Wheel alignment woes


>I own an 80 series LandCruiser which is wearing the outside edge of the
>front tyre.

In the beginning there was the live axle; and the 4WD Gods said "Thou shalt easily adjust toe-in, but woe and strife will come to those who attempt caster and camber adjustments". They were wrong AND right of course; wrong because they did not take
into account the 4WD enthusiast's ingenuity and ability to stuff up their divine engineering; and right because when it did get stuffed up, the woe and strife quickly followed.

On Land Cruisers:

Front wheel alignment can be affected by several occurrences. The most common of these are:

Unfortunately (at least down under), minor manifestations of 1 and 3 above are often corrected by the use of eccentric king pin bearings (cups) or adjustable king pins. In most cases the axle is already out of concentricity with the axle oil seal, and correction by these methods can throw it further out. As pointed out by Mark Whatley, this leads us back to one of the banes of driving a Land Cruiser i.e. leaking knuckle housings!

The practice of changing camber/caster on the left front wheel came about ostensibly because of the high crowns generally built into Aussie roads. Closer to the truth is the fact that the left axle is the longer and that side of the housing is very prone to slight bending, causing negative camber. Again, camber/caster changes upset the concentricity of axle and oil seal.

While manufacturers tolerances may mean slight differences side to side, front wheel alignment IS NOT (despite rumours to the contrary down under) set up by the manufacturer to any left hand drive configuration with different specs on either side.

The first generation of "fixes" was a tapered shim fitted between the spindle and knuckle housing. These changed camber only and were by necessity quite thick. Up to 3mm (1/8 inch) on the thick side for a 1.5 degree correction. In many cases, the Birfield joint was forced so far sideways and outwards that it rubbed in the housing and outer axle circlips
were simply left off to allow the joint to float in and gain clearance. Most of these mods occurred on part time 40s and 60s (fortunately), but any that were used with hubs locked for some time soon showed the tell tale oozing mess.

The second generation was eccentric bearings (cup). With these caster and camber adjustments were possible, but took a lot of setting up. This was an improvement but the bearing cone, with smaller and less rollers than OE, was hard pressed to support the weight, wearing quickly. The off centre axle problem did not go away.

The third generation included complete replacement king pins. These came in their own mounting plate in which they could be turned eccentrically. These again allowed caster and camber adjustment and are still popular. Off centre axle problem still there.

Current generation is eccentric rotatable pin inside quarter sphere with bearing cup replaced by sintered bush. This gives much greater support area. Can't comment on longevity as we have not seen one in prolonged use yet. Still creates off centre axle problem.

Off centre axle problems caused by the fitment of any of these devices can be alleviated to some degree by the application of geometry and shimming of bearings accordingly. The result is a compromise because any great corrective movement causes the felt/rubber wipers to be off centre on the housing.

Sometimes shims can not move the knuckle far enough to get the axle back on centre. My humble opinions are: If you suspect a bent housing, straighten and strengthen it. If you have steering problems, try and correct them with caster/toe-in adjustment. Please use the above devices as a last resort only.

Norm Needham
Traction 4, Sydney, Australia