Rust...why?

Gents. Been watching the forum on the fringe for awhile. Over this time, the board been helpful on a number of cases that have assisted me trouble shoot when needed. However, I've come across an issue on my 2012 335i w/o a reference. In the pics below, you'll see my rear brakes housing group w/ rust. I'm not sure if this is a natural occurrence or if the factory missed treating the part or left a part of entirely. Just looking to engage the audience for feedback and guidance.

rotors are made of cast iron, both the rotors themselves and the iron dust from normal wear will rust... the rotors are usually lightly cadmium plated to prevent rusting during parts storage, the coating is designed to wear off quickly and expose the cast iron.

if it bothers you, you can sand/, mask, then hi temp paint the rotor hats. its not a materials defect, here in the north east, most rotor rats will look like that or alot worse. the chemicals used at car washes for brake dust removal seem to accelerate the rusting. being near the ocean will also accelerate the corrosion

Seems to me like BMW has a lot of rust issues. And BF has a lot of BMW apologists who don't give a hoot about your problem so long as it doesn't affect them.
http://www.bimmerfest.com/forums/sho...d.php?t=678606
I suggest you Google your problem to ascertain if it's a known issue or isolated to your particular vehicle.

Appreciate the input and explanation.

BMW's logic just doesn't compute on my smell checker here. I treat my wife's Enclave and all other vehicles I've owned over the years w/o the signs of corrosion. Gross oversight BMW.

Thanks for the rudder steer Pappy.

Originally Posted by Orient330iNYC

rotors are made of cast iron, both the rotors themselves and the iron dust from normal wear will rust... the rotors are usually lightly cadmium plated to prevent rusting during parts storage, the coating is designed to wear off quickly and expose the cast iron.

if it bothers you, you can sand/, mask, then hi temp paint the rotor hats. its not a materials defect, here in the north east, most rotor rats will look like that or alot worse. the chemicals used at car washes for brake dust removal seem to accelerate the rusting. being near the ocean will also accelerate the corrosion

this.

Originally Posted by ReddRight88

Appreciate the input and explanation.

BMW's logic just doesn't compute on my smell checker here. I treat my wife's Enclave and all other vehicles I've owned over the years w/o the signs of corrosion. Gross oversight BMW.

Thanks for the rudder steer Pappy.

You haven't been paying very close attention over the years. This type of rust on brake rotors is not unique to BMW in any way, shape or form. It occurs across the board with virtually every vehicle manufactured on the planet and has for at least the more than thirty years I've been driving.

Originally Posted by tturedraider

this.

You haven't been paying very close attention over the years. This type of rust on brake rotors is not unique to BMW in any way, shape or form. It occurs across the board with virtually every vehicle manufactured on the planet and has for at least the more than thirty years I've been driving.

Totally agree w/ everything you said about rotors. However, the rotors aren't the issue here. It's the brake housing group our whatever the component is called in the picture above. Not sure what the proper name is, but it supports the linkage joining the tire to the car.

Originally Posted by ReddRight88

Totally agree w/ everything you said about rotors. However, the rotors aren't the issue here. It's the brake housing group our whatever the component is called in the picture above. Not sure what the proper name is, but it supports the linkage joining the tire to the car.

Looks like what is called the HAT of the rotor or the FLANGE of the wheel, or both. Hard to make out from the picture.

Originally Posted by Jamesonsviggen

Looks like what is called the HAT of the rotor or the FLANGE of the wheel, or both. Hard to make out from the picture.

You nailed it. Just Googled it and the description matches the root issue. Appreciate the assist. Interesting to note, on the front wheels the car has a protective shield or guard. The rear is w/o.

Originally Posted by ReddRight88

You nailed it. Just Googled it and the description matches the root issue. Appreciate the assist. Interesting to note, on the front wheels the car has a protective shield or guard. The rear is w/o.

I havent looked into it that much but I think bmw is using a 2 piece rotor up front, which is why the "hat" looks like a shield. the rear is still a one piece. The rotor and the hat are the same unit, one piece cast iron.



Sent from my GT-N7105 using Bimmer App

Originally Posted by Orient330iNYC

The rotor and the hat are the same unit, one piece cast iron.

This. The hat IS PART of the rotor. So, I'll say it again, you haven't been paying very close attention over the years.

Originally Posted by tturedraider

This. The hat IS PART of the rotor. So, I'll say it again, you haven't been paying very close attention over the years.

There's always one....

Originally Posted by ReddRight88

Gents. Been watching the forum on the fringe for awhile. Over this time, the board been helpful on a number of cases that have assisted me trouble shoot when needed. However, I've come across an issue on my 2012 335i w/o a reference. In the pics below, you'll see my rear brakes housing group w/ rust. I'm not sure if this is a natural occurrence or if the factory missed treating the part or left a part of entirely. Just looking to engage the audience for feedback and guidance.

Attachment 364489

Attachment 364490

My wife's 535xi had the same problem. Our dealer painted the wheel or brake "hubs" (remember hub caps?) under warranty and they have not rusted through since '09. My SA told me at the time that it is most prevalent with cars driven short distances to work and where the brakes don't have a chance to really heat up and burn the moisture off of the brake assembly. Whether I buy this or not, I'm not sure. Our '11 M3 has some rust on the hubs and it's getting worse. This car is a daily driver of 30 miles each way to work.

