Author Topic: Brake Bias Valve  (Read 331 times)

Offline Rosebud

Brake Bias Valve
« on: October 01, 2017, 10:16:13 PM »
Having a dual circuit braking system w/ separate master cylinders for the front & rear circuits, and despite biasing the front cylinder to max and the rear to minimum, I continued to lock up the rear brakes before the fronts. This proportional valve should do the trick. https://youtu.be/hEzcMAu8cYE

When it came time to bleed the brakes I tried using this vacuum brake bleeder system (see pic) and decided it was an unnecessary hassle. When I built up a vacuum in the system using the vacuum gun, air would enter around the brake bleeder valve threads. Then the reservoir container would tip over and the vacuum gun would back-fill with fluid. So I gave up on the gun and since there was no one around to pump the brakes for me, I resorted to the "Restoration Shop" or gravity system. I put a clear tube on the valves and opened them one at a time a let gravity do it's job, topping off the reservoir as necessary. Easy-peezy.
« Last Edit: October 01, 2017, 10:28:38 PM by Rosebud »
Rosebud
...the sled, not the flower
https://www.facebook.com/PoserMotorSports

Offline MiniDave

Re: Brake Bias Valve
« Reply #1 on: October 02, 2017, 08:53:31 AM »
I also haven't has a lot of luck using those vacuum style bleeders, I have a pressure bleeder I use - it's like a garden pump type sprayer - you put a quart of fluid in it, put about 15 psi in it and hook it to the reservoir - add a tube and container to the furthest bleeder, open it and wait for clear fluid to come out - makes flushing a brake system super easy as you just watch for the clean fluid to replace the nasty brown stuff - then move to the next bleeder and so on till you're done.

Are you sure you have the right sized rear wheel cylinders for your brake system? That can cause locking too......along with the wrong tire pressure, too stiff an anti roll bar and so on. You do want some brake pressure in the rear......
1989 Cooper Racing Green
2009 Clubman S
1969 Jaguar XK-E FHC
2004 Audi Allroad 2.7 TT

Offline Rosebud

Re: Brake Bias Valve
« Reply #2 on: January 04, 2018, 02:09:56 PM »


Are you sure you have the right sized rear wheel cylinders for your brake system? That can cause locking too......along with the wrong tire pressure, too stiff an anti roll bar and so on. You do want some brake pressure in the rear......

After 500 miles or so, including some "spirited" driving, I'm still locking up the rears a little too early, esp on loose surfaces despite having installed a proportioning valve. So, I'll be installing a pair of new 5/8" rear brake cylinders this weekend. Will advise.
Rosebud
...the sled, not the flower
https://www.facebook.com/PoserMotorSports

Offline BruceK

Re: Brake Bias Valve
« Reply #3 on: January 04, 2018, 03:33:26 PM »
Also, if a drum is slightly out of round that can cause locking.  So can shoes contaminated with brake fluid. (things I learned the hard way)
1988 Austin Mini
2002 MINI Cooper S
2007 Triumph Bonneville

Offline Rosebud

Re: Brake Bias Valve
« Reply #4 on: January 04, 2018, 05:06:43 PM »
Also, if a drum is slightly out of round that can cause locking.  So can shoes contaminated with brake fluid. (things I learned the hard way)

Nope. New Superfins, new shoes, new cylinders... and the adjusters are backed off all the way. Just too much pressure I think.
Rosebud
...the sled, not the flower
https://www.facebook.com/PoserMotorSports

Offline MPlayle

Re: Brake Bias Valve
« Reply #5 on: January 04, 2018, 05:29:14 PM »
Even the Superfins can be out of round.


Offline Rosebud

Re: Brake Bias Valve
« Reply #6 on: January 04, 2018, 06:08:34 PM »
Even the Superfins can be out of round.

Yeah, I guess. I have 4-pot KADs in front, Superfins at the rear and sticky Yoko 032 tires. When I tromp down hard (i.e. all the way) the rears lock up but the fronts don't. It stops well enough—slams me into the safety belts. But I'd like the fronts to lock up as well—same time as the rears on a smooth surface going straight. Am I expecting too much?
Rosebud
...the sled, not the flower
https://www.facebook.com/PoserMotorSports

Offline MPlayle

Re: Brake Bias Valve
« Reply #7 on: January 04, 2018, 06:10:53 PM »
In a Mini?  Yes.


Offline MiniDave

Re: Brake Bias Valve
« Reply #8 on: January 04, 2018, 06:11:14 PM »
I think you should be able to balance it out......
1989 Cooper Racing Green
2009 Clubman S
1969 Jaguar XK-E FHC
2004 Audi Allroad 2.7 TT

Offline Rosebud

Re: Brake Bias Valve
« Reply #9 on: January 04, 2018, 06:13:04 PM »
I think you should be able to balance it out......

You'd think. No luck so far. I'm hoping the ⅝" cylinders at the rear will do the trick.
Rosebud
...the sled, not the flower
https://www.facebook.com/PoserMotorSports

Online Willie_B

  • CREW
  • 1380cc
  • *****
  • Posts: 644
  • Total likes: 34
  • Karma: 7
  • He who laughs last, thinks slowest.
    • Lilburn, GA,
Re: Brake Bias Valve
« Reply #10 on: January 04, 2018, 06:26:42 PM »
There is a way to convert the rear proportional valve to make it adjustable also. Was in an article several years back by Calver in one of the mini magazines. I have it around somewhere.

Offline Rosebud

Re: Brake Bias Valve
« Reply #11 on: January 04, 2018, 06:36:40 PM »
There is a way to convert the rear proportional valve to make it adjustable also. Was in an article several years back by Calver in one of the mini magazines. I have it around somewhere.

I have a dual circuit braking system w/ separate master cylinders for the front & rear circuits and a proportional valve on the rear circuit [https://youtu.be/hEzcMAu8cYE]. Seems like smaller rear brake cylinders is the only trick I have left.
Rosebud
...the sled, not the flower
https://www.facebook.com/PoserMotorSports