Master cylinder bore size for hydroboost brakes

[bigmuddy]

If you are missing the parts shown in post #36, they all are replaceable with out disassembling the hydroboost. Go to the powerbrakes dot com website, and read their tutorial on trimming and installing the pushrod.

I read it the install and trimming part which is what gave me pause when I pulled the old one apart. I wasn't expecting it to be that involved..

Check with them tomorrow. Thanks

 

[catfan]

I read it the install and trimming part which is what gave me pause when I pulled the old one apart. I wasn't expecting it to be that involved..

Check with them tomorrow. Thanks

Am I missing something , your new h-boost should only be missing the spring , retainer and rod and
those can be installed without taking anything apart ?

 

[toddz69]

Yeah, you don't need to take anything apart internally. Swapping the pushrod, spring and retainer over like @catfan mentions should take 5 minutes if you're slow....

Did learn something new in this thread though - I didn't know there were 2 different diameters of spider retainers.

Todd Z.

 

[catfan]

Yeah, you don't need to take anything apart internally. Swapping the pushrod, spring and retainer over like @catfan mentions should take 5 minutes if you're slow....

Did learn something new in this thread though - I didn't know there were 2 different diameters of spider retainers.

Todd Z.

Yes I bent a superduty one and made it fit in a mustang unit , I thought there was more than 2 .

 

[bigmuddy]

Yeah, you don't need to take anything apart internally. Swapping the pushrod, spring and retainer over like @catfan mentions should take 5 minutes if you're slow....

Did learn something new in this thread though - I didn't know there were 2 different diameters of spider retainers.

Todd Z.

So, the spider and rod will pull out the front?

 

[bigmuddy]

leave it to me to make it more complicated than necessary...

I assumed that since the spider "clips" into a groove it would need to be pulled from the back of the unit.

 

[toddz69]

So, the spider and rod will pull out the front?

Yes, use a needle-nose pliers and/or flat blade screwdriver to pry the little "legs" out. Sometimes I have to reshape them a bit before reassembling.

Todd Z.

 

[bigmuddy]

Yes, use a needle-nose pliers and/or flat blade screwdriver to pry the little "legs" out. Sometimes I have to reshape them a bit before reassembling.

Todd Z.

roger that!

thanks Todd!

 

[nied4speed]

roger that!

thanks Todd!

big muddy how did this all turn out for you on the brake system, I am about to the same point in my build and did not see an end to this thread, maybe I missed it. just curious if everything fit alright under the hood, and what did you end up with exactly for parts. thanks

 

[bigmuddy]

big muddy how did this all turn out for you on the brake system, I am about to the same point in my build and did not see an end to this thread, maybe I missed it. just curious if everything fit alright under the hood, and what did you end up with exactly for parts. thanks

I ended up using a compact wilwood unit that has 1-1/8 bore. Works fine and fits the space I need it in.
As others have said one with a 1-1/4 bore would have been better but you can't it, in compact size.

 

[widowmaker77]

Oldtimer linked the thread where this was addressed and yes it does change pedal ratio but I have made changes
to the bell crank since then .

@catfan. Can you send me some information on the ratio and what changes you have made? I also
Have one of your brackets with astroboost and Astro master. My brakes are good at the bottom of the pedal travel but feel mushy.

 

[ntsqd]

@catfan
if you don't mind posting the pedal ratio here I'd be grateful. I know how to arrive at an ideal ratio for manual disc brakes (I've built a spreadsheet for it), I'd like to start figuring out an approach to doing it with H-B brakes.

 

[ksagis]

We had a really long thread on this with @jamesroney some time ago when I think when he was installing one of catfan’s units. My take is 1.15 to 1.25 is roughly right.

But I think MC bore size plays in, and also the bore of the HB.

 

[ntsqd]

The way that my mentor approached manual discs was overall leverage ratio. No reason that I know of that the same approach can't be done with H-B. Pedal ratio, m/c bore area, and caliper piston bore(s) area are all factors. The overall leverage ratio is easy, determining where the boundaries are is the hard(er) part.

 

[catfan]

@catfan. Can you send me some information on the ratio and what changes you have made? I also
Have one of your brackets with astroboost and Astro master. My brakes are good at the bottom of the pedal travel but feel mushy.

Just a quick check looks like 6.5 .

 

[catfan]

@catfan. Can you send me some information on the ratio and what changes you have made? I also
Have one of your brackets with astroboost and Astro master. My brakes are good at the bottom of the pedal travel but feel mushy.

The changes I made were to reduce pedal travel , I raised the b ell crank where it attaches to the brake pedal and lowered
at the h-boost side .

 

[bigmuddy]

I should also say I am now using a newer style firewall bracket from Catfan.