Painting Rusted Rotor Bells on M35?

[40belowceo]

Hey All,

So winter is finally here in NYC. I plan on getting new rims/tires when spring arrives and I also want to do something about my rear rusted rotor bells. Besides looking ugly on my M, they still function properly and I don't want to purchase new ones so I thought about painting them. Has anyone else done this to their rotors? See a pic of one of them below.



I read somewhere that you can sand them down a little and purchase hi-temp paint in either silver or black and it will make them look brand new. I am thinking this will be the cheapest solution to make them look nice. I would hate to have the bells rusted sitting on a new pair of 20" rims.

Any thoughts or suggestions?

Thanks as always...

[elwesso]

You can use a high temp paint, like you would use on a grill or something.. The key is making sure you get all the rust off and it's nice and clean. I would personally use a high temp primer too.

[40belowceo]

Another Pic.

[40belowceo]

You can use a high temp paint, like you would use on a grill or something.. The key is making sure you get all the rust off and it's nice and clean. I would personally use a high temp primer too.

Thanks elwesso. So primer than paint got it. Any suggestions on what kind of sandpaper to use? How long will it take to get that rust off?

[elwesso]

It all depends how much rust is there. I would probably suggest hitting it with a wire brush first, then maybe some 120 grit sandpaper.. I wouldn't worry about going too much further than 120 grit since you probably aren't worried about getting a perfect surface finish, and the surface will smooth out with more coats of paint.

After you get it down to bare metal, be sure to wipe it down real good with acetone or something to clean the surface really good. Remember the better that your surface is prepared, the better the paint will look and the longer it will last.

I would expect to have at least an hour per corner of prep and paint per corner...

[40belowceo]

It all depends how much rust is there. I would probably suggest hitting it with a wire brush first, then maybe some 120 grit sandpaper.. I wouldn't worry about going too much further than 120 grit since you probably aren't worried about getting a perfect surface finish, and the surface will smooth out with more coats of paint.

After you get it down to bare metal, be sure to wipe it down real good with acetone or something to clean the surface really good. Remember the better that your surface is prepared, the better the paint will look and the longer it will last.

I would expect to have at least an hour per corner of prep and paint per corner...

Awesome thanks! I was also looking into Metal Rescue rust remover. Might be less of a hassel but I will look into it.

[atlM35]

http://www.ebay.com/sch/i.html?_sacat=0 ... _PrefLoc=1

[elwesso]

Awesome thanks! I was also looking into Metal Rescue rust remover. Might be less of a hassel but I will look into it.

Maybe others have used that stuff before, but I've not had a lot of luck using it, especially when using it with the intention of paining over it.. The paint did not stick to that surface very well, and I used primer as well.

Another thing I've used before that works well on rust is POR-15..

http://www.por15.com/

That stuff works really well, I used it to paint some surface rust I had on some underbody parts on my car and it works great. I did it about 2 years ago, and the areas that I painted still look good. It is good to about 450°F.

[40belowceo]

http://www.ebay.com/sch/i.html?_sacat=0 ... _PrefLoc=1

Thanks for the link ATL. Over $300 to get all 4 new. Not too bad but if I can just simply paint my rotors without having to take them off I just may have to go with sanding, priming & painting.

[40belowceo]

Awesome thanks! I was also looking into Metal Rescue rust remover. Might be less of a hassel but I will look into it.

Maybe others have used that stuff before, but I've not had a lot of luck using it, especially when using it with the intention of paining over it.. The paint did not stick to that surface very well, and I used primer as well.

Another thing I've used before that works well on rust is POR-15..

http://www.por15.com/

That stuff works really well, I used it to paint some surface rust I had on some underbody parts on my car and it works great. I did it about 2 years ago, and the areas that I painted still look good. It is good to about 450°F.

wow so no sanding just paint over it with this? Im not too concerned with how smooth it will look because it will really be unnoticeable, just more concerned with removing that rust look on it.

