Depowering brkaes.

Hi guys. Thought Id ask this here since not many over at FEOA like manual brakes. 

I'm building a ford EXP and the cam I have nuls out the brake booster. So I'm looking to delete the booster.

I wanted to make sure I did not miss anything before putting it all back together.

The car will be about 1800lb with me in it. Has bigger rear dums, drilled, slotted and vented disks up front. New rubber brake lines, power master, calipers and so on. I will be moving the master's push rod mount up higher on the brake peddle and useing dot5.1.

Id like to get a manual master, but the manual master for these cars are a 2 line master and I don't want to have to re do all the steel lines and was hoping to keep it a 4 line system. I driven the car with the vacuum line to the booster unhooked and did not mind the heavier peddle to much but would like to make it a little more street friendly without going hydoboost witch is why I'm moving the master's push rod mount up higher on the brake peddle.  

So given everything listed above am I missing anything? Anything I should do to make the manual setup more effective?

Thanks.

Someone brought a very modified mustang to cars and coffee once that had an automatic electric vacuum pump to run the booster. Maybe something like that would work?
 

 I know the Volvo C30 had a vacuum booster pump from the factory so maybe you can find a jy solution. 

I would add a vacuum pump and tank, the pumps are in uses on a number of cars.

BTW: Manual brakes are not very good IMO, stick with the power booster. 

In reply to Strizzo :

Honestly I don't need the power brakes, nor the weight of them. I'm mostly asking if there is anything more I can do to make better use of a depowered system. There is not much out there for the 1.9l CVH motor, most everyone I know just crams boost down it until it blows up and then they just get another motor. I don't like that route 

Stripping every last pound from the car is one of the few things I'm doing to pep up the car. That and some head work a cam along with 2.0l pistons.Other then that and some basic tuinning stuff there is not much one can do to a 1.9l unlike the 1.6l

I wouldn't move the pushrod on the pedal. You'll get more leverage, but at the cost of less travel. In the extreme, you may go too far the the pedal bottoms out while the master cylinder only sees 1/2 travel. 
Huge safety concern even if done well. I would think the 2/4 line problem would be easily solved with some sort of T fittings or a proportioning valve like what Samurais use. Two lines from the master to the valve, 4 lines from the valve to the wheels. 

In reply to Donebrokeit :

Don't want the weight nor need power brakes. Like I stated in the OP I unhooked the vacuum line to the booster and I did not mind it. I just wanted to know if there was anything I could do a shuch a manual setup that would help me better utilize it.

Two things...

1) drilled and slotted rotors are typically not used on regular track vehicles.  They have a tendency to crack and have failures.

2) use a good quality race fluid like motul 600 or even the ATE fluid.  Should be fine on a car of that weight and will make adding a bit of fluid much easier than using dot 5.1

As far as manual brakes, you can play around with just moving the pivot point of the brake pedal like you are, and you can also decrease the master cylinder size to decrease pedal effort.

In reply to barefootskater :

I thought about a T fitting and the stock manual master, but to be honest the manual master and power master are only .05 of an inch difference in bore size. Would it be worth the trouble of making new steel lines at that small of a size difference? The manual master being the bigger of the two.

 I was going to move the pivot to the same spot ford put them on the manual cars.

In reply to wvumtnbkr :

odd, everyone and I mean everyone at the tracks I go to use drilled/slotted brakes.

To clarify; this is primarily are track car or exclusively a track car?

If it's exclusively a track car just redo the brake lines and be done with it. You can order the hard lines in the lengths you need so you shouldn't have to make up all new lines. Bending them is easy enough.

I'd really even do it if it were sometimes street driven. 1/2 a day doing up new lines is nothing when it comes to a build.

Your focus should be on sizing the master cylinder to get the performance you want.

