12” 6 piston Wilwood brakes

[338Raptor]

Does anyone here have first hand knowledge of what it feels like to drive a car with 12” Wilwood 6 piston brakes (4 piston on the rear) without a brake booster. Then drive the exact same car with the same brakes except with a booster?
I’m curious if a brake booster is really that necessary when running big brakes with 6 piston calipers.

(3100lbs car with very sticky tires. Occasional autocross.)

[cleandan]

With all things being equal the booster simply assists the brake pedal effort required.
This means, in your scenario anyway, the perceived brake pedal effort will be less with the boosted system as compared to the manual system.

If things are set up correctly both will provide proper braking and both can be made to have the same pedal effort. The manual system will likely have a bit more pedal travel than the other due to the smaller bore diameter.
One thing to keep in mind when comparing boosted brakes to manual brakes is the master cylinder bore diameter.
They are often not the same between a boosted and manual system.

Because they are not the same in terms of physics and math, making literal direct comparisons is not an even race.

In real simple terms a smaller master cylinder bore diameter will increase the applied pressure when using the same pedal effort.
A couple things to keep in mind when going to a smaller master cylinder bore.
1) less fluid moved.
2) longer pedal travel required to move the same amount of fluid.

Another factor in pedal effort and fluid volume being moved is the pedal fulcrum point, or leverage.
You can radically alter how the pedal feels to push, as well as the amount of fluid being moved with the location of the pedal fulcrum. A distance change of 1" to the fulcrum location is an exponential change in pedal effort and fluid moved.

I am curious what you are building that may require 6 piston brake calipers?

[frnkeore]

This one of my favorite sayings:

“Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. ”
― Archimedes

And applies to the braking system. I guess you could say that the MC is the fulcrum and the WC is the lever.

But, as stated above, w/o a vacuum or electric booster, petal movement increases.

Are you using a balance bar or a proportion valve?

[Heo]

With all things being equal the booster simply assists the brake pedal effort required.
This means, in your scenario anyway, the perceived brake pedal effort will be less with the boosted system as compared to the manual system.

If things are set up correctly both will provide proper braking and both can be made to have the same pedal effort. The manual system will likely have a bit more pedal travel than the other due to the smaller bore diameter.
One thing to keep in mind when comparing boosted brakes to manual brakes is the master cylinder bore diameter.
They are often not the same between a boosted and manual system.

Because they are not the same in terms of physics and math, making literal direct comparisons is not an even race.

In real simple terms a smaller master cylinder bore diameter will increase the applied pressure when using the same pedal effort.
A couple things to keep in mind when going to a smaller master cylinder bore.
1) less fluid moved.
2) longer pedal travel required to move the same amount of fluid.

Another factor in pedal effort and fluid volume being moved is the pedal fulcrum point, or leverage.
You can radically alter how the pedal feels to push, as well as the amount of fluid being moved with the location of the pedal fulcrum. A distance change of 1" to the fulcrum location is an exponential change in pedal effort and fluid moved.

I am curious what you are building that may require 6 piston brake calipers?

One of the basic physical laws. What you gain in force you loose in traveled distance. If thats translated correct

[338Raptor]

The car is a 67 fastback. The Wilwood superlite brakes came with the car when I bought it (in pieces) I’m assembling it now and I’m at the point where I need to decide between power or manual brakes.  My thought is with 6 piston calipers in the front and 4 piston in the rear with aggressive brake pads and a properly sized master cylinder I should have good strong manual brakes. I could easily go with power brakes if needed but I’m thinking it might not be necessary.

My brake pedal has a 8 to 1 ratio (12” overall length with 1.5” from pivot to MC link)
I’ll run a proportioning valve. 

[machoneman]

The car is a 67 fastback. The Wilwood superlite brakes came with the car when I bought it (in pieces) I’m assembling it now and I’m at the point where I need to decide between power or manual brakes.  My thought is with 6 piston calipers in the front and 4 piston in the rear with aggressive brake pads and a properly sized master cylinder I should have good strong manual brakes. I could easily go with power brakes if needed but I’m thinking it might not be necessary.

My brake pedal has a 8 to 1 ratio (12” overall length with 1.5” from pivot to MC link)
I’ll run a proportioning valve.

