Hydroboost pedal effort

[BoostedSUV]

Re: Hydroboost pedal effort

BINGO CORRECT> THAT IS THE ANSWER> RATIO IS TO SMALL100% correct and counting. Good job BOOSTED

The length of the bottom of the pedal to the pivot over the length of the pushrod connection to the pivot.

6:1 ratio pedal assembly
¾" master cylinders
Applied force of 100 pounds with your foot

The formula shows that this combination produces 1359 psi,

Eh, got 1 out 2 right on this thread. :lol: at least being wrong about the rear drum hydraulic pressure makes more sense for what I have going on. Now I'm going to have to look into a disc/disc prop valve or bypass mine and use an adjustable one.

 

[Don W.]

Re: Hydroboost pedal effort

A little searching found this. Self energizing "disk" brakes:

http://www.imperialclub.com/Repair/Brakes/lambert.htm

And

https://en.wikipedia.org/wiki/Ausco_Lambert_disc_brake

Enjoy

 

[Fire Ty]

Re: Hydroboost pedal effort

Are you sure your lines from your master cylinder correct, can you put up a diagram of how you have your lines coming from your master cylinder to your brakes.

 

[mattw]

Re: Hydroboost pedal effort

BINGO CORRECT> THAT IS THE ANSWER> RATIO IS TO SMALL100% correct and counting. Good job BOOSTED

The length of the bottom of the pedal to the pivot over the length of the pushrod connection to the pivot.

6:1 ratio pedal assembly
¾" master cylinders
Applied force of 100 pounds with your foot

The formula shows that this combination produces 1359 psi,

Yep, exactly... To fix this I plan to mount the rod from the hydroboost up higher on my brake lever. Unfortunately that is going to throw the angle that the rod leaves the hydroboost unit way off. To fix that my plan is to create a wedge shaped hydroboost mounting plate. This plate will actually tilt the front of the hydroboost unit down some. This will actually level the master cylinder and and provide better hood clearance. My dad has an astro van that came stock with hydroboost and the brakes feel great. The hydroboost unit is the same one I put in my truck and my brakes feel stiff. I'm 99.99% sure that the difference is the mechanical advantage being provided by the brake pedal due to the differences in the fulcrum points..

 

[BoostedSUV]

Re: Hydroboost pedal effort

Matt I'd be very curious to see what you come with it and what difference it makes. I was trying to come up with a way to do this my welding and fabricating skills aren't there yet. Lol

 

[BoostedSUV]

Re: Hydroboost pedal effort

One more Question. What was the H BOOSTER FROM???? You know make model ETC that was used. That would answer the pedal ratio numbers. Just saying!!

Most of use a HB unit off an Astro van. I picked a 94 astro when I picked mine up.

 

[Black Knight]

Re: Hydroboost pedal effort

Can someone get the pedal assembly from an Astro to compare with a SyTy and see the differences?

 

[BoostedSUV]

Re: Hydroboost pedal effort

Can someone get the pedal assembly from an Astro to compare with a SyTy and see the differences?

I've seen a picture somewhere comparing pedals. Can't remember if it was on here or during my searches on google while doing this conversion.


Couldn't we just Lengthen the sy/Ty pedal with a J shape that will bring the pedal portion up to stock position? We could gain the leverage needed without going nuts repositioning the HB unit itself. I guess I'll have to take a look at the clearance between the pedal and the floor in our trucks. Might not be enough room.

 

[Don W.]

Re: Hydroboost pedal effort

Are you sure your lines from your master cylinder correct, can you put up a diagram of how you have your lines coming from your master cylinder to your brakes.

No pic but lines are correct. Front of MC to rear brakes, rear to front brakes. Using the original proportioning valve and master cyl.

I understand all the talk about pedal ratio but disagree that that is my issue. IMHO pedal effort, IE ratio, WILL have a bearing on how much push equates to how much brake gets applied but NOT on how fast the pedal moves. :2cents:

 

[Black Knight]

Re: Hydroboost pedal effort

Hey Don, how much boost can you make now sitting still with the hydroboost?

I just finished mine and now pushing on the pedal hard I can only get about 2psi before it starts spinning the rears and pushing through the fronts.

Can't imagine how people are getting 10-15psi?

 

[BoostedSUV]

Re: Hydroboost pedal effort

Hey Don, how much boost can you make now sitting still with the hydroboost?

I just finished mine and now pushing on the pedal hard I can only get about 2psi before it starts spinning the rears and pushing through the fronts.

Can't imagine how people are getting 10-15psi?

That's exactly what mine does too. I can maybe hold 5psi before the backs start spinning and push the fronts. That's with a 94 astro HB unit, master cylinder, and 4 wheel C5 discs.

