I'm still completely baffled that the brakes on my 99' Trans Am are better than a C6 Z06. Would the braking force be atleast somewhat equal to the LS1 calipers compared to the Z06 after having the "appropriate/OE spec" master cylinder bores, boost assist, and pedal ratio etc?

Josh (Banko) has an award from Wilwood, so he's upgrading his brakes. Josh is the one that started this thread because his car is not braking strong enough. He PM'd me the system he's considering.

Brake piston sizes
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.75"
Rear: 0.75" or 0.875"
Brake pad brand & compound name
Front: PolyMatrix H
Rear: Hawk HPS

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I ran the calcs on this system ... an whoa Baby ... it swings the pendulum too far the other way. In the chart below, this is the system on the left. Look down at the total braking force #. It would have 7000# of braking force, which would simply lock the wheels up upon braking.

Now look at the chart on the right. By changing the pad compounds & the M/C sizes, we adjust the total braking force to about 4000#. That is a strong braking system.

Did you guys ever watch the Lassie TV show?
If you did, you remember the Dad always sat down with Timmy at the end of the show to explain the moral of their lesson. This was a planned in moment every show. The writers called it the "Ya know Timmy ..." part of the story.

Well ... Ya know Timmy ...
The lesson here is when building your braking system working out the details is just as important as buying great parts.

Hi Scott,

My concern is you're coming to a conclusion about braking systems, looking only at one part of the system ... the caliper piston area. Frankly, that's why many brake & pad manufacturers don't release specs. They're concerned a little information ... without the whole picture ... can lead to bad brake choices & incorrectly operating brake systems.

As covered above, the C6 Z06 Brake system has slightly more braking force than the '99 Trans Am. The GM engineers just got there another route than caliper piston area.

that would be correct.

Scott asked this in a separate post & I answered it there ... but felt it should be included in this thread too.


Hey Scott,

I'll outline my thoughts on the pros & cons of different brake rotor features & everyone can decide for themselves what makes sense for their individual needs. I think if you ask 5 different brake experts you will get 7 different opinions, so decide yourself & go with what makes sense for your goals.


Drilled: In the early years, before we knew better, many racers thought that drilling rotors made them run cooler. Wrong. Brake experts had rotors drilled to give the brake pads boundary layer of gasses a path to escape, while the edges of the holes helped clean the pads of debris somewhat.

For a rotor to deal with the heat generated, having more “mass” increases its thermal capacity. Drilling a bunch of holes in the rotor reduces the rotor’s mass & reduces the thermal capacity of the rotor. If the rotor gets overheated often & for long periods of time … the drilled holes become "stress raisers" that can lead to three problems: Elongation and/or distortion of the rotor, cracks between the holes … and breakage. Drilled rotors still have their place. I’ll explain at the end.

Slotted/Grooved: The grooves in the rotor … often called slots … help "clean" the debris from the brake pad. That’s it. It’s a good thing. The grooves/slots need to run a specific direction. See the illustration below.

J-Hooks: AP brakes offers a neat rotor a lot of road race & short track oval guys use. Instead of a straight slot grooved into the rotor, they have these “J”s machined into the rotor surface. The “J” goes all the way through the rotor, unlike grooved slots. The perform the same function as a slot and “maybe” they’re helping the boundary layer of gasses to escape. See them HERE.

Cooling: is not achieved with slots or drilled holes. There are three ways to cool rotors: Vanes inside the rotor, air ducting, with or without fans, to blow cooler air on the rotor, and the Ultra Cool brake fans that mount on the hub. See them HERE.

Important: I learned long ago, if we cool the rotor optimally, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a serious priority. I don’t want to provide the rotors “a little cooling” … I want to provide “as much cooling as practically possible” so we can run lighter rotors & reduce that rotating mass.

Vanes: Are the most important cooling feature of the rotor itself. The vanes of the rotor … spinning on the hub axis … create a vortex, sucking air into & through the rotor’s vanes … helping to cool the rotor. These are simply referred to as vaned rotors & they come in a lot of configurations. The details matter here. The air travels from inside the rotor to the outside, not the other way around as is commonly thought. So the vanes must face rearward when viewed from the outer diameter of the rotor.

Straight vanes do not work as well as curved vanes. There are made & sold as an economy product, because they can go on either side & the parts store doesn’t need to stock left & ride side rotors.

Curved vanes are the way to go. Just think of fan blade design. The vanes scoop the air from inside the rotor … suck it through the inside of the rotor … cooling both sides … and out the top.

More curved vanes provide more cooling … and add mass (weight) to increase the rotor’s thermal capacity. This is my preference instead of adding diameter. If we can get a 12” rotor with 48 vanes that weighs around 11# … that would be my preference over a 13” rotor with 32-36 vanes that also weighs around 11# … because the thermal capacity is the same, the 48 vanes cool better & the 12” rotor has the mass closer into the center, so it’s easier to accelerate & decelerate it.

The only advantage the 13” rotor offered (besides cool looks inside the big wheel) is 10% more braking force. But I can get that 10% braking force four other ways (pad, pedal, piston size & M/C size) … and not have the disadvantage of that weight rotating so far out there. A .05 CoF change in brake pad compound can achieve that.

Note: The vaned rotor is shooting hot air onto the inside of the wheel surface. This is where some of the tire’s heat comes from. If the brakes are overheating, this may over heat the tires too. (Seen it MANY times). Another reason to cool the brakes better.

Rotor Width: Making a vaned rotor wider adds several things: More weight & thermal capacity … and better cooling because the vane channels are bigger, flowing more air. Typical rotor widths are .81”, 1.0” 1.1”, 1.25” & 1.38”. Of course you have to have calipers capable of working on the wider rotor. I like to use the wider option as it adds minimal flywheel effect … as compared to adding rotor diameter.

If you’re not familiar with the math …
Changing the weight of a rotating mass is a one-for-one change in “stored energy” … which I think of, and call, “the flywheel effect.” Moving the weight of a rotating mass increases the stored energy by the SQUARE of the radius change. OMG! This is because as you move weight OUT from its rotating axis, you are increasing the weight's circular velocity (speed).

On the track where speeds are up significantly higher … than everyday passenger car speeds … it really matters. The faster we spin a rotating weight, the more energy it stores (flywheel effect). If we double the RPM of a rotating weight, we multiply the stored energy four times. So at twice the speed … say going into a corner at 100 mph instead of 50 mph … everything rotating has four times the flywheel effect. This is why it’s key to have lighter tire & wheel combos & not run larger or heavier rotors than we really need. My belief is to run as large as I need for thermal capacity & no more.

Rotor Diameter: A larger rotor diameter adds several things: Increased braking force, potentially more weight & thermal capacity, increased flywheel effect of moving the weight out from the centerline ... oh, and the cool factor. :)

Let’s outline braking force gains first:
Going from 10” to 11” adds 12.5% braking force
Going from 11” to 12” adds 11.1% braking force
Going from 12” to 13” adds 10.0% braking force
Going from 13” to 14” adds 9.1% braking force

Why I said potentially increases weight & thermal capacity … is because rotor designs vary. It’s possible to have an 11# 12” rotor & an 11# 13” rotor. If that is the case, you didn’t gain mass (weight) or thermal capacity. But, you still moved the weight OUT & increased the flywheel effect. Of course it is probable that you increased the mass (weight) & thermal capacity … as most 13” rotors are heavily than the same design 12” rotor … typically in the 3-6# range. So then, not only did you move the weight OUT & increase the flywheel effect … you added weight to the flywheel effect. UGLY!

I exhaust every option BEFORE I go larger on diameter. I go more aggressive pad compound, wider rotor, curved vanes, more vanes, better rotor material, no drilled holes and lastly more rotor material. Then, if I still need more thermal capacity than that … think GT/Trans Am road race cars … by all means I’m going up in rotor diameter.

.

Ron, thanks so much for running the numbers, I appreciate you showing me that every little detail matters in the system.



If I have a goal of running Wilwood J or H on the track and E's on the Auto-x / street can I do the following: 0.875" bore on the front, 0.875" bore on the rear dropping the line pressure via my existing proportioning valve to what a 1.0" bore would provide?

I'm running the Wilwood high volume master cylinders that run in (0.75", 0.875", and 1.0" bores, no 13/16" available). I have a duplicate set of 0.875" bore master cylinders and would like to put them to use instead of buying another new MC.

So the system would be:

Scenario 1: Street / Auto-x

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix E
Rear: Hawk HP+

Scenario 2: Track Only

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix J or H
Rear: Hawk HP+

Hey Josh,

The proposed packages you laid out work for the street & AutoX events ... if you put a 1" M/C on the rear. Do not run a .875 M/C on the rear even with a PV.

You end up with a LOT of braking force ... total = 3893# ... with a natural 67.4% front & 32.6% rear bias ... that can be fine tuned with the Wilwood pedal system you have.

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For the road course track days, the combo you proposed does not work ... but I showed it anyway ... obvious by the big red letters. :confused59:

With almost 5000# of braking force, you would just lock up the tires. The F/R bias doesn't work either.

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The 2nd chart shows the same street & AutoX set-up ... but shows the Track Day set-up with different brake pads.

4387# is still a lot of braking force. You will need good tires ... like Hoosier R6's or comparable ... or you'll constantly be on the edge of lock up.

This package uses:
Wilwood BP-20's in the rear which are an excellent rear pad with their steep CoF curve. For the front, either PFC's new 12 pad or Porterfields R4 pad. I know the R4 has a nice flat curve from 450 to 900 degrees, which makes for predictable braking.

I "believe" the new PFC 12 has the same CoF & flat torque curve ... and should last longer. It is an endurance pad with medium bite that was on the 2013 Daytona 24 Hour Overall Winner.