No 6-pistons calipers here but on my 70' Mach 1, Baer Racing 4-piston PBR fronts (late Vette type brakes) on 13.2" rotors, OEM Lincoln 11" disc back with Lincoln intergral parking brake single puck calipers, adjustable prop valve, power master cylinder.

 I could go on about all the foolin' around I did on manual versus power but here's my take. There are far too many variables that differ from car-to-car (like some mentioned above, more to consider are the hardness of your brake pads, slow to warm the brakes on cold 'race type' pads, tire size and grip level, engine vacuum level to fully charge the brake booster and much more) to give you a hard answer.

Anyway, some tips include that if you do elect to go power and your engine vac. is less than about a steady 12", you will need a Crane Cams type vacuum boost canister to store higher vac. when decelerating, cruising, etc. Pad hardness, where high-wear race pads will not stop the car at the end of your block at the first stop (!) at all, is key to good overall braking. They are deisgned for warm-up laps and regular heavy use at a track. Not the hot set-up for street rides. Anti-squat suspension is also a factor. If you car nose-dives a lot under heavy braking, you're losing a lot of the brake power of your rear brakes. Testing your ride under max effort stops (with well-heated up brakes by way) is the best way to set your prop. valve's adjustment to where the rears just barely do not lock up (see nose-diving above).

Point is, you really have to try manual stopping after checking all these boxes above before deciding on it or power. And yes, if that means it's virtually impossible to plug in your power booster w/o yanking the engine back out, then go power now.

Whew!   
   

[CV355]

I had Brembo 6-pistons on my GT500, but that was power brakes.  You could brake so fast it felt like your eyes wanted to leave the sockets.  Roller coaster brakes felt gentle after that car.

As for manual brakes, I will NEVER run manual brakes again in my life (on a car), nor recommend.  I went from a mild stock hydroboost setup to a manual setup on my old drag car.  I somehow snapped both studs holding the master cylinder against the reinforcement plate on the firewall (no, I can't leg-press 46,000lbs...).  The brake feel was terrible to begin with, but that got much worse when the pedal went limp while I was headed into an intersection.  It always felt like I was on ice.  This can be mitigated with a proper MC bore and piston volume ratio, but it will never operate quite as well as vacuum or hydro assist. 

I am reading good things about electric conversions, though I don't trust electrogarbage enough yet. 

[338Raptor]

Good info.
I think I’ll go with a vacuum assist and a vacuum pump.
Thanks for the opinions.

[frnkeore]

To begin with, I never had power brakes on a car or truck, until I was well into my 40's.  But, I have always had strong legs and I guess, never spoiled by PB's

I agree, 100% on Mach Ones opinion on hard pads. You do not need them, except on a road course or a drag car, that goes over 160.

The real test, is whether or not, you can lock the front wheels at your highest speed, with a leg pressure you feel safe at. In racing, your adrenaline is up and you don't notice the amount of pressure you exert, unless it's not enough

I'm 75 and if it where me, I'd do it w/o the booster, using soft pads, all around. I also hate touchy brakes, not good at slow speeds, at least for me.

[Falcon67]

My door car weighs 3250 lbs staged.  I use single piston front disks from the 70s with organic pads.  Car has over 3000 rounds on it and runs between 89 and 96 MPH in the 1/8 depending on which motor is in the car.  Plus it gets driven around some.  I haven't put pads on it in over 10 years.  Rear is 10x2 drums.  The Dragster weighs 1650 staged, has 12" rear  rotors and one 4 piston caliper per side, soft pads, 7/8 bore MC and no power, no front brakes.  Takes effort to stop it for sure from 126, but nothing extraordinary. 

Per Strange, for the calipers I'm using, harder compound pads are for 150 MPH+.  When I tried semi-metallic pads on the door car, I could not hold it against the converter for staging and it would roll in the burnout box too.  I threw those pads in the trash. 

[TomP]

I am reading good things about electric conversions, though I don't trust electrogarbage enough yet.

Ha, I had a Lincoln Mark VII... I change that Teves setup to a vacuum booster and got rid of the 50 pounds of wiring to trunk mounted control module.
  I like MANual brakes though I did have girlieman power brakes on my ramptruck.