Our '11 Audi S4 has a discoloration on the brake hubs but not rust. I think it's from the brake dust. My 335is does not have any rust issues there but it usually only gets driven in nice weather. None of our American cars have ever had the problem.

Originally Posted by tturedraider

this.

You haven't been paying very close attention over the years. This type of rust on brake rotors is not unique to BMW in any way, shape or form. It occurs across the board with virtually every vehicle manufactured on the planet and has for at least the more than thirty years I've been driving.

I think this problem is mostly with BMWs. None of our other car have had this issue including cars made by Mercedes, Audi, Porsche, VW, Chevy, Nissan, Jeep, Ford, etc. Our '01 BMW 740il never had this problem. Our '08 BMW did. Our '11 M3 has some and it's starting to get worse.

I just checked the hubs on my '08 Tahoe with 63,000 miles on the odometer. No rust whatsoever. GM uses a medium to dark grey paint on the hubs and they still look new. The same finish was on my '09 Corvette ZO6 and it too had no rust.

The other thing GM does right is to design wheels that cover the brake hub, so even if it did rust, you can't see it.

Originally Posted by beden1

My wife's 535xi had the same problem. Our dealer painted the brake "hubs" under warranty and they have not rusted through since '09. My SA told me at the time that it is most prevalent with cars driven short distances to work and where the brakes don't have a chance to really heat up and burn the moisture off of the brake assembly. Whether I buy this or not, I'm not sure. Our '11 M3 has some rust on the hubs and it's getting worse. This car is a daily driver of 30 miles each way to work.

Our '11 Audi S4 has a discoloration on the brake hubs but not rust. I think it's from the brake dust. My 335is does not have any rust issues there but it usually only gets driven in nice weather. None of our American cars have ever had the problem.

Likewise, all my US owned vehicles never had this issue. Same can be said for my Japanese owned cages. Thanks for the confirmation beden1 -- we'll see what the service rep has to say after I use the warranty alibi for justification.

Rust is oxidation. AS previously stated this is common in all makes/models.
Walk through car lots after rainy weather. Common.

Originally Posted by beden1

I think this problem is mostly with BMWs. None of our other car have had this issue including cars made by Mercedes, Audi, Porsche, Chevy, Nissan, Jeep, Ford, etc. Our '01 BMW 740il never had this problem. Our '08 BMW did. Our '11 M3 has some and it's starting to get worse.

Oh, don't tell him that, you'll become BMW apologist. The point is my front AND rear rotor hub on the DRIVER side are completely rusted. Both front and rear on passenger side look like OP's pictures (some rust, but almost like new). It seems pretty obvious to me that slush from salted roads thrown at you from vehicles you pass coming from opposite directions are causing this non-issue. Disgusting looking nonetheless.

Even stranger is the fact that my Jetta TDI that rides these same roads 4 years longer than my BMW has no such issue.

Originally Posted by dalekressin

Rust is oxidation. AS previously stated this is common in all makes/models.
Walk through car lots after rainy weather. Common.

Not talking about the brake discs. They quickly rust from oxidation. Talking about the hub, and it's not a problem on all makes of cars.

Originally Posted by Mark K

Oh, don't tell him that, you'll become BMW apologist. The point is my front AND rear rotor hub on the DRIVER side are completely rusted. Both front and rear on passenger side look like OP's pictures (some rust, but almost like new). It seems pretty obvious to me that slush from salted roads thrown at you from vehicles you pass coming from opposite directions are causing this non-issue. Disgusting looking nonetheless.

Even stranger is the fact that my Jetta TDI that rides these same roads 4 years longer than my BMW has no such issue.

We agree then. Your BMW has the rusted hubs. Your VW did not?

It is a cosmetic issue and not a structural problem non-the-less.

Originally Posted by beden1

We agree then. Your BMW has the rusted hubs. Your VW did not?

It is a cosmetic issue and not a structural problem non-the-less.

Correct. And that's why I'm not making an issue out of it. Nice, however, it isn't. Normal neither, considering other makes you and I had owned. As a matter of fact, it pis*es me off just a little. Especially when I put on OEM summer tires rims (those in sig picture).

I have also encountered it on a variety of aftermarket rotor hubs. Some brands rusted, others the coating was top notch. Sometimes OEMs even swap brake manufacturers. I would have non rusty ones for my Viggen, buy new OEM and then they rusted, come to find out they went from being made in Sweden to being made in Asia.

Originally Posted by Jamesonsviggen

I have also encountered it on a variety of aftermarket rotor hubs. Some brands rusted, others the coating was top notch. Sometimes OEMs even swap brake manufacturers. I would have non rusty ones for my Viggen, buy new OEM and then they rusted, come to find out they went from being made in Sweden to being made in Asia.

If they rust, just do what I did and have the dealer paint them under warranty. My dealer was really good about it, and was the one who offered to paint them.

Originally Posted by Jamesonsviggen

I have also encountered it on a variety of aftermarket rotor hubs. Some brands rusted, others the coating was top notch. Sometimes OEMs even swap brake manufacturers. I would have non rusty ones for my Viggen, buy new OEM and then they rusted, come to find out they went from being made in Sweden to being made in Asia.

Rotor hubs. I think you nailed it.

The brake calipers on our 535xi are also rusting, which is another reason why I'm pissed that BMW does not have finished brake calipers. Unfortunately, these started rusting after the original warranty ran out.