mikey D

Is anyone running without a booster? Did you change anything to offset the effort required without the booster. I'm asking in regards to a first gen if it matters at all.

misterstyx69

iTrader: (142)

i am curious as to why you would not want to run a booster or if you are having issues with the placement of the booster due to your powerplant choice.
Honestly there are alternative sizes and fir that mater aftermarket parts that will work at the stock location.

I got this "case and Point" thinking where a 6 pound part that can help assist a 2000 Pound car from smacking into a concrete wall is kind of a good thing to keep on the car.

mikey D

Zepticon

iTrader: (1)

Is it even possible? When the car is off and i put it in neutral, it have a really hard time stopping it from rolling downhill without the booster. it does _a lot_ og work on the brakes.
Stopping a car doing 100km/h with no booster would take several hundred meters.

billyboy

IDA manifolds here usually have a provision for vacuum, no great hardship to drill and tap any of them I would think.

Other than going to dual master or re-engineering the pedal ratio, no simple fix to save metal fatiguing the bulkhead! Unlikely there's space issues on a LHD, but if you wanted to reduce clutter in the engine bay, a remote booster could be used, they date back to the 60s at least.

Valkyrie

Don't eliminate the booster unless you're going to completely redesign the brake system to work without it.

Even then, you'll basically have to kick the brakes to stop the car, like with a Super GT car...

mikey D

Sounds good, was just something to think about.

j9fd3s

iTrader: (3)

my friend and i have been running without the booster for a long time, in 1st gens.

it does take more effort to stop the car, and this is really alarming to most people, but the brake effort is still less than my 1958 Triumph Tr3, which doesn't have a booster.

i think i've learned that most people under the age of 60 have never driven a car without power brakes, and the idea freaks them out.

Valkyrie

Keep in mind it supposedly takes like 300 pounds of force to stop an F1 car....lol

mikey D

Thanks for the reply, did you use a different mater cylinder?

teeson

jputnamii

I have run my vintage race FB (ITA/IT7 car with a 13b motor) with the booster unhooked for the last 3 years. It does require a bit more pedal pressure so it can be done, you just need a stronger right leg.

Kenku

Did this one on an old EProd race car - Tilton made it at the time but now Wilwood does - https://wilwood.com/Pedals/PedalList...ru-Bar%20Pedal So you have a place to mount two racing style master cylinders, a rod you connect to the pedal and you build a little steel bracket to hold it. It incorporates an internal lever ratio too so you don't have to move the pivot point on the pedal.

Personally I prefer to the pedal feel with good manual brakes vs power assisted brakes - braking force is less proportional to how far you move the pedal and more proportional to how hard you push it.

mikey D

peejay

Thread is timely because I really want to get rid of the booster on my '84. I have brake boost for maybe half a brake application and if I have to pump the pedal up or apply the brakes twice then I have to rev the engine up first, which is annoying.

I already drilled my '81's brake pedal for a 7:1 ratio while I had its steering box out (it's a 1st gen thing) and it'd be a piece of cake to do on my '84 since it has a power steering column, but the main thing I am sticking on is what bore master cylinder to use. I'm using stock FB/FC single piston front calipers and my rear calipers have the same bore size as RX-7 calipers. Stock master bore is .875 or something like that, not sure if I should stick with that or go for a smaller one. Apparently the first couple years of two stage ACVW masters had .625 bore which is probably overkill.

mikey D

I'm going to end up replacing my booster, their like 50 bucks and in an emergency situation the value of the time it takes me to press really hard vs just easily push down is significant.

That being said stock 85 gslse calipers and no booster, i was pretty comfortable slowing the car down fron 120 mph into turn 1 at my recent track day.

I did have some issues being able to modulate the pressure required and still rev match to downshift. I ended up braking really deep into turns and missing my turn in points.

Kenku

Trying to remember what we were running... I think in the 5/8" to 7/10" range for the dual masters, with that leverage multiplier dealie giving probably around 7:1 mechanical advantage. Gets to a "how long is a piece of string?" things though.

j9fd3s

iTrader: (3)

we're just running stock masters, boosters are still there too, just not hooked up. didn't bother to change pedal ratio, as the un-assisted Rx7 brakes were lighter than my stock Tr3 brakes...
ideally you probably would want to get rid of the booster, and lower pedal pressure a little.

the real trouble is that the last car without power brakes is 60 years old, so nobody has really driven one.

peejay

Chevy sold S10 and Blazers with manual brakes in the 1980s. The Blazer with manual brakes had a larger wheel cylinder than anything else of that form factor, so it is good for people with Grand Nationals who want to be able to brake torque the engine harder at the dragstrip without breaking the rear tires loose.

I also know someone who had an S10 with manual steering and brakes. 6 turns lock to lock. Six freaking turns.


I drove three cars today with manual brakes, incidentally Further it seems like the standard drag racing brake is 10" solid rotors (well, heavily slotted non-vented) with four 1.75" piston calipers all around, and an aluminum Mopar master cylinder of something like 7/8 bore.

But I think the FB is just about unbrakable when the booster is run out. Which is "all the time".