Caster Setting Help
- Thread starter Lucky!
- Start date
When it has risen above the rim of the dish, has a nice brown top, and feels mostly firm with only a little jiggle when you tap the top.
Adding detail. My initial message didn't have enough information. Need some help with front pinion and caster. I have 04 TJ lifted 3 to 3.5 inches, running on 31s. No death wobble to speak of but it wanders on the Hwy and steering wheel doesn't come back to center when turning without help. I have OEM control arms, switching to adjustable all the way around. I know pinion is more important than caster based on other threads, but need some help to determine both. Pics are from front drive shaft, where drive shaft goes into the axle and flat spot on front of axle. What am I missing to figure out current pinion and caster?
I go off the way @mrblaine explained it, but I’ll probably Jack up the details.
1. Set the new adjustable arms so the pinion points down (the top of the Axke Inner C is further to the rear of the Jeep than the lower).
The exactl number can be different per Jeep.
Go until slight vibes and then go back up with the pinion until no vibes. If your Caster is good, and no vibes, you’re set.
Your driveshaft is 5.3 degrees, your pinion angle is 7.6 degrees. In a perfect world those two numbers would match.
Since there is roughly 12 degrees of separation between pinion and caster from the factory your caster is roughly at 4.4 degrees.
Castor can also be measured from the machined flat on the bottom of the inner C.
Factory caster is 7 degrees. With larger tires the need for castor is reduced, but I still would like to be above 5 degrees of castor
So, with this info what do you do? With stock arms not much, but once you get adjustable arms you can dial this in.
Do you currently have any front driveshaft vibrations? If not I would start with your current settings then slowly adjust the pinion angle down, which will reduce that 5.7 number, but will increase your castor.
Keep adjusting the pinion down until you get good return to center, or you start getting vibrations, then back it off till you don’t.
It’s a delicate dance between castor and pinion angle, one affects the other
Since there is roughly 12 degrees of separation between pinion and caster from the factory your caster is roughly at 4.4 degrees.
Castor can also be measured from the machined flat on the bottom of the inner C.
Factory caster is 7 degrees. With larger tires the need for castor is reduced, but I still would like to be above 5 degrees of castor
So, with this info what do you do? With stock arms not much, but once you get adjustable arms you can dial this in.
Do you currently have any front driveshaft vibrations? If not I would start with your current settings then slowly adjust the pinion angle down, which will reduce that 5.7 number, but will increase your castor.
Keep adjusting the pinion down until you get good return to center, or you start getting vibrations, then back it off till you don’t.
It’s a delicate dance between castor and pinion angle, one affects the other
Generally you'd like to start with it straight at the driveshaft. Then start adding caster (pinion down) until it drives nicely with minimal to no wandering and nice return to center. The numbers don't matter as much as how it works. And, be aware that you can add too much caster which will make the steering very heavy. Rare to get that much, but very possible with a hub kit so something to be aware of. If you can't get it to where you have no vibes with good steering, then it is time to investigate a hub kit.
Perfect. Thank you for all the input! I'll let you know how it goes, no vibrations today from front or back, so I do like the idea of starting with swapping out the arms at current length and tweaking from there. However, because the front wheel is a little back from center in the wheel well, I was also thinking of adding a 1/4 inch to bottom control arms. Or should I add a 1/4 inch to top and bottom and then tweak?
LONGJP2
TJ Expert
Lengthening the bottom will also increase castor, which you need anyway.
Then you could dial it in with the uppers.
To get 1/4" of movement, you would need to lengthen both.
However, ideally the axle should be centered at full compression (not at ride height), so the bump stops are lined up.
I want my axle centered at ride height. The bump stops are plenty forgiving for a fraction of an inch of misalignment.
Quick update. I just did the lower CAs. Set them to just over 16 inch on center. See pics for new angles. Might fine tune a little but drove it and it was so much better. Steering wheel came back on a turn most of the way but I was only at 15 miles an hour assuming it’ll come back faster and higher speed but still much better.
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