Date: Mon, 22 Feb 1999 14:27:11 -0500 Rob's web site
has pictures and diagrams.
Do you need bigger brakes?
The stock 3rd gen RX-7's brakes work fine for everyday sports car driving
but on the race track when exposed to continual high speed deceleration the
11.5 inch front brakes are shown to be a weak link. The stock brake rotors
are too small, thin and retain too much heat. The heat is transferred to the
brake calipers which in turn heats the brake fluid beyond its boiling point.
When the brake fluid boils the gas bubbles in the brake lines compress and
absorb the pressure placed on it from the brake master cylinder. The brake
pedal gets spongy and you experience brake fade.
Hot brakes can warp your rotors and Sandy Linthicum fried his front wheel
bearings after 40 hours of track time because the stock rotors got and
stayed too hot. The small brake cooling ducts in the R1 chin spoiler don't
help much and a more direct form of brake cooling would be beneficial, but
nothing beats more "swept" area for the brake rotors. Brakes work by
converting the car's kinetic energy to heat and the larger the rotor (the
larger the swept area) the more rotor you have to dissipate heat. Converting
the front brakes to a larger rotor (usually 12 3/4 to 13 inches in diameter)
is the best way to prevent brake fade and damage caused by overheated brake
rotors.
Note: An RX-7 with upgraded rotors and calipers will not stop any shorter
than stock until brake fade is encountered--as long as the stock brakes can
lock-up and activate the Anti Brake Skid (ABS) system the stopping distances
will remain virtually the same as a car with upgraded brakes. After repeated
stops an upgraded car will begin to out perform a stock braked car. Braking
distance will immediately improve when stickier tires are used because more
tire grip will allow more deceleration before and during skidding (ABS
operation).
The bottom line is a big brake upgrade is a benefit experienced only during
track style driving, although there is always the aesthetic benefit of large
rotors behind the spokes of your wheels.
A potential downside of a brake upgrade is increased brake pedal travel. If
the big brake kit has larger (or more) brake caliper pistons than stock,
more brake fluid will have to be pushed through the brake system to move the
pistons. Some people have upgraded the brake master cylinder to the larger
one from the 93 Mazda 929. See the 929 Master Cylinder Install How To.
The brake bias may also shift to more front brake bias because a larger
front rotor gives the caliper more "leverage" to stop the wheel. The ABS
system will mask this problem by activating on the front brakes until enough
brake pressure is applied to the rear brakes to cause them to activate the
ABS too. You can install a brake proportioning valve to tweak the bias back
to the point where the front brakes lock-up just before the rears. See the
Brake Proportioning Valve Install How To.
Warning:
Don't install a big brake kit yourself unless you are a very competent
mechanic. A single point failure in the brake system will result in the
total loss of brakes and possible damage/injury/death! A brake shop can
install a big brake kit.
I followed Sandy Linthicum's lead and decided to install the big brake
upgrade from Mandeville Autotech (Roger Mandeville, (864) 582-0038,
rmandeville@mndspring.com, 350 Simuel Rd, Spartenburg, SC 29301, mail: PO
Box 1867, Zip 29304). For $995 Mandeville sent me two 13 inch diameter by 1
1/8 inch wide vented rotors (not 12 3/4 like most other 3rd gen upgrades)
with CNC machined aluminum rotor hats, brake caliper widening adapters,
longer caliper bridge bolts and brake pad retaining pins, and two brake
caliper extension brackets. The kit widens the stock calipers to reach
around the wider rotor. The Mandeville kit uses the stock calipers because
they are quality, light weight units that work great with a larger rotor. An
added benefit is that you won't have to upgrade the master cylinder. By
modifying the stock calipers Mandeville can charge less than half of what
everyone else charges for a big brake kit. The aluminum rotor hats reduce
weight so Mandeville's rotors actually weigh less than the stock all iron
rotors. The kit does requires 17 inch or larger wheels and doesn't include
stainless steel brake lines. See the Brake Line Install How To.
[I will enclose info specific to the Mandeville kit in brackets.]
Hammer type impact wrench with large Phillips head bit, 1/2 inch breaker bar
for high torque bolts, large and small torque wrenches, 8mm and 10 mm
wrench, 14mm and 17mm sockets [Mandeville kit: 10mm and 8mm (big) Allen
wrenches or Allen sockets, tin snips and grinder or power sander.]