[elwesso]

Actually, I ran across this stuff......

http://www.por15.com/POR-20_p_52.html

The POR-20 is good to 1400F, which should definitely be adequate... It brushes on pretty easily too..

Once you open the can, you can't reuse it, and I think one can would be plenty to do what you're doing. If you could get all 4 tires off the car at the same time that would be best so you could do all the prep work before.

[Mark Mellott]

Greetings, The disc rotor can see temperatures well over 400 degrees. Slots and holes are machined in many types of rotors to keep them cooler. Your rotor bells will absorb a great deal of this heat so a very high temperature paint is your best choice. Typical high temperature paints advertising a heat resistance up to 650 degrees are still not good enough if you have repeated hard braking action. The temperature of the disc will go from ambiant temperature to over 400 degrees is a few seconds. Even higher with hard braking when the discs are already hot. The polymer resins in these high temperature paints will get soft near their temperature limits. This is particularly problematic where your wheel bolts against the bell because if this area was not masked off and if the thickness of the paint coating squishes when the paint gets soft then you loose some of the applied torque on the lug nuts. That's never good. The soft paint can in turn begin to stick to the wheel so when you take the wheel off some of the paint will come with it.

I learned all of this the hard way but never gave up. Exhaust manifold paint is your best choice. I use it now and have not seen any problems. It has ceramic fillers in the paint which holds up under temperatures exceeding 1000 degrees. Application and curing is key to making this manifold paint work. All of the brands I have seen and the one I used called for curing the paint in an oven for the best results. These paints come in several colors as well. Any automotive store will carry one or two brands.

Do not paint the areas where the bell bolts onto the dics. This is a precision mounting surface and just a few thousandths of an inch out of an out absolute flatness and flush fit will throw the balance off on your entire wheel. Keep the paint lightly coated or preferably masked off completely where the wheel mounts to the bell as well because of the same sort of balance issue. More of a wobble issue really.

[40belowceo]

Greetings, The disc rotor can see temperatures well over 400 degrees. Slots and holes are machined in many types of rotors to keep them cooler. Your rotor bells will absorb a great deal of this heat so a very high temperature paint is your best choice. Typical high temperature paints advertising a heat resistance up to 650 degrees are still not good enough if you have repeated hard braking action. The temperature of the disc will go from ambiant temperature to over 400 degrees is a few seconds. Even higher with hard braking when the discs are already hot. The polymer resins in these high temperature paints will get soft near their temperature limits. This is particularly problematic where your wheel bolts against the bell because if this area was not masked off and if the thickness of the paint coating squishes when the paint gets soft then you loose some of the applied torque on the lug nuts. That's never good. The soft paint can in turn begin to stick to the wheel so when you take the wheel off some of the paint will come with it.

I learned all of this the hard way but never gave up. Exhaust manifold paint is your best choice. I use it now and have not seen any problems. It has ceramic fillers in the paint which holds up under temperatures exceeding 1000 degrees. Application and curing is key to making this manifold paint work. All of the brands I have seen and the one I used called for curing the paint in an oven for the best results. These paints come in several colors as well. Any automotive store will carry one or two brands.

Do not paint the areas where the bell bolts onto the dics. This is a precision mounting surface and just a few thousandths of an inch out of an out absolute flatness and flush fit will throw the balance off on your entire wheel. Keep the paint lightly coated or preferably masked off completely where the wheel mounts to the bell as well because of the same sort of balance issue. More of a wobble issue really.

Thanks for your input Mark. Rustoleum also makes hi temp paint that can hold up to 1200 degrees. Dupli_Color also makes hi temp paint as well.

I am going to attempt to brush and sand the rust off, then primer and paint. My only concern is how I will mask of the surface that touches the caliper as it is shaped in a circle.

[elwesso]

You don't need to mask off the part that the brake pad touches, as soon as you stop the first time it will rub it all off, nothing to worry about.

[40belowceo]

You don't need to mask off the part that the brake pad touches, as soon as you stop the first time it will rub it all off, nothing to worry about.