My .02

if you delete the brake booster, you're giving away about a 6:1 force multiplier.  it sounds like the same model was available with manual brakes, so i'd say the safest and most reliable path would be to use the pedal that goes with that master cylinder.  like someone pointed out above, if you increase the pedal ratio you increase the pedal travel required to reach a certain hydraulic pressure, and if you go too far with pedal ratio you could put the pedal up against its mechanical stop before reaching maximum hydraulic pressure, and that is what we call "a bad thing."

austin86 said:

In reply to barefootskater :

I thought about a T fitting and the stock manual master, but to be honest the manual master and power master are only .05 of an inch difference in bore size. Would it be worth the trouble of making new steel lines at that small of a size difference? The manual master being the bigger of the two.

 I was going to move the pivot to the same spot ford put them on the manual cars.

Change the master and yes, 0.050" in bore size is significant

austin86 said:

In reply to wvumtnbkr :

odd, everyone and I mean everyone at the tracks I go to use drilled/slotted brakes.

Are they all high end cars?  Cause those are significantly different.  

Cheap slotted and drilled, even like a brembo  blank that was then drilled seem to develop cracks around the holes and fail.

Plus, there is no reason for it with today's brake pad compounds.  They don't outgas like pads of yesterday. 

Plus, it takes thermal mass away from the rotor which is NOT a good idea.

austin86 said:

In reply to wvumtnbkr :

odd, everyone and I mean everyone at the tracks I go to use drilled/slotted brakes.

Drilled and slots are used when needed to alter the thermal mass of the braking system or to resolve issues with the existing brake system that can't be solved through other methods (adjusting brake bias, replacing rotors with different diameters or material, etc.)

Generally you'd only use drilled rotors if you're unable to get the brakes up to and stay at temperature or if you're running extremely old brake pads that "gas out" and create a layer of gas that reduces the initial effectiveness of the braking system.

Basically, just because everyone is doing it, doesn't mean that you should.  Too many racers fall into the rubber ducky syndrome where they see someone win or do well with a rubber ducky on the dashboard.  Soon every shows up at the track with a rubber ducky on their dashboards.

Honestly, power brakes are fine on track, but if you don't have enough vacuum to pull them off you can use a vacuum bulb to help add vacuum volume to the system.  Going with manual brakes means you'll have more pedal throw to deal with, but it should work fine with the proper pedal ratio.

In reply to Stefan (Forum Supporter) :

i would suggest that drilling rotors is also done to reduce rotating unsprung weight when there's enough thermal mass by nature of the diameter of the disc

AngryCorvair (Forum Supporter) said:

In reply to Stefan (Forum Supporter) :

i would suggest that drilling rotors is also done to reduce rotating unsprung weight when there's enough thermal mass by nature of the diameter of the disc

You are absolutely correct and I've seen this firsthand on a Formula Ford I helped out with a long time ago.  The rear brakes were drilled to reduce weight.  Drove the driver a bit crazy since there's nowhere to run from it in a small formula car :)

All I got to add is a cool article on brake pedal ratio my friend wrote: http://knowhow.napaonline.com/how-to-measure-brake-pedal-ratio/

Firstly.  Do not use DOT 5.1 fluid.  DOT 3 and 4 are perfectly fine, and DOT 5 is a completely different formulation.  It is silicone based and will destroy your brake parts in days.  Hoses, seals, hard line diameter, master cylinder cups, the works.  A system that uses DOT 5.x fluid is a ground-up, from-scratch completely different animal.  Seriously.  It's like filling a gas tank with diesel.  It won't work.

You need to dive down a very deep rabbit hole here.  The easy button is to get the manual-brake parts from a manual brake car and swap them in.  You can solve the two/four brake line issue with a little creative plumbing.

I know you mentioned that you disconnected the vacuum and "didn't mind it," but you will.  The booster amplifies your input by anywhere from 5 to 13 times your foot pressure.  You might not mind it, but the fact is that you will be reducing the peak hydraulic pressure you can effectively apply by at least a factor of 5.  The first time you need lots of braking and you stand with both feet on the pedal and you end up hitting the wall or another car, you'll wish you did it right.  This is like the folks who do a single flare on their brake lines and mention how it doesn't leak.  Of course it doesn't, but it will likely explode right when you need it the most... during a panic stop.

