Once the vacuum booster is removed, what returns the brake pedal to the top? My master cylinder doesn't quite do it. Maybe it will be fine one the brakes are bled, I just don't want my brake lights to flicker.
Once the vacuum booster is removed, what returns the brake pedal to the top? My master cylinder doesn't quite do it. Maybe it will be fine one the brakes are bled, I just don't want my brake lights to flicker.
I've been doing some research on building a custom manual brake setup, I've not seen that noted as an issue, but I have seen diagrams on wilwood or speedway motosports websites where they will use a spring to make the pedal return to the top of stroke
Don't most cars have some sort of return spring on the pedal?
akylekoz said:what returns the brake pedal to the top?
Most, if not all, cars and trucks have a spring that brings the brake pedal back into position. Usually they are mounted to the pedal arm and somewhere under the dash. The spring can age and need replacing or it could have come loose from its mounts.
my first question is always "why are you removing the booster?"
followed immediately by "how are you going to make up for that 6-9x force multiplier that you're taking out of the system?"
In reply to AngryCorvair (Forum Supporter) :
My booster died. One less failure point and creates more room under the hood.
The stock pedal box has multiple hole locations for the pedal arm fulcrum, using a new pedal arm and alternate hole location combined with the stock 7/8 bore master cylinder.
This is on a Fox Chassis, I assume there was a manual and power brake option, so not really reinventing the wheel stopper.
L5wolvesf said:akylekoz said:what returns the brake pedal to the top?
Most, if not all, cars and trucks have a spring that brings the brake pedal back into position. Usually they are mounted to the pedal arm and somewhere under the dash. The spring can age and need replacing or it could have come loose from its mounts.
My return spring was in the booster, the master has a bit of a return spring in it but not enough to A. return it while bleeding and B. engage the brake light switch.
I use a wilwood manual pedal box and there are no springs and it seems fine. You may just need to adjust the pushrod length.
akylekoz said:In reply to AngryCorvair (Forum Supporter) :
My booster died. One less failure point and creates more room under the hood.
The stock pedal box has multiple hole locations for the pedal arm fulcrum, using a new pedal arm and alternate hole location combined with the stock 7/8 bore master cylinder.
This is on a Fox Chassis, I assume there was a manual and power brake option, so not really reinventing the wheel stopper.
If that is true, then you will be replacing the entire braking system, since they would be totally different. At a bare minimum, you will require a new master.
Seems so much easier to replace the one part vs the whole system.
In reply to akylekoz :
track car, yes?
In reply to AngryCorvair (Forum Supporter) :
Yes, 4 cylinder Mustang with all the weight reduction. 11" rotors, rear drum.
In reply to 93gsxturbo :
Mostly for simplicity, less parts, more room under the hood, better feel. I'm using an engineered kit from Maximum Motorsports, it's not like I just removed the booster and hoped for the best.
We also have manual steering and just an alternator and water pump on a small belt.
Minimalist you might say.
If you're using an engineered kit, why not ask the people who engineered the kit?
Pretty sure it was early Fairmonts available with manual brakes.
They had the same calipers, maaaaybe larger wheel cylinders but probably not. Can't find evidence that they did, might be thinking of GM. What is interesting is that the master cylinders are different but they both had 7/8" bores. Probably different mounting and/or they had the pushrod positively retained.
Thank you for all of your input, I have installed a return spring and will contact MM for their answer but the hive always knows best.
track car, 4cyl Fox mustang, the 11" front rotor is probably more than enough heat sink. rear drums are as simple as gravity.
i'd install an adjustable prop in the rear circuit and call it good.
Yes, our seventh or so season of Lemons with a 95 degree 24hr race in there and we get about three races out of a set of pads. The "system" is fairly proven so why not change it?
So for an update, we raced this at Gingerman and Road America with the manual conversion. It took a bit to get used to the pedal travel being more than it was with power brakes. All drivers agreed that it was easier to modulate with a linear response to pedal force. They just work, press harder, stop faster, fronts lock up before the rear except for the time that I had one rear adjusted a bit too tight, why does that matter? Either way they work best if the rears have just a bit to no drag to start with.
Probably something to do with trailbraking/down shifting coming into a corner. Will this cause vacuum to go up with rpm and a closed throttle?
It is mostly black now after the most recent paint job and the quarter windows are covered.
akylekoz said:I had one rear adjusted a bit too tight, why does that matter? Either way they work best if the rears have just a bit to no drag to start with.
Drums are "self-energizing", meaning that as they begin to engage the forces will pull them into further engagement like a wedge. They take very little external energy to actuate, which is why you can run them on a trailer with a couple amps of 12v electricity. Unfortunately this makes them difficult to balance against the front brakes because the response curve to brake line pressure is different, and the positive feedback loop means that small changes in the initial location of the components (such as being adjusted a bit tight) can have a large effect on how quickly they lock up.
I understand your desire for simplicity, but there's a reason why disc brake adoption came from race cars. Drums are just not the right tool for the job.
In reply to codrus (Forum Supporter) :
That makes sense, of all the years of racing this thing it only happened once. Biggest problem area was that damn chicane in the kink at RA. We have a Cobra, 13" dual piston set up on the shelf and a disc rear for it but it weighs more and we are already slow. With the current setup we are out braking at 90% of the field typically.
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