Stock Caliper Rebuild

[m5bb]

Totally understand Don. I did not try to order.
Posted this because not everyone on here has a perfectly restored coupe?
Some of us like to do our own work too.

I checked BMW, autohausaz Bavauto, Cardone last week.
No stock. No date.
Last 3 I got off ebay leaked from the bolts.
I don't paint raw metal with rattle cans on $100k cars and I can't leave them raw and rusty in 2 months.
I have done about 50 calipers myself- no zinc.....no deal on a major restoration.

 

[Luis A.]

I believe Zinc was the original finish.

That's what Eric at PMB has told me. It's my feeling after talking w him for a while that few people know more about ATE calipers from that period than he does.

I've now done two complete sets now, fronts and rears, and it's not hard at all to do. If you have a plater you trust, have the halves done in yellow zinc, the bolts done in black, get the sealing square-section O-rings from PMB and seals sets from BMW or elsewhere as they are readily available. Heed the advice on the PMB website regarding the unusual bolts found on these calipers. The rear bolt sizes, IIRC, are absolute unobtanium. Regardless of what BMW indicates on the repair manual, Eric tells me that these bolts are not stretched and he has reused them, after black plating them, for many years (100's of bolts...?) without any problem.

 

[sfdon]

Sorry- beat from moving into new shop.....

 

[Luis A.]

I thought I'd provide a visual of my own rebuild. There's a certain amount of satisfaction for me in knowing all components are original to the car and ready to deliver another 40 years of reliable service.

The black schmutz applied to the underside and calipers was very difficult to remove even with a wire wheel.

 

[sfdon]

That's gorgeous Luis.
What is your local guy charging for plating?

 

[Stevehose]

objet's d'art

 

[Luis A.]

That's gorgeous Luis.
What is your local guy charging for plating?

$25 per color for a 'bucketfull'. The real expenditure is the time to get them prepped. They will dip for light surface rust but you have to deliver it free of any surface coatings.

They looked like this when I delivered them to the platers. Now that I think about it, I actually glass bead blasted them leaving the pistons in place to protect the bores and brake line holes well plugged.

 

[Nicad]

Did you do anything to prep the bores Luis?

I just finished redoing an old Empire blast cabinet yesterday and when I went to hook it up, found out my compressor is not working. Dang, it's got power going to the motor. Turned over about a quarter turn when I switched it on then stopped. Bad timing.

 

[Luis A.]

Did you do anything to prep the bores Luis?

I just finished redoing an old Empire blast cabinet yesterday and when I went to hook it up, found out my compressor is not working. Dang, it's got power going to the motor. Turned over about a quarter turn when I switched it on then stopped. Bad timing.

Nothing other than thoroughly cleaning them. Honing brake caliper bores (at least the ATE design I'm familiar with) has never made sense to me. The pistons don't touch the bores, nor do any seals or rings, such as it happens with engine piston rings. Maybe other style calipers do have piston/bore contact...??

 

[m5bb]

Nothing other than thoroughly cleaning them. Honing brake caliper bores (at least the ATE design I'm familiar with) has never made sense to me. The pistons don't touch the bores, nor do any seals or rings, such as it happens with engine piston rings. Maybe other style calipers do have piston/bore contact...??

I agree Luis that the pistons don't really hit the bores.
I usually hone as it smooth's the bores from any potential area that might wear or be inclined to pit. Honing doesn't really remove any metal at least that you could measure.
Just the way I have done this for 40 years.

 

[sfdon]

The same for me- just trying to make it look good.
Nice work Luis.

 

[Stan]

Beautiful work! Car porn
I would hate to see brake dust on them!

 

[fredp]

What size ribe bit is needed for the caliper bolts?

 

[stphers]

Calipers

Hi Luis,

Can you supply me the name and number of your plater? here in Vancouver we have to pay 6 times that amount for a 4 lt bucket of parts to be plated. Even with shipping, it might work out a lot less from your guy.

Thanks, Rick

 

[Nicad]

Hi Luis,

Can you supply me the name and number of your plater? here in Vancouver we have to pay 6 times that amount for a 4 lt bucket of parts to be plated. Even with shipping, it might work out a lot less from your guy.

