Brake booster delete (Page 1/2)
Yellow-88 OCT 02, 01:28 PM
Hi

I may be alone in this but I'll throw it out and see what happens.
I've never really liked the "feel" of vacuum assisted brakes and I was reminded of that yesterday when a friend from my British car days stopped by with her beautifully restored 1967 MGB Roadster. Thrashing it through the back roads of southern New England convinced me that I want to revisit my early thoughts about deleting the vacuum booster. The "intimacy" and "connected" feeling of those cars is something I'd like to recreate in the Fiero.

Of course in our case, no booster means no brakes. Back when I first started considering losing the booster I found that both peddle ratio and hydronic ratios are just to low for mechanical brakes. Looking at how to "fix" it, I found that the windshield wiper system gets in the way of increasing peddle ratio. Higher hydraulic ratio would be the only solution left. After doing some math and couple of mockups the project ended up on the shelf. I never put it in a car.

If I was starting with a bare monocoque, building a pure sports car, (Yellow 2.0), I'd just go with a Willwood setup and a modern wiper system.

Has anyone done anything like this?
cartercarbaficionado OCT 02, 01:54 PM

quote
Originally posted by Yellow-88:

Hi

I may be alone in this but I'll throw it out and see what happens.
I've never really liked the "feel" of vacuum assisted brakes and I was reminded of that yesterday when a friend from my British car days stopped by with her beautifully restored 1967 MGB Roadster. Thrashing it through the back roads of southern New England convinced me that I want to revisit my early thoughts about deleting the vacuum booster. The "intimacy" and "connected" feeling of those cars is something I'd like to recreate in the Fiero.

Of course in our case, no booster means no brakes. Back when I first started considering losing the booster I found that both peddle ratio and hydronic ratios are just to low for mechanical brakes. Looking at how to "fix" it, I found that the windshield wiper system gets in the way of increasing peddle ratio. Higher hydraulic ratio would be the only solution left. After doing some math and couple of mockups the project ended up on the shelf. I never put it in a car.

If I was starting with a bare monocoque, building a pure sports car, (Yellow 2.0), I'd just go with a Willwood setup and a modern wiper system.

Has anyone done anything like this?


I'll put it this way. it's possible but difficult.. you have to redrill and reinforce the existing brake bracket and use a wilwood dual master with a much larger bore. around 1.6 or 1.7 should be enough to be pushed easily and should eliminate the oem proportioning valve and can be mounted directly to a modified booster bracket
and I get it but why? the fieros brake system benefits greatly from power brakes unless you change all of it to be a non low drag disc setup and if you really want that experience just put a vaccum limit on how much enters the current booster. ~50% of original is enough to assist but not nearly enough to make it easy. Tangerine feels like it has manual brakes and I haven't found why yet
Yellow-88 OCT 02, 03:13 PM

quote
Originally posted by cartercarbaficionado:

I'll put it this way. it's possible but difficult.. you have to redrill and reinforce the existing brake bracket and use a wilwood dual master with a much larger bore. around 1.6 or 1.7 should be enough to be pushed easily and should eliminate the oem proportioning valve and can be mounted directly to a modified booster bracket
and I get it but why? the fieros brake system benefits greatly from power brakes unless you change all of it to be a non low drag disc setup and if you really want that experience just put a vaccum limit on how much enters the current booster. ~50% of original is enough to assist but not nearly enough to make it easy. Tangerine feels like it has manual brakes and I haven't found why yet



I know it's not easy. So you've done it?
You do have the hydraulic ratio backwards for no booster. Larger master bore is lower ratio. With our short peddle, 3/4" or even 5/8" is in the right direction. The stock P valve is right on so it's dumb to lose that if a single master is used. Dual masters with a balance bar is the next step up.

Why? "Feel". It's something one needs to "feel" to understand. It's about be closer to "at one with" the car. And .... loose weight and gain space up front. It's almost comical to see that giant booster on a 2,750 pound (with me in it) mid engine sports car with 10.3 " ventilated rotors at all 4 corners.

Reducing the vacuum would feel worse. That would be higher peddle effort with the same power brake feel.

