XJ brake upgrade

[my90xj]

I have a 1990 jeep cherokee. It has the 4.0 liter motor.
It has a 8in lift on 35" Mickey Thompson tires. Bought it with the disc brake swap of the rear. Was having trouble stopping.( soft pedal). The first thing done was to bleed the brakes. No improvement. The 2nd was to replace OEM brake booster and master cylinder. Bled the system no improvement in stopping. The next, I looked up was to do a swap to dual piston calipers. So I bought WJ knuckles Explorer sport trac rotors and dual piston calipers for a WJ. Changed the knuckles and now the rotors are same bolt pattern but studs are to big for rotors. I am stuck I need to know what to do. Do I drill out the rotors and hope it all goes back together. Do I look for what master cylinder would bolt on and be able to increase fluid volume to make jeep stop. Please help with answers

 

[RCP Phx]

My WJ rotors are re-drilled for a XJ bolt pattern!

 

[XJlimitedx99]

I think most people that do the WJ knuckle swap use WJ rotors and drill the XJ bolt pattern into the WJ rotors. I have seen people say the Explorer rotors can work too.

Quick Google search shows the Sport Trac has 1/2" lug studs just like the XJ's. You sure you have the correct rotors?

I'd just drill them out bigger and move on. Ain't no big thing.


About the MC, you're thinking about it wrong. Brake fluid volume does not increase stopping power. Increased pressure squeezing the pads to the rotors increases stopping power. Pressure is ratio of force to area (hence pounds per square inch), so a bigger master cylinder will actually have LESS stopping power with the same amount of force applied to the brake pedal because you have the same amount of pedal force over a larger area.

If you want better stopping power, you need more pressure in the lines and/or more clamping area on the rotors. You're already working on more clamping area with the bigger WJ brakes (which is a great choice btw). When you changed the booster out, did you go to the newer style dual-diaphragm booster? That will also make a significant difference. Leave the MC alone.

 

[my90xj]

Thank you but no at first I replaced with original booster and MC then no improvement so I tried the swap.
I could be running in to the issue of different studs. Would a WJ hub and studs be a route to do?

 

[XJlimitedx99]

WJ hubs have a 5x5 bolt pattern. They would probably work if you wanted to deal with that.

What do you mean "running in to the issue of different studs"?

Look into the dual diaphragm booster swap after your WJ swap is complete.

 

[Anak]

Post pics of your fitment problem.

We are on a new system now. Should not be nearly so difficult to post pics anymore.

 

[75SV1]

2007-08 Doge Nitro Rotors are a direct fit for a WJ Big Brake Swap. Give up about 1.5mm of the OD.

 

[RCP Phx]

FYI, the WJ knuckles also require the use of a spacer and late model unit bearings.