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picklito · 08-06-2015, 11:27 AM

No, you're right that you'd have 2.7 + 6.35 degrees of caster. You're also right that nobody is getting that much caster increase. The math is right, the numbers are right, but the model it's based on is poor and doesn't really represent what actually happens in the truck...

We're assuming the lower ball joint is moving around the circumference of 9" circle. It actually moves straight forward. And we'd need to use the center-to-center distance between ball joint pivots. If that's (just guessing) 12" rather than 9", then the circumference is 37.68" rather than 28.26" and moving the control arm forward by .5" produces 4.77 degrees of additional caster rather than 6.35. Then add in the (small but real) cosine error and you'd get slightly less. So,

2.7 + 4.77 = 7.47 degrees of caster in your case before removing the cosine error. That's probably closer?

08-06-2015, 11:27 AM	#104
picklito Registered User Join Date: Sep 2013 Location: Vacaville CA Posts: 490	Re: My caster mod (with pictures) No, you're right that you'd have 2.7 + 6.35 degrees of caster. You're also right that nobody is getting that much caster increase. The math is right, the numbers are right, but the model it's based on is poor and doesn't really represent what actually happens in the truck... We're assuming the lower ball joint is moving around the circumference of 9" circle. It actually moves straight forward. And we'd need to use the center-to-center distance between ball joint pivots. If that's (just guessing) 12" rather than 9", then the circumference is 37.68" rather than 28.26" and moving the control arm forward by .5" produces 4.77 degrees of additional caster rather than 6.35. Then add in the (small but real) cosine error and you'd get slightly less. So, 2.7 + 4.77 = 7.47 degrees of caster in your case before removing the cosine error. That's probably closer?