Control arm question

[Gren71]

I’ve been looking at a lot of geometry correction stuff and trying to better understand caster and all that.

Starters I have a 2in iron rock spacer lift and will not be doing any significant off roading, really a mall crawler that will be out on the beach.

I have a slight pull to the right and it’s got me just wondering about what else may be needed. I already have an adjustable track bar installed. If I don’t need anything that would be good info, but it seems the consensus is 2in and above needs a little correction.

I haven’t gotten an alignment yet so I’m not sure my caster is off or anything, but I’m just trying to get a better idea of what it would take to square the entire geometry away appropriately. Rear track bar? Sway bar ends? Front drag link? Ect?

also...are the rubicon sway bars any thicker or stronger than standard?

I’ve realized that I messed up my old jku by lifting and never correcting geometry. Ended up with a gnarly death wobble and was just chasing the problem with expensive repairs. Trying to avoid that going forward.

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[LostWoods]

To oversimplify, caster alone cannot cause a pull on a solid axle so that isn't your concern. On a solid axle, cross caster being out to where it can cause a pull is a symptom of a greater problem (e.g. bent control arm) and not the cause 100% of the time.

So the answer is to get a 4-wheel alignment done first. If the adjustable track bar was installed too long, your Jeep will dog track to the right because the axle will be offset and the tires no longer square with each other. The alignment printout should show you axle alignment.

If you did larger tires at the same time, know that wider tires are more prone to tracking with the crown of the road and will drift right on most surface streets. Best way to check is to get it up to speed in the left or middle lane of a larger freeway where the road surface is more level.

 

[Gren71]

To oversimplify, caster alone cannot cause a pull on a solid axle so that isn't your concern. On a solid axle, cross caster being out to where it can cause a pull is a symptom of a greater problem (e.g. bent control arm) and not the cause 100% of the time.

So the answer is to get a 4-wheel alignment done first. If the adjustable track bar was installed too long, your Jeep will dog track to the right because the axle will be offset and the tires no longer square with each other. The alignment printout should show you axle alignment.

If you did larger tires at the same time, know that wider tires are more prone to tracking with the crown of the road and will drift right on most surface streets. Best way to check is to get it up to speed in the left or middle lane of a larger freeway where the road surface is more level.

gotcha, thanks. I have 285/75/17 so not a massive change to footprint like a 12.5 would be. I saw on here that it was suggested to get the LCAs from the Mopar performance lift to help correct caster, also drive shaft angle?

I have a shop, just waiting for my work schedule to open for them the do alignment.

 

[LostWoods]

Yeah at 2" I'd be looking into LCAs because the unequal length control arms (top vs bottom) will angle the axle pinion upwards a bit. That means reduced caster and an incorrect driveshaft angle.

 

[Gren71]

Yeah at 2" I'd be looking into LCAs because the unequal length control arms (top vs bottom) will angle the axle pinion upwards a bit. That means reduced caster and an incorrect driveshaft angle.

Thanks, I pulled the trigger on the MPP lift LCAs a moment ago.

 

[Gren71]

Back at watching videos today.

If Im getting this right adjusting the LCAs only will correct the caster, but it will negatively impact the pinion angle since the UCAs are still stock. Its only a 2in lift so im sure its not a problem, but im curious if im getting this right.

Will correcting the caster angle with the slightly longer LCAs make the pinion angle for the front axle worse?

 

[LostWoods]

Better if you make the lower longer. Upper arm is shorter so it has a smaller arc that forces the axle to twist as it moves downward. At a stock config, the pinion angle is roughly perfect at rest but when you lift the truck, it puts it out just enough that you are likely to see premature u-joint wear down the road. Longer LCAs account for this by removing some of that axle twist and putting the joint in a more neutral position.

 

[Gren71]

Better if you make the lower longer. Upper arm is shorter so it has a smaller arc that forces the axle to twist as it moves downward. At a stock config, the pinion angle is roughly perfect at rest but when you lift the truck, it puts it out just enough that you are likely to see premature u-joint wear down the road. Longer LCAs account for this by removing some of that axle twist and putting the joint in a more neutral position.

makes sense. Thanks! This is all stuff i should have learned years ago

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