Dual m/c brake system w/bias for manual brakes

[Yeller]

I've run them, never checked for heat but never got noticeably hot, but didn't really drive far either. I barrowed some from the race team when I was playing with my brakes, it didn't really help my long throw pedal issue so I pulled them out and put them back in the race car......

 

[Apogee]

Well, the Manual Brake guy who sells systems/conversions for GM cars said the step bore m/c's only work on the front... so my monster sized rear calipers would probably be suffering from the same symptoms if I went with a step bore than a straight bore...

Can anybody verify this? I can't so far.

Has anybody run a 2# residual valve on the rear before? Do the rotors get hot from 2# or is it just about enough to wipe water/slush off the rotor??

I have no idea...

That is true and something I didn't really think through entirely for your application...the large quick take-up bore only feeds the bore for which it is directly adjacent to, so if you have the front brakes hooked up to that port, then that's the way it would work. If you swapped the outlet ports and ran the rear brakes off that outlet port, then you'd fix the rear issue and potentially create one up front.

Mico, the company that makes various industrial line lock devices, actually has a fairly extensive catalog of quick take-up master cylinders and might be a good resource, though their stuff tends to be a bit spendy and we're not talking about OEM quantities.

As for the residual pressure valves (RPVs), you should be able to run 2PSI units front and/or rear without any issues...there's more seal drag than that in the calipers, so they're really just good at keeping the fluid where it's supposed to be, in the caliper, even if/when you're upside down. Wilwood now offers a 4PSI unit that would be more appropriate for attacking pad/piston knockback and/or trying to restrict how far the pistons retract upon release. The 10PSI units will definitely cause excessive drag, heat and reduced fuel economy with most disc brake systems.

 

[nvrstuk]

Good stuff...

Mico just got a bunch of my money for a line lock thats not dependant on electricity to hold it. I looked for months and months and then when they came out with one, it took 3 more months to get it. Sitting on my bench waiting for a decision on m/c's.
lol

I will check Mico mc's out too.

Broncobowsher, myself and many others know that the infamous "Camper Special" mc at 1.25" bore has way too much pedal pressure...

Maybe with an 8:1 or a 10:1 ratio pedal will take care of the super stiff pedal and the pedal travel distance would still be ok??? Thoughts on that?

Good to know about the 2# residual valves not making any noticeable difference. Maybe the 4# ones in combination with a longer pedal at 8 or 10:1 ratio and 1.25" bore mc might do it????

Ever hopeful...

I found a 1.25 alum body leakproof cap mc off a mid 90's truck which would be nice... no rust, no leaks if the differe t pedal ratio would help with the pedal pressure issue!

 

[toddz69]

Good stuff...

Maybe with an 8:1 or a 10:1 ratio pedal will take care of the super stiff pedal and the pedal travel distance would still be ok??? Thoughts on that?

I found a 1.25 alum body leakproof cap mc off a mid 90's truck which would be nice... no rust, no leaks if the differe t pedal ratio would help with the pedal pressure issue!

I think getting something with that big of a pedal ratio might be a challenge to fit up in there under the dash and I'm not sure you could logistically do it unless the master was way up against the top of the firewall or the pedal was hanging way low.......just spitballin' - haven't actually tried it!

That 1.25" bore Mopar master cylinder I told you about some time ago would be a good one if you could get the pedal ratio worked to your advantage.

Todd Z.

 

[nvrstuk]

Right on Todd... I can fit the pedal assbly (which means nothing) but the mc reservoir would have to be remotely strapped to my cage cross bar on my A hoop and the 10:1 pedal would be about 2" off the floor. lol

The centerline of any m/c with this pedal assbly would have to be mounted appr. 3.25" higher than it is now to have a 10:1 pedal in place... appr 2" off the floor-unless I didn't read my tape right...

I will check and see if there is any viable way to make a 8:1 ratio pedal assbly work/fit.

Anything less including the Bronco appr 6.2:1?? pedal ratio (am I correct??) then the hope of using manual brakes w/o a step mc is fading.

 

[68ford]

Hey Brian, just wanted to clarify my bronco set and my race truck set because I think you mixed the 2 a little. Both are parallel assembles, but the bronco has both 7/8 masters. 6piston dyna something small calipers Todd knows which ones on the front. Larger 4 piston superlites in the rear. Rear rotors are also 1in larger. Bronco is 500 pounds heavier on the rear but rear brakes are still to big for only 500lb extra weight. System is biased to the front pretty heavy. The only issue at first with the 2 not being "even" was adjusting the pushrod length on the masters. Basically the rear master travels farther because the caliper is bigger. So that pushrod is longer so that when I'm at a very hard application the balance bar is even distance or "square" on both sides or looks what you would call normal. You also adjust the pushrod lengths so when at a max brake application the angle between pushrods and pedal line through pivots is at a 90 degree angle(most effective).
The race truck, which I think is more like yours because of the large calipers that are all the same size, has CNC 6 piston TT calipers which Todd knows about. It has a 1in master for the rear and 1.125 front. It is rear biased because 65% of the weight is in the rear. Same pushrod set up to achieve proper angles at hard application.
Both stop great and easy. Again, not sure if pad compound is helping the race truck stop so easy.
Not sure the pedal ratio but I gave you the measurements.
I really think if I could have put the 1in larger rotors on the front of my bronco and the same 4 piston superlites on the front, the bias would be about even and pushrod travel the same in theory and worked really nice. Your set up would be basically the same just larger I think.

 

[nvrstuk]

I'll get back on this... squirrel sighting... Snow is on the horizon and I've decided to bolt my sled deck thru my "aircraft grade alum" F150 box... with plates under it. Don't trust it...

Back to brakes soon... lol

 

[ntsqd]

The guy that I worked for in road racing had an Astro van with the stepped-bore m/c. I HATED driving the f-ing thing! Just about the time you were sure that the brakes had failed and you needed to find something soft to crash into they started to work. EVERY. SINGLE. BLOODY. TIME! You'd have thot that I'd have gotten used to it, but I never did and I hope to never, ever drive one of those stoopid things again.

(Don't hold back Thom, tell them what you really think of stepped bore m/c's!)


2 lbs RPV's were originally intended to be used in systems where the m/c is at the same height or lower than the brake calipers (dragsters, VW's, etc.). The idea was to prevent the fluid from draining back and over-flowing the m/c reservoir(s). As such they shouldn't present any problem with drag. Do not confuse those with the 10 lbs RPV's intended to keep drum brake springs from pulling the shoes back too far. Those have caused the pads to drag where people DID make that mistake. wilwood color codes them to make it even more obvious which version you have. The 2 lbers are sometimes used in systems with sloppy floating rotors to prevent excessive pad knock-back and occasionally to fix odd little issues that some systems have.

 

[nvrstuk]

TS.... lol. That's agood , frustrating story!!

I ran the Astro mc and I thought was causing my rear caliper bleeding problem a few yrs back... never could understand why rhe frts bled in 5 min and the rears never did..
Pressure, vacuum, pedal pumping...nothing..and I was the GM dealership brake guy... frustrating. Best friend had a 4 man shop in town and. Etween the two of us... well, its in my old thread.

But, I'm thinking now that it might have been caused from my now inoperative rear line lock. I don't know how lo g its been bad as I engage them at the same time, except when locking the frt for a burn out.

Anyway, I have my new Mico line lock and I'm thinking of trying a straight 1.125 or 1.25 w/o my HB. If it doesnt work or take a ton of foot pressure I'll try all the stuff Waynes helping me with. First I'll try it with hydroboost since it all fits. Then move the still working mc back 7 inches to the firewall for full manual brakes

 

[Yeller]

I’ve run an 1-1/8 with my brakes on a 10” vac booster, on the suburban and k5 that the axles were in previously. Had plenty of over boosted power, could push the pedal to the floor easily with with my hand, to the point it felt like there weren’t any brakes sitting in the shop but actually driving it there was plenty but spongy. Making me think and remember all of this is good, might actually work and not being boosted might not be excessively spongy.

 

[nvrstuk]

Decks anchored, new Racelines and KO's... everything but Bronco today...

 

[nvrstuk]

I will be doing this... like I said, squirrel sighting...snow's coming...

 

[ntsqd]

Cruising Summit for some of the parts needed for my 408 build (guess where that block came from) I found the m/c that I used on the Valiant's manual brakes.
https://www.summitracing.com/parts/str-b3359ta
This was used with a set of 1.75 DynaPro's up front and Ranger rear drums. Pedal feel was on the edge of firm without being objectionable. My 100 lbs wife drove the car and didn't even mention brake pedal feel. Getting her close enough to the pedals and steering wheel was the challenge. After that she could rip thru the T-5's gears and told me it "was a fun car to drive!"