Brake Booster Myth Busted

[vetracer]

I am trying to reduce brake pedal travel on my 2011 Mustang track day car after installing 6 piston "Bullitt" Brembo front calipers. During my search for solutions I came upon a post showing a .312" rubber washer in between the brake booster fork rod and the master cylinder actuation rod. The post was on a Mustang forum and supposedly the booster shown came off a Ford Mustang. The idea of replacing the .312' Rubber with delrin was too good to pass up. I purchased an S197 booster on E-bay and took it apart and removed the valve assembly (shown without the seal).

 

[vetracer]

I am trying to reduce brake pedal travel on my 2011 Mustang track day car after installing 6 piston "Bullitt" Brembo front calipers. During my search for solutions I came upon a post showing a .312" rubber washer in between the brake booster fork rod and the master cylinder actuation rod. The post was on a Mustang forum and supposedly the booster shown came off a Ford Mustang. The idea of replacing the .312' Rubber with delrin was too good to pass up. I purchased an S197 booster on E-bay and took it apart and removed the valve assembly (shown without the seal).

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The valve rod assembly in made in two parts, the fork shaft and a floating piston swaged to the end of the fork rod. The floating piston can swivel but it is seated firmly to the fork rod. The whole valve assembly is installed on the fork rod and the the floating piston is swaged to the fork rod to hold everything together. The seal is molded over a steel washer and is 5mm thick. The steel washer is 1.5mm thick. .

 

[vetracer]

The valve rod assembly in made in two parts, the fork shaft and a floating piston swaged to the end of the fork rod. The floating piston can swivel but it is seated firmly to the fork rod. The whole valve assembly is installed on the fork rod and the the floating piston is swaged to the fork rod to hold everything together. The seal is molded over a steel washer and is 5mm thick. The steel washer is 1.5mm thick. .

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I came to several conclusions after the booster tear down. 1) THERE IS NO RUBBER BETWEEN THE BRAKE FORK ROD AND THE MASTER CYLINDER ACTUATION ROD. The floating piston seats into the master cylinder actuation rod for a solid mechanical connection between the brake pedal and the MC. 2) there is nothing to be gained by messing with the brake booster with regard to reducing brake pedal travel. 3) Power brake boosters are not something you want to mess with for safety reasons. 4) In order to reduce brake travel with larger calipers playing with the internals of the brake booster is not a path you want follow as it will lead to a dead end. It cost me a booster but it was worth the effort. I have another idea in mind for reducing the pedal travel and have ordered parts to try it out. I'll post results once I've tried it

 

[satisfaxtion]

I came to several conclusions after the booster tear down. 1) THERE IS NO RUBBER BETWEEN THE BRAKE FORK ROD AND THE MASTER CYLINDER ACTUATION ROD. The floating piston seats into the master cylinder actuation rod for a solid mechanical connection between the brake pedal and the MC. 2) there is nothing to be gained by messing with the brake booster with regard to reducing brake pedal travel. 3) Power brake boosters are not something you want to mess with for safety reasons. 4) In order to reduce brake travel with larger calipers playing with the internals of the brake booster is not a path you want follow as it will lead to a dead end. It cost me a booster but it was worth the effort. I have another idea in mind for reducing the pedal travel and have ordered parts to try it out. I'll post results once I've tried it

Thanks vet racer-

I'm right in the middle of finally doing the front brake upgrade on my 12 Boss 302-

got the GT 15" front rotors- the 2015-2019 6 pot brembos -these part number are newer now ( i think) BRCF 430 & 431
and Power stop PST1792 pads

Pulled off the stock boss 302 street rims
tecs fit all parts-except the ss brake lines- I upgraded to the Goodrich ss lines years ago- do the fit or do i need to enlarge the seat area on the 6 pot Brembos?

My track tires are on the Ford 302s rims- they clear these brakes no problem- however the old original Boss 302 rims do not- maybe I will get spacers to keep the original look for street use-

Reading about the pedal travel and general difference in brake pedal feel-

keep posting about what you are doing with your situation-
my reason for going with six pot brembos and 15" rotors- I need more and better braking-
even on the shorter tracks the standard braking on the Boss needs help- but in 2011 when it came out- its brakes were advanced- now these same size are used on Honda Accords- so thats telling- a 3600 lb. car needs good and a lot of braking- never have too much braking, IMHO

 

[vetracer]

Thanks vet racer-

I'm right in the middle of finally doing the front brake upgrade on my 12 Boss 302-

got the GT 15" front rotors- the 2015-2019 6 pot brembos -these part number are newer now ( i think) BRCF 430 & 431
and Power stop PST1792 pads

Pulled off the stock boss 302 street rims
tecs fit all parts-except the ss brake lines- I upgraded to the Goodrich ss lines years ago- do the fit or do i need to enlarge the seat area on the 6 pot Brembos?

