99 Brakes/Wheel Bearings

The background: I just picked up a 1999 sport 2-door 5 speed 4x4 in gunmetal last weekend and I have to change the wheel bearings/U joints out. Since I'm changing the bearings, I figured I might as well change the brakes since I'll have them off.

The issue: It's a 99 (the year that has both cast and composite rotors in the build) and the rotors on it are cast. They could be factory cast replacements or the cast composite replacements.

The question: If I change the wheel hubs, can I just pick the set? IE: Cast hubs and cast rotors or compound wheel hubs with compound rotors (cast replacements)? Will everything else (calipers, shields, knuckle etc.) work with both sets?

Thanks in advance!

--Roman

I'm not sure of the answer, but just to add confusion, you should know that there are cast replacement rotors that match the composites in dimensions, so you really can't tell for sure which setup you have unless you see composites. For example, I just replaced the composite rotors on my 95 with cast rotors off a junkyard Grand. They fit perfectly.

If you get the correct rotors that match your unit-hubs you can swap the rest of the brakes either way across the years, 1990 thru 2001.

Three different hub/bearing units were used over the years on XJ's. The hub/bearing units are the same part number for both sides of the vehicle. The model years for hub/bearing assemblies were:

1) 1984 through 1989 (early style rotors)

2) 1990 through mid-1999 (composite rotors)

3) late-1999 through 2001 (cast rotors).

** You need to match brake rotors to the unit bearing/hubs on your XJ. **

Lay the rotor on your bench and measure from the bench to the top of the rotor.

Composite rotors will have an overall height of 3 3/16". Composite rotors will have a thin sheet metal like appearance at the lug nut holes where the studs come through and measure about 1/8 "(.125) thick in this area. Composite rotors have a rounded off corner at the wheel mounting surface and look like two pieces joined together.

Cast rotors will have an overall height of 3 1/16". Cast rotors are thicker at the lug nut holes and measure between 1/4" (.250) to 5/16 (.320) in this area. Cast rotors have a square corner at the wheel mounting surface and look like they are one solid piece of metal.

*** Parts store replacement rotors may have a different appearance.

On late 1999 - 2001 unit bearing/hubs the ring around the 36MM shaft retaining nut is almost 3/4 inch tall and the hub has longer lug nut studs than older hubs.

On early 1990 - 1999 unit bearing/hubs the ring around 36MM shaft retaining nut is about 1/2 inch tall.

Two steering knuckle designs were used: 1984 to 1989 and 1990 to 2001. Left and right side knuckles have different part numbers.

Two types of brake caliper styles were used: 1984 to 1989 and 1990 to 2001. Left and right sides are different part numbers.


1999.5 to 2001 unit bearing/hub on the left, 1990 to 1999.5 unit bearing/hub on the right
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COMPOSITE ROTOR below -
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CAST ROTOR below -
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Tim MN said:

If you change your rotors to the style that matches your unit-hubs you can swap either way across the years, 1990 thru 2001.

Click to expand...

Awesome, Tim, thanks!

I've searched and seen your post before, but I just wasn't sure the rest of the equipment would bolt into the same place (worried about rotor offset).

Thanks again!!!

--Roman

Interesting.. I'm actually looking up the same exact thing! The grinding is getting annoying so I figured its time to get it all fixed up. Although I don't think its the hub anymore. I noticed that there is a ridge on the outside of the rotor like the pad is too narrow for the rotor.
:anon: