Camber adjustment vs wheel poke

[cjldad]

I think I remember reading on here somewhere the math on how much a 1 degree change in camber changes wheel/tire poke on the front and rear?
Can someone refresh my mind please..

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[NightmareMoon]

Something like a quarter inch of poke per 1 degree would be my estimate.

 

[cjldad]

So, I think I figured it out..

1/ ((tan (angle) / diameter))

So for 1 degree of negative camber it would be
tan (91) = -57.29
-57.29 / 27.7 (diameter of 305/30/20 tires) = -2.106
1/-2.106 = .4748 inches......

1 degree = -0.4748
1.2 = -0.5698
1.4 = -0.6647
1.6 = -0.7598
1.8 = -0.8548
2.0 = -0.9498
2.2 = -1.045

Looks like 0.47 per degree..
I think..

 

[Norm Peterson]

Tire height is too much, since the tire can only pivot mechanically about either the ball joint (for the lateral link) or somewhere within the strut to knuckle attachment. It does not pivot about the contact patch.

I think you need to use the length measurement from the lateral ball joint's pivot height and the top of the tire if you're making camber adjustments at the strut top. This will be somewhat shorter than the tire diameter (5" to maybe 9" less), so the change in poke per degree of camber change would be a little less than you get using tire diameter directly.

For adjustments made at the strut to knuckle attachment, you'd use the difference in height between the center of the strut fastener that you don't use for adjusting and the top of the tire. If you were to adjust at both of the strut to knuckle fasteners, the midpoint between the two fasteners should be close enough. Any of these will be even less than the balljoint-based math.

27 * tan(1°) is 0.47" . . . basically half an inch (and too much)

Roughly for camber pivoting about the ball joint, 20 * tan(1°) is 0.35", around half that for adjustments made at the strut to knuckle attachment.


Norm

 

[cjldad]

That makes sense.. Listen to him people, not me..

 

[Norm Peterson]

Just meant to mention that I was guessing at the balljoint height. But an inch or so either way on the balljoint height isn't going to change the calcs much as far as visual appearance is concerned.


Norm

 

[cjldad]

That's right.. Also, I like your math better.. Much cleaner than mine..
Smart fella!

 

[NightmareMoon]

Yup, I was estimating closer to pivoting just below the center of the wheel (trying to guess at those suspension joint pivot points), thus the 1/4" instead of 1/2".

 

[Grintch]

And you thought you would never use Trig in real life.

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