Brake booster delete master size?

[2joejoe2]

I think I read some where that the Volvo Calipers have 38mm pistons, and the VW calipers also have 38mm pistons

 

Piston area = 1134mm^2 or  1.7578in^2

pedal ratio  4:1  

If I use a 20mm dual master  = area of .4869in^2 

 

60lb leg force will result in 

60*4/2 = force on master per circuit = 120lb ( assuming force is divided between each circuit evenly) 

Pressure = 120/.4869= 246.433Psi 

Front Clamp force = 246.433*1.757*4 =  1731.93lb

Rear Clamp force = 246.433*1757*2 = 865.96lb 

 

Doesn't seem impressive 

what is Ideal Clamp force to foot pressure? 

 

 

 

 

 

[Dick R]

I once saw an older English car with a remote brake booster mounted.  I had never heard of this before,  You can find more about that and places that sell them on google.  I have no personal experience other than seeing one that the owner claimed worked great.  That was on a car that did not come with any vacuum assist. 

[Simeon]

1 minute ago, Dick R said:

I once saw an older English car with a remote brake booster mounted.  I had never heard of this before,  You can find more about that and places that sell them on google.  I have no personal experience other than seeing one that the owner claimed worked great.  That was on a car that did not come with any vacuum assist. 

 

Funnily enough you don’t have to look far from the 02 for this. Both the early 1600’s and RHD cars all used combinations of remote brake boosters. 

[andyleonard]

I put a new remote booster on the front circuit only of a big kit car I built because the original boosters got lost in the build and the pedal was too stiff. It mounted up behind the headlight in the front fender and has worked fine for 35 years. Brake balance F/R isn't perfect but the car's been on the track and no one died. I think it's a Lockheed. Hotrod parts. Short money.

[TobyB]

18 hours ago, 2joejoe2 said:

I think I read some where that the Volvo Calipers have 38mm pistons, and the VW calipers also have 38mm pistons

 

Piston area = 1134mm^2 or  1.7578in^2

pedal ratio  4:1  

If I use a 20mm dual master  = area of .4869in^2 

 

60lb leg force will result in 

60*4/2 = force on master per circuit = 120lb ( assuming force is divided between each circuit evenly) 

Pressure = 120/.4869= 246.433Psi 

Front Clamp force = 246.433*1.757*4 =  1731.93lb

Rear Clamp force = 246.433*1757*2 = 865.96lb 

 

Doesn't seem impressive 

what is Ideal Clamp force to foot pressure? 

 

 

 

 

 

It's not divided-

 

Both circuits will see your full foot pressure of 60 * 4 (pedal ratio), or 240 pounds of force at each piston.

 

It's a stacked master,

so the same pressure is transmitted to each circuit at the expense of travel. 

 

That should double your line pressures, and from what I recall on the E30,

(with not- dissimilar caliper areas),

 500 psi in the lines is a pretty aggressive, not- locked- up stop.

With significantly- grippy pads.

 

And 60 pounds at the pedal isn't much if you're in 'oh shit, gotta stop' mode.

 

Seems like you're in the ballpark.

 

t

 

[deschodt]

I know you know because you mentioned changing the MC to compensate... just chiming in because my mechanic once mistakenly put in a tii M/C in my non-tii car and my Booster died shortly after... All of a sudden braking took superhuman effort with that combo. It was rock hard and I had to stand in my seat to stop ?  When you find a combo that works, please let us know !  Good boosters are disappearing fast. 

[bento]

I drove a boosterless car for the first time over the weekend. The car was a bit heavier than a 2002, but rotors were likely proportionally larger. Pedal travel was fairly short, so maybe not the best case to base an opinion on. Don’t have precise specs. It was fine on dirt/mud, but when I pulled the car in to swap drivers, I was surprised how much pressure it took to bring the car to a stop. I don’t imagine I’d enjoy that level of pedal effort in traffic, stopping on hills, etc.

 

And I’ve never lost assistance from the stock booster on my turbocharged 02. I did kill a booster a year ago, but not sure if that had anything to do with the turbo. 

 

I’ll keep the booster on my car, but I’m interested to see how some of the projects from other posters in this thread turn out.

[Doug Riparetti]

Until you change the ratio at the bell-crank, the pedal will feel uncomfortable stiff. 

[andyleonard]

1 hour ago, Doug Riparetti said:

Until you change the ratio at the bell-crank, the pedal will feel uncomfortable stiff. 

 

I'm with Doug.

I believe the difference between my successful 22mm MC mounted on the pedal box and the "Oh Shit!" experienced by 22mm Tii MCs when the booster quits is pedal ratio, as a result of the bellcrank and linkage for upstairs. 

