Brake booster... removal?

Ludachris · 02-21-2008, 08:49 AM

I noticed the RRE race car doesn't have one. What are the advantages/disadvantages of removing it? I don't know what I'd really gain by removing it other than a few pounds (if that) shed from the front of the car and some extra room under the hood. But anything that can be removed without much consequence is fair game in my book.

talonTSIDriver · 02-21-2008, 08:53 AM

Quote:

Originally Posted by Ludachris

I noticed the RRE race car doesn't have one. What are the advantages/disadvantages of removing it? I don't know what I'd really gain by removing it other than a few pounds (if that) shed from the front of the car and some extra room under the hood. But anything that can be removed without much consequence is fair game in my book.

Have any of you tried to brake while your boosting after all the vacuum is gone in the brake booster, its nearly impossable.

aves911 · 02-21-2008, 04:56 PM

With the brake booster disconnected, it doesn't matter what load is on the engine - pedal modulation will still be the same. Without the booster in place, the brakes will operate as they do with the engine off, i.e. impossibly firm pedal.

My guess is RRE is using either different pedal linkages or a different master cylinder to bring the mechanical advantage back into check.

Regardless, is there even anything to bolt the stock master cylinder to if the brake booster is removed?

Defiant · 02-22-2008, 01:13 AM

Try blocking off the booster vacuum before you think you want to do this. The easiest way is to just install the vacuum line (and its internal check valve) backward.
I'd hope setups running without boost have changed the size of their master cylinder.

Oh, do the test far away from traffic.

Dave532 · 02-23-2008, 10:26 AM

I have found 3 potential reasons to remove the booster...

1. better pedal feel...threshold braking is easier
2. Installation of aftermarket pedal system, removing the need for vac assist.
3. Weight reduction

I have never seen acceptable results from removing the booster alone on any factory built car.

My guess is that they have a Wilwood pedal system (or something similar) which requires/allows removal of the vac assist booster.

IMO Mitsu's have OUTSTANDING pedal feel even with the vac assist booster.

Zero Bar · 02-23-2008, 04:47 PM

^Agreed, if your system is in good working order a couple simple upgrades like stainless lines, slotted rotors, and good pads make for darn good braking in our cars.

talonTSIDriver · 02-24-2008, 08:37 AM

Quote:

Originally Posted by Zero Bar

^Agreed, if your system is in good working order a couple simple upgrades like stainless lines, slotted rotors, and good pads make for darn good braking in our cars.

I'd say i 2nd (or maybe 3rd) that, UNTILL you start doing 20 minute sessions on a larger, faster road course. My stock brakes with just Hawk HP+'s (and some SuperBlue Fluid) works great until I went to BlackHawk Farms and starting running lap after lap chasing down evo's. Its then i experienced my first true brake fade, not a good feeling!

Zero Bar · 02-24-2008, 08:49 AM

I personally havn't had to experience that, nor did the original owner as the car isn't fast enough!! It only manages 75mph at the top of the hill on the main straight of Road America!!

underradar92 · 02-24-2008, 01:01 PM

Quote:

Originally Posted by Ludachris

I noticed the RRE race car doesn't have one. What are the advantages/disadvantages of removing it? I don't know what I'd really gain by removing it other than a few pounds (if that) shed from the front of the car and some extra room under the hood. But anything that can be removed without much consequence is fair game in my book.

I love brake threads!

Most full-on race cars are sans power brakes, one less system to fail. Less weight and clutter on the drivers side front of a DSM? Heck yeah! Re-working the firewall/pedal interface may be a lot of work, but I'd love to see it done.

Quote:

Originally Posted by Zero Bar

I personally havn't had to experience that, nor did the original owner as the car isn't fast enough!! It only manages 75mph at the top of the hill on the main straight of Road America!!

75mph at the top of the hill? What speed do you see just before turns 1, 5, & Canada Corner?

Zero Bar · 02-24-2008, 03:34 PM

^I'd have to ask, I personally havn't had the car to a course yet but the car has been on there, Lime Rock, and pretty much every course in the midwest.

aDee · 02-25-2008, 01:09 PM

Modulation, consistency and feeling that don’t change with boost\vacum changes. Maybe not that important in road racing but in rally when using left foot braking is priceless. I got it on my rally car and I love it. You need to change the location of the hole that master cylinder pushrod connects to the brake pedal. That changes leverage, so the pedal isn’t rock hard anymore and you can actually stop. I removed the booster completely, made a plate, pushrod and moved everything up by 3/4.

