didn't say wear = stupidity. You don't turn rotors because they're worn, you turn them because you've warped them.

Quite a bit, actually... Rotors do wear, and they wear uneven. Not only that, but they glaze also.

Turning the rotors gives the new pads a perfectly flat surface to seat into. No, you don't "have" to turn them, as is proven every day. But to NOT machine them is so much more "half-ass" than not doing anything with them.


In short... Machining the rotors and honing them with a cross-hatch pattern will result in a much better performing brake system than not doing anything at all.

With all due respect and being aware of your past occupation I have never seen glazed rotors. I have seen glazed pads and a couple passes on flat concrete fixes that. I have also not seen any significant wear to the rotaors through normal use. If you let the brake pad dwindle to nothing you will score them, if they are substandard metal or they change temperatures quickly you will warp them. Then theywill need to be turned. However turning them or honing them is not going to give you any noticable performance difference.

In Wingznut's defense (didn't see this coming, did you?) I have seen glazed rotors, but only on really old, worn rotors which should just be replaced anyways. Not to say that it couldn't happen earlier, but then again I'd probably relate that to poor braking habits. An old mechanic friend used to laugh and say he'd get some women bringing their cars in with rotors so shiney he could see himself in them.

 

[Pacfanweb]

Originally posted by: Delleet

I don't know anyone that knows anything about cars that has ever turned rotors. On the other hand, I know a lot of women (sorry for the generalization, but it's true) that have had their rotors turned.
[/quote]
You obviously don't know what you're talking about. There are some cars you can get away with not turning the rotors on, and some you really can't.
When you machine/turn/resurface rotors (all the exact same thing), you are getting rid of all the little grooves and imperfections that occurred during the wearing out of the previous set of pads.
Some vehicles have pads that tend to really wear the rotors, some to the point that the rotor is already either at or under its minimum thickness at the end of the pad life, so they usually have to be replaced. The Ford Focus is notorious for this.
Some manufacturers use softer pads, which don't last as long, but are very gentle on the rotors, so they are usually nice and smooth at the end of the pad's life, and often won't require machining.
Others pads are in-between; They don't wear the rotors totally out, but really put a lot of grooves in them, so machining them is necessary so the new pads will seat properly.
To the OP: The minimum thickness on most rotors is stamped ON the rotor itself, usually on the back. If the rotor needs to be machined/turned/resurfaced, (again, all mean the same thing), you are supposed to replace it if it is below the minimum thickness after the machining is done. If it is still over, you are fine.
There isn't a dime's worth of difference in heat disapation or mass resulting from machining a few thousandths of an inch off of a rotor.

 

[cavemanmoron]

Originally posted by: QuitBanningMe
I always replace and never turn rotors. As to the OP's question there is a maximum and minimum rotor thickness which varies depending on the caliper. The rotors can be turned until they reach the minimum thickness.

I have done both,

I see Napa has a better quality rotor available now,for a little more money,
they are a denser casting/forging,and look nice.I may try them the next time.

 

[QuitBanningMe]

Originally posted by: Delleet

Originally posted by: QuitBanningMe

Originally posted by: Wingznut

Originally posted by: Delleet
What does pad composition wearing out rotors quickly have *anything* to do with turning your rotors? I didn't say wear = stupidity. You don't turn rotors because they're worn, you turn them because you've warped them.

Quite a bit, actually... Rotors do wear, and they wear uneven. Not only that, but they glaze also.

Turning the rotors gives the new pads a perfectly flat surface to seat into. No, you don't "have" to turn them, as is proven every day. But to NOT machine them is so much more "half-ass" than not doing anything with them.


In short... Machining the rotors and honing them with a cross-hatch pattern will result in a much better performing brake system than not doing anything at all.

With all due respect and being aware of your past occupation I have never seen glazed rotors. I have seen glazed pads and a couple passes on flat concrete fixes that. I have also not seen any significant wear to the rotaors through normal use. If you let the brake pad dwindle to nothing you will score them, if they are substandard metal or they change temperatures quickly you will warp them. Then theywill need to be turned. However turning them or honing them is not going to give you any noticable performance difference.

In Wingznut's defense (didn't see this coming, did you?) I have seen glazed rotors, but only on really old, worn rotors which should just be replaced anyways. Not to say that it couldn't happen earlier, but then again I'd probably relate that to poor braking habits. An old mechanic friend used to laugh and say he'd get some women bringing their cars in with rotors so shiney he could see himself in them.

Don't get me wrong I have heard (and even seen due to wrong pads contrary to my statement) people talking about glazed rotaors however I have yet to see one that could be fixed by turning rather than replacement. Usually a new set of pads will clear it right up but a quick rubbing of sandpaper can do it to.

 

[Green Man]

I'm not sure if it is because of the Northern climate and all of the salt that is dumped on the roads or what, but in Wisconsin the brake pads often outlast the rotors. Especially of FWD cars, the insides of the rotors rot out so bad that machining or "turning" them won't help. Many times the rotors look like they have blisters on the inside surface, but as soon as they are put on the lathe the blisters open up to huge cancerous sores that get bigger the further they are machined. The resulting pits in the surface cause the brakes to pulsate or shake and 9/10 times they rotors could be machine well past minimum spec with no sign of getting rid of all the pits. In this area there is almost no such thing as machining rotors on a FWD car.

