How Hard of a Brake Pedal for Hydroboost

[LCAM-01XA]

What happens if you reuse the original master cylinder? (is it even possible?)

It's possible, may or may not need to grind the mounting holes outwards a bit (I had to hog them out). It works very good, pedal is pretty stiff (feels like manual brakes really) but it has enough power to lock up the fronts and slide even on dry asphalt. I'd say I have no more than 2" of pedal travel, if even that.

 

[OLDBULL8]

Sure glad I read this thread. Was thinking of putting the HD on my 99 truck. While changing oil today I looked at it and I do have the HD brake system. What made me think I should do that was because I ran a Red Light coming down a hill towing a 30ft 5er in a City in Washington on my way to Alaska last summer. Thank God no vehicle's were ahead of me and the light was a delayed Red for traffic the other direction. Peddle was almost to the floor then . Checked them out today, and with the engine running the pedal will go all the way to the floor with full pressure. I don't know if I have the large MC or not. With the info I read on here I'll check the MC. The truck has 4W disc.
My lady friend with me pissed her pants thinking there was going to be one hell'va accident.

Question is, is my MC shot? Can't lockup the wheels. Has new rotors and pads on the front. Only 146XXX on the clock.

 

[69dieselfreak]

What happens if you reuse the original master cylinder? (is it even possible?)

for our year of truck we are able to keep the original MS i used my original and it fit just fine but the newer aluminum u half to widen the holes been there done that

 

[LCAM-01XA]

You can't lock up your wheels cause you got 4-wheel ABS, possibly also TCS and VSES - that's what they're designed to do, prevent wheel lockup and following loss of control over slippery surfaces. Pedal should not go to the floor tho, that's way too much pedal travel...

 

[tknomaj]

Pedal Travel

I recently converted my brakes to Hydrbost 1997 f450 hydro/ master and braided stainless brake lines. When I first Installed it and flushed brake system the pedal was so hard it felt like non power brakes and little if no movement. then i remembered TOWCAT had posted something about pedals and that i would need the f450 pedal assy or redrill existing pedal assy. they stoped OK but pedal feel was all wrong so i ordered the new pedal assy from dealer installed it and now it feels just like it is suposed to and if a passenger is not wearing a seat belt i can almost make them kiss the dash it stops so hard. if i had stock size tires it would lock up for sure but with 36's it does not but it sure stops now and pedal feel is fantastic so check your pedal assy.

 

[LCAM-01XA]

Oh, I am not converting to the F450 pedal assembly, I used t drive a '79 shortbed Chevy with manual brakes so stepping on the pedal a bit harder is no problem for me, and I actually do like the feel of it.

 

[tknomaj]

Pedal Feel

Did not say it was bad just not right i work on vehicles with hydroboost all the time and know how it is supposed to feel and that bothered me. If you are happy all is GOOD. but the pedal assy is avail from the dealer and 85.00 was the price so i did it and now it feels right. i dont know how to explain it but pushing on the brake pedal did not feel right . the only thing i can think of would be french kissing your sister (not that i would know) but that would not feel right either

 

[Chevyboy_0]

Don't mean to hijack but what is hydroboost and what are the advantages, also what years and models of Chevys did the hydroboost come on?

 

[tknomaj]

HYDROBOOST

Hydroboost is a brake booster system that instead of vacum that a diesel does not produce without a external pump. It uses Power steering fluid as the pressure for braking assistance. and increases your braking power or capability about 3 times over the stock vacum assisted braking and chevrolet started to use hydroboost on one ton trucks in the 70's. ford did not put any hydro boost in trucks until the 90's. My date for the years may not be correct but if you still have a vacum system and a looking for more brake then hydroboost is the answer

 

[LCAM-01XA]

One thing to consider with the pedal assemblies is that the F450 hydroboost has a fairly short pushrod for the pedal so when you put it in a vacuum-assisted truck the pedal pin being lower results in the pushrod being angled down, which throws the whole geometry off and really screws up the pedal feel - my pushrod is 2-1/2" longer to begin with (makes for less angular deflection within the pedal travel), and I also have the whole booster tilted backwards right at the firewall so the pushrod is pointing straight at the pedal pin from the get-go, so I don't have that issue.

Your years for hydroboost use sound about right. Chevyboy_0, the GM boosters are not a direct bolt-in for our trucks, they are for GM fullsize trucks but Fords have a very different dimensions - I had to space the booster out of the firewall by over 2", good thing is this way I was able to adjust my pedal height to where it's more comfortable for my foot, but still it's not as easy as simply pulling the vacuum stuff out and putting the hydro stuff in. F450 boosters are a direct bolt-in tho, it's good to have the pedal pin higher like Tknomaj corrected the geometry, but they certainly will work with the factory pin location too and will still be better than the vacuum stuff.

 

[david85]

Did I read that right? 3 fold increase in breaking force?

 

[LCAM-01XA]

A bit less than twice, actually - IIRC the good vacuum boosters can crank up to 1400psi line pressure, whereas the hydroboost bumps that up to 2200psi. Or maybe it was pounds of pushing force at the master cylinder plunger, not sure, but numbers should be about right.

 

[towcat]

Sure glad I read this thread. Was thinking of putting the HD on my 99 truck. While changing oil today I looked at it and I do have the HD brake system. What made me think I should do that was because I ran a Red Light coming down a hill towing a 30ft 5er in a City in Washington on my way to Alaska last summer. Thank God no vehicle's were ahead of me and the light was a delayed Red for traffic the other direction. Peddle was almost to the floor then . Checked them out today, and with the engine running the pedal will go all the way to the floor with full pressure. I don't know if I have the large MC or not. With the info I read on here I'll check the MC. The truck has 4W disc.
My lady friend with me pissed her pants thinking there was going to be one hell'va accident.

Question is, is my MC shot? Can't lockup the wheels. Has new rotors and pads on the front. Only 146XXX on the clock.

it's time for a rebuilt hydro for you.

 

[LCAM-01XA]

Even if his booster was bad tho, he shouldn't have a low pedal - stiff pedal yes, but not a low pedal.

 

[Dsl_Dog_Treat]

Did I read that right? 3 fold increase in breaking force?

Got it on Goldie and yes it pretty dang close to that.
I bought a 29.5' fifth wheel and I didn't have the brake controller installed on the truck yet and ran it 60 miles back home.

Kept plenty of distance, between the vehicles in front of me, ok and only had to hit the brakes hard one time. The truck had nooooo problem stopping that big ole fiver behind me.

Yes I'll be getting the controller wired in but at least I know the truck can safely stop that big rolling mass behind me if the trailer brakes fail.