BEARING HUBS!!!! What's the deal?!?

I've read on here, and confirmed by my own measurements that there were at least three different bearing hubs used on XJs between 1984 and 2001. I'm mainly looking for the change that occured between 99-00 (when they went with the low pinion axle)

I'm 400 miles away from my stash of extra parts but I need the following if possible:

Part numbers for the different hubs, (dealer says that ALL hubs from 90-2001 are the same, as well as those found on TJs. I KNOW that this is incorrect!)

measurement of the flange diameter (where the wheel studs press in)

measurement from the knuckle mounting surface to the rotor mounting surface. (depth of the unit bearing)

I know that there was a 1/8" change in depth of the bearing hub somewhere between 90 and 2001. I'd like the info of when this change was.

I believe the change was in the DC consolidation between 1990 and 1991. The "Jeep Thing" is that the early hubs/knuckles/rotors were mixed-in on axles as late as 1993 (as the existing pallet stock of axles was depleted).

The hub depth design change was between 1990 to 1991. The likelyhood of a 1991-1993 having the early hubs is a crapshoot gamble (Jeep s#it happens).

The TJ hubs (including all 1999-2002 low pinion XJ's) are the same as the later design, the 1991-2002 design.

There are two styles of XJ/YJ D30 hubs, and only one style ZJ/TJ D30 hubs, and the WJ hubs are different from any of the others.

Clear as mud?

explain this:

"90-99" rotors on 2001 knuckles and bearing hubs require a 1/8" spacer to keep them off the knuckle

SeanP mentioned THREE different XJ hubs in an earlier thread, and there was another thread about different rotors not fitting properly on a newer XJ (needing the same spacer that I'm running)

the early hubs that you mention are the ones with the smaller diameter, but they are the EXACT same depth as the hubs I'm running on my junk now (ran the spacers before with those hubs on 89 knuckles. I was told that swapping the knuckle would make it work. I was right back to square one. still using the spacer)

so where does this mysterious third-style hub that sean mentioned fit in? most places that sell replacement hubs omit the last few years from the hubs that fit the "91-96" XJ.

what hub is it that I have that has the same spacing as the 84-89 hub but a larger diameter on the flange where the rotor mounts?

Guess I gotta wait a month and go to the junkyard myself and measure. Are part numbers stamped on the hubs?

The conclusion of the attached thread has no proof of three hub designs, just the valid advice to match the hub/knuckle/rotor/caliper all from the same year donor.

The conflict experienced is what occurs when you try to fit later hubs on an early knuckle, or an early hub on a later knuckle: the hub flange is 1/8 to 1/4-inch out of alignment (into the knuckle or outboard). The conflict also occurs with trying to fit a later rotor and hub on the early knuckle, and with the later rotor on an early hub and knuckle. There are three parts that have built-in offset: the knuckle, the hub, and the rotor (the flange thickness is different). Try to fit either unmatched part with the other two and you can have a problem.

The sage advice is to keep the assembly together with all parts from the same year. I would not waste time trying to find a missing magic "third hub" when the proven combination is available (and relatively cheap).

how do the kunckles have a different offset?

if that was true, then wouldn't the resultant swapping also put the axle u-joints out of alignment and need to be addressed with spacers such as used when swapping WJ knuckles on?

discard the early knuckle from the discussion (the one with the bolt-on caliper bracket)

since they appeared as late as 93.

so ALL knuckles from 93 on up (excluding WJ knuckles) are the same.

and all bearing hubs from 93 on up are the same.

yet, this happens:
http://www.naxja.org/forum/showthread.php?s=&threadid=1800

I remember reading about THREE different offset bearing hubs on the old forum about two years ago.

so what is the difference? there is SOMETHING that HAS to be DIFFERENT.

Sean? what is this third hub that you speak of? I'm pretty sure it was you who told me the measurements and everything way back when.

I'm not that familiar with the 93 on down. But, the way I see it is--

93 and up exceptWJ share the same knuckles
There are two different hubs 93 and up
There are also 2 different rotors 93 and up
there is your 3 hubs!!! Rensing

CheapXJ said:

how do the kunckles have a different offset?

if that was true, then wouldn't the resultant swapping also put the axle u-joints out of alignment and need to be addressed with spacers such as used when swapping WJ knuckles on?

discard the early knuckle from the discussion (the one with the bolt-on caliper bracket)

since they appeared as late as 93.

so ALL knuckles from 93 on up (excluding WJ knuckles) are the same.

and all bearing hubs from 93 on up are the same.

yet, this happens:
http://www.naxja.org/forum/showthread.php?s=&threadid=1800

I remember reading about THREE different offset bearing hubs on the old forum about two years ago.

so what is the difference? there is SOMETHING that HAS to be DIFFERENT.

Sean? what is this third hub that you speak of? I'm pretty sure it was you who told me the measurements and everything way back when.

Click to expand...

This is what I know from experience:

Bolt a late model hub on the early knuckle with early rotor and the rotor hits the knuckle. The late hub/rotor face to the bolt flange distance is offset in, compared to the early hub. I believe this is the "shorter" hub mentioned in all these posts. Add washers under the rotor to hub flange, more than one or two washers, and the alignment can be "shimmed" back to "normal" for the early knuckle.