" ... like it has manual brakes ..." Do you mean peddle effort?
Spadesluck OCT 02, 03:22 PM
I do not know to many that have done it, but there are some that have. John (no longer active) is the one guy that comes to mind that performed this.

Booster Delete
cartercarbaficionado OCT 02, 07:34 PM

quote
Originally posted by Yellow-88:


I know it's not easy. So you've done it?
You do have the hydraulic ratio backwards for no booster. Larger master bore is lower ratio. With our short peddle, 3/4" or even 5/8" is in the right direction. The stock P valve is right on so it's dumb to lose that if a single master is used. Dual masters with a balance bar is the next step up.

Why? "Feel". It's something one needs to "feel" to understand. It's about be closer to "at one with" the car. And .... loose weight and gain space up front. It's almost comical to see that giant booster on a 2,750 pound (with me in it) mid engine sports car with 10.3 " ventilated rotors at all 4 corners.

Reducing the vacuum would feel worse. That would be higher peddle effort with the same power brake feel.

" ... like it has manual brakes ..." Do you mean peddle effort?


yes I mean pedal effort. it's nice and firm and requires a decent amount of force to press down making the formula fun and responsive to drive but I have been told the fact that the pedal with the engine running refusing to move more than 1 inch before the brakes are at full lock is wrong for an 88
according to some fords I have I am correct. larger bore with smaller brake fluid chambers will move more with less effort for the same amount of braking.
all of my manual brake fords are 1.5 Bores and the power brakes are closer to 1.
yes I have done it but not on a fiero. I did it on my 69 toronado so I could fit a hydraulic clutch in a vehicle never intended for a clutch
that was just grabbing parts for a chevelle and making brakets to use the stock rods and such. other than that I did a power brake swap on a 1970 Nissan patrol using the small bore wilwood dual resivoir master on a fiero booster
Dennis LaGrua OCT 02, 08:10 PM
If you do this booster delete and have an accident the insurance company will most likely deny coverage because you fooled with your cars braking system. First step; read your policy and call them to check. Speaking of mods, I doubt if there will be a problem with the S-10 booster as its looks stock.

------------------
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"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

fieroguru OCT 02, 08:33 PM
The brake booster provides virtually all the line pressure to the calipers. So while eliminating it is possible, you will need to add ALOT of mechanical gain.



quote
Originally posted by cartercarbaficionado:
use a wilwood dual master with a much larger bore. around 1.6 or 1.7 should be enough to be pushed easily



This is exactly the wrong direction that is needed. You will need a smaller master cylinder bore (stock is 15/16), larger piston calipers, and more pedal leverage.
The link above shows someone who did this modification. He used the smaller wilwood masters, 4 piston calipers which have a larger piston area than stock, and the wilwood pedal assembly for more mechanical leverage.
cartercarbaficionado OCT 03, 02:01 AM

quote
Originally posted by fieroguru:

The brake booster provides virtually all the line pressure to the calipers. So while eliminating it is possible, you will need to add ALOT of mechanical gain.



This is exactly the wrong direction that is needed. You will need a smaller master cylinder bore (stock is 15/16), larger piston calipers, and more pedal leverage.
The link above shows someone who did this modification. He used the smaller wilwood masters, 4 piston calipers which have a larger piston area than stock, and the wilwood pedal assembly for more mechanical leverage.


please direct all of your complaints to 70s ford then. only going off of knowledge I've learned so far while repairing cars.
fieroguru OCT 03, 07:11 AM

quote
Originally posted by cartercarbaficionado:
please direct all of your complaints to 70s ford then. only going off of knowledge I've learned so far while repairing cars.



Whatever the ford master size was for manual brakes (and I find it hard to believe it is 1.6" in diameter), I am sure it was properly sized to match the size of calipers (and/or wheel cylinders) and pedal on each of the specific applications.

Ford didn't recommend changing from a 15/16" brake master to a 1.6" one. Doing this results in a 65% reduction in brake line pressure at the calipers, which would be a 65% reduction in braking force.

Yellow-88 OCT 03, 09:25 AM

quote
Originally posted by Spadesluck:

I do not know to many that have done it, but there are some that have. John (no longer active) is the one guy that comes to mind that performed this.

Booster Delete




Thank you. There's some good stuff in that thread.