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.

 

[Evan03]

From what i can tell anak you basically gotta pay to post photos. For me thats the first step in members like me hitting the road.

 

[Bent]

From what i can tell anak you basically gotta pay to post photos. For me thats the first step in members like me hitting the road.

Although I don't think there's anybody here that's going to believe that, you can try Imgur. It is free to use as well as the Forum that us members here support to keep online.

 

[RCP Phx]

From what i can tell anak you basically gotta pay to post photos. For me thats the first step in members like me hitting the road.

You been posting pics for 7 years and your still here?

 

[Goose_XJ88]

It's much easier than it used to be for all. Just so happens that it's 10x easier when a paid member.

Maybe @macgyvr or someone else that posts pics as a non paying member can explain how to post now.

 

[Anak]

From what i can tell anak you basically gotta pay to post photos. For me thats the first step in members like me hitting the road.

FWIW, I have the opposite perspective.

I do not trust anything "free". I figure if I am not paying for the product then I am the product. And I am philosophically opposed to being someone else's product. To that end, I pay for my own domain and host my own photos.

It is good to have different options for different folks. "One size fits all" fits no one.

 

[Jeepin_JD]

Post in thread '92 XJ Sport - Resto Mod'

Thursday at 7:36 AM

I have a gearing dilemma... Because my XJ will be my daily driver, I don't want to over or under gear the axles. I have tried to stick with the factory ratios for tire sizes. Example. the XJ was originally equipped with 225/75-R15 tires. That's a 28.29" tire. The axles were 3.08s and top gear of the AX-15 is .79. This combo is what engineers figured would provide the best mileage and performance given the engines capabilities. With this setup, my XJ spins just a hair over 2000 at 70mph and gets approximately 23 mpg. The real world test of this was my drive from Idaho to Wisconsin. I...

• Jeepin_JD

With my WJ knuckle swap, I am running all WJ parts. Calipers, Rotors, and unit bearings. I did this so that I could run JK wheels. My issues is which ball joints to use. Everyone has a different opinion it seems. I have two concerns, Camber and longevity of the joint. The technical drawings of the two knuckles show there is a difference in the kingpin angle between the WJ and the XJ axles. There is also a difference in the taper of the lower ball joints. Some say run JK ball joints for the upper and lower, others say just run Spicer XJ joints for both, and yet those with truly deep pockets prefer all the HD aftermarket stuff. I will be running bigger tires and wheels, but I am not lifting the XJ... If anyone has some actual technical writeups of the advantages and disadvantages of the various options, please share.

 

[75SV1]

I do run or have run WJ wheels on my '98 XJ. I did use the WJ bearing hub. I used WJ rotors. On the ball joints. The upper is the same for the XJ and the WJ. The lower needs to be a WJ ball joint. The taper on the lower of the XJs vs the WJs is different. I forget what my upper is on the '98. I used a Mevotech TTX for the lower latter on. On my '00 I used FRX, upper and lower. I ran the '98 for say 6-8 years. No issues with the ball joints. I do run across route 15 in WV. Also part of the Hellbender trail. I'd look at Teraflex. ball joints. Mainly, as to the zerk fittings look to be more accessible. I did put low profile Zerk fittings on the FRXs. I haven't tried to lube them yet with a 90 degree grease probe. I ran 32's on the '98. I run 31's on the '00.

 

[Jeepin_JD]

I do run or have run WJ wheels on my '98 XJ. I did use the WJ bearing hub. I used WJ rotors. On the ball joints. The upper is the same for the XJ and the WJ. The lower needs to be a WJ ball joint. The taper on the lower of the XJs vs the WJs is different. I forget what my upper is on the '98. I used a Mevotech TTX for the lower latter on. On my '00 I used FRX, upper and lower. I ran the '98 for say 6-8 years. No issues with the ball joints. I do run across route 15 in WV. Also part of the Hellbender trail. I'd look at Teraflex. ball joints. Mainly, as to the zerk fittings look to be more accessible. I did put low profile Zerk fittings on the FRXs. I haven't tried to lube them yet with a 90 degree grease probe. I ran 32's on the '98. I run 31's on the '00.

That's awesome... I was pretty sure that your setup was the way to go. How was your tire wear on the front?

I'm doing a resto mod kid of thing. I will be using WJ disc brakes an all four corners. I have already modified the rear axle shafts to a 5x5 bolt pattern so the brakes will be a direct bolt on application. I am using a Durango Master cylinder with a dual diaphragm vacuum booster. I modified the steering box with a WJ relief valve and spring to give it a little more pressure. I'm regearing for bigger tires. Leveled it front to rear. However, I am not lifting it any more than the new springs provide. Since the old springs were original, I have no idea how much lift the Jeep has. My guess is about 1.5" over a new stock suspension. With the wheels I am using, the tires sit completely inside the wheel wells front and rear. When I tested the suspension for rub, the only point of contact was the inner fender liner of the front wheel wells, but only when I turn the wheels. I'll probable have to make my own liners for max clearance. Since I will not be flexing it out on the trails, I am not worried about rubbing during full articulation.

 

[75SV1]

My wear on the tires was/is good. I have a set of Falken Wild Peaks. I forget the metric designation. Sort of a 32 x 10.5. Rides smooth, no pucking etc. I did wheel it twice and in the mudd. I kept up. I had to be pulled out once. I also have been planning a 'full' WJ brake system. I was at 4.5 lift on the '98. I am having a '01 worked on. I also run the WJ cross over steering. Worth the extra $. Also OTK trackbar. I do get some Akerman effect scrubbing on tight turning. Just parking lot stuff. Possibly with a wider tire, it would be worse.