[Mk23]

I essentially have what appears to be a brake pad burn in on my rotors (which are fairly new too). I think the local dealership did it as I was told the service manger test drove the car and applied lots of braking to heat up the brakes for an issue I was having once the brakes were hot. So I think he braked hard down to a dead stop on brand new pads and it burned into the rotor. At least that's what it looks like. I have the etch in on both front rotors and if you run your fingers along the rotors, the rotors are smooth and then when you hit the spot it is rough. I've been having a squeal problem and I got ceramic pads and just happened to notice this on the rotors when cleaning the hubs.

Anyone know if I can get rotors resurfaced? And do I need new pads after it is done? Or can I re-bed in the brake pads I am about to put on? I can wait to put on my new brake pads if need be.

[idrift4wd]

Rotors only need to be resurfaced if they are warped. Meaning there is an uneven braking feel.

you dont exactly need new pads, you could re-bed old pads if you resurface your rotors.

[SharkBait]

Yes, you can get them resurfaced. As for the pads, if the surface looks OK, they should be fine. Rotors do get grooves in them but they should be concentric rings if anything and not too deep. And ceramic pads are more likely to squeal on you.

[williamf]

Originally Posted by SharkBait

Yes, you can get them resurfaced. As for the pads, if the surface looks OK, they should be fine. Rotors do get grooves in them but they should be concentric rings if anything and not too deep. And ceramic pads are more likely to squeal on you.

+1 Exactly

[dreamspeed]

I'm going to say there is a very limited amount of situations where resurfacing the rotors is actually a good idea and/or necessary. I highly doubt your rotors got messed up from some hard breaking at the dealership.

Does it actually feel bad/weird when you are braking ?

[Mk23]

Originally Posted by dreamspeed

I'm going to say there is a very limited amount of situations where resurfacing the rotors is actually a good idea and/or necessary. I highly doubt your rotors got messed up from some hard breaking at the dealership.

Does it actually feel bad/weird when you are braking ?

The braking itself feels good. The problem is that the noise is coming from the front brakes and it squeals every rotation like there is one spot on the rotor that is causing it. FYI the squeal happens from 25mph down to zero when brakes have been heated after 20-40 mins of driving and is sometimes squeals at low speeds after brakes were applied.

It is very rough when you feel the spot on the rotor and it makes me wonder if it might be the squeal. And since when do ceramics make more noise than OEM? I thought ceramics were supposed to be low dust/low noise? I thought that was the whole reason people buy ceramic pads.

[nOshi]

sounds like the infamous brake squeal issue.

[shata]

I agree and disagree with what was said. If its wrapped its trash imho. Reason most people resurface rotors is the edge that gets worn into them from pads. Unless you find place that can do it real cheap these days in some cases its almost cheaper buy all new rotors specially when you consider the price of resurfacing and labor associated with all that. Another thing when you resurface you should get new pads also because the small groves that you have on rotor they are also in the pads cause they match up after miles and miles so if you resurface and use old pads after while your going to have grooves again.

Moral of story: If you can cheaply resurface use new pads, if you cant get new rotors and pads and install them yourself. Price it out.

[JustROLLIN]

I understand that these are high-end cars and therefore folks tend to assume that different rules apply, and in some cases they do. However, I will contend that rotors can be machined on virtually any vehicle, provided you have enough material on the rotor itself. If you have at least 0.030 of metal to cut, before you reach the minimum specification, you should be fine. A typical cut will run 0.030, unless you have a high degree of warping or other conditions that would not allow for a "standard" cut.

The Bentley manual agrees with the above statement, although in metric measurements. It says the max allowable machine work per (front) rotor is 0.8mm or 0.030in.

[JustROLLIN]

Oh, and new pads are not required unless you are below the min thickness. 2.4mm.

I would however, rough up the surface of the pads that will be going back on the car in case they have any grooves, etc.

[ashmostro]

Just flex hone the pad transfer off the rotors and re bed properly. No need to resurface or to buy new rotors just yet...

[Mk23]

Originally Posted by ashmostro

Just flex hone the pad transfer off the rotors and re bed properly. No need to resurface or to buy new rotors just yet...

What is flex honing? I was told I could try emery cloth or sandpaper on the rotors to get a small amount of surface area refinished. Couldn't I do that and just re-bed the brake pads?

[ashmostro]

Flex honing when done per instructions only takes off the pad transfer layer and also introduces a nice irregular hatch pattern on the rotor surface- it does not take off a large amount of material like resurfacing, which simply reduces your thermal capacity (nevermind introducing its own thermal and mechanical stresses!).





