89-90 brake question...

Awright - what's so damn different between the two? Is it the rotor hat, or is the diameter of the rotor actually larger/smaller, or what?

Some of you probably recall my searching for slotted rotors for my wife's 89 Limited to help cool things off. I found TRW/Powerstop rotors, crossdrilled & Cd plated thru 4WD Hardware for about $75 each, that list apps for 84-89XJ. No luck with slotted, but Powerstop does have them for 90-92. What, exactly, is the difference - this is driving me more than a little mad...

5-90

The hub bearing is different. From what I recall when Autozone gave me the wrong hubs the hat of the hub is slightly larger on the newer ones, therefore an old rotor will not fit on. You could probably put a newer rotor on an older hub, but I wouldn't really want to do that (I'm anal about braking), I plan on doing a conversion for the same reason, here's what I've come up with as a list of parts to replace:

Hub Bearings
Rotors
Spindles (the caliper mount is cast on the spindle instead of bolted on the newer models)
Calipers
Brake Lines (slight difference, you can probably make the '89 ones work though)
Pads
And while I'm at it I'm converting to non-disco axle shafts.

Sequoia

Sounds like just enough work it will probably wait until I do an axle swap (since a D44 will want different brakes anyhow!) Besides, she's a considerably more sedate driver than yours truly, so I'm sure she won't have trouble with drilled rotors (I'm just picky.)

Are you planning on doing a writeup on your front brake conversion? Might be interesting...

I noticed a few other small oddities on the parts list for PowerStop, so I'm waiting for them to reply to my questions. For anyone wanting milled rotors with a 90 or later, tho, they're your people to go with. They're good enough that TRW will distribute them!

I'll be sure to let everyone know what I come up with. However - crossdrilled rotors for 84-89XJ are available as of the last catalogue (which got into my mailbox three days ago!) from 4Wheel Drive Hardware, XJ/ZJ/WJ/KJ catalogue, p. 43. Part #8303L/R, $75.95 each.

Rotors are vented, crossdrilled, and Cd plated for corrosion resistance (why plate a rotor? How long can THAT last?)

Just passing the word along...

5-90

Yup, I'm gonna do a write up when I get teh funds to do the conversion. It'll go along with a dual diaphram booster. And in time, probably after I do the front, getting ZJ brakes on the 44 sitting in my garage.

GSequoia said:

You could probably put a newer rotor on an older hub, but I wouldn't really want to do that

Click to expand...

you DON'T want to do that.

aftermarket replacements for 90+ are composite-style rotors, and with the hub being shorter, there is approx 3/16" of unsupported hat material hanging off the hub.

running this unsupported can cause the center of the rotor to tear out of the casting.

don't ask me how I know

CheapXJ said:

you DON'T want to do that.

aftermarket replacements for 90+ are composite-style rotors, and with the hub being shorter, there is approx 3/16" of unsupported hat material hanging off the hub.

running this unsupported can cause the center of the rotor to tear out of the casting.

don't ask me how I know

Click to expand...

but if the rotor is not cast, the only worry may be the 1/8" difference in hat depth. you may need to have a spacer cut to fit between the rotor and the hub to keep the inside surface of the rotor from contacting the steering knuckle.