Tom Jones

Rebuilding Miata Rear Calipers

I now turn my attention to rebuilding the rear calipers. Since rebuilt rear calipers typically cost from $70.00 to $120.00 or more there is much savings(incentive) to rebuild your own calipers, provided the donor calipers do not have pitted bores and are suitable cores for rebuild. I priced at AutoZone the rear caliper rebuild kits, they  will only set you back about $15.00 for both calipers and Miata OEM part # NAY1-26-46ZB will set you back about $34.00.I have noticed some builders are a bit reluctant to take on rebuilding the rear calipers due to the rears having the e-brake  mechanism. This is not a good reasnon to fear this job (with the right pliers).

Refer to the enthusiast manual page 9:14 section 18 and 19. You will soon discover they cheated and did not do a complete rebuild! In the manual they did not remove the  c-clip and remove the adjuster screw to replace the o-ring. Possible they did not have the correct c-clip pliers. The o-ring on the adjuster screw is what separates the caliper hydraulics from the emergency brake mechanism. If you remove the e-brake adjuster’s cover bolt and there is the presence of brake fluid then you must replace the 0-ring seal, you do not have a choice.

If all is dry you could possible elect to just remove the hex adjuster screw and clean and repack its bore with fresh grease like in the manual, but since the rebuild kit comes with the o-ring and new lever arm seals why not use them? This is not hard to do provide you have suitable C-clip pliers. I almost took the easy way out too. A few years ago I bought a c-clip pliers set that I forgot I had in my tool box. I bought these thinking the day will come I may need them, that day is today. You need C-clip pliers with a min of 2 inches from pivot point to end of pliers, more would help. So just plan ahead and buy some before you start this job, you possible could use 2 picks to insert the c-clip, I tried this as I used the 2 pick method to remove the C-Clip (worked OK for removal) but realized I was in trouble as I could not get clip in position with the two pick method, though it may be possible with more time and frustration. That is when I found my pliers, hurray! I am in business. With these pliers I inserted the clip first time in less than a minute. So with the correct C-clip pliers do not fear rebuilding the rear calipers.

What is important to know is that the lever arm and its dust seal can not be removed until after C-clip and adjuster bolt is removed. But it is important to know that the first part to install in the caliper is the seal and the lever arm as you must do this first before install of adjuster screw and connector link (the hot dog) or you will have to remove the C-clip and start over.

As a good pre requisite please review this link Parking brake operation

This is an excellent article by Lance Schall, after reading this you should be ready, provided you have your pliers. I will present the rebuild in gallery format up to install of new pin bushing as I want paint first, so let’s get started. Rememeber to clean your parts typically after any polish or use of hone.

Rear Caliper & mounting bracket cleaned of road grime
Pics are helpful for rebuild
This is a MUST have tool!
use 12 mm to remove banjo bolt & flex line
use line wrench to remove bleeder screw
use 10 mm to remove pin
rotate mounting bracket to seperate mounting from caliper
caliper now free of slider pin and mount bracket
remove lever arm spring
used razor blade to assist removal of pin bushing
pin bushing removed
use 14 mm to remove adjuster cover bolt & copper washer
view of 6 mm allen head adjuster & cover bolt
use 6mm and turn CW to push piston our of bore
after piston is free of adjuster screw remove boot and by hand free piston from bore
now is good time to remove allen adjuster, so you do not lose it
piston and integral adjuster
discard the old boot
piston bore and adjuster screw & circip
use pick to assist square seal removal
First of several cleanings
used 3m cloth to clean & polish pin guide bores
cleaning the pins, inspect and polish with 2000 grit
thoroughly clean seal grooves
clean piston and all parts
blow out passage ways with air
polish piston with 2000 grit
polished nice and shinney
used 2000 grit to poish bore
the infamous C-clip
removing the C-Clip
easy with right plier
piston, adjuster bolt with
O-ring and hot dog
we now can remove the
p brake lever arm
lever arm with eccentric pocket
hot dog,adjuster screw with o-ring & piston
remove old lever arm seal
and discard
piston adjuster bolt and O-ring
remove O-ring and discard
3 NAY1-26-46ZB Mazda OEM
rebuild kit
cleand and new parts ready
for assembly
install new O-ring on adjuster bolt
Install new lever arm seal
used 1/4 x 9/16 socket
to assist seat of seal
grease all P brake parts that are
below the o-ring
Install the lever arm, make sure
you have installed the new seal
Install lever arm spring
grease pocket of adjuster bolt
and install the hot dog(retainer link)
rotate lever arm so the grease
pocket is positioned to receve hot dog
I used magnet to help lower
the adjuster bolt and hot dog into
push down on aduster bolt
to seat O-ring seal
Install the C-Clip,
easy with right plier
put grease in bore and
insert adjuster hex scew
install cover bolt to prevent
loosing the hex adjuster,
will remove later for piston install
apply DOT 4 to cylinder bore,
square seal and boot
position the dust boot as shown
for easiest install
verify the boot out seal is
in caliper groove
push on piston and use 6mm allen, turn adjuster CCW to draw in piston past seal
verify boot piston seal in groove
and continue to retract with 6mm wrench
piston fully retracted in caliper
Caliper rebuilt ready for paint


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