Hydroboost Brake Pedal Throw

[kiteoregon]

Trying to figure out the proper brake pedal rod length, what is a good travel for the brake pedal? How far is it from the floor when at rest?

Thanks.

 

[thegreatjustino]

Should be even with the clutch pedal if you've got a manual transmission.

 

[kiteoregon]

Nope,have an auto.

 

[thegreatjustino]

Well, if you have a brake pedal in there now, measure the distance from the floor and use that measurement for your hydroboost system. If you're building from scratch and haven't got pedals at all, I can take a measurement for you if you need.

 

[toddz69]

I haven't had a clutch pedal in mine since '98 so I don't have that as a reference. Mine measures 4 3/4"-4 7/8" off the floor to the top of the pedal pad depending on where on the pad you measure. With the amount of travel in my system and my personal preferences for how high the pedal is at full engagement, I've found it to be a good setting.

Todd Z.

 

[DirtDonk]

Manual trans equipped brake pedal is more in the 6" range, but a little less for the big auto pedal isn't out of line. And might be just right from the sound of Todd's experience with it.
A lower pedal does limit your fudge factor when it comes to a soft pedal however, so make sure yours is bled to within an inch of it's life, and there is no slop in the mechanism (rods, etc.) that would allow the pedal to travel too far before any business starts happening.

And remember, while setting everything up don't push the pedal until the master cylinder is installed, so you don't over-travel the hydroboost unit.

Paul

 

[00gyrhed]

Whoa, pay attention to everything else but the pedal height and the pedal ht. will take care of itself. First make sure the rod between the HB and MC has right at or slightly less than 0.020" of endplay. Basically, the MC shouldn't move when you put it all together but as soon as you move the pedal the MC should move too.

You have to set the rod length under the dash such that when the entire system is bottomed out the pedal does not hit the floor. Period. if the pedal hits the floor before you bottom everything out you are limiting brake travel and in the event of a single chamber of the MC you may need all of that travel to get stopped, especially if you loose the front brakes.

With mine once I set the travel to have the pedal stop 1/4" above the floor. I have to admit I hammered the floor some to get the clearance rather than remake my rod, the top travel just happened to work itself out. Go figure since that's probably how Ford set up the original MC in the first place. In theory you should have about 3/4" to 1" of slack at the top of the travel but the main thing is making sure you can run completely through the stroke of the MC without bottoming out the pedal on the floor.

Another thing you need to be careful of is the rod itself. I have see a lot of people cut the rod, thread it and then bend it. that little rod id designed for a straight through push, the bend puts stress on it that it may not be able to take. You will never know as long as the HB is working but if you loose the HB and need to get all over it to stop in a hurry that bent rod could buckle.

 

[ransil]

I would like to see some numbers from the hydro boost conversion compared to the stock application, some day i'm gonna measure when I'm in the junk yard.

here is how to measure & calculate ratio

http://www.mpbrakes.com/techtalk/how-to-series/correctly-calculating-pedal-ratio

http://cf.linnbenton.edu/hhs/pe/gibbsr/web.cfm?pgID=7736

 

[toddz69]

I would like to see some numbers from the hydro boost conversion compared to the stock application, some day i'm gonna measure when I'm in the junk yard.

here is how to measure & calculate ratio

http://www.mpbrakes.com/techtalk/how-to-series/correctly-calculating-pedal-ratio

http://cf.linnbenton.edu/hhs/pe/gibbsr/web.cfm?pgID=7736

What aspect of the stock hydroboost application would you like to compare to the conversion?

Todd Z.

 

[ransil]

What aspect of the stock hydroboost application would you like to compare to the conversion?

Todd Z.

most get boosters from the 90-93 astros.
they get put on the angle brackets so there is added math in there from the linkage of the angle bracket. ( or am i over thinking it) .
When installing them on a bronco they almost go thru the windshield, the ration is wrong or different from the astro setup that is not so touchy when the pedal is applied.

 

[toddz69]

most get boosters from the 90-93 astros.
they get put on the angle brackets so there is added math in there from the linkage of the angle bracket. ( or am i over thinking it) .
When installing them on a bronco they almost go thru the windshield, the ration is wrong or different from the astro setup that is not so touchy when the pedal is applied.

10-4. That's definitely something for consideration. It was in my thoughts when I first did a Super Duty booster on mine years ago, I was curious about the stock pedal ratio in the SD vs. the EB so I did some measuring. EBs have a 6:1 pedal ratio and I was surprised that my SD had a similar ratio.

It's been a long time since I put a tape measure on the angle bracket linkage but as I recall the stock one reduced the mechanical advantage by about half, which seems to be in line with a lot of power booster pedal ratios that are in the 3:1 range.

Todd Z.

 

[toddz69]

most get boosters from the 90-93 astros.
they get put on the angle brackets so there is added math in there from the linkage of the angle bracket. ( or am i over thinking it) .
When installing them on a bronco they almost go thru the windshield, the ration is wrong or different from the astro setup that is not so touchy when the pedal is applied.

10-4. That's definitely something for consideration. It was in my thoughts when I first did a Super Duty booster on mine years ago, I was curious about the stock pedal ratio in the SD vs. the EB so I did some measuring. EBs have a 6:1 pedal ratio and I was surprised that my SD had a similar ratio.

It's been a long time since I put a tape measure on the angle bracket linkage but as I recall the stock one reduced the mechanical advantage by about half, which seems to be in line with a lot of power booster pedal ratios that are in the 3:1 range. I'd be curious what the Astro pedal ratio is too.

Todd Z.