84-87 vs 88 front suspension (Page 3/10)
Bloozberry JAN 31, 02:14 PM
You can't change the kingpin angle by moving the upper control arm further in or out... that only changes the wheel camber. The reason you can't change the kingpin angle that way is because the kingpin angle is measured between a line drawn through the upper and lower ball joint centerlines and a line that's parallel to the wheel flange. Moving the upper control arm tilts both an equal amount so the angle between then doesn't change. As mentioned before, the kingpin angle is cast into the knuckle so you can't do anything to change it.

Set your wheel camber in accordance with the OEM's recommendations for the best compromise between cornering and straight line traction.
WHEELIE JAN 31, 03:33 PM
No worrys then, I didn't want to mess up the king pin angle when I adjusted my camber.
thanks, wheelie
Gall757 JAN 31, 04:00 PM
Sometimes it helps to know where these terms came from. The Kingpin used to be an actual pin!.....not just an angle...
Will JAN 31, 09:58 PM

quote
Originally posted by zkhennings:

Is it desirable to package everything well to reduce kingpin angle while maintaining the same scrub radius? Because the kingpin angle is going to create negative camber anytime the wheels aren't pointed straight, while caster is more friendly as it adds negative camber to outside wheel and positive camber to the inside wheel.

Edit for some reading material:

http://www.wheels-inmotion....ngpininclination.php





quote
Originally posted by Bloozberry:

You can't really reduce the king pin angle because it's cast into the knuckle by the location of the upper and lower ball joint mounts.



The behavior of the kingpin angle mentioned above--the weight jacking and self-centering effect--is dependent on the kingpin angle relative to VERTICAL. The kingpin angle does change with camber when the camber is adjusted by pulling the upper ball joint inward. IE, if camber is zero and kingpin is 6 degrees, then when static camber is -1.0, then kingpin will be 7 degrees.

Kingpin produces *negative* camber with steering. Kingpin angle counteracts caster-induced camber gain.

Also, tire DIAMETER affects scrub radius.

Also don't forget that scrub radius is made up of two components: mechanical trail (longitudinal) and steering offset (lateral).
Will JAN 31, 10:01 PM

quote
Originally posted by WHEELIE:

And... how do I check the kingpin angle with the camber gauge? Nobody seems to mess with the kingpin angle but it seems important to me.
thanks Wheelie




Kingpin angle is fixed relative to static camber. Per the above drawing, if static camber is zero, kingpin will be 6 degrees. If static camber is -1.0, kingpin will be 7 degrees.

EDIT: Does anyone know what the kingpin angle for the '84-'87 suspension is? I don't think I've ever seen it in print.

[This message has been edited by Will (edited 01-31-2015).]

Will JAN 31, 10:03 PM

quote
Originally posted by fireboss:

Just if the pre 88s could be upgraded at a reasonable price instead of what all is involved in swapping the 88 in.



For feel, the '88 is far superior.
The lower scrub radius only tells part of the story. I've read that the kingpin angle changed as well. The hub offset from the steering axis is certainly much larger on the early suspension than on the '88.
Bloozberry JAN 31, 11:20 PM

quote
Originally posted by Will:
Does anyone know what the kingpin angle for the '84-'87 suspension is?



7.5 degrees.

Edit to add:


quote
Originally posted by Will:
The kingpin angle does change with camber when the camber is adjusted by pulling the upper ball joint inward. IE, if camber is zero and kingpin is 6 degrees, then when static camber is -1.0, then kingpin will be 7 degrees.



For all intents and purposes kingpin inclination is specified relative to camber. For instance, the reference material I have for both '84-'87 and '88 specify 7.5 and 6.0 degrees kingpin inclination respectively. When measured on the actual knuckles, those are the angles found between the wheel flange and ball joint axes. If the kingpin inclination were specified the way you suggest, then the reference material should have shown inclination angles of 8.5 and 7.0 degrees respectively since stock camber is -1.0 degree. Regardless, none of this changes the discussion relative to WHEELIE's desire to reduce scrub radius by altering the camber.

[This message has been edited by Bloozberry (edited 02-01-2015).]

FieroWannaBe FEB 01, 11:29 AM




from GM press material.
theogre FEB 01, 12:43 PM

quote
Originally posted by Gall757:
Sometimes it helps to know where these terms came from. The Kingpin used to be an actual pin!.....not just an angle...


Many Trucks still use Kingpins, including many Ford light to medium trucks w/o 4WD.

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Knight FEB 01, 01:09 PM
So would changing caster or tilting the front crossmember to afftect mechanical trail to any signifigant degree if at all?
I am curious because I have wondered if the front end dive could be reduced by tilting the front crossmember.