Manual Brake System Trouble Shooting: Expected Line Pressure?

[Ron Sutton]

Good morning Rob,

Originally Posted by FETorino

Yes very clear this am. Something was making them a little fuzzier to review last night Not certain what that was
I have a pretty good idea "why".



The chart assumes a 100lbs of driver force on the pedal resulting in a 300lb force on the master.

So I guess the question boils down to why the 100 lb number is used and how do we relate the figure to an amount of pedal pressure that is familiar?

Read my post to Josh & that should provide clarity.

[Ron Sutton]

Hey Josh,

Originally Posted by BANKO

Ron, thanks for the charts! I've been studying and pondering many questions. It is great to see a line up of all the calipers. Interesting that the GM single piston on and 11.88" rotors have almost as much clamping force as the Wilwood massive TC6R.
That's what fools a lot of car guys. You see all those pistons & think the math adds up but it often does not. The formula for piston area (or area of any circle) is Radius x Radius x Pi. Remember radius is half of diameter.

So a stock GM Camaro, Impala or C10 pick up caliper from the 70's has a piston size is 2.9375. Divide by 2 for radius = 1.46875.

1.46875 x 1.46875 x 3.1416 = 6.777 inches of piston area. Times 2 calipers on the front = 13.55 total piston area for the front.

The PBR/Z06 Caliper has 6 pistons, but you only account for one side, so 3 all the same size at 1.30". When you run the braking formula, you end up with 7.964 total piston area for the front.

There isn't anything wrong with these PBR/Z06 calipers. The Z06 system was designed with larger rotors, higher CoF brake pads & more pedal ratio than the Camaro, Impala or C10 pick up. I'm not sure if the M/C size if different. But when you're swapping a brake system into a car, you need to account for these details in the total system.

Important Note: I'm not sure if I read this correctly or incorrectly ... but if you have the proportioning valve all the way "out" ... that should reduce the rear brake force by 57% ... and is reducing your total braking force.

If that is correct ... you need to start by opening it up to restore rear braking force ... and then go test your brakes in a safe place & see how it does. If you get it where it's locking the rear brakes up ... reduce the rear braking force just to the point it doesn't lock up the rears ... and let's see if that's better.


Can this TC6R caliper be used on a 13" rotor, the smallest size rotor i saw offered is 16", reading the caliper drawing shows it may accomodate a 14" rotor.
I do not know, as I have not worked with this caliper. It was designed by Wilwood to be a street caliper for pickups & SUVs. That's outside my wheelhouse.

With a 16" shouldn't this lead to a dramatic brake torque increase?
You don't need 16" rotors. I have designed brake systems with 5500# total braking torque utilizing 11-3/4" rotors front & rear. The main reason to increase rotor size is to increase the thermal capacity of the rotors to survive long races.

I never run a rotor larger than needed, because the rotational weight KILLS performance. It adds to unsprung weight ... making the suspensions job of controlling that wheel harder. And it adds to the rotating weight. Not only is the rotor heavier ... but you're moving it out on a bigger radius.

I cringe when I see guys spend $1200 a wheel to shave 2-4# off ... then add rotors that weigh 6-8# more.

I learned long ago, if we cool the rotor properly, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a priority.




This got me thinking it might be an alternative to the W6A (5.4) on a 14" rotor since it provides 6.9 piston area!!! Key downside is the availability for more tack oriented pads, looks like the highest CoF is .40, comparable to the HP+ pads.
The W6A is a real race caliper with a wide variety of pads available ... including race track compounds. The TC6R is a street caliper with a lot of piston area ... but a narrow selection of street pad compounds.


I was also thinking of the benefits of adapting the GM single piston caliper to a larger rotor. Not very sexy, but effective. Quite disappointing to see the Z06 6 pistons have such low clamping force.

Again, nothing wrong with the PBR/Z06 caliper. I think your application may need more aggressive pads & more rear braking force to be a good system. Also nothing wrong with upgrading it as you've mentioned doing.

Please go test the proportioning valve adjustment to confirm that is not a part of the problem.

[Ron Sutton]

Originally Posted by Flash68

Another thread made even better by our main man Mr. Sutton.

Ron, do you happen to have a chart for the AP6000 fronts and AP6050 rears?

Hi Dave,

I have worked with AP calipers a LOT ... but I am not familiar with those part #s, other than knowing they're 6-piston calipers.

Two questions:
1. What is/was their intended design purpose?
2. Can you measure the piston sizes & we'll run some calcs?

