M20_Fever's RX-7 caliper rebuild

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M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Mon Mar 28, 2011 12:46 am

Of those of us looking to do the RX-7 conversion, many will end up with some second hand calipers sourced from, at best, questionable places. This leaves two options, use the used calipers as core trade-ins for new units ($$$), or rebuild the used calipers to "like new" condition. I chose to go with the later since $40 for a kit that rebuilds both calipers sounded better than $130 each for new calipers.

What I started with:

2 used RX-7 calipers, in less than perfect condition.
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and a rebuild kit from Mazadatrix.com; http://mazdatrix.com/getprice.asp?partnum=49-2400-FB05, one kit does both calipers, but it should be noted that the small rubber seals that go between the caliper halves are not included, so save yours.
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Tools you will need:
14mm socket/wrench
10mm line wrench
10mm socket
Loctite - red
grinding wheel
goggles
brake fluid
air compressor w/nozzle
brake cleaner (I used 6 cans)
caliper paint (optional)
non-abrasive metal polish
torque wrench
small pry bar
channel locks
needle nose pliers
impact gun (optional)
dental pick

First order of business is to remove the old pads if your calipers came with some loaded. Remove the cotter pins holding the support bars in place, slide the support bars out of the side of the caliper and remove the pad tensioners as support bars slide out.
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You should end up with this.
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next remove the steel dust cover things from the ends of the inner caliper.
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I soaked the bolts and line adapters with penetrating oil to loosen them up.
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then remove the brake line fitting if it's still attached.
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Now is one of the more difficult parts of the whole rebuild, getting the pistons out. This will require compressed air, and an extra set of hands. Before you attempt to blow the pistons out PUT ON GOGGLES because there will still be brake fluid in the caliper that will spray everywhere, including your eyes. Put either the old pads or a small block of wood between the pistons because they are going to come out like a bullet. If any are being stubborn you can grab the piston where they touch the pad and slowly rotate it while working it out.
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you will quickly find out all 4 pistons will not come out simultaneously, and once one pops out the seal is gone so there is no pressure on the rest of them. The solution I found was to place the piston(s) that popped out back into place, and use a wrench or small pry-bar to press the old pads/block of wood against them to keep pressure against them so they seal the caliper and force the other pistons out. This would have been very difficult to do alone, luckily I had a helper to hold the pistons in place.
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Now you should have the pistons, dust boots, and boot retaining rings removed from the caliper body.
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Now is when soaking the bolts with penetrating oil pays off. Remove the 4 bolts that hold the two caliper halves together, I found them to be pretty stubborn so I got out the impact and they came right apart.
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Remove the old piston seals with dental pick or similar tool.
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then remove the rubber rings that seal the fluid channels between the caliper halves.
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At this point I took advantage of my helpers patience and the fact that paint hates brake cleaner, and let him remove all the horrible blue paint that came on the calipers.
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which resulted in this.
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I didn't want any Mazda logos on my BMW, so that had to be ground off next. I opted not to remove any of the nub on the side because as you can see inside the caliper, a fluid channel runs through it. You could probably take a little off the nub but I didn't want to risk it.
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next I used a soft brass wire brush to clean the mating surfaces between the calipers since they where pretty dirty.
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after all the grinding, brushing, scrubbing, cussing, etc. is done, it's time to clean, clean, clean, then clean a little more. You have got to be 100% sure there is no dirt/debris in any of the fluid channels or in the seal grooves before reassembly, including the bleeder zirks. After a good cleaning with brake cleaner use compressed air to blow out all the fluid channels. Remember, only use brake cleaner on the calipers, anything else will leave a residue that can cause problems somewhere, or so I'm told. I also took and cleaned the 8 bolts that hold the calipers together with a steel wire brush wheel since the threads and the bottoms of the bolt heads where pretty cruddy.

now to help the bling factor a little I hit them with some VHT high temp caliper paint. I choose the VHT because last calipers I rebuilt I used Duplicolor caliper paint which is rated to 500* and it turned black after one lapping day from the heat. The VHT is rated to 900* so I'm hoping it will hold up a little better. I used 3 coats, 2 light and one heavy.
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while the paint was drying I addressed the condition of the pistons. Take a close look and make sure there are no major scores that will tear up the nice new seals your about to install. If they are smooth, but show signs of crud/corrosion you can use some polish to bring them back to operating condition, I used Mothers metal polish.

before:
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after:
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once the paint fumes cleared I was left with this.
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now it's time to reassemble. Make sure to lube all the new seals and pistons with fresh brake fluid. First put the new piston seals in, then press the pistons in using the palm of your hand. It may take some persuasion, but they should slide in. Next install the dust boots, and retaining rings. Don't forget to put the rubber seals that go between the caliper halves back in place.
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now put the caliper halves together and finger start the 4 bolts. I put a dab of red Loctite on there to be sure they don't back out.
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snug the bolts up with a ratchet, then torque them to 10 lb/ft in a staggard pattern, then to 15-18 lb/ft for final torque. Reinstall the bleeder zirks. Since these calipers are going on an e30 I installed the required brake line adapters that will allow me to hook the stock e30 brake lines to these calipers. Be sure to put the metal inner dust cover things back on before putting the pad support bars back on.