My track tires are on the Ford 302s rims- they clear these brakes no problem- however the old original Boss 302 rims do not- maybe I will get spacers to keep the original look for street use-

Reading about the pedal travel and general difference in brake pedal feel-

keep posting about what you are doing with your situation-
my reason for going with six pot brembos and 15" rotors- I need more and better braking-
even on the shorter tracks the standard braking on the Boss needs help- but in 2011 when it came out- its brakes were advanced- now these same size are used on Honda Accords- so thats telling- a 3600 lb. car needs good and a lot of braking- never have too much braking, IMHO

View attachment 86264

I really don't remember what I for brakes lines with 6 piston Brembos. I think I just used the Goodrich lines I had on with the original Brembos.

 

[twistedneck]

I really don't remember what I for brakes lines with 6 piston Brembos. I think I just used the Goodrich lines I had on with the original Brembos.

Thanks vet racer-

I'm right in the middle of finally doing the front brake upgrade on my 12 Boss 302-

got the GT 15" front rotors- the 2015-2019 6 pot brembos -these part number are newer now ( i think) BRCF 430 & 431
and Power stop PST1792 pads

Pulled off the stock boss 302 street rims
tecs fit all parts-except the ss brake lines- I upgraded to the Goodrich ss lines years ago- do the fit or do i need to enlarge the seat area on the 6 pot Brembos?

My track tires are on the Ford 302s rims- they clear these brakes no problem- however the old original Boss 302 rims do not- maybe I will get spacers to keep the original look for street use-

Reading about the pedal travel and general difference in brake pedal feel-

keep posting about what you are doing with your situation-
my reason for going with six pot brembos and 15" rotors- I need more and better braking-
even on the shorter tracks the standard braking on the Boss needs help- but in 2011 when it came out- its brakes were advanced- now these same size are used on Honda Accords- so thats telling- a 3600 lb. car needs good and a lot of braking- never have too much braking, IMHO

View attachment 86264

Here is my secret for the S197 brakes - Brembo fronts and the single piston rears.
1. 600F Motul
2. Girodisc rotors front and rear
3. Glock pads R12 front R10 rear (thinking EBC next time maybe due to the stainless pad backing material).
4. Remove rear dust cover
5. Laguna Seca Boss brake cooling ducts
6. Racing Brakes rebuild kit for the fronts that includes the stainless steel pistons and high temp blue seals.
7. Remove wheel beauty center cap - makes a big difference.
8. Vorshlag brake lines going to each corner (the red ones)

If that doesn't work, have you considered the Brembo or AP 6 pots - they are $7900 and $5900 respectively but they give you the 25.4mm thick pads.

 

[blueboss302]

Here is my secret for the S197 brakes - Brembo fronts and the single piston rears.
1. 600F Motul
2. Girodisc rotors front and rear
3. Glock pads R12 front R10 rear (thinking EBC next time maybe due to the stainless pad backing material).
4. Remove rear dust cover
5. Laguna Seca Boss brake cooling ducts
6. Racing Brakes rebuild kit for the fronts that includes the stainless steel pistons and high temp blue seals.
7. Remove wheel beauty center cap - makes a big difference.
8. Vorshlag brake lines going to each corner (the red ones)

If that doesn't work, have you considered the Brembo or AP 6 pots - they are $7900 and $5900 respectively but they give you the 25.4mm thick pads.

4.remove rear dust cover? I don't understand what this is or maybe I call it by a different name?

7. remove wheel beauty center cap? Are we talking about the center caps on the wheels? I don't understand how that makes a big difference.

 

[xr7]

4.- I think he means remove rear brake dust shields
7.- Can't see any benefit removing the center cap from the wheel no air flow there

 

[twistedneck]

4.- I think he means remove rear brake dust shields
7.- Can't see any benefit removing the center cap from the wheel no air flow there

yes i meant the dust shields.. my syntax is getting crusty! i think it was Terry or Jason at Vorshlag that found out at least with the gforce wheels that removing that small center dust cap of the wheel helps with front brake cooling.

 

[blacksheep-1]

@vetracer very well done post, thank you very much for the information, especially the details.!