Adjustable Control Arm Effect on Caster

[LukeDagny]

I recently installed a Clayton Offroad lift kit on my JLUR. I'm really happy with the quality of the components. It included adjustable upper front control arms. Clayton give guidelines for what length to set the control arms and track bars, based on lift height. Per the instructions, this is a starting point, and additional adjustments may be necessary.

I measured caster before/after installation. After installation, my caster was about 1 degrees less than original. I did a test drive and wanted to add a little caster. My thought was adding one degree put me back to stock, adding two degrees would be even better. I shortened the upper front control arms, two full revolutions. With a 1-14 thread pitch, two revolutions is slightly more than 1/8". This increased my castor 2 degrees. Going forward, my rule of thumb is one revolution equals one degree of caster.

What are other peoples experiences when changing control arm length? Upper or lower? With my LJ, I had double adjustable control arms, and adjustment was easy. With adjustment at only one end, its a little more time consuming.

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[lashlee]

In my book, whatever is easier is the way to go. When I did the install for the MC GC 3.5 on my wife's JLUR, I adjusted the lower links since it was easier! It did take a couple of trips to the alignment shop to get it dialed in, but it's great now!

 

[LukeDagny]

In my book, whatever is easier is the way to go. When I did the install for the MC GC 3.5 on my wife's JLUR, I adjusted the lower links since it was easier! It did take a couple of trips to the alignment shop to get it dialed in, but it's great now!

How much change in length of your lower control arms made a measurable difference in caster?

 

[kah.mun.rah]

You have to find the balance between your caster angle and your pinion angle. Ride quality with the caster angle vs avoiding driveshaft vibration/binding with the pinion angle.

 

[LukeDagny]

You have to find the balance between your caster angle and your pinion angle. Ride quality with the caster angle vs avoiding driveshaft vibration/binding with the pinion angle.

I agree. Before the lift kit was installed, my pinion/driveshaft angle was the same as the axle. Drive quality was good.

After the lift, pinion angle changed less than a degree, but I lost 2 degrees of caster. I didn't like how it drove.

Now, after adjusting the control arms, my caster is back to original specs, but the pinion angle is 1 degree different. Drivability is good and no vibration.

 

[kah.mun.rah]

Sounds like you found the sweet spot. That said, you might not be able to test the vibration until you have it in 4WD if you a FAD axle.

 

[Terrymo]

Here’s a video from Tom Woods if you want more general info on pinion and driveshaft angle. Some of it is over my head but it was informative.

 

[lashlee]

How much change in length of your lower control arms made a measurable difference in caster?

I'm not sure. I would do a full turn and go have it checked but I didn't keep up what that change corresponds to.

 

[Deleted member 107602]

Here’s a video from Tom Woods if you want more general info on pinion and driveshaft angle. Some of it is over my head but it was informative.

nothing against Tom Woods or what they say but that video drives me nuts.

 

[LukeDagny]

I'm not sure. I would do a full turn and go have it checked but I didn't keep up what that change corresponds to.

I'm thinking most control arms use the same thread pitches either 1-16 or 1-14, so one full turn ~ 1/16 of an inch.

 

[Terrymo]

nothing against Tom Woods or what they say but that video drives me nuts.

Yeah the information is there…I think? But the production quality of all their videos is pretty low. We’re not all born to be on YouTube myself included. Or is there something you have a different opinion on?

 

[Deleted member 107602]

Yeah the information is there…I think? But the production quality of all their videos is pretty low. We’re not all born to be on YouTube myself included. Or is there something you have a different opinion on?

My issue is that they really just gloss over the main challenge that exists with many lifted 4x4’s and especially Jeeps and so many people reference it, focusing on the theoretical ideal that he is describing. In fairness he says it, you won’t get a front driveshaft to that ideal. Then someone is going to post that stupid diagram of a double cardan perfectly pointed at a completely level transfer case and say it has to be like that. None of which is even close to reality unless you custom build the entire suspension and drivetrain and even then you’re going to compromise something else. Idk I need to let it go, it’s Friday. Long week

 

[Terrymo]

My issue is that they really just gloss over the main challenge that exists with many lifted 4x4’s and especially Jeeps and so many people reference it, focusing on the theoretical ideal that he is describing. In fairness he says it, you won’t get a front driveshaft to that ideal. Then someone is going to post that stupid diagram of a double cardan perfectly pointed at a completely level transfer case and say it has to be like that. None of which is even close to reality unless you custom build the entire suspension and drivetrain and even then you’re going to compromise something else. Idk I need to let it go, it’s Friday. Long week

I always appreciate other viewpoints…well almost always. Thanks

 

[Deleted member 107602]

I do find this one interesting. It’s focused on the measurements but his conclusions on what’s acceptable are interesting and are different than what a lot of others say.

Dana Spicer Measurement Video

 

[WannFly]

I know this is somewhat old and OP has figured everything out. I am on the same journey of figuring out Caster once I get the Clayton lift installed. After reading about 10 threads and watching various YT videos, I was very confused, until I found this one. For layman like me, this helps very much to understand the whole alignment thing



On a somewhat related note, how on earth did you torque the jam nuts to specs?

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