GTRay

thespring clips that ZZ is refferring to are different on his BMW. the 8 doesn't have that giant clip holding the outboard pad in place. what i think ZZ thinks is that clip is actually the pad bracket on the 8. just flip the caliper up and swap the pads! couldn't be easier!

the spring clips that Vivid is reffering to are the sheet metal shims at the pad-to-bracket contact points. or (if our car is like other mazdas, the thin wirey vibration damping springs between the caliper and the pads) those shims shouldn't need to be removed for the track pads.

Ray

VividRacing.com

Just an update here as well. In one of my replys to this post I mentioned the Motul RBF600 not being a good idea to run in the 8 since the clutch and brake cylinder share the same reservoir. Well I've since been told different from the folks at StopTech and Motul. They say that it is safe to run the fulid throug the system and shouldn't cause any problems with the clutch.

Ike

Hey Huff, I heard some of you vivid guys were out at Willow this weekend for the big Mini/STi shootout. Way to crash the party, I heard the Blue WRX Turned the fastest lap of the day. Did you by chance bring the RX-8 out there?

VividRacing.com

Acctually, we took the EVO out there for some fun on the track. I wanted to go but couldn't swing the time off to go out there. I haven't talked to the guys yet as they haven't come back yet. I would have loved to take the RX8 out there but I would have needed to drive it out there and back. We ended up loading the EVO on a trailer for the trip out there since we spend the days prior to the race setting up the suspension and preping it. Mabey next time. There is an event coming up in May at PIR that me and the RX8 will be attending and we'll see how she handles on the banks of the NASCAR section of the track.

Ike

So you didn't have the Blue WRX out there? Must have been a lookalike, whoever it belonged to it was fast and I guess turned a 1:36 which was ahead of most of the field by 4 seconds.

GTRay

This makes me suspect that the motul fluid is DOT spec 5.1

DOT 3, 4 and 5.1 are all glycol based fluids and are interchangeable, the only differences being boiling points for the most part. The higher the number the higher the boiling point.

DOT 5 on the otherhand is a silicone based fluid and is NOT interchangeable with 3,4 and 5.1! It's like trying to mix oil and water, it just won't work :-)

if you do decide to upgrade your fluid i would suggest doing a complete system flush and make sure you get your bleeding sequence right. the old "furthest from the cylinder" technique has long been outdated. with todays ABS systems, master cylinders, and brake biasing hardware you can trap air, debris and dirty fluid in your system fairly easily using the wrong bleeding sequence.

Ray

VividRacing.com

The RBF600 is a DOT 4. Your right about the 5.1 not being mixable with other fluids. So what is the correct beeding sequence for ABS? I'm all ears.

GTRay

it's not just one sequence for any ABS system.

call your local carquest and ask them for a current brake parts spec book. Individual cars have their own needs for bleeding sequence. it's related to how the master cylinder is designed and which system componants it contains.

if you want to do the job right and you work on a wide variety of vehicles then it is in your best interest to look up the bleed sequence for each job. similar makes and models may even have differences in the sequence based on brake package on the car and how it might relate to ABS and traction control. If in doubt, look it up.

also on a very extreme side note i have a pop quiz for everyone!

What is the Minimum Rotor Thickness spec for?

A) To prevent technichians from machining too much material out of a rotor and causing too much heat to build in that rotor and thereby prematurely warping the rotor?

B) To prevent technichians from machining too much material out of a rotor and causing the caliper piston to over-extend itself?

C) A & B
D) none of the above

quiz will continue when propperly answered :-)

Ray

syntrix

Minimum front rotor thickness 22mm, 22.8 if an on hub lathe is used.

Usually the minimum is recommended NOT for caliper piston runout, but for heat that can warp the rotor. This is with panic braking or track use, very easy to warp a rotor, especially if you hold the brakes after the rotor gets hot (1800 deg F +). Good idea after panic braking to NOT use any brake force as the brake system cools off. You may wish to discuss warping and rotor runout tolerances (> .05 mm, remount and if still, lathe the bizzo).

GTRay

anyone else care to comment?

Ray

VividRacing.com

Hmmmm.... Both caliper hyper extension and heat warping are good guesses and make thier own respective arguments. I'm going to go with the latter.

red_rx8_red_int

My vote is D. A is wrong because (well nevermind an explanation, I'm leaving now, and don't feel like explaining it).

But D, final answer.

GTRay

the final answer is...

B

the "machine-to" spec or sometimes the "discard at" spec exist to prevent techs from turning a rotor beyond the point where you can actually risk a piston blowout when the pads are worn out.

this spec is not related to how much heat a rotor can absorb or disipate - i once thought it was. turns out engineers are smart :-) and they are apparently smart enough to figure out that they can design a disc brake system with enough surface area to prevent heat soaking for normal driving conditions and even frequent panic braking menuevers.

however, Factory engineers aren't paid to be racecar engineers for mass production vehicles so often times people who do race their street cars do heat soak brake parts and warping does occur when brakes get hot.

but remember, engineers are smart :-) they thought of this too and have designed modern braking componants to compensate to a certain degree for warped rotors. most of todays OEM calipers on the road are floating caliper designs that allow for the movement of the rotor when it is warped (also known as lateral runout).

this means that a warped rotor is NOT the direct cause of a pulsing brake pedal. When a rotor gets warped it moves the caliper back and forth on its slides. this back and forth movement of the caliper starts with the rotor when it acts on the pads. for every push that the rotor causes on the pads it takes a small amount of material out of the rotor's high spot. by reducing the amount of material at the high spot on one side of a rotor a thin spot is being created. if there is a thin spot there must be a thick spot.

this variation in thickness is where your pulsing pedal comes from. instead of the pads moving back and forth in the same direction as one another they are forced apart and the high spot and come together at the low spot causing the piston to move in and out in its cylinder and then causing the fluid to move in and out of the caliper and then causing the fluid to move back and forth in the lines all the wy up to the master cylinder where it translates that movement through the brake pedal and into your foot. :-)

inhale.... whew....

Ray

GTRay

fixed caliper designs like those from brembo, porsche, stoptech, the TII... they all work similarly. instead of the whole caliper sliding the fluid inside the caliper is just moved from one bank to the other until the high and low spots develop at which point the same thing happens to those brake parts that happen to the floating calipers.

Ray

VividRacing.com

So, Ray, tell them what they've won! Oh....wait, that was Bob Barker talking. My bad.

GTRay

our lucky winners have each won a brand new stoptech big brake kit courtesy of Vivid Racing!

hehe

Ray