EGbeater

iTrader: (35)

I'm in the process of replacing the dust boots and internal seals on my front brakes, and I'm discovering that the grayish smooth finish on the outer walls of the pistons is damaged... there's small pock marks in it. On one of the smaller-diameter pistons, much of the finish on the back side of the piston is actually peeling, so I'm guessing it's heat damage (I've boiled the fluid at the track repeatedly, even with brake cooling ducts, and my Brembos are way beyond "Brown-bos," they're black).

Looking through the online parts catalog at mitsubishiparts.net, it seems like only the complete caliper is available from the dealer - there's no listing for replacement brake pistons for the Evo.

Is this right? If so, I guess my best option for getting replacement Brembo pistons would be by buying used calipers from a salvage yard.

jid2

iTrader: (62)

See if Girodisc can get them, that's probably your best bet for new parts.

EGbeater

iTrader: (35)

Good call; thanks for the suggestion.

apex electric

My front calipers were toasted after 5 seasons. I bought a used set for $350 that still had red/white finish on E bay. Just find a fresh used set from a street car.

electricman

iTrader: (12)

i thought i saw a rebuild kit on ebay before

EGbeater

iTrader: (35)

FIVE seasons?? That'd be wonderful if I'd gotten anywhere that much life out of mine. My Brembos turned black after the first season of track days (I only did 4 or 5). I've probably done a grand total of 10-12 track days now.

I don't want to spend the money at this point, but I'm coming to the conclusion that a BBK is the only solution for me... but besides the cost, I hate to be forced to migrate to 18" wheels, even on the street.

I'm thinking of seeing if someone can strip these OEM pistons and ceramic coat them with something that is similarly smooth but can withstand 1,000+ degrees... then at least it won't happen again. I figure if they have ceramic coatings for piston tops, and EGTs are easily in the 1300-1500 degree range (probably hotter in the actual combustion chamber), that stuff should easily handle my brake heat long-term.

Just in case someone feels the urge to tell me "all I need to buy is..." to solve my braking issues, this is my current brake setup:

Castrol SRF fluid
Technafit S/S lines
Girodisc 2-piece slotted rotors
Girodisc ti shims
Hot Lap brake ducts
Hawk DTC-70 pads (bent the backing plates last track day as the pads wore thin)

Also, my Evo only weighs about 3,000 lb. when I hit the track... and I only weigh a buck-fifty. If I could lose 100 lbs myself to help my Evo stop, I would.

DaveK

iTrader: (21)

Nah...parts are fine, you just need pitch it sidewayz to scrub speed! Brakes are for parking.

If you need parts on short notice, I've got a set of brembos in the garage...I'd just need you to replace whatever you used.

LMK,

Dave

EGbeater

iTrader: (35)

Hey, that's really thoughtful Dave; thank you very much. But I can live w/o my Evo for a while; I've got commuter Honduhs to drive.

A couple of places I'll call today about ceramic coating:

http://www.swaintech.com/store.asp?pid=10296

http://www.airborncoatings.com/alumcerm.html

Seems like Swain has at least done something brake related - from the bottom of that webpage:

Thermal barrier and heat emitting coatings for brakes should not be overlooked for race applications. A braking advantage can be as, or more important than power gains.

As long as the new coating is impervious to brake fluid, and it can be applied with a surface as smooth as the original coating, it should work great.

'Course, if it's going to cost substantially more than acquiring a set of still-red OEM calipers from a junkyard...

EGbeater

iTrader: (35)

Found these, but they're stupid expensive ($60 each = $480 for the eight pistons inside both front calipers), plus the pistons in the Evo 8/9's front calipers are 40mm and 46mm diameter... the 46mm size doesn't seem to be available:

http://www.hrpworld.com/googlebase.c...action=product

honki24

iTrader: (23)

You guys make me worry about mine. I've been running them black for 4 seasons now. I just noticed a small brake fluid puddle at the front left. Concerned about my seals. Ah well, at least all that experience with fade and boiling makes me comfortable if they mechanically fail on me. Run 'em till they're dead. (Mine's not a street car any more)

EGbeater

iTrader: (35)

any brake fluid leak = a very bad thing

I found the same as I tore into this rebuild... apparently I cooked one of the seals in the front right caliper for the last time at the track, and then at an autox a few weeks later, the fluid finally pushed past the hardened seal.

I found this page today, which explains why/how overheated/cooked seals can contribute to even MORE heat and faster pad/rotor wear:

http://www.patentstorm.us/patents/67...scription.html

The high heat generated during braking has several adverse effects to the caliper assembly. First, the piston seal typically only has an operating range up to 300° F. When the heat generated during braking exceeds that temperature, the seal can become degraded and crack or lose its elasticity. When the seal does not function properly, brake fluid can leak from the bore, which causes the brake to malfunction. The loss of elasticity prevents the seal from pulling the piston back into the bore, which causes the brake pad to continue to rub on the rotor surface. This condition is called "drag" and will slow the vehicle, create excessive wear on the rotors and pads, generate additional heat, and adversely affect fuel economy.

It also suggests that overheated aluminum calipers will flex enough to add to squishy pedal feel/long pedal travel:

Increased temperature affects the caliper itself. It is preferred that the caliper be as stiff as possible to securely and uniformly hold the pistons in position for braking. Many calipers are formed of aluminum for its lightweight strength. However, aluminum functions best at temperatures below 350° F., with the stiffness dropping considerably at higher temperatures. These higher temperatures will cause more deflection of the caliper, which in turn leads to increased brake fluid disbursement. As a result, the driver will experience a long pedal.

I've used an IR temperature sensor to confirm that my front calipers are over 800 degrees after a track session... and that's after a partial cooldown lap, with air ducts pushing air to the gap between the caliper and the hub area.

boomn29

iTrader: (47)

I've found you need to replace the seals yearly.

I also picked up an extra set of used calipers in the forums, and plan on getting another backup as well. I'll switch out the seals on all of them (thank u Girodisc) and have a spare set.

If you're running SRF and boiling; damn! My suggestion is to double-check your cooling ducts. Use an air hose to push in air from the front and have someone check the other end to see how much is really getting through.
I plan to rerun mine to SHORTEN them as much as possible. I boiled my fluid this year once I put on an undertray; so my cooling ducts aren't doing enough!

george3

iTrader: (39)

What I found was that I was outdriving my brakes, putting way too much heat into the pads and rotors, so they pads would get toasted and I've actually cracked a rotor in about 10 heat cycles with my Brembo's with R-compound tires.

Here's what I did. I took off my oem front Brembo's and replaced them with a 355mm StopTech BBK (big brake kit). The "out" price was reasonable after selling the Brembo calipers and the stopping power is stupid crazy now. Pads and rotors last longer, too.

GL

boomn29

iTrader: (47)

How much are your pads now though? I know some of the BBK's need specialized pads that are pricey.

george3

iTrader: (39)

Nobody's buying StopTechs for the street!

So for track use if pad price is your only consideration, stay with the Brembo's. I was using race compound pads even with the Brembo's, which I'd change-out at the track. The ST60 pads for the 6-piston BBK is barely a case of beer more (depending on your brand).