Manual Brake System Trouble Shooting: Expected Line Pressure?

[carbuff]

Rob,

Looking at the math, I think the answer is that the Brake Torque line represents the amount of work that the front brakes on an application would be doing while the Total Braking Torque if 70% line means that if 70% of your total car braking is done in the front, and 30% in the back, then you have a combined braking torque equal to that last line. Thus, if you multiply the value in the bottom line by 70%, you get the number in the Brake Torque line (at least for your W6A caliper):

3141 * 0.7 = 2198.7 (2199 rounded)

Now, exactly what the Total Braking Torque number actually means, I'm not sure. I think it refers back to Ron's Guideline, meaning that the 3141 total would fall between the 3000# (Performance Production Car) and the 3500# (Good street & track braking system) areas. Ron, could you please confirm that I'm understanding what that row of the table is referring to?

(I've said it before, and I'm saying it again... I love all this tech you are providing!!! THANX! )

[Ron Sutton]

Originally Posted by carbuff

Rob,

Looking at the math, I think the answer is that the Brake Torque line represents the amount of work that the front brakes on an application would be doing while the Total Braking Torque if 70% line means that if 70% of your total car braking is done in the front, and 30% in the back, then you have a combined braking torque equal to that last line. Thus, if you multiply the value in the bottom line by 70%, you get the number in the Brake Torque line (at least for your W6A caliper):

3141 * 0.7 = 2198.7 (2199 rounded)

Now, exactly what the Total Braking Torque number actually means, I'm not sure. I think it refers back to Ron's Guideline, meaning that the 3141 total would fall between the 3000# (Performance Production Car) and the 3500# (Good street & track braking system) areas. Ron, could you please confirm that I'm understanding what that row of the table is referring to?

(I've said it before, and I'm saying it again... I love all this tech you are providing!!! THANX! )

Bryan,

You have it correct. You can look at my post answering Rob for more detail.

.

[FETorino]

Ron

As always thanks for the detailed explanation. Looking at Brian's math I see it is obvious.

Brian you obviously have a better skill set with calculations than as a food critic.

On my set up in the rear I have a 14" rotor and a Wilwood FNSL 4 piston caliper 120-11782-BK.

[Ron Sutton]

Originally Posted by FETorino

Ron

As always thanks for the detailed explanation. Looking at Brian's math I see it is obvious.

Brian you obviously have a better skill set with calculations than as a food critic.

On my set up in the rear I have a 14" rotor and a Wilwood FNSL 4 piston caliper 120-11782-BK.

Hey Rob ! What are we both doing up so late ?!?!

Here are the calcs for your brake system with Wilwood BP-20 brake pads & two different M/C sizes for the rear. The BP-20's CoF curve climbs pretty rapidly, hence the difference in CoF numbers for front & rear.

I'm going to suggest we find brake pads that have a flatter CoF curve but in the .50-.55 range. Once we land on brake pads, then I'll recalculate this so we can see which rear M/C is best.

[FETorino]

Originally Posted by Ron Sutton

Hey Rob ! What are we both doing up so late ?!?!

Checking brake specs after a night out with friends. What else?

[Ron Sutton]

Originally Posted by FETorino

Checking brake specs after a night out with friends. What else?

Me too ... sorta. We were at a family get together for a birthday party. I couldn't resist checking stuff on here when I got home.

Did the brake calcs make sense with your system?

[carbuff]

Ron,

Do you happen to have the piston size numbers for the Baer 6P caliper? My guess is that it's very similar to or the same as the 6S. I'm running the 6P front and rear on my car with 14" rotors.

Given your definitions, I would consider my setup to be more conventional, not a high-travel setup. So I would be leaning towards the 65/35 setup. I'm using the DSE booster and master cylinder, which is obviously a power brake setup instead of a manual setup...

[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. 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. With a 16" shouldn't this lead to a dramatic brake torque increase? 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.

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.

[carbuff]

Originally Posted by FETorino

Brian you obviously have a better skill set with calculations than as a food critic.

Hmm, 25 years as an engineer vs. 45 years of eating, what's wrong with this picture?

[FETorino]

Originally Posted by Ron Sutton

Me too ... sorta. We were at a family get together for a birthday party. I couldn't resist checking stuff on here when I got home.

Did the brake calcs make sense with your system?

Yes very clear this am. Something was making them a little fuzzier to review last night Not certain what that was

Originally Posted by carbuff

Hmm, 25 years as an engineer vs. 45 years of eating, what's wrong with this picture?

Formal education has helped you on the engineering front. Your eating habits are Feral.

Originally Posted by BANKO

Another thing I noticed on your charts is an assumed static line pressure of 499psi for 7/8" MC and 679psi for 3/4" MC, can you speak to the what is an expected maximum line pressure in a manual setup. Some guys have mentioned measuring pressures of 800-1000psi. I assume this is primarily achieved by a greater input to the pedal rather than reducing MC size. Do you have numbers for the following driving styles: normal (non fatiguing pedal input), semi-aggressive pedal input (spirited driving / auto cross), aggressive pedal input (high speed track braking and panic stop situations).

As always thanks for your wealth of knowledge and willingness to educate us!

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?