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So, I took the front brake calipers of my 90 GT some time ago, and I have some questions:
1.) Does anybody rebuild these calipers? They are in cosmetically great shape, so I think a rebuild is worth it.
2.) Is there a shelf life on rebuild calipers? As we know, brake fluid draws water. So, if the bores are rebuild and lubricated with brake fluid, I guess the shelf life would be very short.
NOTE: regarding the front brake calipers, they are still relatively affordable. But the rear brake calipers are freakin' expensive. These I would definitely want to have rebuilt, but by whom?
its there anything proprietary or difficult involving about rebuilding the 928 calipers? unless there is something
I am not aware of, can't you do it yourself? I've read some of your posts involving much more difficult procedures
and you seem very well equipped to rebuild the calipers?
Nothing proprietary. A lot of it comes down to the experience of the tech doing the job to recognize what can be rebuilt, re-used, or must be discarded. You need to have a sharp eye to look for corrosion and pitting in the pucks and the bores. Then you will need the patience to locate the odd little bits you might need like spring clamps and seals and such.
By all means: DO NOT BEAD BLAST THEM. I have seen many calipers ruined by to aggressive of a media blast. The bores are ruined by this.
I do have a stock of Brembo caliper pistons and seals on hand for the 87-91 calipers.
For a ‘90+ I would expect a complete refurbishment to include pistons, seals, guide plates, button-head guide plate bolts, color coat and the “Porsche” decal. Do you include all of these for your rebuilt-and-painted price of $358 per caliper?
For everyone else, here are finished and polycoated calipers in both red and black. Please note that they are NOT painted. Our polycoat actually penetrates the surfaces of the metal and makes a chip-free color coating that does not build up heat like paint does. Another problem with painting calipers is the paint thickness can make the pads stick and not retract. This polycoat process avoids that problem too.
Carl, in the above picture the front Calipers are '87-89 and the pad guides and button-head bolts have been painted-over. I assume, then, that they were the original guides and bolts and were not replaced during the rebuild process. And in any case, replaced or not, the guides and bolts should not be painted.
Dave, I sent your questions to my rebuilder, and this is what he sent back:
Carl, pistons plates and bolts are not replaced, all other items listed are done. Pistons are only replaced when the coating is ruined like they were on that set you sent in awhile back. The plates and bolts don't wear out.
All of the additional parts, pistons plates and bolts are available, just like the ones you supplied for that other project, but it adds a considerable cost with no need or benefit. If the customer insists on having these parts replaced, buy them and send them in with the calipers and I will install the parts at no additional cost, and I keep the old parts.
They have not been painted. They were covered by the polycoat, but not painted.
Polycoat, Paint, Powder Coat, whatever....
they should not be coated. There isn't a ton of clearance between the guides and the pads. Those guides warp as a result age (poor maintenance procedures actually(*)) and thus any additional 'thickness' of the guides due to surface treatment thickness will shorten the period between pads fitting and not fitting. If the guides are even slightly warped and then coated I wouldn't be surprised if pads don't fit right out of the box or if they squeal like oiled pigs set on fire.
If not warped, the guides should be removed before coating and re-installed after coating.
Calipers need to be heated to 300°F+ before the button-head bolts will come out. And again heated upon re-install.
(*) The caliper bores need to be thoroughly cleaned periodically so that brake dust doesn't 'work under' or around the guides. The effect of the brake dust is like a tree root: it will grow through anything. With every heat/cold cycle the dust gets further/deeper between the guide and caliper body. The continual buildup of dust between the guides and the caliper body over time warps the guides to the point where pads stick in the bores and new pads cannot be inserted without grinding-down the edges.
EDIT: Guides warping is almost always a rear caliper problem since they get 'touched' half as often as the fronts.
Are the crossover 'Connecting Lines' painted when they were new?
No. Not through '91 at least. They do turn dark and nasty due to dust, dirt, corrosion and look like they might be black but, originally, they were not coated like the caliper bodies.
On modern Porsches the connecting pipe is coated (where 'coated' means whatever process is/was used.)
I respect your input, Dave, and a lot of what you mention makes some sense.
I only would note that you have not held or used OUR rebuilt calipers. So, as such, you are commenting on a rebuild service that you have never actually seen or used.
Is that True?
I have been using this re-builder for several years and they do a fantastic job. Brake caliper rebuilding is all they do - nothing else - and they've done hundreds. As a result of their skill and expertise, we are able to provide a complete one year full-replacement warranty against leaks and failure, and have never had a claim.
01-07-2019, 07:25 PM
Rebuilding Brake Calipers
