4ward
NAXJA Forum User
- Location
- Dayton, OH
Need to figger something out, thanks.
Sean
Sean
Who's got the control arm length formula?
- Thread starter 4ward
- Start date
- Location
- Wasatch Range
A + B = C Simple math for you.......Simple-Ton 
Last edited:
- Location
- Indiana-Missouri
the answer is five.
- Location
- Wasatch Range
Since you're too lazy/disabled/intoxicated to formulate a Search.......I'll hook you up. Cut and pasted from a thread back in May 03.
Here you go, compliments of Bones.....yes, the proper LCA length will bring your XJ back to 101.5" WB, and the proper UCA length will dial in the caster. 7.5 degrees is stock, you can live with 4 degrees, but the closer to stock the better. And your front shaft will be happier too.
For future reference, you can rely on that old geometry formula for a triangle. A stock XJ has horizontal control arms (they are parallel to the body within a minor degree of error). When you lift, they go to an angle. To maintain stock wheelbase, use the A squared + B squared = C squared formula.
A = stock LCA length (15.75")
B = lift height
C = Control arm length need to maintain wheelbase
So for a 6" lift:
A = 15.75 squared = 248
B = 6 squared = 36
C = square root of 248 + 36 = 16.85
I just use 16.75 because 17" is a bit too long.
For a 5" lift:
A = 248
B = 25
C = 16.52
Here you go, compliments of Bones.....yes, the proper LCA length will bring your XJ back to 101.5" WB, and the proper UCA length will dial in the caster. 7.5 degrees is stock, you can live with 4 degrees, but the closer to stock the better. And your front shaft will be happier too.
For future reference, you can rely on that old geometry formula for a triangle. A stock XJ has horizontal control arms (they are parallel to the body within a minor degree of error). When you lift, they go to an angle. To maintain stock wheelbase, use the A squared + B squared = C squared formula.
A = stock LCA length (15.75")
B = lift height
C = Control arm length need to maintain wheelbase
So for a 6" lift:
A = 15.75 squared = 248
B = 6 squared = 36
C = square root of 248 + 36 = 16.85
I just use 16.75 because 17" is a bit too long.
For a 5" lift:
A = 248
B = 25
C = 16.52
4ward
NAXJA Forum User
- Location
- Dayton, OH
A hearty smack for the both of you. I wouldn't expect anything less from 2 of 
's most sophistimicated minds.
I'm just not feeling the need for simple trig today.
edit: mr. turner, you're swell
's most sophistimicated minds.I'm just not feeling the need for simple trig today.
edit: mr. turner, you're swell
Ed Wulfe+
NAXJA Forum User
- Location
- Apple Valley, CA (So Cal)
What is the formula for the UCA length relative ti LCA length that will yield 7.5 deg caster? Trekker mentioned a chart?
Thanks,
Thanks,
lunghd
NAXJA Forum User
- Location
- New River Valley, VA
Bones
NAXJA Forum User
- Location
- Mid Missouri
Ed Wulfe+ said:
Check this thread: CA and caster q's
With the chart giving arm length then the specs I came up with it should get you close.
Bones :skull1:
