Need Coaching on Caster Angle--Did I Get it Right?

[DanW]

So I installed @Rancho geometry correction brackets mainly to improve caster angle, which I did not measure before doing, but eyeballing it, I think it was not good. I'm running the Mopar 2" lift with its slightly longer lower control arms. Before getting a better steering dampener, I'd get some slight shimmy hitting bumps on the road accelerating from 35 to 55 mph. When my orignial steering dampener failed, it ws pretty significant on occasion, if the bump and speed were just right. So I put on a Fox 2.0 dampener that cured it. But it bugged me that it was there and I'd read of folks either installing adjustable LCA's or geo correction brackets. The Geo correction brackets promised some slight improvement in ride, so I went that route. I saw one member who had a similar lift and was running the Mopar lift's longer LCA's. He went with the Rancho brackets and used the middle hole and he wound up at 5.7 caster and it drove/steered much better.

After installation (I used the middle hole), it appears to be a little better than 5.5, so I may have landed at the same 5.7. The steering feels fine, as before, but definitely handles bumps and jolts a little softer and better than it did before.

So here is my question.....Based on the photo, did I measure the caster the correct way? I haven't put it on the highway yet, but I'm hoping it feels a bit better (It didn't feel badly before, though). I've read that caster between 5.5 and 6 is what the JL likes and others have said the steering feels much better, especially on the highway. I've got an off-road adventure coming up with about 10 hours of highway to and from, so it'll get a real test then.

SO I put the meter up to the little round hole on the front of the differential/axle housing. That's what I've seen others do. Is that the place to take the measurement?

And here is the result, at least at the best I could position the camera. I may try and take another couple shots just to be sure I was straight-on. But if you zoom in, if you see what I see, it looks to be above 5.5, possibly touching 5.6 or even 5.7. But its a cheap guage from Amazon, so it may be hard to be that precise.

So let me know what you think. I'm thinking it is pretty good and in the range where it needs to be. I just wanted to let the experts around here critique it. I do have the ability to adjust it a little either way. I think if I go to the bottom hole on the brackets, it will increase it a little, but I don't know how much. The LCA's are pretty close to level now.

Fire away!

Sponsored

 

[AnnDee4444]

So I installed @Rancho geometry correction brackets mainly to improve caster angle, which I did not measure before doing, but eyeballing it, I think it was not good. I'm running the Mopar 2" lift with its slightly longer lower control arms. Before getting a better steering dampener, I'd get some slight shimmy hitting bumps on the road accelerating from 35 to 55 mph. When my orignial steering dampener failed, it ws pretty significant on occasion, if the bump and speed were just right. So I put on a Fox 2.0 dampener that cured it. But it bugged me that it was there and I'd read of folks either installing adjustable LCA's or geo correction brackets. The Geo correction brackets promised some slight improvement in ride, so I went that route. I saw one member who had a similar lift and was running the Mopar lift's longer LCA's. He went with the Rancho brackets and used the middle hole and he wound up at 5.7 caster and it drove/steered much better.

After installation (I used the middle hole), it appears to be a little better than 5.5, so I may have landed at the same 5.7. The steering feels fine, as before, but definitely handles bumps and jolts a little softer and better than it did before.

So here is my question.....Based on the photo, did I measure the caster the correct way? I haven't put it on the highway yet, but I'm hoping it feels a bit better (It didn't feel badly before, though). I've read that caster between 5.5 and 6 is what the JL likes and others have said the steering feels much better, especially on the highway. I've got an off-road adventure coming up with about 10 hours of highway to and from, so it'll get a real test then.

SO I put the meter up to the little round hole on the front of the differential/axle housing. That's what I've seen others do. Is that the place to take the measurement?

And here is the result, at least at the best I could position the camera. I may try and take another couple shots just to be sure I was straight-on. But if you zoom in, if you see what I see, it looks to be above 5.5, possibly touching 5.6 or even 5.7. But its a cheap guage from Amazon, so it may be hard to be that precise.

So let me know what you think. I'm thinking it is pretty good and in the range where it needs to be. I just wanted to let the experts around here critique it. I do have the ability to adjust it a little either way. I think if I go to the bottom hole on the brackets, it will increase it a little, but I don't know how much. The LCA's are pretty close to level now.

Fire away!

You need to either add or subtract 6 degrees from the measured value, depending on which side of the axle you're on. This is because the Cs are welded on the axle with 6 degrees of caster built in. So for example: if you measured 90 degrees at the round holes next to the differential cover (which would mean the holes are perpendicular to pointing straight up), you actually have 6 degrees of caster. This is built into the axle and cannot (easily) be changed.

Looking at your photos, I see a measurement of about 84.75 degrees. This is 5.25 degrees away from pointing straight up, which means you have around 11.25 degrees of caster. The biggest issue with this much caster is probably going to be that the driveshaft angle is too extreme, especially with your lift (assuming all other components have enough clearance). Also I'm not certain that the differential gears were designed to run at that angle, and could possibly have oiling issues (this is probably only an issue in 4WD at high speeds, so only if you have the full-time AWD transfer case).

I've never driven with anything beyond 8 degrees of caster, and it wasn't a Jeep (or even straight front axle). How does it drive? Did the amount of brake dive noticeably change?

 

[DanW]

You need to either add or subtract 6 degrees from the measured value, depending on which side of the axle you're on. This is because the Cs are welded on the axle with 6 degrees of caster built in. So for example: if you measured 90 degrees at the round holes next to the differential cover (which would mean the holes are perpendicular to pointing straight up), you actually have 6 degrees of caster. This is built into the axle and cannot (easily) be changed.

Looking at your photos, I see a measurement of about 84.75 degrees. This is 5.25 degrees away from pointing straight up, which means you have around 11.25 degrees of caster. The biggest issue with this much caster is probably going to be that the driveshaft angle is too extreme, especially with your lift (assuming all other components have enough clearance). Also I'm not certain that the differential gears were designed to run at that angle, and could possibly have oiling issues (this is probably only an issue in 4WD at high speeds, so only if you have the full-time AWD transfer case).

I've never driven with anything beyond 8 degrees of caster, and it wasn't a Jeep (or even straight front axle). How does it drive? Did the amount of brake dive noticeably change?

It drives fine, very smooth over bumps, but I know it isn't right and went too far. I'm either going to take them off and ultimately put some adjustable LCAs or try and pick up some regular length Rubicon LCA's, which is what these brackets were designed to work with. It didn't drive badly before. I was just looking to fine-tune it. and saw another forum member went this route and was very happy. However, I think he over shot on his, too, and just didn't know it. He had a different lift, but bought the longer Mopar lift LCA's.

I'm not sure what the caster angle was before the geo correction brackets, but I believe it was too low.

If you or anyone knows someone who has a set of Rubicon take-off LCA's, let me know. I'd be interested, for sure.

 

[GATORB8]

Double check the angle of the surface you are parked on, as well.

 

[DanW]

Double check the angle of the surface you are parked on, as well.

Flat, level garage floor. I measured on two different garage floors and got the same readings.

I'm pretty confident you are right. The pinion needs to come up/the caster needs to be decreased.

Sponsored