.

[FETorino]

Originally Posted by Ron Sutton

Hey Josh,



You don't need 16" rotors. I have designed brake systems with 5500# total braking torque utilizing 11-3/4" rotors front & rear. The main reason to increase rotor size is to increase the thermal capacity of the rotors to survive long races.

I never run a rotor larger than needed, because the rotational weight KILLS performance. It adds to unsprung weight ... making the suspensions job of controlling that wheel harder. And it adds to the rotating weight. Not only is the rotor heavier ... but you're moving it out on a bigger radius.

I cringe when I see guys spend $1200 a wheel to shave 2-4# off ... then add rotors that weigh 6-8# more.

I learned long ago, if we cool the rotor properly, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a priority.



[/COLOR]

Guilty as charged.

You see a lot of oversized rotors in the PT world because of the aesthetic value of filling the wheel. Many of us know better and still commit the crime.

I fell victim but reading this reminds me why I really wanted to run smaller rotors out back.

Originally Posted by Ron Sutton

Hi Dave,

I have worked with AP calipers a LOT ... but I am not familiar with those part #s, other than knowing they're 6-piston calipers.

Two questions:
1. What is/was their intended design purpose?
2. Can you measure the piston sizes & we'll run some calcs?

.

Technical questions for Flash, this should be good.

[carbuff]

I have found the solution for all of our braking concerns! And it's cheap too!!!

Brembo Red Disc Brake Caliper Covers

[Ron Sutton]

Originally Posted by carbuff

I have found the solution for all of our braking concerns! And it's cheap too!!!

Brembo Red Disc Brake Caliper Covers

That is hilarious.

I'm sure they're licensed by Brembo ... NOT.

.

[Track Junky]

This is great stuff guys.

I think I'm just going to add a "Thanks Ron" to my sig.

[Flash68]

Originally Posted by Ron Sutton

Hi Dave,

I have worked with AP calipers a LOT ... but I am not familiar with those part #s, other than knowing they're 6-piston calipers.

Two questions:
1. What is/was their intended design purpose?
2. Can you measure the piston sizes & we'll run some calcs?

.

I got these from James Shipka as they were used on his One Lap Camaro a couple years before he switched. Their intended purpose is dual street/track. I have the slotted-only version (not drilled). Here are the links he sent me:

http://www.brake-pros.com/product_fi...0S%7Ebroch.pdf
http://www.brake-pros.com/product_fi...0S%7Ebroch.pdf

Piston sizes (Hey Rob, look at that!) we measured to be as follows:

1.05 / 1.05 in the rear and 1.5 / 1.25 / 1.05 in the front.

They also came with some Mintex Xtreme and Raybestos pads. Not sure which we will try out first.

After some discussions with a couple people I was planning on starting with 3/4 / 3/4 MC bores.

Thanks Ron

Originally Posted by FETorino

Guilty as charged.

You see a lot of oversized rotors in the PT world because of the aesthetic value of filling the wheel. Many of us know better and still commit the crime.

I fell victim but reading this reminds me why I really wanted to run smaller rotors out back.

Yep. Nothing looks worse than an 11" rotor inside a 20" wheel.

But then a lot of this talk is really helping to validate that form can be trumped by function and then form can actually be aesthetically appealing because of it.

Originally Posted by FETorino

Technical questions for Flash, this should be good.

hey Roberto..... see this post by your new Crew Chief below. He has posted this more than once.... FYI.

Originally Posted by Ron Sutton

6. I want people to ask questions. There are no stupid questions

[Ron Sutton]

Dave,

You didn't give me all the details to work with, so I "assumed" a 6-1 pedal ratio & worked up a chart with 13" rotors & 14" rotors. If you have different details, let me know what they are & I'll plug them into my calcs.

Also, since I don't know what pads you're going to run, I adjusted the pad CoF until I got the 14" rotor version to about 4000# braking force. That will require pads in the .52 CoF at the temperature range you'll use them at. That is the lower end of race pads. You may want less braking force on the street.

For less braking force, go to a pad with a lower CoF. For more braking force, go higher on the CoF.

[Flash68]

Thanks Ron.

Yes, 6:1 on the pedal ratio and 14" front and rear rotors.

I need to see if I can get an exact number/model # of the brake pads I got. I was also considering going with Carbotech XP-12 and/or XP-10 pads. I used them on my previous Wilwood setup (XP-10 front / XP-8 rear) and liked them.

Any experience with them?