Axle Tire match

I just brought my new 98 XJ home and have a couple of concerns. In an earlier post, I said it had the Rock Road 8" lift and found that it wasn't a very popular lift. Most said is was rough riding and noisy. I rides pretty smooth on the road and is quiet, but it is still new. I haven't had it on the trail yet. The johnny joints on the lower arms look stout, but not like the Claytons going into my ZJ. It's still higher than I want, but might change that. The front axle is the hp30 with 488s, alloy shafts and an ARB locker. The rear is an 8.8 with 488s, alloy shafts and a detroit locker. All 5 tires are new 36/13.5X16 bias IROC Swampers on new Daytona 8X16 wheels. ( should be 10" wheels but won't get rock damage) Everything in both axles is new.

First: Is this too much tire for the axles? Second: Can I air down to 10-12#s on them without losing a bead? (no experience with bias tires) Third: If I go down to 6"s of lift, will the tires fit, or would I have to go to 35s?

I think if your smart when wheeling it you should be ok, with the ARB you can engae the front when you only need it.
With 6 inches of lift you will probably have to trim the fenders.

We crossed it up yesterday and went over a couple of big piles and found a couple of things. I was surprized that is is more stable at 8"s when off cambor than my ZJ at 5 1/2" of lift. I also found that although the 36" IROCs and wheels are brand new, the wheels have a 5" BS. The fronts hit the lower control arm before a full turn and the rear tire touches the leaf spring when the oposite rear wheel is up the ramp. Because the rear is an 8.8, it has 1 1/4" spidertrax spacers. As I see it, I have 2 options. Put 2" spacers on the rear axle and move the 1 1/4" spacers to the front. That would put the rear wheels tracking the front. Or buy wheels with 3 3/4" BS and leave the 1 1/4" spacers on the rear axle.

The other potential problem is the front pinion angle. After the lift was installed, the Jeep didn't sit level. The builder added ACOS on top of the 8" coils to level it out. To be correct, the pinion should come up another 4-5 degrees to be at the same angle as the driveshaft. That would, however, change the castor to where it would wander all over the road and the coil pockets would tip forward and the springs would bow forward. If I left it where it is now, (it drives great at 60 mph) what will happen to the front ujoint that isn't correct?

Some of you are a lot smarter than I am. What do you suggest??

The front axle is always going to require a compromise between caster and pinion angles. At your height, it'll be a pretty major compromise.

Generally, the caster (which matters all the time) is considered more important than the ds angles (which really only come into play in 4wd, and don't matter as much at lower, offroad speeds.)

I'd leave it as is. Maybe lose the acos, since I like a little forward rake, anyway.

I wouln't mess with the track width, either. 5" is a lot of BS (ha ha), but a little rubbin' won't really hurt anything.

"Rubbin' is racin'!"

Robert

I don't remember which section they're in but there are stickies somewhere from one of the mods that have lots of good info on max tire size and optimal gearing and whatnot.