You need: Flex Hone bit

Flex Hone oil


Emery cloth works perfectly fine, but flex honing is just much faster and takes less effort.

*Don't* use sandpaper because any silicon left behind can convert into silicon carbide once in operation which can lead to further hardspotting on the rotors, which basically will just make things worse!

[Braumin]

Originally Posted by JustROLLIN

I understand that these are high-end cars and therefore folks tend to assume that different rules apply, and in some cases they do. However, I will contend that rotors can be machined on virtually any vehicle, provided you have enough material on the rotor itself. If you have at least 0.030 of metal to cut, before you reach the minimum specification, you should be fine. A typical cut will run 0.030, unless you have a high degree of warping or other conditions that would not allow for a "standard" cut.

The Bentley manual agrees with the above statement, although in metric measurements. It says the max allowable machine work per (front) rotor is 0.8mm or 0.030in.

First off I agree that the rotors can likely be turned. However rotors seem to be so thin these days that they won't have enough thickness left if you even turn them once. Back in the day, it was rare to change rotors, now, no one turns them anymore.

Also, another reason why I think no one turns rotors anymore is warranty. If you turn rotors for someone (as a shop) and they come back in a month for pulsating brakes, you are screwed. You likely can't turn them again, so you'll need to replace the rotors. You'll have to eat the cost of that initial turning for sure, and possibly some of the next repair to keep the customer happy. That doesn't happen with replacement rotors - they have warranty, so you can just swap them.

Also the time it takes to properly turn rotors is pretty substantial, where as replacing rotors takes about 10 minutes per side. It may take over an hour per rotor to properly turn them.

Nobody turns rotors anymore, at least no one I have seen lately. It just doesn't make business sense anymore.

[JustROLLIN]

Originally Posted by Braumin

First off I agree that the rotors can likely be turned. However rotors seem to be so thin these days that they won't have enough thickness left if you even turn them once. Back in the day, it was rare to change rotors, now, no one turns them anymore.

Also, another reason why I think no one turns rotors anymore is warranty. If you turn rotors for someone (as a shop) and they come back in a month for pulsating brakes, you are screwed. You likely can't turn them again, so you'll need to replace the rotors. You'll have to eat the cost of that initial turning for sure, and possibly some of the next repair to keep the customer happy. That doesn't happen with replacement rotors - they have warranty, so you can just swap them.

Also the time it takes to properly turn rotors is pretty substantial, where as replacing rotors takes about 10 minutes per side. It may take over an hour per rotor to properly turn them.

Nobody turns rotors anymore, at least no one I have seen lately. It just doesn't make business sense anymore.

I can assure you that many, many people/shops still turn rotors. I cannot speak for BMW facilities as I do not work with them very often, but for the large majority of repair facilities, dealers included, they still turn rotors on nearly every make and model. I work with repair shops of all types all day long in my line of work as well as being an ASE certified master tech...its not yet a thing of the past.

I do not disagree that manufacturers are going lighter and lighter on rotor weight/thickness as this is unsprung weight and can have an impact on your MPG. And, that if you cut rotors too thin, you will warp them more quickly the second time around. All that said, they can still be turned, provided you are careful with the specs.

[DanielGonz]

Originally Posted by JustROLLIN

I understand that these are high-end cars and therefore folks tend to assume that different rules apply, and in some cases they do. However, I will contend that rotors can be machined on virtually any vehicle, provided you have enough material on the rotor itself. If you have at least 0.030 of metal to cut, before you reach the minimum specification, you should be fine. A typical cut will run 0.030, unless you have a high degree of warping or other conditions that would not allow for a "standard" cut.

The Bentley manual agrees with the above statement, although in metric measurements. It says the max allowable machine work per (front) rotor is 0.8mm or 0.030in.

LOL at all the wanna-be metallurgists and mechanical engineers in this thread…

[ashmostro]

You mean materials engineer?

Granted, i haven't been in the trade for about ten years, but still...

Just going there cuz you did!

[Mk23]

Would just like to give an update on what I did and the effect it had.

I sanded the rotors with 120 grit sandpaper using lots and lots of brake cleaner while doing it. May have not been the best method based on what some of you say, but it worked. No more squeal, and brakes feel great!

I happened to miss the post about brake honing and the bit used otherwise I would have gone that route. But hopefully everything worked out okay and I won't have any future issues. I'm guessing if I haven't seen/heard any extra etchings into the rotor by now (3-5 days after) that I should be good?