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Tip:

For road course racing, front brake pads ... with a flat torque curve in the operating range your running ... provides predictable, consistent stopping ... even when you're braking differently ... shorter/longer, softer/harder ... for different speed corners.

For road course racing, rear brake pads ... with a steeper climbing torque curve in the operating range your running ... provides the best overall stopping performance ... because the rear brakes don't bite so hard when you first get on the brakes ... and then brake progressively harder the longer you're on the brakes ... which the car can handle.

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.

Ron, I'm using a carbon kevlar brake pad with a .50 CoF. Is there any specific rotor manufacturer or type of rotor you can recommend for my application. Weight is just under 3200 lbs with me in the car......probably will lose at least 180 lbs for next season though. I will also be going to slicks next season. Should I bump the CoF up?

Pads had a stronger initial bite when I first got them and that seems to have faded. I do like a strong initial bite and am looking for a combo that will heat up quick and be best on short runs for time trials.
I haven't ever tried to lock them up so I couldn't answer that but as I previously stated I loved the way they worked when I first put them in.
So far no fade issues.
I'm running the same brake set up that Dale has but rotors are slotted only..

Remind me what calipers those are.

.

PBR 2 piston C5

When you are on slicks ... and have the grip ... the Wilwood H pads produce "mean" braking force & right now.

The braking force would go up 22% from your .50 CoF pads. Could be worth a try. Just an FYI ... never go to the track with new pads ... or anything new ... without taking your old stuff with you ... just in case you don't like the new stuff.

Thanks Ron....I'm going to look those up. :thumbsup:

I forgot to discuss when, where & why drilled rotors have a place.

For the type of competitions you're running, if ...
a. The track is short or has tight corners
b. The difference in corner speed & top speed is significant
c. Your lap times are affected significantly by your ability to accelerate & decelerate
d. Your brake temps are well within the safe range from overheating
e. You already have small diameter rotors
f. The drilled rotor is priced modestly for your application
g. You are serious about your maintenance program
h. You are serious about competing at the top level

Drilled rotors make sense then, because:
1. You can afford to replace them at the first sign of heat stress
2. The lighter rotating weight will accelerate & decelerate quicker
3. Improving your lap times

AutoX doesn't build much brake heat at all. So I love drilled rotors for AutoX competition as long as your maintenance program is good.

Same with other short track racing. We ran them on the rear of our 2550# NASCAR Modifieds, where the temperature window was around 400° or less.


P.S. Since I wrote this before having my morning coffee, I expect I'll need to edit this later. :)

.

Wow, great thread. Ron you add so much helpful info, thank you very much.

Darn now I have to make some more decisions.... :confused59:

Here is a link to a good 101 on brake system design.
Brake Systems 101 SAE

I came upon this thread in a search for finding the appropriate sized master cylinder for my application. I am building a 69 firebird track-street car with a 570 horse Texas Speed LS3, Ridetech stage 2 front and rear, Toyo R888 275 and 315's, Wilwood FNSL 13" 6 piston front and 12" D154 2 piston rear. I was considering the DSE master cylinder-booster combo, but don't know which one to order if it is even appropriate. Thoughts?

Ron I have a C3 Corvette with a custom frame and currently C4 12 rotors and calibers and may upgrade to 13 inch with C5 calibers. The car is 3200" build is in the below site. I have not had a manual master cylinder in my car since 76 but I am leaning twds it in this build. Any help in steering me to what manual master I need would be great or if you think I should stay with vacuum assisted as well. Many thanks, oh the car will be manly on the street, some auto cross events and one road race course a year.

https://lateral-g.net/forums/showthread.php4?t=44704

C4 Vette brakes leave an awful lot to be desired
 

My input is that the C4 brakes are not adequate - go straight into at least C5 class or better with aggressive pads (they're going to dust just by looking at them, but they will stop). C4 brakes ran a 7/8" bore MC with power assist and still left an awful lot to be desired. Running them on a manual brake scenario with a 7/8" bore MC is like yanking the vacuum hose off of a C4 Vette vacuum brake booster and hoping to stop (though you will have a slightly better mechanical brake pedal ratio with your C3 as I see it is a factory manual brake car in your build pics).

If you do everything "right" and still don't like how your brakes feel, we have an exceptionally powerful highly engineered direct fit conversion package available that provides a 100% true bolt in straight into your factory manual brake car:

http://www.hydratechbraking.com/C3Co...920161312A1BD0

We had a customer recently get back to us after installing his model 3007 system into his Vette, reporting back that it stops better than his CTS-V and his sport bike.

I say get with Tobin at Kore3 either way to get into at least C5 class items at the wheels. You could then evaluate how you like the pedal feel in manual brake mode, knowing that you could install one of our manual to power brake conversion systems in place at any point if you wanted to supercharge your brakes from there on in.

Kore3 is also a Hydratech dealer by the way.

Many thanks for the feedback. I have not run manual brakes in a very long time and I may not like the feel and boosted is certainly an/the option