 

[Delleet]

Originally posted by: Pacfanweb

Originally posted by: Delleet

I don't know anyone that knows anything about cars that has ever turned rotors. On the other hand, I know a lot of women (sorry for the generalization, but it's true) that have had their rotors turned.

You obviously don't know what you're talking about. There are some cars you can get away with not turning the rotors on, and some you really can't.
When you machine/turn/resurface rotors (all the exact same thing), you are getting rid of all the little grooves and imperfections that occurred during the wearing out of the previous set of pads.
Some vehicles have pads that tend to really wear the rotors, some to the point that the rotor is already either at or under its minimum thickness at the end of the pad life, so they usually have to be replaced. The Ford Focus is notorious for this.
Some manufacturers use softer pads, which don't last as long, but are very gentle on the rotors, so they are usually nice and smooth at the end of the pad's life, and often won't require machining.
Others pads are in-between; They don't wear the rotors totally out, but really put a lot of grooves in them, so machining them is necessary so the new pads will seat properly.
To the OP: The minimum thickness on most rotors is stamped ON the rotor itself, usually on the back. If the rotor needs to be machined/turned/resurfaced, (again, all mean the same thing), you are supposed to replace it if it is below the minimum thickness after the machining is done. If it is still over, you are fine.
There isn't a dime's worth of difference in heat disapation or mass resulting from machining a few thousandths of an inch off of a rotor.
[/quote]You really didn't say a single thing to counter my points. One would be that you might as well get new rotors rather than paying someone to shorten the life of your existing ones. Also, show me where the small, rather insignificant grooves really need to be machined out. Show me a groove that's so bad that the rotor needs to be machined and I'll show you a rotor that might as well just be replaced.

 

[Pacfanweb]

Originally posted by: Delleet

You really didn't say a single thing to counter my points. One would be that you might as well get new rotors rather than paying someone to shorten the life of your existing ones. Also, show me where the small, rather insignificant grooves really need to be machined out. Show me a groove that's so bad that the rotor needs to be machined and I'll show you a rotor that might as well just be replaced.[/quote]
Don't read/comprehend well, do you? I can show you rotors all day long that should be machined. How many do you want to see? 100? 1000? I've seen thousands and thousands.

And your point about shortening the life of the rotor....that's ridiculous. What shortens the life of the rotor more than replacing it?
There are plenty of cars out there whose rotors cost much more than the price to machine them.
THAT is why you do it.
There are plenty of cars nowadays that come with hard, semi-metallic pads that groove the rotors. You do not want to just pad-slap these cars and not turn them.
The pad won't be contacting all of the rotor surface for quite awhile, resulting in reduced stopping effort.
I'm not talking about huge grooves, either, it doesn't take much. And all you need to do to these rotors is basically smooth them up with the lathe. A few thousandths of an inch will do, and they surface is like new.
Better than paying over 100.00 each for new rotors, and many of them cost that much or more.
Again, I mentioned this in my first post that you said didn't refute anything you'd written.
I suggest you read AND comprehend before you type next time, and leave topics like this to us professionals.

 

[Ausm]

Originally posted by: andylawcc
a mechanic said it depends on various things (rotors quality, driving style, brake pad's quality), but generally he said a rotor can be turned two times before being replaced.
anyone agree?

I do because there are specs on the thickness of the rotors that must be maintained.


Ausm

 

[Wingznut]

Originally posted by: Pacfanweb

Originally posted by: Delleet

You really didn't say a single thing to counter my points. One would be that you might as well get new rotors rather than paying someone to shorten the life of your existing ones. Also, show me where the small, rather insignificant grooves really need to be machined out. Show me a groove that's so bad that the rotor needs to be machined and I'll show you a rotor that might as well just be replaced.

Don't read/comprehend well, do you? I can show you rotors all day long that should be machined. How many do you want to see? 100? 1000? I've seen thousands and thousands.

And your point about shortening the life of the rotor....that's ridiculous. What shortens the life of the rotor more than replacing it?
There are plenty of cars out there whose rotors cost much more than the price to machine them.
THAT is why you do it.
There are plenty of cars nowadays that come with hard, semi-metallic pads that groove the rotors. You do not want to just pad-slap these cars and not turn them.
The pad won't be contacting all of the rotor surface for quite awhile, resulting in reduced stopping effort.
I'm not talking about huge grooves, either, it doesn't take much. And all you need to do to these rotors is basically smooth them up with the lathe. A few thousandths of an inch will do, and they surface is like new.
Better than paying over 100.00 each for new rotors, and many of them cost that much or more.
Again, I mentioned this in my first post that you said didn't refute anything you'd written.
I suggest you read AND comprehend before you type next time, and leave topics like this to us professionals. [/quote]Very well said, Pacfanweb. I was so baffled by the "shortening of the life" comment, that I wasn't even sure how to respond.

Like I mentioned before, it is incredibly rare to put a rotor on the lathe and have it be perfectly flat the first time. It just doesn't happen.