Moby
GOLD Star
About a year ago I dumped my 31x10.5 BFG ATs and moved to some Nitto Terra Grappler 265/75R16s (32x10.5s). I noticed that they tended to wander and pull more, especially on grooved roads, at highway speeds and on washboard. I recently started reading about caster and the role that it plays in steering and handling and decided to experiment a little.
Solid axle Toyota mini trucks, Jeeps... seem to be in the 3-6 degree range (positive). SO guys (40s and 60/62s) that do a cut and turn seem, from what I could find, to aim for around 5-5.5 degrees with good results (again, positive). Stock caster for 60/62s is basically 0 degrees +-1 degree. Not sure why Toyota blessed us with no positive caster but they did.
I decided to try some caster shims (4Crawler Offroad Products - Custom Leaf Spring Shims - very happy with these by the way). I first had my caster measured and found that I was at 1 degree positive. I'm only running a mild OME lift but since adding caster via shims will point your pinion down I decided to be somewhat conservative and have 3 degree shims made to bring total caster to 4 degrees positive. I was hoping that 3 more degrees would be enough to make a difference but not so much as to cause 4wheel high problems.
I finally found an afternoon to install the shims and have been very happy with the results so far. Over a local section of heavily grooved road that previously required very attentive steering, especially while braking, the truck now tracks cleanly with very little steering correction necessary. Tracking at highway speeds is somewhat improved as well. No chance to gauge impact on washboard yet.
Steering effort might be slightly higher but I could easily be imagining this. Certainly not a problem.
In 4wheel high at speeds of up to 45-50mph and during deceleration I couldn't detect any additional driveline vibration (I had just a little bit before the shims which is another reason I was conservative with the shims but the shims don't seem to have negatively effected this).
Anyway, your results may vary but so far this has been a good improvement for my truck.
Solid axle Toyota mini trucks, Jeeps... seem to be in the 3-6 degree range (positive). SO guys (40s and 60/62s) that do a cut and turn seem, from what I could find, to aim for around 5-5.5 degrees with good results (again, positive). Stock caster for 60/62s is basically 0 degrees +-1 degree. Not sure why Toyota blessed us with no positive caster but they did.
I decided to try some caster shims (4Crawler Offroad Products - Custom Leaf Spring Shims - very happy with these by the way). I first had my caster measured and found that I was at 1 degree positive. I'm only running a mild OME lift but since adding caster via shims will point your pinion down I decided to be somewhat conservative and have 3 degree shims made to bring total caster to 4 degrees positive. I was hoping that 3 more degrees would be enough to make a difference but not so much as to cause 4wheel high problems.
I finally found an afternoon to install the shims and have been very happy with the results so far. Over a local section of heavily grooved road that previously required very attentive steering, especially while braking, the truck now tracks cleanly with very little steering correction necessary. Tracking at highway speeds is somewhat improved as well. No chance to gauge impact on washboard yet.
Steering effort might be slightly higher but I could easily be imagining this. Certainly not a problem.
In 4wheel high at speeds of up to 45-50mph and during deceleration I couldn't detect any additional driveline vibration (I had just a little bit before the shims which is another reason I was conservative with the shims but the shims don't seem to have negatively effected this).
Anyway, your results may vary but so far this has been a good improvement for my truck.
I don't think that it should effect turning radius though. At least from my understanding of the caster, which is likely incomplete. It might feel harder to go to lock though and thus indirectly effect turning radius...
I have the Dakkars too, so I'll likely order the same, perhaps 4 degrees. 
