Nicole

I was able to get a pair of previously loved front calipers from a 91 GT, that I want to refinish and swap onto my car. They will need new dust boots, but otherwise look great. Maybe I'll put new bleeder nipples in as well, just to avoid future deasaster. I already have the PORSCHE stencils from Canada.

So, here are my questions:

1. If I decide to have them powdercoated - is there any way to get the PORSCHE lettering onto the powdercoated finish? Or will it flake off in no time? I assume that going that route means rebuilding EVERYTHING on the caliper - which I'm not sure I'm ready for.

2. If I decide to repaint - I hear the brush-on stuff is more durable than the spray-on. What are the experiences here with spray-on paints, and their resistance to brake cleaner? Are there any spray-on types that work, or should I forget about those alltogether? Can the brush-on material be clear coated?

3. In order to get the dust boots, I need the diameter of the pistons. At http://www.zeckhausen.com/Brembo/Con...es.htm#Rebuild the instructions say the pistons must come-out to measure their diameter. Unfortunately, I have no pressed air here, and wonder, if there is any way to
a. measure the size of the pistons
b. replace the boots
with the pistons in place.

Does anybody know the exact piston size on the S4 front calipers?

bfellows

Nicole, I used tony's excellent write up for brake refinishing using spray paint and have to say i'm more than happy with the results!

http://members.rennlist.com/v1uhoh/brakerf.htm

Have a look through these threads for piston sizes, in there somewhere If i remember correctly....

https://rennlist.com/forums/928-forum/385988-s4-gt-brake-confusion-more-pics.html
https://rennlist.com/forums/928-forum/423363-trying-to-tell-big-blacks-gts-from-medium-s4-s-gt-calipers.html

JHowell37

I can answer your second question.
The spray on types are either a lacquer or a fast drying enamel. These paints aren't as durable because they dry as a result of solvent evaporation, and what doesn't evaporate is the material left as the finish. The problem is that if you reintroduce a solvent (such as brake cleaner), that finish will become fluid again and likely wash off. The brush on type I just looked at is a catalyzed urethane. This is a paint with a hardener. The benefit to most products with a hardener is that once they cure/harden they tend to be highly resistant to solvents. My concern with brushing the material on is how well it levels itself out and whether the final result will have brush marks.

If I were doing this, and didn't have an air compressor, I would get the brush on stuff and pick up what is called a "preval sprayer" which is a cheap disposable sprayer that uses its own propellant cartridge. They can be purchased at any decent auto parts store. Then I would spray it on the calipers as it will be far more likely for it to flow or level out. As for putting on a clear coat, it doesn't need it. This is what is sometimes called a single stage paint so it will have the proper level of gloss already. And since these kits are meant for ricers trying to mimic Porsche big red brakes, the color should be a good match. Additionally, that paint is not even meant to use a clear coat so adding one might cause an undesirable reaction.

One thing to remember with catalyzed urethanes is that the hardeners contain isocyanates which are the most toxic chemicals used during the painting process. Whether brushing it on or using a Preval sprayer, you would be wise to pick up an activated charcoal respirator from 3M

If you try the Preval sprayer which I recommend, you might want to pick up a small quantity of universal medium temp, urethane reducer since you might have to thin the paint a little bit to make it spray better.

Let me know if you have any more questions about this.

the flyin' scotsman

4 pistons per caliper.........2 x 44mm and 2 x 36mm.

I also followed Tonys write up using spray on brake caliper paint with a short oven bake to fully cure the paint (its was cold outside at the time; whats new!). No worries after many years of cleaning.

Nicole

I just looked at Tony's write-up. That looks very beautiful!

Those brake lines that connect the sides of the caliper - how did he get those looking so nice?

the flyin' scotsman

I used a wire brush and a power drill then once clean polished with Solvo. Before painting I taped them with masking tape. After painting and curing remove the masking tape and clear coated.

Nicole

Well, it looks like I'll go the epoxy route. I leant that if I want to powdercoat the calipers, they'd have to come apart in the middle - and it's not clear to me how they would seal afterwards. It looks like too big of a risk to me, while the epoxy seems rather simple.

