[Etnier]

I drive my 968 in the winter. My brake calipers have been having repeated problems seizing due to corrosion of the aluminum components. We've applied workarounds such as grinding down the brake pads to better fit the corroded calipers, but now my fronts are beyond such measures and must be replaced.



Is there any reasonable alternative to new calipers? We aren't really looking at used ones, given the vagaries of the used marketplace and the possibility used calipers could be well on their way out already.

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[rustech]

Have you ever removed the steel liners from the inside of the calipers to clean out the corrosion behind them? It's a PITA job, but makes a huge difference, and eliminates the need to grind down the edges of the pads. I would be surprised if your calipers were beyond repair. Short of this, I would go used and probably upgrade at the same time.



Good luck.

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[ether_joe]

isn't there a cat who 'rebuilds' calipers? In the northwest somewhere?

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[Etnier]

[quote name='ether_joe' date='Oct 25 2006, 04:11 PM']isn't there a cat who 'rebuilds' calipers? In the northwest somewhere?

[right][post="27248"]<{POST_SNAPBACK}>[/post][/right][/quote]



My understanding is that caliper rebuilding involves more the pistons, but I could well be wrong.



My mechanic finally got them opened (corroded screwholes and the like), cleaned things up and packed the insides with waterproof grease. He wants me to try this out to see what happens.



It seems clear that despite all the pix of 968's coated with ice traversing Siberia and all that bulls*** the calipers, at least, are not suited for winter driving.

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[rustech]

Rebuilding calipers is divided into two main parts. The first is to make sure the brake pad has free range of motion, and the second is to make sure the pistons move freely. It is external variables that cause corrosion behind the steel liners on the calipers, and usually internal variables that cause the pistons to get gummed up (unless you have a ripped seal). I think your mechanic has the right idea.

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[Dave]

As noted above, the spring plates on the ends of where the pads slide in are steel. These corrode alongside the aluminum of the calipers, move in towards the pads... no fit... folks start grinding the pads to make 'em fit... no fun.



[color="red"]So, what to do?[/color]



[color="blue"]The spring plates came from Porsche in a little kit complete with two new mounting screws that have loctite pre-applied. These are the ticket. You really can't "fix" the old plates and, at about $25/kit (IIRC), it ain't worth it.



Getting the screws out is the DEVIL. Porsche says heat them to glowing red with a torch, then remove. I've had the entire bloody caliper smoking hot with screw glowing red... they don't budge! Evil little screws.



I had to CAREFULLY get them to rotate with a cold chisel and hammer. It's the ticket and it WORKS.



Then, you'll try to scrub/sand/grind the caliper clean under the old plate. Forget it. CAREFULLY take a nice flat razor scraper and your favorite cleaning pad and carve that nasty stuff outta there. Careful, the aluminum is soft. You CAN actually "slice" it away if you don't pay attention. Then brush/wipe nice and clean.



The new plates go in with a little copper-based grease on the back, which seems to prevent the corrosion from quickly returning. It will, but it should be another 30-40k miles before it's an issue. I drive mine through Chicago winters and it holds up fine (now that the original 120k miles of corrosion has been corrected).[/color]



[color="red"]So, now you can get pads in/out again quickly and at will. Good for you![/color]



[color="blue"]But what about the caliper piston seals and dust boots? Well, Porsche (in its infinite wisdom) only sells replacement kits containing a piston, seal, and dust boot. These are EXPEN$IVE!



Unless you NEED to replace pistons (damaged/scratched/etc.), you replace the seal and boot. They are available by specific size from your friends at Paragon Products. Be specific, get the right ones, check them before you plan to get it all back together.



One must be careful removing the pistons so as not to scratch piston or bore. A little emory cloth or 3000 grit sandpaper will remove any tarnish on piston/bore surfaces. Must be kept clean (NO GRIT).



The old seal comes out with careful use of a dental pick (it will fly 20 feet, but it WILL be out). Dust boots come off in pieces as they are usually pretty well toasted.



Blah, blah, blah on the rest of the assembly process. Good rebuild link is shown below.



If you use compressed air to move the pistons to full travel, be careful. They will shoot out like a gunshot when they reach the end of their travel. I "shimmed" the space between the opposing pistons with piece of wood to avoid projectiles. No kidding, these will break your thumb if it's in the way.



Not terrible really. Of course, these are your brakes... so, if you're not comfortable with any of this, don't take a chance (disclaimer mode ending now).[/color]



Buena suerte!



Caliper Rebuild Link Here: http://vista.pca.org/sch/tech_articles/cal...per_rebuild.htm

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[rustech]

Dave, excellent right up. The only thing I want to mention is that the steel plates don't get damaged, they are simply pushed out by the corrosion towards the pads. If they are dissassembled, cleaned, greased, and put back together with new screws and some blue loctite, they will be perfect. It will only cost a few cents per bolt...oh, and make sure the bolt heads are tapered like OEM so they don't interfere with the pad motion.

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[Etnier]

Thanks guys! All this is much appreciated.

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