All done!
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Update: 11/11/14
8020Valve wrote:The flat o-ring seals between the caliper halves ARE included in the Centric kit. PN: 143.45011 One kit does one caliper. I bought two kits just for these seals and it turned out the steel keeper rings are better in the Centric kit than the Mazda OE kit, which I used for the other seals. :)


Update 11/17/14 - Brake line adapter info
M20_fever wrote:M10 male inverted flare/M10 female bubble flare

from WhoDwho on tech:
The SAE/double (inverted/45degree) flare and the DIN/ISO bubble flare. We will refer to them as SAE or DIN flare.

Concave Seat
For use with I.S.O.
Bubble Flare

Convex Seat
For use with S.A.E.
Double inverted flare

ISO is a Bubble Flare - having a Convex (rounded) tip which mates with the concave part in the fitting -ISO brake line))ISO fitting

SAE? is a double flare - having a concave tip which mates with a convex part in the
fitting SAE brake line((SAE fitting

metric European (not Asian) fitting

m10x1 inverted male - bubble flare female

http://www.lawsonproducts.com/webapp...BRAKE+FITTINGS

http://brassfittings.thomasnet.com/i...39621?&seo=110
http://www.parcelparts.com/servlet/Detail?no=750

SAE 45 degree - double flare - inverted flare

DIN/ISO or blubble flare female - inverted flare male

10mm x 1.0 Male thread inverted Flare
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Re: M20_Fever's RX-7 caliper rebuild

Postby ten2doyle102 » Mon Mar 28, 2011 1:11 am

Very nice write up!
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Re: M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Mon Mar 28, 2011 1:19 am

Thanks!
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Re: M20_Fever's RX-7 caliper rebuild

Postby ponycarman » Mon Mar 28, 2011 2:53 am

Awesome write up! About how much in all did the swap cost?
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Re: M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Mon Mar 28, 2011 10:46 am

I'd have to total up my receipts, but roughly $450-500 which includes good pads for front and rear, new rotors front and rear, SS brake lines, RX calipers, adapters, and complete Super Blue racing fluid flush. So basically a complete brake overhaul/upgrade.
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Re: M20_Fever's RX-7 caliper rebuild

Postby ponycarman » Mon Mar 28, 2011 12:15 pm

Ok awesome! Thats not bad at all for what your getting.
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Re: M20_Fever's RX-7 caliper rebuild

Postby Yoshi » Mon Mar 28, 2011 3:08 pm

did you rebuild the rears too?
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Re: M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Mon Mar 28, 2011 3:31 pm

Rears where rebuilt last year.
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Re: M20_Fever's RX-7 caliper rebuild

Postby ponycarman » Mon Apr 18, 2011 9:10 pm

What year and model rx7 do these have to come from? Are they all the same? Found an rx7 with the calipers on it today in the junkyard and Im thinking about snagging them for future use when I get some 16's.
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Re: M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Mon Apr 18, 2011 10:05 pm

If they look like mine they will work. They come off '86-'95 RX7 Turbos, but its a very common upgrade for the non turbo models also so check any RX7 you find.
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Re: M20_Fever's RX-7 caliper rebuild

Postby ponycarman » Mon Apr 18, 2011 10:12 pm

This one was a turbo. Deffinately in that year range as well. I think it was a 87-91ish. They all look similar. So Ill probly head back and grab them if they are still there. The price at the yard is $27 plus a $3 core charge so $30 a piece. That sounds fair I guess.
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Re: M20_Fever's RX-7 caliper rebuild

Postby ///ivane30 » Thu Apr 21, 2011 7:27 pm

yes great i know this conversation , i love this .... rx7 is too expencive here we use brakes from 728TDS and rotors from audi TT its same :-)
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Re: M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Thu Apr 21, 2011 7:39 pm

Isn't the audi 5 lug? How do you use those rotors?
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Re: M20_Fever's RX-7 caliper rebuild

Postby ///ivane30 » Thu Apr 21, 2011 7:50 pm

u make it 4x100 :mrgreen:
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Re: M20_Fever's RX-7 caliper rebuild

Postby M20_fever » Thu Apr 21, 2011 8:00 pm

Yikes, I don't know if I'd feel safe running that rotor. Looks like some of those holes are awful close together. Ever get cracking? Do people run that setup on track or just on the street?
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