Rotor Hat Refinishing

JHZR2

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My 2011 BMW 135i is a ~10 month car, never sees salt, but will be out in the rain and elements the whole time Im using it. It has pretty wide open 18" wheels, with large rotor exposure. The hats on the rear rotors were painted/coated when I got the car new, but that coating was starting to be compromised, so I decided to refinish them. I had the car up on a lift for brake fluid exchange and oil change, and it was easier to flush the brakes with the wheels off, so I did this all at once. As you can see, the coating was starting to fail from 10 month use and sitting outside. First I thought a roloc type disc on an electric grinder would be good, so I tried it for the first one (80-100 grit IIRC). But it really was hard to control and use: The other side I used a brass brush, a nylon brush, and a nylon wheel on a dremel, which was a much better option for prep: After brushing, scraping and prepping, I did a wipe down with 3M high power, non-chlorinated brake cleaner ($2.49 at NAPA), and then used CRC Zinc it, which really is an easy to apply product for this use: Masking off the caliper is important, but I didnt mask the rotor. Splatter/spray onto the car was non-existant, due to the direction that I sprayed. I let the zinc layer on the rotor surface, as it is easily removed with a rag and some of the high power brake cleaner. Its very easy to do a bulk removal away from the hats, and then a finer job close in to the hats, to get a proper edge. The finished product: Before re-installing the wheels, I also went after the rust inside the hub flange a bit, to get the big loose rust off, and then out of there. I spread some clear CRC spray grease in the hub area to help provide corrosion protection, and since the outer lip (that the wheel rests on) was rusty, after brushing and wiping that, I applied a thin film of copper anti-seize. Not all cars are done like this, but I know that from the factory, my S-10 had a grease on the hub in this area, and from the factory, my Saab had green grease in this area. Ive made it a habit to put something there ever since. Much better: I was going to tackle the fronts, but they didnt appear to be plain steel. Not sure if they are stainless, but they werent corroded the same way. It looks like a multi-piece rotor: What I did for them was just use the dremel with the nylon wheel to generally clean the surface off a bit, then wiped down with the brake parts cleaner, and then wiped again with a rag wetted with Corrosion X oil to leave a very thin film. Im sure it will wash off the first time I drive in a big rain, but Im not that concerned. I wiped the rotor surface off after with more brake cleaner, and dont feel that it could wash to compromise the friction surface. Time will tell how well/if any of this lasts. I hope the cold zinc works to hide the surface rust, and if it doesnt, Ill probably try to re-wipe it off, and then clean the hats with ospho and re-coat another time. It wont be before two years (next brake fluid exchange), that's for sure. I dont plan on taking the wheels off before then. My PSS tires are wearing REALLY well and I just dont put that many miles on. Hope this helps someone...
 

JHZR2

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The front ones are stainless or some other alloy and were just dirty. I bought the cay (MY11) new in July 2010, so its really seven years of living outdoors 10-ish months per year...
 

Kestas

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I prepped the calipers on my 71 Cutlass by sandblasting the rust. After using Rustoleum primer and topcoat, they were rust-free for 30 years, the last I checked. Of course this car never sees salt duty.
 
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Looks good! I think i will try the Zinc-it on my next set of new rotors. Curious whether navel jelly would help remove rust prior to coating (probably would not want that on the calipers and brake pads though).
 
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Originally Posted By: E150GT
man youre changing brake fluid on a 10 month old car?
The car is 6 or 7 years old. He's keeping it at peak performance. The "ten month" car terminology is probably referring to ten months out of the year that it sees use.
 

JHZR2

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Originally Posted By: L_Sludger
Originally Posted By: E150GT
man youre changing brake fluid on a 10 month old car?
The car is 6 or 7 years old. He's keeping it at peak performance. The "ten month" car terminology is probably referring to ten months out of the year that it sees use.
+1. 2011 BMW 135i.
 

JHZR2

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Originally Posted By: spasm3
Looks good! I think i will try the Zinc-it on my next set of new rotors. Curious whether navel jelly would help remove rust prior to coating (probably would not want that on the calipers and brake pads though).
That's why I was thinking if this fails in two years, Ill wipe/remove the zinc, and then use ospho. I think that would do the trick... I was tempted to do more than just a brush and wipe, but I was doing two oil changes and a brake fluid flush at the same time, and had only limited time to do the work... Plus I kind of wanted to experiment with how relatively poor/incomplete prep will hold up... not that I want to do a lousy job, but kind of wanted to see if it will work. Do more than just spray a dirty rotor, but not a huge, time intensive job either. After setting up for the first one, time per rotor was probably 20 minutes including masking and removing the zinc from the friction surface. On my old 318i, I painted the rotor hats when I installed them with some high-temp black paint. That lasted forever. I didnt think black would look right on these. It does hide lots of issues.
 

JHZR2

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Originally Posted By: Mr Nice
Nice work. What type / brand lift are you using ?
EZ Car Lift
 
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Originally Posted By: L_Sludger
Originally Posted By: E150GT
man youre changing brake fluid on a 10 month old car?
The car is 6 or 7 years old. He's keeping it at peak performance. The "ten month" car terminology is probably referring to ten months out of the year that it sees use.
oops I missed that 2011 part..
 
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Originally Posted By: JHZR2
Originally Posted By: spasm3
Looks good! I think i will try the Zinc-it on my next set of new rotors. Curious whether navel jelly would help remove rust prior to coating (probably would not want that on the calipers and brake pads though).
That's why I was thinking if this fails in two years, Ill wipe/remove the zinc, and then use ospho. I think that would do the trick... I was tempted to do more than just a brush and wipe, but I was doing two oil changes and a brake fluid flush at the same time, and had only limited time to do the work... Plus I kind of wanted to experiment with how relatively poor/incomplete prep will hold up... not that I want to do a lousy job, but kind of wanted to see if it will work. Do more than just spray a dirty rotor, but not a huge, time intensive job either. After setting up for the first one, time per rotor was probably 20 minutes including masking and removing the zinc from the friction surface. On my old 318i, I painted the rotor hats when I installed them with some high-temp black paint. That lasted forever. I didnt think black would look right on these. It does hide lots of issues.
If it holds up in NJ then it should definitely hold up down here. Good to know the high temp black held up. I have cars where that will not really show.
 
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Great job, looks like an OEM Zimmerman! Fronts are aluminum alloy hats, Zimmerman and others make a one piece replacement that would match the rears perfectly now.
 
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How about trying some EvapoRust on the rusty rotor? Then the Zinc-It spray.

For those of us in the rust belt the inside of the hat that touches the hub is probably more important to keep rust free so one can easily get the rotor off.
 
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