Resurfacing brake disks
 

I ordered new rear disks for my W123 - They came and they were wrong ones :( They were fronts. Costs more to return them than what they are worth. So I need another set. But for the coming winter I think I can get by with existing. However, I would like to clean them up. They are almost full thickness still, but have rust around periphery that has been grinding pads away and causing rough braking.

I have seen several Youtube videos on resurfacing using regular tools. I might try that, but have a question:

Has anyone used abrasive cleaning pads? The 107 FSM shows them in section 42-260. Dealers used to use them when customers had complaints about brakes pulsing. Looks like they are still available - at a price ($123 list for 4)!

Wondered if anyone had tried to make something similar using old pads?

https://www.dropbox.com/s/54s1pf18e4...0pads.JPG?dl=1

Most major auto parts stores will resurface brake rotors for free or minimal cost if you buy new brake pads from the same store. Make sure and check the minimum thickness of the rotors (should be stamped on the rotor). Rotors that are uneven will cause brake pedal pulsating when the brakes are applied.

None in our neck of the woods.

mine neither that I know of or have heard.

Most oreilly auto parts around here turn discs and drums.

Just looking at those pads. They look like they use sandpaper. The screw must screw into a clamping plate that has a couple of pins that keep it aligned. Much like a hand sanding pad. Shouldn't be too hard to adapt a set of old pads to do same. But whether the sandpaper will do the job, is another thing. I do have some aggressive stuff that was used on a small belt sander.

I should/will buy another set of rotors. But reluctant to buy from same vendor who screwed me (autopartsway). Old ones with or without resurfacing will get me through winter when most rotor damage occurs and in meantime I can source new ones locally.

There is a full resurfacing machine sitting in the basement of a shop near me, they want someone to take it out…

On solid rotors, I usually hit the lip with an angle grinder, and then block sand the surface with 400 grit.

Sounds like a plan, rather than mess around making pad cleaner blocks that might not work too well. Might use engine to spin wheels while grinding/polishing. They are the rears.

To do the rears, remove caliper, remove disc/drum, bolt disc/drum to hub with disc outwards (reversed). Now there is access to both sides of the disc.

Yes, that is the plan. Just have to decide what to use to abrade. Will experiment on another old set on the bench.

Taking a break!

Anyone trying this, a tip. In order to mount the rotors without the wheels, you will need some short bolts. Just hex head M12x1.5. Short enough so the thread does not protrude and contact the emergency brake parts. I was able to use an old set of caliper mounting bolts with a larger nut under head as a spacer. Threads didn't protrude at all.

Trying to do both sides may work if up on a hoist. I suspect I will have to reverse the rotor and do both sides from outside.

Did some experimenting and not sure I can get the rotors in good enough shape. May have to bite bullet and buy a new set. But we will see.

I set rotor up on car as described above. Was able to get surface reasonably smooth and most of rust removed. But there was still some pitting and in particular in one or two spots across the braking surface. A proper machine could no doubt have removed this, but rotor was now just over 9mm and this was just the first side. Called store and new rotors will be here on Monday (Zimmerman)!
https://www.dropbox.com/s/arv0tmgr1s...rotor.JPG?dl=1

Here labor eclipses the cost of the new rotor fairly rapidly. Standard Bay Area shop rate is 175-225$ per hour depending on locality. I could buy rotors for $30 have them mailed to me free if I purchase enough for the free shipping deal, or I could spend some hours to take them in to be surfaced at 25$ each. If I count my time at 25$ per hour, it is not hard math to figure out the best choice. In my locality, the base labor rate is 25$ per hour, even for stuff like raking leaves or trimming bushes.

Not quite as high here, but same logic applies. That is why I was considering DIY resurfacing.

You probably don't have the kind of corrosion we get. When I replace rotors, they usually have less than 1mm of wear. Present rears The good one) measured about 9.2mm (vs 10mm new).

They get changed because of corrosion. This for some reason, is always worse on the back surface that you can't see easily. Here is the back of the passenger side that I had not looked at before I started to try resurfacing. I gave up the resurfacing idea as soon as I saw it! It did tell me that I better check the caliper piston is not stuck.
https://www.dropbox.com/s/9cxd7iivr4...inner.JPG?dl=1