 

[Quickstop [UK]]

Re: Hydroboost pedal effort

I posted a while back asking what people were holding at the line. I had an Astro unit and was holding with 15 psi before launch. I have a 2800 stall/ GT 35, vortecs etc so that may have had something to do with it but it sounds like your systems aren't right.

I had a caliper work loose and then had constant brake trouble so switched to a hydratech unit. My pedal before that was very responsive and aggressive. Pedal ratio/ effort was not a factor.

Edit: the rears would break loose first and start to push the Ty so I bought a Wilwood prop valve but have no idea how to install it. Seems like it just limits fluid to one system rather than diverting it to the other.

:dunno:

 

[BoostedSUV]

Re: Hydroboost pedal effort

I could hold 10-12psi no problem with my stock brakes. Only thing I changed was HB unit, and 4 wheel discs. :dunno:

 

[Quickstop [UK]]

Re: Hydroboost pedal effort

And I had C5s up front. Have since put larger drum pistons in the rear.

Could disc brakes in the rear be your prob? The line to the front is bigger as they need more fluid to hold. The smaller rear line means not as much pressure applied so you're seeing them break loose?

 

[Black Knight]

Re: Hydroboost pedal effort

Well I had stock rears and could hold about 4psi, went to hydroboost and now they break loose at 1.5psi. I spend half an hour trying to bleed them some more thinking maybe air still trapped, but no change.

 

[mattw]

Re: Hydroboost pedal effort

So I've decided to "fix" my hydroboost setup before my engine goes back in.. I took some measurements today and compared an Astro brake pedal to a S10 brake pedal. Both pedals are 14" long from top pivot point down to the pedal. On the Astro the hydroboost rod attaches 2.5" down from the top pivot point. On the S10 the attachment point is 4.25" below the top pivot point. This is why so much pedal effort is required when a hydroboost unit is installed in our trucks.

If you do the math applying 10lbs of force to and Astro van brake pedal will push on the hydroboost bar with 56lbs of force.

If you apply 10lbs of force to our brake pedal it will only transfer 32.9lbs of force to the hydroboost bar. To get that same 56lbs of force to the hydroboost unit with our brake lever you would need to apply 17lbs of force to the pedal..

Here is how the math is done:

W = (F x L) / X

Now to fix this I am going to remove my brake pedal and move the attachment point up so that it is 2.5" below the pivot point just like the Astro. The problem is that the rod needs to come straight out of the back of the hydroboost unit. So, to fix it properly, the hydroboost plate needs to be remade so that it mounts the unit higher and angles it down some to maintain the proper angle of the rod from hydroboost to brake pedal..

Here is the hydroboost plate that came with my hydroboost unit. I welded the little half-moon up top but other than that it is stock.

This is the new plate I am going to cut out.

The 4 mounting holes will get drilled manually. I've moved the hole up for the hydroboost unit 3/4". The new mount point on the lever will actually be ~1.5" higher. The other 3/4" will be made up with the new angle. The lines around the hydroboost hole will be cut and will allow me to re-angle the unit. This will actually level it out and give me the correct angle from the hydroboost unit to the new mounting point on my brake lever. Once I get the angle right I will just weld that cut closed. I plan to have my truck back on the road in a couple of weeks so I should be able to report back relatively quickly with some results...

 

[Don W.]

Re: Hydroboost pedal effort

Interesting. I've got a smaller (bore) diameter master cyl I was gonna try. Might do that next week. So far though if I mash hard on the pedal I can hold 3-4 lbs pretty easy. I usually launch with 0-2 though.

 

[mattw]

Re: Hydroboost pedal effort

I pulled the pedal out today.. In the pic you can see the stock stud and I've marked in yellow where the new stud will be installed..

A 7/16" bolt is the perfect size to make the new stud out of. The nut and bolt on the top of the pedal are both 18mm.

 

[mattw]

Re: Hydroboost pedal effort

More progress..

Brake pedal drilled out with a U bit.. U (.3680)

Brake pedal tapped 7/16-14.

New stud drilled out with 7/64 bit for pin. I used that coupler nut as an alignment fixture so that it was in the exact same position as the stock stud..

New stud installed. I used a grade 8 7/16-14 bolt.

I used loc-tite and welded the nut just to be safe..

Painted black..

Cut out a test plate..

Installed and bent to correct angle..

The rod leaves the hydroboost unit nice and straight..

Rod connected to new stud..

The hydroboost unit and master cylinder are now level..

Thats all for now.. Next step is to weld that plate up..

 

[blacktyaffair]

Re: Hydroboost pedal effort

Is this going to require a custom/adjustable rod or will this work with a stock rod? Everything you've done looks great. Keep up the good work. :tup: