lifting the xj and was wondering whats the best way to center the axle, front to back. it will have static uppers and adjustable lowers, would like to know what I can use for a reference point, the front fenders are hacked from the previous owner, or I would just go off of those. should i just look for the front spring to be as straight as possible? 99 6.5" with r/c drop brackets

 

Center as in thrust angle? Adjustable track bar.

 

 

Will also need adjustable uppers to 'center' the axle in wheelwell, aka wheelbase. The drop brackets move the axle forward a small amount.
With fixed uppers, any adjustment made to the lowers will be to change caster, not wheelbase.

With adjustable uppers and lowers, use the lowers to set wheelbase, uppers to set caster.

To accuratly measure wheelbase, I remove tires, vehicle on jackstands, center the steering (can place a straight edge on hub face and 'sight' to rear hubs, make even on both sides), then measure from hub to hub. Stock is 101.4"
You will likely find a difference of up to 10mm in passenger to driver side wheelbase.

 

The adj. uppers also set the pinion angle of the differential in the front also. At 6 1/2" of lift you need a long arm kit for real "NOT DROP BRACKETS" you need to give this serious consideration the other way you will have issues long-term.

 

If you just installed a lift my advice is get it done professionally by somebody who frequently aligns lifted vehicles. It's really good piece of mind knowing everything is spot on and having all the angles printed out in front of you.

I would also recommend adjustable uppers, especially if you did happen to get it done by somebody.

 

thanks for the info. I am going to swap out my fixed uppers for the adjustable ones then.. should I be keeping the stock wheel base, or centering in the wheel well? I am planning to run a 33 or 35. not set on the size yet.

it already has a iro track bar, I am trying to get it close enough so I can drive it to the allignment shop