Ludachris · 02-25-2008, 01:58 PM

Quote:

Originally Posted by aDee

Modulation, consistency and feeling that don’t change with boost\vacum changes. Maybe not that important in road racing but in rally when using left foot braking is priceless. I got it on my rally car and I love it. You need to change the location of the hole that master cylinder pushrod connects to the brake pedal. That changes leverage, so the pedal isn’t rock hard anymore and you can actually stop. I removed the booster completely, made a plate, pushrod and moved everything up by 3/4.

So you're saying that the booster can be removed without any ill effects as long as you move the location of where the master cylinder comes through the firewall up about 3/4"?

turbosax2 · 02-25-2008, 03:19 PM

During my search for adjustable prop valves yesterday I came across this page. You guys probably know about this already, but I figured I would throw it out there.

Quote:

For over 30 years race cars have used dual master cylinders, this is the use of two master cylinders that are side by side being applied at the same time. The mounting is generally done on the fire wall, but special applications have made it possible to mount these on the floor, under the dash or in a remote location. A balance bar is used to balance the force to each master cylinder. Think of a bar with a pivot point in the middle, when pressure is applied to the pivot point both ends move the same distance. Now think of the same bar with the pivot point move more to one side, when pressure is applied the shorter end will move before the long end. That is basically how the balance bar works. In a race car there is a cable connected to one end of the balance bar, this cable would go to a knob in the drivers compartment, so he can make adjustments as the condition of his brakes and road condition changes. The balance bar also eliminatesthe need for a proportional valve. On certain applications a remote reservoir(s) are used, in these applications it deletes the use of residual valves on disc brake applications. Master cylinders of this type do not have built in residual valves in them so if you have a drum brake application you will still need an inline ten pound residual valve, this is needed to retain pressure against the cups of the wheel cylinders.

There are major advantages to using dual master cylinders: (1) Smaller diameter master cylinders can be used to increase output pressure. The design allows the application of two master cylinders being applied at the same, thereby doubling the volume output. Because of this high pressure output you will not need a vacuum booster. If you are running any type of camshaft, chances are you do not have enough vacuum to run the booster anyway. (2) The balance bar eliminates the use of a proportional valve and gives you the optional remote adjustment. (3) The remote fill applications deletes the need for residual valve normally used when the reservoirs are lower than the calipers.

Master Cylinders: The basic design of master cylinders are single reservoirs or dual reservoirs.

eclipsh · 02-25-2008, 04:53 PM

Thanks for that info

I was curious how you'd set this system up and how to design the center bar so here's what I found. Nice to see an interesting thread show up on a boring day at work

http://www.stoptech.com/tech_info/Pe...ster-Guide.pdf

aDee · 02-26-2008, 12:25 PM

Quote:

Originally Posted by Ludachris

So you're saying that the booster can be removed without any ill effects as long as you move the location of where the master cylinder comes through the firewall up about 3/4"?

Not exactly. There is still an increase in pedal effort but that's overcome by the consistency and modulation characteristics. I would say about 15% more but it's a combination of tires, pads, MC, surface, etc. I mainly use it on loose surfaces with ferrodo ds3000 pads and works for me. The feeling is different and you might need to use to it. Moving it up decreases pedal effort but increases the stroke. You might have to put some more aggressive pads if used with sticky tires. I won't rally with booster anymore.

schemauer · 02-26-2008, 12:42 PM

The ex-Archer car that I use for my track car now was not built with a booster. I would imagine that this was one less thing that could fail - and removed a bit of weight. The brakes are easily modulated, but higher pedal pressure is needed. It takes about half a lap when coming out of a street car for "muscle memory" to kick in and compensate.

3literpwr · 06-10-2008, 02:37 PM

My rally car uses dual 3/4 MC's... The feel is ok and the pedal is hard... My pedal ratio is now 6:1 vs the 3.5:1 or so thats in the stock system... Im still not crazy about the feel, but if you left foot brake then you MUST have it or you lose brake boost whilst mid corner and that stinks....

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