Jack the car and remove the front wheels, it's best to raise the entire
front end because you will have to bleed both sides after the install
anyway. Turn the steering wheel to make access to the caliper easier. It's a
good idea to disassemble one brake at a time so you can reference the other
caliper when you're putting the caliper and brake pads back together.
Remove the brake pads by removing the brake pin M clip and then sliding out
the retaining pins (hold the M springs while you slide out the pins or they
may pop out). You may have to spread the pads a little to loosen them enough
to slide them out of the caliper. A pair of needle nose pliers works pretty
good as a spreader. Warning: Do not touch the brake pedal while the pads are
out.
Put down some newspaper to catch the brake fluid. Use a 12mm wrench to
disconnect the brake line at the caliper (where the brake line meets the
caliper's hard brake pipe) and plug the brake line. I used a small rubber
vacuum hose plug.
[If you don't plug the line all the brake fluid will drain from the system
when you split the calipers. Trust me on this one. Remove the caliper's four
14mm bridge bolts and split the caliper. I had to use a 1/2 inch breaker bar
to loosen them. Watch for the rubber ring seals that are sandwiched between
the caliper halves. Install the new rubber seal rings into the circular
groove cut in the caliper widening spacers and install the two spacers with
the ring seal placed against the caliper half still mounted to the car. Use
the new longer bridge bolts to secure the caliper halves and spacers. Make
sure all four (two stock, two new) rubber seal rings stay in place while you
bolt the caliper halves back together. Torque the caliper bridge bolts to 35
foot pounds]
[Mandeville big brake kit specific instructions are in brackets]
Remove the two large 17mm bolts that hold the caliper to its mount and
remove the caliper (or hang it with safety wire or a bungee in place from
the coil spring). I had to use a 1/2 inch breaker bar to loosen the bolts.
Don't mistake the caliper's four 14mm bridge bolts for the two caliper mount
bolts. The RX-7 Workshop Manual cautions you against loosening the bridge
bolts. You will see two large Phillips head screws and one empty hole in the
brake rotors. Use an impact wrench with a large Phillips head bit to remove
the two rotor screws. You will have to use an impact wrench, there is no way
these screws are coming out by screwdriver. After you get the screws out put
one of them in the empty hole and drive it in using the impact wrench. This
will break the rotor loose and allow its removal.
[The brake rotor air guide needs to be modified or removed so it will clear
the top and bottom of the new rotors. I trimmed off about1/4 inch on the top
flange and removed the bottom flange completely using tin snips. Just slide
on the new rotors and you'll see what you have to remove (see photo above).
You can ditch the thin metal shim that went between the caliper and caliper
mount. The caliper mounts have to be slightly modified to fit. See the
caliper modification diagram below to see what to grind or sand off. I tried
a die grinder but I got much better results using 6 inch circular 60 grit
sandpaper with my electric drill. Just keep grinding until the caliper
extension brackets and calipers fit. Mount the supplied caliper extension
bracket using the supplied Allen head bolts and torque them to 58-72 foot
pounds. Slide on the new rotors and then mount the caliper to the caliper
bracket and torque it to 58-72 foot lbs.]
Reverse the removal instructions above to install the new rotors.
[The Mandeville rotors do not use the Phillips head screws.]
Torque the Phillips head screws to 87-130 inch pounds (8-11 foot lbs.) and
the caliper mount bolts to 58-72 foot lbs. Install the brake pads, [new
longer] retaining pins, M springs and pin retaining M clip. Reconnect the
brake line and torque it to 113 to 190 inch pounds (10 to 15 foot pounds).
Bleed the brakes thoroughly. See the Bleed Brakes How To. If you followed my
advice and plugged the brake line you should have a minimum of air in the
brake lines [and calipers] and you shouldn't have to bleed the rear brakes.
Make sure you have a firm brake pedal and apply brake pedal pressure for
about 30 seconds to check for any fluid leaks at the brake lines and
calipers. Test the brakes carefully before trying them at speed.
Enjoy your new brakes.
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[Copyright Notice]
From: "Rob Robinette" How To Install a Big Brake Kit (and Replace the Brake Rotors) on a 3rd Gen
The Mandeville Auto Tech Big Brake Kit
What's needed for the install:
How to install a big brake kit
How to replace the brake rotors
