Repair-It

kevm14 wrote:

Adam wrote:I'm going to see if they can be saved by turning. Should be OK, they are vented on the front and rear, so there's plenty of material.

I really wouldn't. I would consider something like sanding them (or maybe just wire wheeling) and then something like a flex hone if that finish isn't good enough that a brake pad couldn't sort it out.

What do you have against turning rotors? As long as they end up over minimum thickness they are fine.

I also discovered the source of the rattling. There is an exhaust bracket off the transmission which supports the pipes. The clamping part rusted off the bracket part. Sigh. So I've also ordered this:
https://www.ebay.com/itm/E46-323-328-32 ... 2621058927

Adam wrote:

kevm14 wrote:

Adam wrote:I'm going to see if they can be saved by turning. Should be OK, they are vented on the front and rear, so there's plenty of material.

I really wouldn't. I would consider something like sanding them (or maybe just wire wheeling) and then something like a flex hone if that finish isn't good enough that a brake pad couldn't sort it out.

What do you have against turning rotors? As long as they end up over minimum thickness they are fine.

Well, I guess I have a few thoughts on this...

Minimum thickness is sort of an arbitrary determination of min thickness for retaining both "sufficient" thermal capacity as well as structural integrity. But the thing is, thicker is better. It's not binary. It's not "totally fine" before min thickness and then "dangerous" immediately at min thickness. It is just like tires. Tires are much worse in the rain and snow at 4/32" even if that is technically a legal tread depth. And just like tires again, depending on how you drive your car, maybe this is fine. I guess if I knew I had rotors of superior metallurgy or treatment or something, and/or I was going to be easier on the brakes (than some arbitrary standard of brake usage), then maybe it would be totally fine. I have high standards for brakes and while I am quite positive your brakes would be totally sufficient around the island or really any kind of light/casual usage at min thickness, I don't feel nearly as good to them standing up to some real usage. I don't know that the car has "super high performance brakes" with excess capacity, which is maybe another reason I am not real enthusiastic about removing mass and making them thinner.

And, more anecdotally, the few times I had rotors turned on my Caprice, the results were completely underwhelming. I deemed it both a waste of time, waste of money, AND I had mediocre results (i.e. it was not like getting new rotors - they degraded rapidly under heavier usage).

Basically I would never turn a brake rotor, and wouldn't recommend anyone else do it, unless we are talking some industrial/commercial application but that is outside the scope of this commentary. I'm not even sure every shop has a brake lathe these days....

So in the end, in the spirit of getting the car back on the road, I still think the wire wheel/sanding/honing idea is a better usage of money and time, than turning the rotors. Or just replace them if you think they are that bad.

Some thoughts:
- Turning rotors doesn't imply they are at minimum thickness afterwards. They usually aren't
- Turning to remove a rust coating on otherwise lightly-worn rotors will on take off a couple thousandths while turning to remove worn pad ridges will require more than that
- From experience, "normal" people who drive "normally" can get two sets of pads' life out of a pair of rotors. Turning OEM rotors at dealerships is still common practice. No one on this forum is one of those people.

That said, I could have provided more information if I had noted the min-thickness spec and measured the rotors when I did this job earlier today, but I did not.

What I really should have done is see how much brakes cost first before doing any of this.

I ended up using a flap disk to clean up the rotors. The rears were worse, there was some pitting that I couldn't take out in a reasonable time. The calipers and brackets were VERY rusty. There is no way I could bleed the brakes in it's current form.

In hindsight, I should have probably just replaced everything. The "daily driver" Power Stop kit with pads, rotors, calipers and brackets is $349 for from RockAuto. Plus another ~$25 for e-brake shoes and H/W. And whatever hoses cost. And some brake caliper paint.

Anyway.

Some pre-fix pixtures: Bonus strut pic: I didn't take any after pics as I was tired. Good news! I didn't adjust the emergency brake shoes correctly, so I've got to go back and do that. Fortunately this is a German car with wheel bolts so if you remove one, you can reach the adjuster w/o completely disassembling everything. How convenient.

I took it for a 0.7 mile test drive around the neighborhood and the brakes sounded terrible at first. They sound better now. I'll take some pictures when I'm back in there adjusting the emergency brake shoes.

In other news the brake fluid is black. The manual calls for Dot 4 "low viscosity" fluid, whatever that is. Fun fact: this car has "DSC" or "Dynamic Stability Control" which requires different fluid. If it didn't have that, regular Dot 4 is fine.

Light restoration! Used the 3M kit again. I actually did this before the brake work, but posted that first as it was relevant to the discussion.

Before: After: Due to the mounting location, I couldn't completely get the fog lights w/o removing them. I didn't remove them. It's good enough to get light through.
With all the trim back in place: The RH headlight is stamped BMW but the LH one isn't. Not sure what that's all about. The RH one has more pitting, as would be expected for an original headlight.

Not BMW on the headlight, Bosch.

Cowl! I also did this before the brakes.

Gross. Notice the wiper arm stud is keyed. As is the arm: Cleaned up. When you go to put the weather strip back on the front of the cowl, there are some alignment marks to make it easy to center. Shot of the underneath. Lots of clips for strong attachment. Also a foam seal for underneath to help drain water. Installed. Much nicer.

So, is it done yet? No. It still runs pooly just off idle, but there is no CEL so that's an improvement. I'm going to add some Techron with more 93 octane and see what happens.

Also, one of the plate lights is out.

And I still have to re-adjust the emergency brake shoes.

And fix the mirror.

And wash it.

Wow, that was a lot of work. FWIW, I've had pretty good luck with skimming rust off the saabs rotors after a 'sit.' I used a wire wheel on a drill, but I'm sure the flap disk is fine.

Should be a nice car when you're done. How is the actual body for rust?