I think I'll get the sprayer for the front ones, and brush the rears while on the car.

That's all after Sharks in the Park...

PS: A friend of mine insists that given the age of the car I absolutely should replace my brake lines while swapping the calipers. I haven't looked into this before, but if I do this - would the braided types be of any significant advantage for street driving? Do they last as long as the standard ones?

123quattro

New braided lines provide no benefit over new rubber lines. Durability of rubber is much better as well. I used to work in the brake group at Bosch.

AO

Nicole, I sprayed mine and they have, so far, held up very well. One tip, get a couple of bolts that will thread into where the brake line line line goes. If for no other reason this will keep paint out of there, but I used the head of the bolt and wrapped a wire coat hanger around them to hang them up. Makes for easier painting. Also, I use the sicker from xenonmods.com and then clearcoated over it. So far, so good.

As for the the braided lines... they look nice, but for street driving, they offer no advantage. Some will say that the steel braid can abrade the rubber line and shorten the life of the line. I say stay with rubber.

jon928se

Disclaimer
I'm not recomending you do this but.....

The WSM says not to split the Calipers.
So (because I couldn't remove the screws that hold the slider plates in place without splitting the calipers) I did.

The two halves of the Calipers are not connected together hydraulically by seals between the two halves. The only connection is a pipe at the bottom of the caliper that hydraulically connects the two halves together. Halves came apart easily and gently cleaned went together easily again with new Grade 12.9 Cap bolts. I forget the torque but it wasn't huge. I don't know why G12.9 bolts are used as there is insufficient thread in the threaded part of the Alu caliper to warrant anymore than G8.8 bolts. I repainted with local parts store hi temp brake caliper paint. No problems at all after 35,000 miles and at least one stop from rev limiter in 5th (170mph+)

Useful advice - buy some 10mm (3/8") wooden dowels to screw into the bleeder valve ports before painting and remove while the paint is still wet but not likely to drip into the ports. Masking off the pistons - use masking tape for the majority (or circular band aids) then use paint on masking stuff, can't remember what it's called, from a model railway store to get to the edges of the piston seal recess in the caliper.

Tony

I have good access to mine right now..ill snap some pics. Mine were painted, oh, 7 years or more ago? Paint still looks fine when it comes time to clean them up. The areas that arent readily exposed to cleaning with the wheel/rim on are pretty dirty, but the rest cleans up fine. I think it was the regular spray on brake caliper paint.

Nicole, I used a dremel and a fine abrasive buffer wheel to clean up the bolts and metal parts.

Big Dave

I used the brush-on paint. The paint holds up very well unless you start really whacking the calipers with your tools during a brake pad change.

Ron_H

I totally agree with this post. It is the most durable finish. I have used preval sprayers for this kind of painting for the engine parts on my 914/6, which Nicole has seen sitting in my garage. The cam covers, the engine sheet metal, the fan shroud, the fan, all received this method. The paint is awful stuff to breathe as was pointed out above: use a good resprirator. I also use a preval for dying my upholstery which Nicole has also seen. Keep several handy with mixed paint and reducer into which to drop the spray heads when they clog and then re-use them. Keep a spare bottle of reducer to use to clear your sprayers as you go along. Most of all have a way to circulate fresh air throughout your garage or wherever you are painting, because it is so nasty.

Ed Scherer

Another little story/tip:

When I did my rear calipers in red about 6 years ago to match my (then) new front Big Reds, I used G2 caliper paint (brush-on).

Good stuff, but I happened to do it on a really hot day (probably well over 100 °F where I was working) and had a fan blowing on high to keep me cool and keep the fumes under control.

Well, the paint was drying a little too fast, and by the time I was done, the job did suffer a little from unevenness. Looks fine from more than a couple feet away, but if you get really close, you can see the imperfections.

So... if I ever do this again, I'll do it on a cooler day and reduce the air flow a bit.

Big Dave

Here's the process I used with the brush-on paint. I avoided the spray stuff since I didn't feel like masking stuff off to avoid overspray. The calipers still look great, and brake dust rinses off easily.

http://members.rennlist.com/bigdave/Calipers.html