Any thoughts on these alignment numbers?
- Thread starter akajibio
- Start date
All those look fine, though your caster angle might be high enough to cause front driveshaft vibrations due to a possibly excessive front axle pinion angle. If you don't have any front axle/front driveshaft vibrations no worries. If you do, reduce your caster angle just enough to stop the vibrations.
For 35s the caster should be 5.15-6.85" so everything looks in spec but I don't know how the front driveshaft isn't shaking you to death with 6" of lift and 6° of caster.
You probably know most of the mechanics behind this but I'm going to detail it for the general public anyway.
The line through the ball joints that determines the caster angle intersects the ground, and the longitudinal distance between this intersection and the tires contact patch, at least on a motorcycle is called the "trail" though I don't know if that usage is common in 4 wheeled vehicles. A 30" tire with a 14.3" rolling radius and 6-8° of caster has 1.5-2" of trail.
I just filled out a spreadsheet to figure out what range of caster produces the same 1.5-2" of trail for whatever tire size I want to use. The numbers I provided were for a 35" with a 16.75" rolling radius. It actually came out to 5.98 +/- 0.85, but I rounded to 6.
I've done the same using the steering axis inclination to determine the scrub radius.
Local Firestone shop where I have a lifetime alignment deal. Those folks must hate me! Other than, I don’t really feel any bad vibes to speak of, even in 4x4. But I’ll go ahead and adjust for less Castor in favor of better pinion angle.
If you don’t have vibes do not adjust anything. You want as much caster as you can have without vibes.
You don't have "bad" vibes, do you feel any vibes whatsoever?
Is not having vibes that unusual for this much castor ?
Yes. I have 4" of lift and run mine at 5.5 to prevent vibes. Anything over 5.8 degrees of caster and I get vibes.
Everything else looks good.
It looks decent. I questioned it because it you adjust caster while up on the rack and if you don't re-sweep afterwards, you will have an inaccurate reading.
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Jerry I just remembered that I have left the transfer case drop in place, could that be why I don’t feel front vibrations with that much castor?
Possibly. And it's caster, not castor which is a bean that castor oil comes from.
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