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Username Post: power brake changeover        (Topic#358041)
Gene_Schneider 
Ultra Senior Member
Posts: 12260

Loc: Wisconsin..USA
Reg: 09-27-02
09-13-19 08:44 AM - Post#2775455    

My 1957 has factory TreadleVac power brakes. I like the low brake pedal. If I install a conventional master cylinder and a modern replacement power brake booster will I still have the low almost even with the accelerator brake pedal?

ChevGene 1934 Master sedan 1939 Master DeLuxe Town Sedan 1950 Styline DeLuxe Power Glide 1957 Nomad 283 PG 1963 Corvair Convertible


 


Beltfed 
Poster
Posts: 43

Reg: 10-04-18
09-19-19 09:16 AM - Post#2775884    
    In response to Gene_Schneider

No one has responded to this question so I’ll give it a shot. My first suggestion is to contact companies like “Master Brake” or “Wilwood”. I would think this is a question they could answer.
You need to know the bore diameter of your orginial master cylinder. Also, you need to know your pedal ratio. Pluging these values into several simple formulas will give you your answers. Example: pedal ratio is dividing the length from your pedal pivot point to the center of the foot pad by the distance from the pivot point to c/l of the hole where the master cylinder rod connects. 5:1 to 6:1 is considered ok.



Edited by Beltfed on 09-19-19 09:16 AM. Reason for edit: No reason given.

 
sz0k30 
"11th Year" Gold Supporting Member
Posts: 444
sz0k30
Loc: Oakland Co., Michigan
Reg: 10-12-08
09-19-19 12:25 PM - Post#2775896    
    In response to Beltfed

  • Beltfed Said:
Pedal ratio is dividing the length from your pedal pivot point to the center of the foot pad by the distance from the pivot point to c/l of the hole where the master cylinder rod connects. 5:1 to 6:1 is considered ok.



Generally speaking the above is true.

Manual brakes usually have a pedal ratio of approx 6:1. To allow for this ratio the pedal is normally higher from the floor and the accelerator.

Power brakes usually have a pedal ratio of approx 4:1. Because of this lower ratio the pedal can be closer to the floor and more in line with the accelerator pedal.

If your m/cyl has a 1" stroke and your pedal ratio is 4:1, the pedal needs to be at least 4" above the floor to give you the required stroke at the pushrod.

On my power brake equipped vehicles the pedal is approx 4" above the floor.

Many times manufacturers had 2 pushrod holes in the pedal arms so they could use the same arm for both manual & power brakes.




 


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