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Experiences? Just getting the rebuilt calipers probably is the way to go...

i do that on my 412 (with rebuilt kit ) if the piston is not scrah or rust you can do , goog cleaning inside the piston and new seal kit and it is very good

i am came back , for the gaz millage , i cont you story ,,,, during the year 77 with my 412-74 ,,,1.8,,, m.t.4 , i make 1800miles on one tripe ,,canada to miami by the route 89 and i keep the legal speed 55m.h. and i put shifter in neutral some time wend the route geeve me chance (hill)and for this milage i make average of 40 miles gall, us on the autoroute ,,,not bad ,,h

Not bad!

but today with the new gaz (super or régular ) the milage on my 412 is reduce of 2-3 miles gallon imp. on the road today mix city and autoroute the average is 28 and hiway 30-31 with 1.7 mt4 at 6o mh not to bad

smal correction for you with us gallon you reduce of 2-3 mile.gal, ,,,,imp. gal. is .75 quarts more us gall.

Rebuild your own. If they are rebuildable...you will do as well or better than anything I have seen except for factory rebuilds. That wold be Brazilian Cofap/Varga...or FAG/ATE rebuilds only. All else...is junk.
The problem is that the made in taiwan rebuilds available through flaps stores....are just slammed together from cores. They are hot tanked...then bead blasted or tumbles, then honed, regardless if they should be thrown away or not. Then new seals, then packaged for your enjoyment.
Problem is....calipers should not be honed like I have seen these honed. If thats what it takes to get the crud out..fine, but then they need to be lapped so they are smooth....very smooth. If there are pits in the wall...no problem. There are no piston rings at work here..so pits are not a problem...but if any of those pits intersect with the seal groove up near the top.....the caliper...or at least that half, is shot. Throw it away. If there are any pits on the piston....it is junk. Or...you can have it nickle plated and then polish with 2000 grit.
I have found that 2 hours of work and I can rebuild a caliper....if it is rebuildable...better or as well as ANYONE. Be sure to polish the piston till it looks like a mirror. Get good rebuild kits. Either ATE, or FAG. If its Brazilian, make absolutely sure its listed for the BRAND of caliper you have...either FAG or ATE. They are marked. Also, make sure wether you have early or late. ay

allo ray it is very good to see you , wat is this fuking bug ,, to nigt i use old message on samba for to came on s.t.f , curiussly the page open by magic ,, or coinsidence ,, and 5 mi before nothing on s.t.f. ,,,,,

Alas, I believe phBB software for the forum is vulnerable to various worms, etc.created by hackers... Anyway, good to know Ray, thanks. I have confidence that maybe I can do a good enough job rebuilding the calipers. Really, it's kind of a sick DIY tradition in my family to try to do everything oneself. My dad for the longest time did everything, like building our house including plumbing, electrical, roofing, building furniture, fixing cars, rebuilding lawnmower engines, you name it... I can't stand the thought of having somebody else do something if I know I could probably do it just as well or better.

oh uber , wen you remoove the seal on the piston (pressure ring) look the good side , it is very important ,or if you do bad instalation for the new ,seal , you d,ont have pressure on your brake ,,,

I'm sure I'll have some questions as I'm doing it, I haven't started yet.

OK, I have to ask. Why do the T4 calipers have that anti-rotation plate? I've never seen another design with that feature. Why did VW/ATE/FAG not want the pistons to rotate (or, why do they rotate is maybe a better question)?

Actually doing the surfacing of the bore is easy. I use a large brake hone with the caliper half mounted in the vise. Plenty of brake fluid....fine...like 360 grit hones. Just spin it at low speed...no up and down motion...with a loe speed cordless drill. Just make sure the stones are straight. Just want to do this enough to make it "bright". Do not use a bottle brush style hone. The "beads" or bristles can drag on the seal groove and mess it up. Then with a straight piece of steel rod..wrapped carefully in 600 grit to start with, go around in a clean circle...no up and down. Then finish with 1000 grit paper or better. You are not trying to remove metal. Just clean and finish. Use 1000 grit or better on the piston in a "circumferential" polish with your fingers. Again, no up or down movement. Clean the heck out of it. Find some good fuel hose to cut careful slices of to replace the gaskets between the caliper halves. Preferably viton, but Buna N is good. Mind the thickness. No more than .005" thicker than what you can measure. It must be cut evenly...with a sharp razor blade. Try to find kts that have the new anti-rotation plates and pins. If not I can give you sources for hardware kits. If there were no seriou pits on the pistons....like pinprick pits are fine....and as long as they polish smooth...and no intersecting seal groove pits. These will be as new.
I read an article in European car about five years ago. There is a company out there that does rebuilds of BMW,Porsche calipers. They make kits for most with a stainless piston can't remember who they were.
Albert....yeah...this website thing has been bugging me. I wasn't sure if it was my computer..which has issues anyway.....so I wiped my operating system, re-installed...ad wen't out and actually paid money for new and up-to date anti-virus. Then...miraculously....the site can back up at the same time....go figure Ray

Hey Ray, I'll need that hardware kit P/N, too...I had to re-use the rusty (almost gone) anti-rotation plates when I re-did mine. Still wondering why they're needed...

oh i send you complet infor. for that