BlkCJ7Laredo

I was replacing the wheel bearings on my 98 last night and put it all together and wheels locked up then I found out that 99-up has the cast rotors and different hubs, the hubs I got mistakingly for the 99.


Now is anything else different? Can I just swap the rotors for the newer cast type, OR can I put a 1/8" thick spacer onto the hub face before putting the rotor on to space the rotor out to where it's supposed to be? It appears that the hub flange and studs are taller on the new type hub.


Reason why I ask this is I bought 4 of the hubs, 2 for me with my 98 and 2 for my buddy's 99, and his is early build with composite rotors like my 98 and that's a lot of extra parts to throw away since it's ebay stuff that I can't return since I've had them for 3-4 months now.

fb97xj1

Measure the lug studs.

1 1/8" studs = composite rotors (use Timken 513084 hubs)
1 1/2" studs = cast rotors (use Timken HA597449 hubs)

Also, should you ever need to replace the brake drums or shoes in the rear, ribbed drums are 10". Smooth drums are 9".

BlkCJ7Laredo

Ya, I know the difference between the hubs now, my question is if the hub and the rotor are the only things different and if I can just put the cast rotors on in place of my composite ones OR put a 1/8" thick spacer between the hub and rotor and have the same effect.

fb97xj1

I have never heard of this being done, but a spacer between the hub and rotor will push the rotor farther away from the caliper, binding the rotor against the outside pad. Spacers should only be used between a hub and the wheel. Not to space a rotor. Just buy the proper hubs and keep everything as it was meant to be when it comes to the brakes.

fb97xj1

Doubleposted instead of edit. oops

lgrant

1. I have a 96 xj that, no doubt, has the composite rotor and corresponding hub. The lug bolts extend approximately 15/16" out from the outside of the rotor (I measured with a worn metal tape measure). The rotor appears to be 1/4" thick at the hub attachment point and that would give you around a 1 3/16" long bolt. I'm probably off a 1/16th somewhere so that confirms the 1 1/8" bolt for the composite parts. The depth of the rotor from outside of the hub attachment area to the brake pad flange is 2 1/4". The important info here is that, measuring from the outside of the hub, the lug bolt will measure only 15/16" (or maybe 7/8" if you have a metal ruler?).

2. I have a 99 xj, MFD in 10-98. And, without removing the 1.25" wheel spacer that facilitates a 5x5, 16" wheel, it's my best guess that this vehicle has the CAST rotor and therefore the later version of the hub. The lug bolts extend 1 3/16" out from the outside of the rotor, just shy of being flush with the spacer. If the rotor is 5/16" thick (can anyone confirm this?) at the hub, then that would give the 1 1/2" lug bolt length. Also, the depth of the rotor from outside of hub to brake pad flange is 2 1/8", so definitely a different rotor. In addition to this info that may help identify which rotor/hub you have, manufacture date is not reliable for determining which version of rotors are on a 99.

I'll be ordering hubs (Rock Auto) for the 99 in a day or so. If any of the seasoned pros could comment, I would appreciate it.

Tbone289

If you remove one of your spacers, it should be obvious if you have cast or composite rotors. Actually, it should be obvious with it on there, since the cast rotor is one piece vs. the composite two-piece rotor. The cast rotor will have a sharper 90-degree edge at the wheel mounting surface due to being machined, and the composite rotor will have a more gradual, rounded edge due to being pressed. Measuring isn't required, just a quick visual inspection. Once you've determined what you have, you know what unit bearings or rotors you need.

See here: www.remaninc.com/pdfs/compositevsfullcastrotors.pdf

lgrant

Unfortunately, I don't think the visual inspection will work for me. See pic of composite rotor. The edge "looks" machined. At least it is sharp and isn't rounded off. So the visual inspection of this edge doesn't seem to be an effective way to tell the difference.

Tbone289

Interesting. I would certainly identify that as a cast rotor if it's OEM.

The changeover occurred halfway through the 1999 model year. Maybe this will help you:

lgrant

The 2 1/4" vs 2 1/8" measurements is consistent with what I thought I have - cast rotors. And again that's on an XJ manufactured Oct 1998. Did they make the XJ in more than one location? If not, then the change over can more likely be described as "1999.1-1999.9" than mid-year. No worries, I think we have it figured out.

That composite rotor came off of my 96 from last brake job at 280K (currently it has 305K miles). So not OEM.

Tbone289

That makes sense. Interesting about he changeover... Everything I've read online says mid-year 1999, but you can't believe everything you read! Of course, any XJ could be changed over from composite to cast and vice versa as long as the correct unit bearing and rotor are paired up.

Ben Reilly

If you're changing your hubs and rotors at the same time just make sure you get the rotors that match the hub. If you're buying a cast rotor buy the hub for the cast rotor and vice versa. It only really matters if you're changing one but not the other.

diskman

If you are replacing the rotors AND hubs.. Do what I did on my 99.. Order all the parts for a 2000 XJ. That way you WILL get the correct bearings AND rotors. Even if your 99 had composite OR cast.. Ordering parts for a 2000 will match up every time.

Easy Peasy.

kmagoo

Done the brakes before, never questioned about cast or composite. Doing ujoints and hubs now. The rotors measure as cast. I ordered the cast hubs. My 99 had 2 different hubs on it. Never any binding issue, so do the cast rotors work with both hubs or am I missing something?

IJM

What is a composite rotor? I thought all brake rotors were cast iron, except for 2-piece race car rotors, of course.