06-20-2013, 08:16 AM
Join Date: Mar 2009
Location: Georgetown, Guyana
Let me reply to Joe Z first - that's a quick & easy explanation.
A "Z-bar" is nothing more than a Z shaped drag link - it allows the drag link to clear suspension components that it might otherwise foul, but does not in itself alleviate (or cause) bump steer - it's more of a "Band-Aid" solution than a fix. The bump steer is caused by the drag link being at an angle (or effective angle in the case of a Z-bar).
In an ideal situation, with the steering straight ahead and the vehicle at rest, to minimize bump steer, the drag link should be horizontal, if it's not a straight drag link, the end points should be on the same level with respect to the surface the vehicle is on - this is not always possible or easy to do on a lifted vehicle.
There are two other approaches which may be used in combination if necessary - the first is a "drop pitman arm" which lowers the steering box end of the drag link, and the second is a "hi-steer" kit or modification, which raises the knuckle end of the draglink, usually by adding a second steering arm near the top of the knuckle. Both of these solutions reduce the angle of the drag link bringing it closer to the horizontal.
Motor - I believe you have multiple problems - torque steer is the first - the vehicle pulling in one direction under power and the other when coasting. This could be a suspension issue or a steering issue, the lack of "feedback" is more likely to be suspension, specifically caster or lack therof.
Vague steering can be caused by wear at the linkage pivot points, the rod ends, the king pin bearings, wheel bearings and the steering box itself - you say the linkage is tight and that you've replaced the king pin bearings (make sure they are properly shimmed) so you've already dealt with most of the problem areas.
Lifted leaf spring vehicles, especially those with shackle lifts, can suffer from reduced caster, and this directly affects how the steering feels - I can't quote you numbers, but, take the vehicle to an alignment shop and have them put it on the rack - the computer will provide the stock caster settings and will also measure what the actual settings are - it's not adjustable per se, but you may be able to shim the axle to correct it.
Last - SPOA - spring over axle setups can be problematic because of axle wrap - the axle twists as power is applied and this can force the spring into an S shape, causing the axle to twist sideways (I'm talking rear axle now) - this is another potential cause of your torque steer.
Because of the amount of lift than occurs going from SPUA to SPOA a Z bar would be an inadequate solution and there would be significant bump steer.
98 - 1.8 Mitsubishi Pajero iO
98 - 2.0 Suzuki Grand Vitara - SQ420
05 - 2.0 Suzuki Grand Vitara - JB420
15 - 2.4 Kia Sportage