manual brake second gen F bodies

[Skip Fix]

OK guys with manual brakes-if you really stand on them to get max pressure does the dash/steering wheel move? Mine sure does.

[silver69camaro]

Not me. How much force are you applying to the pedal?

[Skip Fix]

Matt alot(150+ leg press at least) as I'm checking max line pressures 1200. Doesn't move that much when I'm just at 400 psi. Pedal travel feels good and pressure needed is about like power brakes with no motor on.

Just had a friend check his original manual brake TA that uses a Wilwood setup and his column does drop some but only about 1/8-1/4". Not sure if they got any extra pedal or firewall bracing.

More info in the line pressure thread.

Basic system Wilwood Dynalite 4 piston 1.75 calipers 10.75 rotor, rear GM front metric calipers in place of the ratchet TA calipers and about 11 1/8" rotor. Adjustable old Mopar prop valve in the rear line T after for the pressure gauge line. Now has a 1 1/8 Strange MC with rears plumbed to rears. Hurst Line lock used to T the fronts and take off for the front pressure line below the solenoid. Had a 1" Vette style MC that had alot of travel and way too easy effort. Gauges showed it was barely leaking at 800+ psi, as it would slowly drop.

Car has not moved an inch as I'm still setting up the brakes and chassis(had to replace the leaking wheel bearing leather seals Wilwood used with a different rubber seal). So I don't know what pedal effort will actually be needed for real driving stopping. Dustin at Wilwood siad 400 is generally adequate in most cases.

[MrQuick]

there is a 1/8" may be 3/16" plate around the master spot to 18 g firewall. not a whole lot.

[Apogee]

"Normal" maximum brake pedal input forces for manual brakes should be in the 75-100 lb range in my experience at which point you should be achieving lockup. Anything higher can cause excessive driver fatigue and depending on what you weigh, begin lifting you out of your seat. Most adults can and will apply 200 to 300 lb of force in a panic stop situation, but that doesn't mean that you want to design for that. Given your setup, I still think that a properly functioning smaller bore MC would be more optimal.

Tobin
KORE3

[a67]

It isn't unusual to fab a M/C brace.

Bob.

[Skip Fix]

Thanks all. Tobin you may be right. I figure I'll get it actually moving and see if it is too much effort to not get fatigued when it is stopping and lockup and if so try downsizing. I know there are also 1 1/16 from Strange as well as back to a 1" Vette or Wilwood aluminum($$). Returned to old bad 1" one and got a replacement, but the Strange/Mopar is so much smaller and saves 7.5lbs.

Is there a 1" Mopar style? and if the "front" port moves more volume would it be better to plumb the low drag rear calipers to it which ever size MC I use?

[nullshine]

Is there a 1" Mopar style?

Perhaps this one?

http://www.dormanproducts.com/p-17301-m39476.aspx

Ok, so it's 24mm, but that's pretty darn close.

[Skip Fix]

Pretty darned close 1.4mm away-.055"

[nullshine]

Ok, again not exactly 1", but how about this one?

NAPA# NMC M2373
1.03125" bore.

It's 1-1/32", so closer to the 1" mark, but this time on the large side of one inch. I noticed in one of your posts above that you said the 1" vette master was too effortless and had too much travel, so maybe the 1-1/32" will tune a little of that out.

Your 1-1/8" bore has a surface area of 0.9935", if we consider this figure to be "100%", then the 1-1/32" has a surface area of 0.8348" and would be 16% smaller. (So 16% more pedal travel and 16% less effort).

Using the same math for the 24mm (0.94488") we come out with 0.7417" surface area and would be 25% smaller, and again, with 25% more pedal travel and 25% less effort.

PS: I think my surface area calculations should actually be doubled since it's a tandem master, however the percentages should still work the same.

Just for the hell of it,
1-1/16" = 0.88619" and 10.8% smaller than the 1-1/8"

So hopefully based on these percentages you can get an idea of what might be ideal, of course real world testing will prove things for you. If you decide the 1-1/16" is the way to go, I'm not 100% sure, but I think I might have the part# of a Mopar style 1-1/16" on a spreadsheet, but right now I'm out of town and don't have access to it. Should be back on Sunday.

HTH

[Skip Fix]

TJames thanks for all the calculations. 25% more travel I think would still be too much. Again that might reduce if I swap the "front" port to the rear larger calipers since they have a larger piston sq in since most are listed as 2:1 volume output for the "front".

Strange has a 1 1/16 also, but probably pricier than a "plain" Mopar one.

[nullshine]

Well, I was wrong about having a # for the 1-1/16" bore Mopar style, I only have the 7/8", 24mm, 1-1/32" and 1-1/8" on file.



And yeah that 24mm would be worse than your previous experience with the 1".

So my best contribution is the 1-1/32", but it would be nice to find a 1-1/16" to round out the lineup.

I'll poke around from time to time and let you know if I find anything.

[Skip Fix]

Strange has a 1 1/16 as well as a 1 1/8 Mopar style, but they are a little pricey compared to a NAPA/Wagner Mopar one.

[Skip Fix]

So got a number for the 1 1/32 in aluminum? So far I've only found cast iron in Cardone.

[Skip Fix]

Finally got her fired up and moved around in the garage and driveway. Just rolling 200 PSI stops a littl efater 400 stops it fine and they are definitely not bedded in. Pedal pressure is fine so far, we'll see how it feels at speed.

Just wonder if since the rears actually have more piston area if they should have the port on the MC that moves more volume than the fronts.

[MonzaRacer]

Now wait, every time I had customers go down in bore size for brake master cylinder the pedal travel goes down and pressure rises faster, also possibly you need some 2psi pressure check valves. Also you might need to lower the pedal actuator rod, farther from the pedal pivot. hmm, also are any brace parts missing from car under dash? Like dash was pulled. My 71 MC had issue of poping out of gear when forst got it, found one of brace rods was broken had to pull one off parts car.

[Skip Fix]

No I pulled just radio and AC/heater stuff out no rods missing.Nothing looks broken. Strange did say even in general for a drag car they recommend to more volume rear port to the rear brakes.

Since going down in size it takes more movement for the same volume to be moved seems like you have to have more pedal movement. So far the pedal feels OK so I'll give it a try for now since it's installed and bled. Maybe swap the front and rear ports.

New problem my nice newly sumped new gas tank has about 4 spots it's weeping race gas out of the welds! So drain it and pull it and reweld. Always something.

[Skip Fix]

OK I found the 1 .032" #10-1822 in aluminum after we ordered all 5 O'Reilley had and found only 1 in aluminum so I have the option to go smaller if it doesn't feel right once moving and actually driving.

[Skip Fix]

Changed the lines for the heck of it so the rear big piston calipers are feed by the rear which moves more volume, bled again. Gets to 200 psi real quick but does have moderate effort getting to 400 and hard effort to get to 1200. Driving factory power brake cars and truck daily where you can use your little toe to stop it is hard to compare what is "too much" pedal effort!

Got the 1 1/32 modified to bolt up(had to grind out for wider GM bolt spacing) if I need it. Now working on swapping seats-the old Recaro and brackets was 50lbs. The Summit Procar copy and brackets are 42lbs a factory seat is 33lbs, a Kirkey aluminum pro street w/ cover no brackets is 17lbs.