08 Superduty Master Cylinder plumbing

[gunnibronco]

I’ve always mildly disagreed with the concept of having the front lock up before the rears.
Yes, having the rears lock up could end up with you skating around and “swapping ends“ as people like to say. But I’d rather retain my front steering and braking capacities by having front wheels that are still rolling, and deal with the much easier to deal with rear skid.
I’ve locked up my rears just before the front many times and have never swapped ends. Now I’m sure there are situations where it’s unavoidable, but I’d still rather not lock up the fronts.
With the rears locking up just slightly before the fronts, it also gives you a good indication of where you are in your braking and that you are just about to lock up the fronts.
In some situations it’s good to know that so you can avoid locking up the front and losing some of the control that you still had up to that point.

Good points.

I'm hoping a proportioning valve will be enough to allow me to dial in a good balance. I'm not even close right now.

I can't even get my fronts to lock up at all (on pavement), but I admit that wasn't the goal. The wheel hop (if caused by the brakes) on the down hill was uncontrollable. It actually turned me sideways across the hill. I was wondering if I was going roll the rig on a "shakedown" run on a simple trail 10 minutes from my house. Derp.

 

[rocknhorse76]

The JB6 calipers aren’t too big. That enormous MC is pushing too much fluid to them. Add that proportioning valve to the rear circuit and your problem will go away. I’m running the same calipers with a 1.25” bore MC and they work perfectly.

 

[gunnibronco]

The JB6 calipers aren’t too big. That enormous MC is pushing too much fluid to them. Add that proportioning valve to the rear circuit and your problem will go away. I’m running the same calipers with a 1.25” bore MC and they work perfectly.

Thanks, I'm hoping that fixes it I knew there were two ways to do it. Swap calipers or add a proportioning valve. I finally found a steel -3 female to 1/8" male npt fitting that will allow me to easily add a proportioning valve to the system without new lines. It's on the way.

I probably overshot with the 1.5" MC but in the end I'm super happy with the pedal feel. So im hoping after the proportioning valve is installed it's going to work well.

Those JB6 calipers were originally meant for the front brakes. I was going to do 5x5.5 lugs but changed to 8 lug mid axle build. The 5x5.5 rears were going to be Explorer brakes. Compared to the Explorer rear brakes a 3" caliper seems huge. My old axles were 79 F150/Bronco axles with rear drums. So I'm in uncharted territory for me.

Sent from my E6910 using Tapatalk

 

[rocknhorse76]

Thanks, I'm hoping that fixes it I knew there were two ways to do it. Swap calipers or add a proportioning valve. I finally found a steel -3 female to 1/8" male npt fitting that will allow me to easily add a proportioning valve to the system without new lines. It's on the way.

I probably overshot with the 1.5" MC but in the end I'm super happy with the pedal feel. So im hoping after the proportioning valve is installed it's going to work well.

Those JB6 calipers were originally meant for the front brakes. I was going to do 5x5.5 lugs but changed to 8 lug mid axle build. The 5x5.5 rears were going to be Explorer brakes. Compared to the Explorer rear brakes a 3" caliper seems huge. My old axles were 79 F150/Bronco axles with rear drums. So I'm in uncharted territory for me.

Sent from my E6910 using Tapatalk

There are countless numbers of us out here using the JB6 calipers in the rear with great success. There’s a reason why so many companies use those calipers in rear conversion kits-they work great! That, and they’re cheap and easy to find lol. I can pretty much guarantee that the pv in the rear circuit will cure your problem.

 

[gunnibronco]

Quick update.

I added a basic proportioning valve to the system on the rear brakes. I've turned the rear brakes all the way down (57% reduction) and still have a little rear brake bias. I test drove it and it performed much better. I descended the same hill that induced crazy rear wheel hop without an issues (twice). So it's not causing any problems and is very driveable. In the future I may try swapping the lines off the MC again and see if I can improve further, but at this point I'm just going to run it.

 

[73azbronco]

I’ve always mildly disagreed with the concept of having the front lock up before the rears.
Yes, having the rears lock up could end up with you skating around and “swapping ends“ as people like to say. But I’d rather retain my front steering and braking capacities by having front wheels that are still rolling, and deal with the much easier to deal with rear skid.
I’ve locked up my rears just before the front many times and have never swapped ends. Now I’m sure there are situations where it’s unavoidable, but I’d still rather not lock up the fronts.
With the rears locking up just slightly before the fronts, it also gives you a good indication of where you are in your braking and that you are just about to lock up the fronts.
In some situations it’s good to know that so you can avoid locking up the front and losing some of the control that you still had up to that point.

Rears should get to lock point before front, as you noted why, you can steer.