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.
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
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?
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
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.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
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.
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.
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.
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.
Yes. This always comes up in modification discussions. If the other guy has a skilled investigative legal team, one could get wicked screwed. Many of us are already screwed in that case.
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
With all due respect Carter, your getting the basics backwards.
" larger bore with smaller brake fluid chambers will move more with less effort for the same amount of braking." Larger MC bore will move more fluid but braking force is related to the difference between MC bore and caliper bore. So a 1" MC bore and 2" Caliper bore is multiplying the force at the caliper. A 1.5" MC bore and 2" Caliper bore is multiplying less. The same thing happens at the peddle. Both are basically levers.
Increasing the MC bore from stock with the booster in place, will make for less peddle travel but require more effort, and that does make a better feel but still has that initial "lost motion" associated with the booster. It's the lost motion, remote control feeling that detracts from the feeling of being at one with the machine.
Personally, I like a "hard" peddle. I like my maximum effort to match the maximum braking force. I don't like lost motion in any control system.
You should be able to get some idea of the feel and how well the brakes work by disconnecting and plugging the vacuum line at the booster. Just do it in a vacant parking lot.
My Dad had a Ford truck with front disk brakes but no power brakes. Factory setup. It took a great deal of effort to stop the truck.
You should be able to get some idea of the feel and how well the brakes work by disconnecting and plugging the vacuum line at the booster. Just do it in a vacant parking lot.
My Dad had a Ford truck with front disk brakes but no power brakes. Factory setup. It took a great deal of effort to stop the truck.
Yes, that condition makes for a really nice pedal feel but has little effect on braking. What I looking for is that balance between peddle effort and peddle travel. When it's right, the peddle immediately moves the MC piston so all peddle travel goes to moving the caliper pistons directly. With the booster the peddle is more like a valve that controls a "pressure chamber" that moves the MC piston with greater force the peddle "lever" alone can do. That's the feeling I'd like to eliminate.
Like Carter says, It's not easy. My first attempt was to increase the peddle ratio and decrease the MC bore. To do that required more room for a longer peddle but the wiper mechanism is in the way. I did manage to mock up a peddle assembly that increased the ratio from roughly 5:1 to about 7:1 using the stock peddle. Master cylinders are readily available in several bore sizes. Along with that was to space the peddles better. Ideally the steering wheel is between the brake and clutch peddles with a dead peddle for ones left foot. I shelved the project because of other priorities.
The MGB mentioned has about a 8:1 peddle ratio and a 3/4" MC bore driving 2 piston calipers (2.13") up front and drums in the rear. Peddle travel is about 1 1/2" before all 4 are locked up. Yes one does have to almost stand on the peddle to do that but locking the brakes is not a good thing. Ask any ABS system.
Currently Yellow has a 1" MC bore and SS flex lines at the calipers. Actually very nice brakes for an assisted system. But, Fiero peddle travel before I feel solid brakes is more than an MGB peddle when I'm standing on it. I think I'm just missing that connected feeling. And that giant booster is kinda silly in these little cars.
Yes. This always comes up in modification discussions. If the other guy has a skilled investigative legal team, one could get wicked screwed. Many of us are already screwed in that case.
The brake booster delete would be a very obvious mod to anyone doing even a cursory examination after an accident. The braking system would be a key place to look. Other items like exhaust are less noticeable and would be less suspect. You are aware of the downside, and of course you are certainly free to do as you please.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The brake booster delete would be a very obvious mod to anyone doing even a cursory examination after an accident. The braking system would be a key place to look. Other items like exhaust are less noticeable and would be less suspect. You are aware of the downside, and of course you are certainly free to do as you please.
Yes, agreed. I certainly wouldn't want to see " ... failure to slow down due to apparent brake failure ..." on a police report. That's one of the contributes to the shelving. Now, almost 20 years later, I'm revisiting the concept back at the design stage. If I actually build a prototype and take it out on the road, I absolutely promises that I won't hurt anybody. That should be an Oath that Designer Builders should take.
I think part of this peddle "feel" thing is the placement and spacing of them. The 4 peddles are, throttle, brake, clutch and dead peddle. So often in production cars we see brake and throttle at dramatically different heights. That's pretty much impossible to heel and toe. The clutch foot often has a rest but most often also at different heights than the peddle.
I think the ideal peddle setup would be 2 peddles to the right of the steering column and 2 to the left of it. A clutch peddle stop is needed to limit unnecessary movement and the dead peddle height can be accurately set. Step off the dead peddle onto the clutch with a foot rotation. I like a heel rest/locator for that foot. The break and throttle will need to be used simultaneously when breaking and matching RPMs for a downshift so both placing and shaping them is important. One beauty of manual brakes is the peddle movement before the driver feels them is much less. That makes it easier to heel the throttle and toe the brakes. Look at the peddles on some of the classic racing Sports Cars from the sixties.
Proper peddles are on the list for the Yellow 2.0 prototype. Yeah .... the list ...
