Hydro boost Pedal ratio?

[Jeff K]

Anyone have an idea what the pedal ratio should be for a Hydro boost on a tube chassis? This is my first ground up build and I'm making the bracket for the Hydroboost unit. I'm not sure how much leverage and movement I'll need.

 

[jeepkevin]

I just dug through my receipts from my build and could not find the part number. I bought an OEM GM pedal from a 2005 Suburban 2500 with the 8.1 gas engine. In fact I bought hydro boost and master from same vehicle. The pedal I got from the dealer for something like $27. it came with the pivot bushing at the top. It did not include the rubber pad your foot touches at the bottom. I put fancy Auto Zone tuner car metal overlay pedals on mine.

The hydro boost and maser I got from Rock Auto. The 2500 has a 1.5" bore

I run a king pin Chevy front with factory calipers and a 14 bolt rear with the lug nut disk conversion.

It's not bad, I also bought a master from same year GM 1500 with hydro boost. It's a 1.25" bore. I get a little easier pedal effort but a longer pedal swing.

I just measured my GM pedal, 16" from top pivot to center of pedal.

From top pivot the center of bolt for push rod is 2.5"

 

[Bebop]

The hydro boost and maser I got from Rock Auto. The 2500 has a 1.5" bore

1-5/16 I think

edit : 37mm which is about 1-15/32 my bad

 

[jeepkevin]

So I double checked also and here is a copy/paste from Oreillys. I did measure mine quickly with a tape and appx 1.5". I was just going from memory.

Bebop, you a very much correct.

Brake Master Cylinder New; Bore Diameter: 1.46 Inch; Brake Code: JH6, JH7; With Hydroboost; Except Active Brake Control (JL4); Brake Codes Are On The Service Parts Identification Sticker
Limited Lifetime Warranty
New Or Remanufactured: New
Dust Boot Included: No
Number Of Ports: 2
Bore Size (in): 1.460 Inch
Reservoir Included: Yes
Bore Size (mm): 37mm
Reservoir Type: Integral
Number Of Pistons: 1
Sensor Included: Yes
Number Of Mounting Holes: 2
Gasket Or Seal Included: No
Bleeder Kit Included: Yes
Reservoir Material: Plastic
Pedal Rod Included: No
Brake Booster Included: No
Port 1 Thread Size (Forward) (in): 1/2-20 Inch
Port 2 Thread Size (in): 1/2-20 Inch
Port 2 Thread Type: Inverted Flare
Master Cylinder Body Material: Aluminum
Port 1 Thread Type (Forward): Inverted Flare

Brake Master Cylinder Remanufactured; With Brake Code: JH6, JH7; With Hydroboost; Without Active Brake Control (JL4); Reservoir Not Included; Brake Codes Are On The Service Parts Identification Sticker
Limited Lifetime Warranty
New Or Remanufactured: Remanufactured
Number Of Ports: 2
Reservoir Included: No
Bore Size (mm): 37mm
Number Of Mounting Holes: 2
Port 2 Thread Size (in): 1/2-20 Inch
Master Cylinder Body Material: Aluminum

 

[Jeff K]

I just found this. Odd that the ratio on the Chevy pedal is similar to the manual brake setup.

 

[Jeff K]

I need to check my CJ. I did an astro booster, and a corvette MC on that. So I can compare the ratios.

 

[Bebop]

I just found this. Odd that the ratio on the Chevy pedal is similar to the manual brake setup.

That drawing is shit.
You're not stopping a buggy with a 6:1 ratio and manual brakes.

 

[Jeff K]

That drawing is shit.
You're not stopping a buggy with a 6:1 ratio and manual brakes.

True, it's probably meant for a street car

 

[crazybluerider]

That drawing is shit.
You're not stopping a buggy with a 6:1 ratio and manual brakes.

Mine was 9:1 and I just swapped to remote hydro boost because 9:1 sucked. When I finally got the master sized right to stop it had about 12" of pedal travel.

Now I need to replace my pedal though because a 9:1 pedal with hydro boost = almost zero pedal feel. The thing stops incredibly but you basically cannot feel when its going to start stopping by the pedal.

 

[Bebop]

Now I need to replace my pedal though because a 9:1 pedal with hydro boost = almost zero pedal feel. The thing stops incredibly but you basically cannot feel when its going to start stopping by the pedal.

Yep

 

[Jeff K]

I was going to run the C20 Corvette style. But it is 1.25 bore. I currently run a Corvette unit on my CJ with 3/4 ton Chevy calipers. It works fine. But the 06+ SD calipers may need more. So, maybe the 2500 1.45 would be better. I'll have to run a remote reservoir the stock reservoir is too tall for this chassis. And, I don't trust the plastic.

 

[The Unknown]

Any suggestions on a pedal and or ratio for remote hydroboost? Currently mocked up with a 9:1(?) that I planned on using for manual brakes but decided on hydroboost. I'm remote mounted now and just need to figure out which pedal to use.