Take the above configuration, and replace the early rotor with a late rotor. Early knuckle, late hub, late rotor: and the rotor disc moves out ~1/8" (less "shimming" is required, but still required).

I have not tried fitting an early hub (with either rotor) on the late knuckle on an assembled axle.

I do know the late rotor will not seat on the early hub flange (tried with spares and it did not fit).

The axle shafts are the same length.

The late hub thickness, flange to knuckle flange distance, is ~1/4" less (appears to move the hub/rotor flange inboard when bolted on the early knuckle).

The late knuckle/hub flange to ball joint centerline is ~1/4 wider. The mounting flange on the knuckle is offset outboard the same change in distance as the reduced thickness of the later hub.

The late rotor centerline to hub flange is ~1/8" less (the composite rotors I have). DC offered a cast one piece late rotor as an option to replace recalled composite late rotors (1997 or 1999). The late rotors are offered in cast or composite construction, the early rotor is only cast construction. None of these rotors are considered thick enough to machine (they are cheap and intended to be replaced when the wear thin or warp).

My experience is that bolting unmatched parts together can place the rotor centerline 1/4 and 1/8 inboard of where you want it on the early knuckles.

I imagine the bolting early hubs on the late knuckle will place the rotor centerline ~1/4 out, or ~1/8 out with a late roter (if you could get it to seat properly, but it will not due to center hole and flange radius machining differences).

The mix of the two rotor/hub/knuckle combinations can place the rotor centerline 1/4 and 1/8-inch inboard, centered where Dana designed the axle assembly, or 1/8-inch outboard (if the early rotor was machined to seat on the late hub flange) and 1/4 outboard. Five rotor centerline offset combinations from two different knuckles, two different hubs, and two different rotor designs.

I believe this explains what everyone is seeing in the various posts (all except a parts vendor trying to pass early rotors as late rotors)?

Thanks, Ed!
That was really helpful for me particularly.

Ed A. Stevens said:

This is what I know from experience:

Bolt a late model hub on the early knuckle with early rotor and the rotor hits the knuckle. The late hub/rotor face to the bolt flange distance is offset in, compared to the early hub. I believe this is the "shorter" hub mentioned in all these posts. Add washers under the rotor to hub flange, more than one or two washers, and the alignment can be "shimmed" back to "normal" for the early knuckle.

Take the above configuration, and replace the early rotor with a late rotor. Early knuckle, late hub, late rotor: and the rotor disc moves out ~1/8" (less "shimming" is required, but still required).

I have not tried fitting an early hub (with either rotor) on the late knuckle on an assembled axle.

I do know the late rotor will not seat on the early hub flange (tried with spares and it did not fit).

The axle shafts are the same length.

The late hub thickness, flange to knuckle flange distance, is ~1/4" less (appears to move the hub/rotor flange inboard when bolted on the early knuckle).

The late knuckle/hub flange to ball joint centerline is ~1/4 wider. The mounting flange on the knuckle is offset outboard the same change in distance as the reduced thickness of the later hub.

The late rotor centerline to hub flange is ~1/8" less (the composite rotors I have). DC offered a cast one piece late rotor as an option to replace recalled composite late rotors (1997 or 1999). The late rotors are offered in cast or composite construction, the early rotor is only cast construction. None of these rotors are considered thick enough to machine (they are cheap and intended to be replaced when the wear thin or warp).

My experience is that bolting unmatched parts together can place the rotor centerline 1/4 and 1/8 inboard of where you want it on the early knuckles.

I imagine the bolting early hubs on the late knuckle will place the rotor centerline ~1/4 out, or ~1/8 out with a late roter (if you could get it to seat properly, but it will not due to center hole and flange radius machining differences).

The mix of the two rotor/hub/knuckle combinations can place the rotor centerline 1/4 and 1/8-inch inboard, centered where Dana designed the axle assembly, or 1/8-inch outboard (if the early rotor was machined to seat on the late hub flange) and 1/4 outboard. Five rotor centerline offset combinations from two different knuckles, two different hubs, and two different rotor designs.

I believe this explains what everyone is seeing in the various posts (all except a parts vendor trying to pass early rotors as late rotors)?

Click to expand...

This is my experience:

late hub on early knuckle. early rotor did not fit over the hub flange.

bought "90-99" composite aftermarket rotors (3 3/16" tall) , these fit on the late hub but required 1/8" spacing to keep them off the knuckle

wanted to get rid of the spacers, so i went and got the knuckles off the EXACT SAME vehicle that the hubs came off of (the rotors were gone, and I have no idea if they were composite or cast, all i know is that it was a 2001 XJ w/ low pinion housing) put these knuckles on, with their original hubs and the "90-99" aftermarket rotors still needed the same 1/8" spacer to make it work.

so these weren't "early" rotors, and they aren't "late" rotors, but they showed them as fitting YJ and XJ from 90-95 and 90-99 respectively.