The size of the master cylinder, wheel calipers/cylinders, pedal ratio, proportioning... all of it has to be spot on or your braking will suck.

About the only thing you can DIY easily is the master cylinder.  You'll need to find one that mimics the factory size, stroke, pushrod depth... but at that point, you might as well just buy a manual master for the car.

If you don't want to go that deep down the rabbit hole, for $20 and about 6 ounces of weight, just add a vacuum reserve canister.  No pump required.  Your car makes a crapload of vacuum every time you decelerate no matter how big the cam is.  The canister stores it for you.  If you really are certain you need to scrap the 8 lbs of power braking (which I don't judge at all... I wish I could lose 8 lbs), then you'll have to do it right or (not exaggerating) create a serious risk of death.

DOT 5  is silicone based and does not play well.

DOT 5.1 is glycol based and is compatible with DOT 3 and 4. Feel free to pour it right in if you need it. FYI. 

I did a video on brake hydraulics a few weeks ago, actually.

Oh... thanks for the clarification on the DOT.

In reply to austin86 :

You'll need to go to a smaller , yes smaller diameter master cylinder 

Its about leverage and your leg only produces x amount of force. Power brakes help that get your leg a extra boost. Take that advantage  and suddenly you may not  have enough force to lock up the wheels. 
Don't forget under racing conditions the brakes will fade. And great braking requires tiny modulation differences to keep on the absolute edge of locking. 
 

realise braking from top speed occurs  in much less time than it takes to accelerate to top speed  So out braking is more important than out accelerating. 

Do you know how much money Ford would have saved by using the same brake master cylinder in both the manual & power brake cars?  Why would Ford (of the 80's!) bother with the cost if their engineers would sign off on using the same parts?

Either prepare yourself for some real engineering work and looking at the system as a whole, comparing it to other cars which are known to work well, or else go all factory with less impactful tweaks.  Also stop worrying about the weight of a brake booster on what sounds like a stock chassis EXP.

In reply to pres589 (djronnebaum) :

Eight pounds is worth removing. Hell, 8 ounces is worth removing when the horse power is this low.

In reply to austin86 :

.05 bore difference is big. If the bore is 1" you have an area of .785". If the bore is 1.05", you have an area of .865", or roughly 10% more. That's not a small difference. 
 

Im all for going to extremes in weight reduction, and I'm a big fan of manual brakes, but please, do it right. In this case, Ford already did the work for you. That's the easy button. Hit the easy button. 

You say you've "driven" the car with the brakes depowered, but not to what extent that means. Being able to take it for a spin around the block and get the car to stop means very little.  Especially considering how much more performance you're probably going to be asking from the system than it was originally designed for based on your stated intentions, I don't imagine many people would want to give advice on how to alter the travel/effort on a braking system without first knowing that all of the functional bases have been covered. Brakes are simply too important to half-ass.

For starters, a math model can be used to calculate if you're even in the right ball park. However, you have to watch out for "junk in = junk out", and ultimately real world testing will be required either way.

Testing it means starting with the highest tire/pavement grip and the lowest pad friction you will run. Then locking up all 4 warm/hot tires with cold pads. During this, you either need to know the line pressure, or at least figure out a way to gauge pedal travel. Measuring the pedal force would also be great, but at least you'll get to feel the true pedal effort required. Now the pedal travel ratio (lockup travel vs total travel) can be used to determine how much overhead you have available for reducing effort by changing your pedal leverage ratio to achieve the same master cylinder travel (line pressure) through more pedal travel within the confines of all the physical limitations.

Once all of that is confirmed, then it's basically making sure you don't run out of total travel before full worst-case-scenario lockup travel is achieved.