Cleaning 930 calipers (early 917 calipers) AND floating 930 rotors? + QUESTIONS

[DW SD]

I want to rebuild these calipers. It is my impression, they are the early 930 (917) Porsche calipers.



1. can anyone confirm, despite my lousy pictures? I can / will post better ones.

2. How would you recommend I prepare them for rebuilding and painting them? Some clever previous owner painted the outboard side red, maybe with a brush or high temp crayon. They are greasy, dirty and I'd like to strip the paint. OR Just use brake cleaner? OR?

3. Are the seals difficult to find between the caliper halves? The pucks do move freely. IE should I completely disassemble them?

Next:
4. Are these the '78 and 79' early floating rotors? How would I clean those? Is there any hardware I should change?

5. What is the minimum rotor thickness?





As always, thanks for taking the time to consider my questions!

Doug

[aturboman]

Those are 78-79 Porsche built calipers and floating from rotors. If you are going to rebuild the calipers then strip them down completely and clean them in a solvent based cleaner that is safe for aluminum. Piston bodies are dry, meaning no seals between the bridges, that is why you have external piping. The rotors should be removed from the hubs. I like to keep the drive rings/dogs matched together. Replace all the rotor hardware and make sure you order the lock tabs for the rotor bolts when you order your caliper kits or you can't properly reassemble them. I like to replate all the steel harware. Rotor thickness machined limits are 30.6 mm front and 26.6 mm rear. Be careful with the orientation of the caliper pistons, and pad retaining spreader springs. Sorry to run on but I've done several sets of these and those are some of the lessons I've learned.
The factory manual does a very good jod of describing this whole proceedure. Good luck.

[jorian]

Don't know about the rotor or caliper types but I would think that media blasting would be the best way to prep for paint.

[Bill Verburg]

Here's what the rotors look like new


and the floating t loks


calipers disassembled

[GeorgeK]

Go there:

930 brakes redo (pics!)

[BertBeagle]

The best way to clean aluminum (or cast iron) calipers is in a soda blast cabinet. If you live in at least a 10 stop light town someone locally will have one. You should also clean up your hubs with the same process.

After blasting you just rense with tap water and dry. They are ready to reasemble. You can put them in the blast cabinet as they came off the car - grease and all.

My shop cleanes calipers, nmaster cylinders, transmissions, etc. every day in a soda blast cabinet. If you have never used one you would be amazed when compared to other cleaning methods. You can clean and rebuild a brake system and the only liquid used is tap water. This is very good as hydracarbon solvents are to be avoided in brake servicing as they are not compatable with the EP rubber seals.

McMaster Carr sells a small hand held blaster for about $55. that works very well. Google soda blast cleaning and you will find sources for soda. It is around $20 for a 50 lb bag and one bag goes a long way when cleaning brakes.

The advantages of soda is that it does not leave a texture on the aluminum and it looks like new when finished. Bead blasting should be avoided if you want them to look new. It leavs a texture that collects everything that touches it. I would not recomend bead blasting anything that will have fluid in it. It is very difficult to get all the media out. Soda is water soluable.


Ashley Page
Davidson NC
www.prosystembrakes.com

[DW SD]

Guys,
Thank you all for the great advice! Sounds good! I'll look into the soda blasting. AND start measuring / gathering parts (seals + hardware).

Doug

[Cory M]

Doug-

The rebuild procedure and pictures of the process can be found here:

http://www.rennlight.com/howto/brakes/index.html

I have these brakes on my 930 and they are great. I run Performance Friction 97 (PF97) pads front and rear and prefer them to the Pagid orange I have run in the past.

My only complaint is the cost of the front rotors, they cost $3-400 a piece and the only really suitable aftermarket replacements I've found come from Steve at Rennsport Systems (www.rennsportsystems.com); he turns down Brembo rotors and fits them to non-floating hats. They cost more than stock replacements and you lose the float but they are supposed to last longer, however the stock rotors should last a long time especially considering that your car is pretty light.

[}{arlequin]

george already posted his meticulous rebuild so there's not much else to add.

mine were painted w/ black paint which i stripped w/ oven cleaner and lots of scrubbing. (before i purchased por-strip) seals were healthy so i left them alone.

[Jack Olsen]

The rotors are stupid expensive. However, the OEM ones last and last.

I am still running the same front (78-79) rotors I had installed six years ago, and I've done about 20 track days every year, in a 2500-pound car, including three week-long Open Track Challenges and a full season of wheel to wheel with the ARC.

You need to replace them when the cracks are longer than 7mm, or reach the edge of the disk or connect any three of the venting holes.

[Bill Verburg]

Maybe Ashley can point us toward some more reasonably priced 304(or so) x32 Brembos

Until something better comes along, the oems(no matter how expensive) are the best available in that size.

[DW SD]

Would any machinist who can resurface a flywheel, resurface the rotors?
Clearly, they are not machined on a lathe. Are they fly cut?
OR ground with a wheel?

Doug

[Bill Verburg]

In my best James Bond voice Rotors should be ground not cut

[DW SD]

HA!

Does every automotive machinist offer grinding?

Doug