Brake booster ?'s

[lutronjim]

My 70 C10 with LS gen 3 has disk front / drums rear with, I'm guessing, an 11" booster. If I have to do a quick stop, the brakes hang at around 20%. I can stop remove the vac hose and everything returns to normal. Replace vac hose and good to go.

The rear hose has been replaced. The petal has about 3/8 inches of play.

I am guessing that the rear chamber seal gets wedged or something letting atmospheric pressure leak in. The booster also will not hold - if I have foot on brake and cut engine the petal comes up.

Since the booster is leaking it needs to be replaced which I hope will solve the hang up problem.

I also would like more assist. I was looking to buy one of Captainfabs mounts and get a dual 9" booster like from an S15.

The stock mount looks to loose about 1/2 of the petal force and gain 2 times the travel because of the linkage. I assume its purpose is to move the booster so it wouldn't hit the shift arms.

My questions: Since I would gain quite an advantage with the direct mount, would the dual booster be too much? Would the extra distance needed with the new mount cause the petal to go to low?

Any help would be greatly appreciated.

[Madkidd007]

Think of the travel in a different way. Say a pry bar. You try to grab it half way up and you move it half the distance you would vs at the very end. Now grabbing in the middle you half to use a lot more force than at the end. So I’m actuality using the factory lever style you gain force or same force exerted with less input. It’s a mechanical advantage. Personally if I was going to start changing the assist system I would skip vacuum and go hydroboost as nothing compares to output vs input force. One important thing though is what size tires and suspension setup are you running. Stock truck, will the tires hold a lot better breaking?

[lutronjim]

Been on the road. Tire size is 265/70R17 on 9" rims.

I disagree with you on lever. It is hinged on bottom and petal rod connects about half way with top of lever pushing master cylinder so you have to use a lot more force than a direct connect.

[Madkidd007]

I get what you mean about force and if it was manual breaks it would be a major issue. But with power assistance it should be irrelevant. As far as the lever action I shoiuld have spoke more clearly with that you get more actual travel going into the master than you are inputting. Without the level setup you have to push the travel physically further than if you did not have it. Personally if it was mine I would use the hydroboost out of an early 2000s gas heavy duty or Escalade. You could get all of the parts that would match the engine and plumbing would be gravy. Only thing would be adapted going to the gear box unless you are running a late model box with metric fittings already. If you want it to stop like a modern vehicle just like your engine performs that would be my vote. I’ve had a few and nothing compares.