Hydroboost push angle / pedal ratio

[ksagis]

Wanted to circle back to the topic of hydroboost pushrod drive angle.

I've heard indirectly that if the brake pedal pushrod wasn't directly inline with HB bore that seals would wear very quickly. @toddz69 said his discussions with Vanco were consistent with that.

@jamesroney had a thread on his bracket modification that ended up with roughly 5 - 7 degree of off angle push here

@ntsqd had commented that his FSB unit purchased from Vanco has an offset pin similar to as shown here. Crappy drawing below to show that I think an offset pin eliminates lateral load on HB bore, which seems to corroborate above, unless the application was trying to not change pedal ratio for some reason.

My Hydratech firewall mounted bracket has about 5 degrees of "side" angle to clear EFI as shown in pic

I modified a Bronco brake pedal to go from 6:1 to 5:1 by moving the pin down 0.47", which will result in about 5 degrees off axis push. Pressing with a pedal force of 20 lbs results in 2 lbs lateral, 150 lbs of pedal force results in 13 lbs lateral which seems to be in realm of non-concerning to me.

Would love to hear if anybody has a configuration with high miles and a drive angle of more than 5 degrees.

 

[ntsqd]

I don't really understand the offset push-rod like the unit in my FSB has. It isn't needed for clearance of anything that I can see other than maybe not making contact with the bore in the rear of the H-B unit when fully bottomed.

That push-rod is clearly an OEM part, and I'll guestimate the force angle to be about 5°, maybe a little more. It would be helpful to know what it's original application is as then some research might turn up if that application is known for wearing out the H-B unit at a higher rate than other applications with more direct push-rods.

 

[nvrstuk]

Well, I"ll admit I have absolutely no idea what angle my HB unit is off the firewall but I know it clears my strut tower by 1/4" so I"m pretty happy! lol

I can measure if someone wants to remind me in 2 weeks when I get back? I have had it like this for 7 yrs. I drive it a LOT, except when waiting for Ford to warranty a block that they totally screwed up machining, that was 10 months. Gotta be the lowest # of miles in that time for me since I"ve owned it. I usually average 150-190 week from Feb thru Nov.

 

[ksagis]

I don't really understand the offset push-rod like the unit in my FSB has. It isn't needed for clearance of anything that I can see other than maybe not making contact with the bore in the rear of the H-B unit when fully bottomed.

That push-rod is clearly an OEM part, and I'll guestimate the force angle to be about 5°, maybe a little more. It would be helpful to know what it's original application is as then some research might turn up if that application is known for wearing out the H-B unit at a higher rate than other applications with more direct push-rods.

You nailed it, the only logical thing is clearance for something.

Edited my note above, after noodling on it some more, the offset feature doesn’t seem to eliminate the lateral load.

 

[ksagis]

By the way, if anybody has an old hydroboost that I can debuild to poke around inside, let me know, thanks.

 

[ksagis]

@catfan is hooking me up, will post up after looking at internals.