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Rear brakes locking up

77broncodriver

Full Member
Joined
Nov 21, 2009
Messages
344
Ever since I swapped in my hydro boost my brakes have been awesome other than the backs locking up.

I bought a proportion valve that I haven’t installed yet but read somewhere that they don’t actually restrict the pressure going to the back but only momentarily slow the pressure to the back. It seems like even if I slowly get on the brakes the backs still lock up and the fronts never catch up (not just when I slam on them) You guys know if this is true and if I need something else other than just a proportion valve?

Evan


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SteveL

Huge chevy guy
Joined
Jun 24, 2001
Messages
11,613
Loc.
Hawthorne ca
I've always thought the proportioning valve reduces pressure to the rear. Bc sells an lbs valve that takes the initial spike from the rear on a panic stop. On my 66 I have the lbs valve. With the vacuum booster the rears never locked. After going hydro boost the rears will lock but it's somewhat controllable. Currently swapping hydro boost onto my 72 with same setup(4wheel disc with lbs). On the 72 I'm gonna add a proportioning valve to fine tune it. If it's a noticeable difference I'll be adding one on the 66.
 

garberz

Bronco Influencer
Joined
Jun 24, 2007
Messages
6,856
Loc.
Conejo Valley, Ca.
I use the Wilwood adjustable valve, plumbed to the rears only. It reduces pressure up to 57%. I’ve used this valve on several hydro boost installs with great success.

Mark
 

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77broncodriver

77broncodriver

Full Member
Joined
Nov 21, 2009
Messages
344
Thanks for the info guys!

That proportion valve is the same one I got I believe. Looks like I have a project for the weekend now.


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Apogee

Contributor
Bronco Guru
Joined
Nov 26, 2005
Messages
6,033
If the adjustable proportioning valve doesn't solve your issue, but does help, then the other thing you can do would be to increase your front brake bias. You can do that by running a larger front caliper piston area, commonly referred to as a big-caliper upgrade with either Chevy or Ford disc brakes. This effectively reduces the pressure required to achieve front lockup, so less pressure is supplied to the rear brakes as well. Alternatively, you can run a more aggressive, higher CoF brake pad up front as well to shift bias forward.
 
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