Even better!!! Thanks again elwesso!!

[DaSerb]

Did mine over the summer....and no you don't have to mask anything off. Spray several coats and you are good to go. I even sprayed the edges of the rotor.

[svard75]

40below - I know this looks appaling but spending the effort in painting these for maybe 1 year of rust free look is not really worth it IMO. I've done this to several rotors in the past and eventually the rust breaks through. I even spent the time and sanded the hats down to shinny metal, applied primer and high temp manifold paint (I think it was the duplicolor spray paint type) it still flaked off and rusted through.

If you still want to go through with it find a circular object slightly larger than the hat and draw it onto a piece of cardboard. Cut the center out and voila you have a mask to use while painting.

Mark - Back in the days when pad compound was more gas producing it made sense for the track racing cars to have drilled rotors. It helped dissipate the heat, gasses and reduce brake fade but they were replacing those rotors fairly often. For daily drivers drilled rotors are not better than solid disk for several reasons.

1. The surface area to pad contact at any point in time is less due to the drilled holes. This means you will need either greater force applied or longer stopping distance. I mean it may be just cm of difference TBH but the fact is still there.

2. Because you have less surface area to pad contact you end up applying more stress to the areas the pad does make contact with promoting stress fractures or cracks around the drilled holes.

3. You will find it almost impossible to resurface the disk with holes. So what will you do when the pads need to be replaced? Replace the disks too? Expensive endeavor IMO.

Some factory cars do come with drilled rotors such as AMG's, CR1's, etc. Have you heard how much a brake job costs on these cars? I mean sure everyone who is either a reseller or manufacture of drilled/slotted rotors will tell you I'm completely wrong. It's definitely a lucrative business to sell something which fails prematurely. Aesthetically is a different story and I would buy them if I was building up a show car.

[svard75]

You don't need to mask off the part that the brake pad touches, as soon as you stop the first time it will rub it all off, nothing to worry about.

If you don't mind contaminating the pads. I only recommend doing this if you're replacing the pads shortly after.

[40belowceo]

Did mine over the summer....and no you don't have to mask anything off. Spray several coats and you are good to go. I even sprayed the edges of the rotor.

WOW that looks great!! Did you sand or just apply the paint? Which paint did you use?

Thanks,

[40belowceo]

40below - I know this looks appaling but spending the effort in painting these for maybe 1 year of rust free look is not really worth it IMO. I've done this to several rotors in the past and eventually the rust breaks through. I even spent the time and sanded the hats down to shinny metal, applied primer and high temp manifold paint (I think it was the duplicolor spray paint type) it still flaked off and rusted through.

If you still want to go through with it find a circular object slightly larger than the hat and draw it onto a piece of cardboard. Cut the center out and voila you have a mask to use while painting.

Mark - Back in the days when pad compound was more gas producing it made sense for the track racing cars to have drilled rotors. It helped dissipate the heat, gasses and reduce brake fade but they were replacing those rotors fairly often. For daily drivers drilled rotors are not better than solid disk for several reasons.

1. The surface area to pad contact at any point in time is less due to the drilled holes. This means you will need either greater force applied or longer stopping distance. I mean it may be just cm of difference TBH but the fact is still there.

2. Because you have less surface area to pad contact you end up applying more stress to the areas the pad does make contact with promoting stress fractures or cracks around the drilled holes.

3. You will find it almost impossible to resurface the disk with holes. So what will you do when the pads need to be replaced? Replace the disks too? Expensive endeavor IMO.

Some factory cars do come with drilled rotors such as AMG's, CR1's, etc. Have you heard how much a brake job costs on these cars? I mean sure everyone who is either a reseller or manufacture of drilled/slotted rotors will tell you I'm completely wrong. It's definitely a lucrative business to sell something which fails prematurely. Aesthetically is a different story and I would buy them if I was building up a show car.

Thanks for the input msvara. Even if the paint holds for a year will be good enough for me. I plan on changing all 4 rotors eventually, but for now this will do until I take care of other more expensive mods on my M.

[Mark Mellott]

I couldn't view the pictures you previous sent because of security blocks on my laptop. Now that I logged on through my home PC, I see that the rotor bell and disc are one piece. Obviouly, no worries about masking bell to disc mounts since these are one piece units. As such, it is a hub/disc unit with bearings and grease and seals and ... yuk. Forget about the oven cured stuff. Sounds like the 1200 degree Rustoleum will work just fine.

However, do not paint the disc rotor braking surface. If you do, it will rub off onto your disc brake pads and seriously compromise your braking performance. It will eventually wear off from the pads but if that means you cannot stop well ... the consequences can be real bad. Use painters tape no more than 3/4" wide and start by sticking the end of the tape onto the friction surface of the disc, right at the edge of the rusted area and work it around the diameter until it is all masked at the rust line. It won't be perfect and the tape will not lay flat at first but when it is all masked around you can then flatten out the tape and then cover the rest of the disc at will. Bias the masking edge ever so slightly away from the rust area. A very small edge of the disc friction surface will get paint on it but it will not be of any concequence when it rubs off.

[40belowceo]

I couldn't view the pictures you previous sent because of security blocks on my laptop. Now that I logged on through my home PC, I see that the rotor bell and disc are one piece. Obviouly, no worries about masking bell to disc mounts since these are one piece units. As such, it is a hub/disc unit with bearings and grease and seals and ... yuk. Forget about the oven cured stuff. Sounds like the 1200 degree Rustoleum will work just fine.

However, do not paint the disc rotor braking surface. If you do, it will rub off onto your disc brake pads and seriously compromise your braking performance. It will eventually wear off from the pads but if that means you cannot stop well ... the consequences can be real bad. Use painters tape no more than 3/4" wide and start by sticking the end of the tape onto the friction surface of the disc, right at the edge of the rusted area and work it around the diameter until it is all masked at the rust line. It won't be perfect and the tape will not lay flat at first but when it is all masked around you can then flatten out the tape and then cover the rest of the disc at will. Bias the masking edge ever so slightly away from the rust area. A very small edge of the disc friction surface will get paint on it but it will not be of any concequence when it rubs off.

Awesome! Thanks Mark. painters tape sounds like a great idea. I seen a picture of someone who used "post it" notes to mask off the friction surface.

[DaSerb]

Did mine over the summer....and no you don't have to mask anything off. Spray several coats and you are good to go. I even sprayed the edges of the rotor.

WOW that looks great!! Did you sand or just apply the paint? Which paint did you use?

Thanks,

I think sanding is a must....especially with that much of corrosion. In this instance I used Rustoleum Engine Enamel. It came out pretty good. I am just waiting to see how is going to handle salt during the winter.

BTW painters tape is a great idea. It will take you extra 10min per disc to put it on.

[CPJ LB]

OP: you may just pick up a set of rotors that already come painted/treated with black rotor caps. I went with a set for my fronts and will get another set for my rear rotors when they wear down.

I have the stop techs





pix with stock rims refinished/powder coated

[40belowceo]

OP: you may just pick up a set of rotors that already come painted/treated with black rotor caps. I went with a set for my fronts and will get another set for my rear rotors when they wear down.

I have the stop techs





pix with stock rims refinished/powder coated

How much did they run you if you dont mind me asking.

[CPJ LB]

^ prices will vary based on fronts/rears... I got mine through my longtime wheel/tire guy, so my cost is relatively low. I also got the rotors that are cryo treated.

I believe you can search tirerack to get retail pricing...fronts should range from $88-$150 each....

I've had mine since spring/summer and going thru this year's "California Winter" LOL...the rotors are still looking great!!!

I'm sure if you search different vendors, you'll get a deal somewhere. Maybe in time for spring when you get your new wheels

[40belowceo]

Thanks CPJ LB. Will do!