I've followed all the listed reccomendations that people have posted to get this to work without using the spacers (I do NOT like having those spacers in there) and I still come up 1/8" off.

so either, I got a one-off hub, one-off knuckle, or a one-off rotor on my XJ. (seriously, I've been chasing parts for almost 2 years now, and I'm getting nowhere)

CheapXJ said:

This is my experience:

late hub on early knuckle. early rotor did not fit over the hub flange.

bought "90-99" composite aftermarket rotors (3 3/16" tall) , these fit on the late hub but required 1/8" spacing to keep them off the knuckle

wanted to get rid of the spacers, so i went and got the knuckles off the EXACT SAME vehicle that the hubs came off of (the rotors were gone, and I have no idea if they were composite or cast, all i know is that it was a 2001 XJ w/ low pinion housing) put these knuckles on, with their original hubs and the "90-99" aftermarket rotors still needed the same 1/8" spacer to make it work.

so these weren't "early" rotors, and they aren't "late" rotors, but they showed them as fitting YJ and XJ from 90-95 and 90-99 respectively.

I've followed all the listed reccomendations that people have posted to get this to work without using the spacers (I do NOT like having those spacers in there) and I still come up 1/8" off.

so either, I got a one-off hub, one-off knuckle, or a one-off rotor on my XJ. (seriously, I've been chasing parts for almost 2 years now, and I'm getting nowhere)

Click to expand...

Are the rotors actually hitting the knuckle? When I tried to use late rotors and hubs with early knuckles, the rotor was rubbing on the inside brake pad. The caliper wouldn't move in far enough. I could get the wheel to turn by loosening the caliper mount bolts.
I think it's the caliper mount that's different. I'm pretty sure I could've made it work by shiming the caliper mount in by a few washers, but I went ahead and swapped the hubs and rotors instead.

I ground down the caliper mounts (spent WAY too much time doing this) and then the inside of the rotor did hit the knuckle itself.

and they were a bitch to get apart

I am confused as hell
If I have a 93 HP D30 , and im trying to swap in the shafts from a 98 LP TJ D30.
Can I just swap in the TJ unit hubs and rotors and shafts onto my XJs D30 and order TJ brake/hub parts from now on to avoid all of this confusion. Im assuming so, because the only thing I can keep straight from this thread is that the 93+ (thats me) knuckles, except the WJ, are all the same. What about my calipers?

welcome to the club.

I've had no trouble with calipers (they're from a 95 or 96)

if you keep the hub WITH the rotor that was originally on it, you will be okay.

there were two different rotors used with TJs (and later XJs) one is full cast, the other is composite. that's all you need to know.

it's when you start mixing and matching different rotors with different hubs that the "fun" begins

SO, how about I take the rotor/hub/axles out of a TJ,
and put my rotor/hub/axles into the the TJ (it still has to drive)?
Would everything work out for the both of us then?
Do I order parts for a TJ or late model XJ to avoid confusion at the parts counter in the future?

Lucas said:

I am confused as hell
If I have a 93 HP D30 , and im trying to swap in the shafts from a 98 LP TJ D30.
Can I just swap in the TJ unit hubs and rotors and shafts onto my XJs D30 and order TJ brake/hub parts from now on to avoid all of this confusion. Im assuming so, because the only thing I can keep straight from this thread is that the 93+ (thats me) knuckles, except the WJ, are all the same. What about my calipers?

Click to expand...

Why not just switch the shafts,thats the part that "is" the same!

So I can just throw in 98 TJ shafts into my 93, and the 93 shafts into the 98 with no problems on either side?
I thought about taking the unit hubs because they only have about 40k on them.

ALL my problems stem from trying to run different hubs because they were good, and I got them free with the shaft (junkyard didn't know the difference, and I wasn't about to argue)

if you swap JUST the shaft, you don't have to worry about ANYTHING.

I'm spent ALMOST enough to buy new bearings as it would have cost me to just get the correct replacements and be done with it.

It's not worth the hassle, 40K or 240K, they're still used

Ohh.... just found this....


I've got a 98 XJ HP d30 on my 2000 XJ. Running (I believe) 93 GC knuckles and 00 rotors. Right now it's running brand x hub/bearings from Pepboys for a 98 XJ. No apparent problems.... If the rotor were rubbing on the knuckle, where would it be rubbing? I see no signs of it rubbing. Are yall telling me my brakes aren't centered on the rotor? Heck I removed the dust shield too....

What is different about the 93- GC Knuckles?

Glad I found this before I tried installing the MM hub conversion kit in my garage..... should I assume I'm screwed since I have 93 GC knuckles for this?

I've read all of this thread but due to Nyquil I am unable to comprehend....

Not sure what a knuckle with a "bolt on" caliper bracket looks like ... but my current knuckles look just like my 00 XJ knuckles.

I'm going to try to put on a MM hub conversion this weekend... so assuming that my knuckles are ok and I'll be replacing the hub & rotors.... as long as the hub & rotors are meant for each other it should be fine right?

I don't care if the hub & rotor stick out too far or anything, but I don't want my brakes to not be centered....

On a side note ..... MM conversion direction say nothing about the overall height of the rotor, only talk about the mounting flange.... and of course I'm unable to find any rotors of the proper thickness....

what?