[Doug Riparetti]

I drove mine for about 500-miles with the E21 master cylinder before the S14 blew. My brother came to California and brought the car back to Idaho, that's when John (my brother) and Dave did the brake booster delete.

 

I did not like the way the Wilwood big brake kit performed with the E21 master cylinder, it left my brake pedal WAY too spongy and my brother felt it was dangerous. That's when Dave Lewis (Caveman Hot Rods) fabbed up the adapter to mate the Corvette master cylinder to the factory mounting points on the foot-box, modified the bell crank, installed the new master cylinder (that I got from O'Reilly's for like $45), an I was off with manual brakes with NO brake bias gauge.

Edited January 4, 2019 by Doug Riparetti

[bento]

10 minutes ago, Doug Riparetti said:

I drove mine car for about 500-miles with the E21 master cylinder before the S14 blew. My brother came to California and brought the car back to Idaho, that's when John (my brother) and Dave did the brake booster delete.

 

I did not like the way the Wilwood big brake kit performed with the E21 master cylinder, it left my brake pedal WAY too spongy and my brother felt it was dangerous. That's when Dave Lewis (Caveman Hot Rods) fabbed up the adapter to mate the Corvette master cylinder to the factory mounting points on the foot-box, modified the bell crank, installed the new master cylinder (that I got from O'Reilly's for like $45), an I was off with manual brakes with NO brake bias gauge.

 

I misread your post on the first page of this thread as one of the projects that was still underway, not as a completed conversion. Sounds like you landed on a combo that works well. That’s good to know in case I keep blowing out boosters.

 

What pads are you running on the wilwoods?

[2joejoe2]

On 1/3/2019 at 12:49 PM, TobyB said:

It's not divided-

 

Both circuits will see your full foot pressure of 60 * 4 (pedal ratio), or 240 pounds of force at each piston.

 

It's a stacked master,

so the same pressure is transmitted to each circuit at the expense of travel. 

 

That should double your line pressures, and from what I recall on the E30,

(with not- dissimilar caliper areas),

 500 psi in the lines is a pretty aggressive, not- locked- up stop.

With significantly- grippy pads.

 

And 60 pounds at the pedal isn't much if you're in 'oh shit, gotta stop' mode.

 

Seems like you're in the ballpark.

 

t

 

Toby I don't understand how both circuits will see full mechanical foot pressure.. If you do a free body diagram it would it seem like the force most be divided between the circuits. two objects are being moved therefor the force should be divided.  For the sake of argument. lets say there are two objects in series that would take 30lbs of force to move each. to move both at the same time it would take 60lbs of force I think the same applies to a stacked master....unless its magic or there is only one piston in the master. 

 

Parallel masters with a balance bar allows the user to  bias the bar to put the different forces on each master but the total input force is still the sum of each. 

 

[2joejoe2]

Im thinking this master cylinder with a modified bell crank should do the trick....and its dirt cheap.

 

https://www.jbugs.com/product/17-2808.html?rrec=true

 

 

[Doug Riparetti]

17 hours ago, bento said:

 

I misread your post on the first page of this thread as one of the projects that was still underway, not as a completed conversion. Sounds like you landed on a combo that works well. That’s good to know in case I keep blowing out boosters.

 

What pads are you running on the wilwoods?

I.E.'s standard street brake pad, nothing special.

[TobyB]

7 hours ago, 2joejoe2 said:

Toby I don't understand how both circuits will see full mechanical foot pressure.. If you do a free body diagram it would it seem like the force most be divided between the circuits. two objects are being moved therefor the force should be divided.  For the sake of argument. lets say there are two objects in series that would take 30lbs of force to move each. to move both at the same time it would take 60lbs of force I think the same applies to a stacked master....unless its magic or there is only one piston in the master. 

 

Parallel masters with a balance bar allows the user to  bias the bar to put the different forces on each master but the total input force is still the sum of each. 

 

Just like you doubled your single piston pressure in back for the VW caliper.

You push on the master.  240 lbs is applied to the entire master stack against the

back of the master.  You have to model it as applied pressure.  

If you sit on a stack of books, each one sees 240 lbs (err, if I  sit on the books)

and if each one was a hydraulic cylinder, each one would generate whatever amount

of pressure that area cylinder managed with those 240 lbs on it.

It's the TANDEM nature of the master.  It's a stack.

If you went to a balance bar, where there's a lever in- between, then your model would 

apply- I made that mistake when I first started to mess with balance bars.

 

So think force.  I shove on something with 240 lbs, EVERYTHING that can move sees that

240 lbs until it hits something that can resist that force.  The pistons inside the master all float.

 

 

I'd draw ya a picture but I suk at that.

 

t