Rear Brake Lockup Help, Help Options

[spaceshuttle]

I am running larger 4 piston Outlaw (read Willwood) calipers on the front of my v6 track car, with 911 M calipers on the rear. I installed a brake bias adjuster knob initially but my rears lockup under heavy braking no matter the adjustment. Switched to a Tilton bias adjustment with the notched rod with multiple positions and still no change. I cannot tell that there is much difference in the pressure to the rears. They will lockup no matter the position under heavy braking. They are not sticking. Not sure which direction to go from here. I am running Hawk blues front and rear. Perhaps a less aggressive rear pad? And yes the factory proportioning valve was removed.
thanks for any help guys.
LC

[stownsen914]

Strange that they keep locking up even with the bias dialed back. I would think that should do it, plus you get some natural proportioning wtih the front calipers being larger than the rears.

Silly question - is your aftermarket prop valve installed in the rear brake circuit like the stock one?

Scott

[Randal]

Strange that they keep locking up even with the bias dialed back. I would think that should do it, plus you get some natural proportioning wtih the front calipers being larger than the rears.

Silly question - is your aftermarket prop valve installed in the rear brake circuit like the stock one?

Scott

We took out the rear proportion valve and simply put in a T fitting. So no proportioning what so ever. Then started playing with the different pads, but actually the first attempt fixed the lockup, i.e., elcheapo pads instead of the Hawks.

And to be honest I really like the set up as I don't have to deal with lockup on a hill where a lockup could get ugly.

[stownsen914]

I wasn't clear in my questions! I meant to ask Spaceshuttle where his proportioning valve is ... if it's where the stock one was, I don't see why it wouldn't limit the rear braking force and keep wheel lockup under control.

[ThePaintedMan]

I wasn't clear in my questions! I meant to ask Spaceshuttle where his proportioning valve is ... if it's where the stock one was, I don't see why it wouldn't limit the rear braking force and keep wheel lockup under control.

..unless it's just simply too much clamping force between the larger caliper and larger pad. Look at how small a stock rear pad is. With good, grippy pads I can definitely see where the rear bias is too much to overcome. Also, I don't think that it's possible to completely dial out all rear bias with most adjustable prop-valves. I think it largely depends on how it's plumbed. I'm with the cheap and simple solution - try some really cheap pads next.