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How to set up adjustable control arms?

bcmaxx

bcmaxx

NAXJA Forum User
Location
The West Kootenays,B.C. Canada
89 xj 4.75 inch lift, Just purchased upper and lower bds adjustable control arms, how do I set them up? is there a certain length they should be?I currently have procrap fixed lowers and stock uppers.thanks
 
Yes

Lift.......LCA dec.......LCA fract.....UCA dec.......UCA fract.
Stock........15.75.......15 ¾........15.00............15
2”.............15.92.......16............14.88.... ........15
3”.............16.09.......16............14.92.... ........15
4”.............16.33.......16 3/8......15.03............15
4.5”..........16.47.......16 ½........15.11............15
5”.............16.62.......16 5/8......15.21............15 ¼
6”.............16.97.......17............15.44.... ........15 ½
7”.............17.36.......17 3/8......15.74............15 ¾
8”.............17.81.......17 ¾........16.09............16
9”.............18.30.......18 ¼........16.50............16 ½
10”...........18.82.......18 ¾........16.96............17
 
Or you could measure the ones that are installed now, with weight on wheels, from bolt center to bolt center. That will give you the same caster and pinion angle as you have.
 
Thanks!!!, couldn't use my current measurements because the procrap ones were a different length arm than stock
 
I usually set the lower one to the length needed to keep the wheel centered in the wheel well, then set the upper to the length needed to get the correct castor/pinion angle.
 
DaffyXJ said:
Or you could measure the ones that are installed now, with weight on wheels, from bolt center to bolt center. That will give you the same caster and pinion angle as you have.
Click to expand...
How would weight on the wheels affect the length of the control arms? Should be the same as if they were out of the truck, or you got some really weak control arms!...Yeah I know I'm a smart azz...
 
bfred said:
How would weight on the wheels affect the length of the control arms? Should be the same as if they were out of the truck, or you got some really weak control arms!...Yeah I know I'm a smart azz...
Click to expand...

Just asking cause steering geometry plumb evades me but that said wouldn't the weight of the vehicle on compressed springs change the angle of the CAs and thus change caster/camber ?
 
mikeforte said:
Just asking cause steering geometry plumb evades me but that said wouldn't the weight of the vehicle on compressed springs change the angle of the CAs and thus change caster/camber ?
Click to expand...
Yes but the original poster was looking for the information in the above chart on the correct control arm length to use for his lift. Once he has them in the ballpark, an alignment shop can use the factory adjustments to get it in spec. When following the recomondations in the chart to set the lengths, it will make no difference if there is weight on them or if they're out of the truck. This is why lift companies can sell lift kits with non adj. arms
 
bfred said:
How would weight on the wheels affect the length of the control arms? Should be the same as if they were out of the truck, or you got some really weak control arms!...Yeah I know I'm a smart azz...
Click to expand...

You're right, length would not change.
 
So I can also center my wheel in the well with the lowers and eyeball the uppers then send her for an alignment? This would help lots because I get a little rub when turning well flexed at the back of the wheel well where the fender meets the rocker.
 
Don't move them to far foward, when you flex the suspension they'll hit in the front then. Keep in mind the arc the control arms move on. susp. hanging-shorter wheelbase, susp. compressed-longer wheelbase. keep an eye on driveshaft length also. hope this helps.
 
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