Thanks, Rick

One thing about plating and cross border is that they might just tax those parts as new ones. They are getting silly at the border these days. These guys in Toronto are who I expect to send my big order to one day , if I can ever figure out what it is.

http://www.mmplating.com

They do CAD plating which I understand is hard to find in areas where they care about Ducks.

 

[Nicad]

Just picked up a set of these for my 3300 pound Forester XT. They are getting rebuilt and De Blinged (painted Silver with no Logo)
They weigh quite a bit less than the E9 Caliper….but not the rotors. Rebuild kits are $250 for a handful of seals.



Sorry for the thread drift

 

[David]

I thought I'd provide a visual of my own rebuild.

That looks fantastic. I wish I had the skill, but I dont trust my life in my own hands.

 

[PMB_Performance]

No Honing Please!

:lol:

No... put the hone down. No honing please! I know they make them... it doesn't mean you should use them.

Honing is the worst thing you can do for a caliper rebuild. Brake fluid is hygroscopic. It attracts water. Water and fresh metal = RUST. I've never seen an ATE caliper that needed the bore honed. They don't grow fangs or anything. Media blast them clean then plate them. The seal is the sealing surface. Small pitting will not matter one bit once it's cleaned properly and replated.

Rust is the number 1 reason 99.9% of all calipers fail gang. They sit, water gathers around the rubber bore seal, rust forms where the piston eventually wore the zinc plating off the bores... now you have a sticking caliper. Dust boots crack and, as mentioned, the hygroscopic nature of the fluid (and the fact that nobody changes the fluid annually... do I sound like your dentist?) brings water in to the system.

So... when you hone the bore, you leave fresh steel inside that bore. Fresh steel and water? We "fixed" a caliper for a friend who rebuilt his own. It was a rare and valuable 914-6 rear caliper. He rebuilt it two months prior. Rust was already building up in his freshly honed bore. They generally last a couple years and they'll need it again. Which brings me to my final point; zinc, not cad.

"MANY" people make the cad mistake. Many of the plated bits on your car are cad. BMW used a lot of it. BMW did not make your calipers. ATE did, and they used zinc because it is a sacrificial coating and a much better protectant than cad.

Luis... GREAT JOB. :-D

P.S. Chinese seal kits on your BMW calipers? I thought I read in this thread that that's a viable solution?? Please do not. They have "NEVER" figured out how to get the proper amount of anti-ozonates in the rubber. Those seals usually crack and crumble in two to three months. That and big box caliper rebuilds that don't have "any" finish on them (they will be useless in two years) are not solid advice for really cool collectable cars. If you must be cheap, go Luis' route and do it right. The zinc plating is the single most important step in rebuilding a caliper, followed by quality seals but, hey, it's only your brakes... (sorry)

 

[sfdon]

For what it's worth...PMB has done several sets for me and

More are boxed and ready to ship.

As good as it gets.

 

[eriknetherlands]

Yellow zinc plating worked, but not on every part...

Got my calipers plated at a local shop; Yellow zinc as per advise here.
Sandblasted them myself, all sides & everything open, including the bores.

The plating went quite OK with the calipers, though not all passages will be coated on the inside, and the caliper bores are not as thick coated as the outside.

But what got me wondering is that my plater was not succesfull in plating the pistons (bought new ones later anyway) and the 10 mm steel plates that fit between the rear caliper halves. They simply havenone, or only a very, very thin layer of zinc. It now a week ago. if you scratch the side of the pistion with your nail, you get rust under it....

All parts were processed in one batch, all was nice & shiny, but not the pistons nor the intermediate blocks
- 1st pic shows the calipers; at first glance nice, but after 2 weeks some white rust was coming up. visible at the corners as white dust.
-2nd pic show my fasteners. They are normal Allen M7 sized bolts. Should be black to be original, but they are not the original bolts (should be RIBE head) so I didn't push it.
- 3rd pic with the pistons and 10mm thick plates (spacers) after plating; they did not pick up any real amount of zinc, so they still look unprotected to me.

I haven't finished the build of the calipers because of this.

Question to the group: is my plater doing something wrong here?


The plating company that cast steels can be difficult, and a solution for cast steel is to use a non accidic type of yellow zinc coating. So that must be a pH<7 treatment; alkaline? (i'm no chemical expert)

PMB, any advice? What type of zincbath is used by your plater? (accidic or alkaline?)

Erik