Recommended Castor Measurement with 3.5" lift?

[AVGeek99]

I have 2021 JLUR with a MC GC 3.5" lift, my net height increase is between 4.5" and 5". I also opted for the new front drive shaft. When I first got the lift back in November the steering was pretty flightly especially on uneven pavement. I would hit an uneven section in the road and it would would veer off in one dirction or the other. I measured the caster and it was only 1.8 degrees.

I know at stock the caster is 6 degrees. I adjusted mine and it is now at 6.2 degrees. When I first adjusted it to 6.2 I tested out 4WD and everything seemed fine. The flightyness was gone so I thought all was well with the world. Tonight I was out driving in the snow and I needed to used 4WD. This time I noticed a not good sound, kind of a grinding vibration that seemed to come from the front drive shaft or maybe the transfer case.
The sound would start at about 30 mph. It seemed like it only made the sound when I was coasting.

If I had enough presssure on the gas pedal to maintain speed or accelerate it seemed to go away. There has never been any such sound when I'm in 2WD. At any rate, it sounded bad enough, that I used 4WD very sparinginly, only when I really needed it.

Before adjusting the caster I did a fair amount of research. Stock caster is 6 degress. But if you maintain 6 degress with a lift it increases the pinion angle, which can cause issues if the pinion angle becomes too steep. In my research it seemed like everyone was running 6 degress or even more, which is why I was ok with setting it at 6.2 degrees.

With the sound it was making tonight I am now second guessing my 6.2 degree caster angle and thinking I should reduce it some. Does anyone have a recommendation on a good caster angle for 3.5" lift, netting 4.5" to 5"?

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[thance]

Stock castor is not an exact science and likely anywhere between about 3 and 6. And yes, 3 will shoot all over at Highway speeds. Because of your lift you will have to compromise. Bring them in 1 or 2 rotations and test it out. Trial and error is your best friend, otherwise known as fine tuning....

 

[Roky]

I have 2021 JLUR with a MC GC 3.5" lift, my net height increase is between 4.5" and 5". I also opted for the new front drive shaft. When I first got the lift back in November the steering was pretty flightly especially on uneven pavement. I would hit an uneven section in the road and it would would veer off in one dirction or the other. I measured the caster and it was only 1.8 degrees.

I know at stock the caster is 6 degrees. I adjusted mine and it is now at 6.2 degrees. When I first adjusted it to 6.2 I tested out 4WD and everything seemed fine. The flightyness was gone so I thought all was well with the world. Tonight I was out driving in the snow and I needed to used 4WD. This time I noticed a not good sound, kind of a grinding vibration that seemed to come from the front drive shaft or maybe the transfer case.
The sound would start at about 30 mph. It seemed like it only made the sound when I was coasting.

If I had enough presssure on the gas pedal to maintain speed or accelerate it seemed to go away. There has never been any such sound when I'm in 2WD. At any rate, it sounded bad enough, that I used 4WD very sparinginly, only when I really needed it.

Before adjusting the caster I did a fair amount of research. Stock caster is 6 degress. But if you maintain 6 degress with a lift it increases the pinion angle, which can cause issues if the pinion angle becomes too steep. In my research it seemed like everyone was running 6 degress or even more, which is why I was ok with setting it at 6.2 degrees.

With the sound it was making tonight I am now second guessing my 6.2 degree caster angle and thinking I should reduce it some. Does anyone have a recommendation on a good caster angle for 3.5" lift, netting 4.5" to 5"?

It’s not an exact number you can go to, as mentioned above, it takes some fiddling….The more height you get the more you want to increase the wheelbase, so you shouldn’t just shorten up the uppers to set caster…you don’t want the wheel like this in the well

You want to push the axle forward as much as you can without the tire rubbing or contacting anything when turning and/or articulating like this…….

then set your caster as low as you can to achieve good steering….. 6 degrees shouldn’t be to much for that much lift…..another possibility though not likely, is your front driveshaft may be out of balance…pic from the side, and pic of pinion would help……

 

[AVGeek99]

It’s not an exact number you can go to, as mentioned above, it takes some fiddling….The more height you get the more you want to increase the wheelbase, so you shouldn’t just shorten up the uppers to set caster…you don’t want the wheel like this in the well

You want to push the axle forward as much as you can without the tire rubbing or contacting anything when turning and/or articulating like this…….

then set your caster as low as you can to achieve good steering….. 6 degrees shouldn’t be to much for that much lift…..another possibility though not likely, is your front driveshaft may be out of balance…pic from the side, and pic of pinion would help……

Here's a shot from the side and the pinion. When I adjusted the caster I didn't touch the uppers. I just lengthened the LCAs. Wasn't sure if I should take a little off the UCAs and lengthen the LCAs, but at the time I thought it would be simpler to just lengthen the lowers. And I know some kits come with fixed uppers and adjustable lowers so I concluded it would be ok just to adjust the lowers.

The Jeep does handle much better at the current 6.2 degrees though I don't want to damage the driveshaft or transfer case if it is too steep.

 

[Roky]

Here's a shot from the side and the pinion. When I adjusted the caster I didn't touch the uppers. I just lengthened the LCAs. Wasn't sure if I should take a little off the UCAs and lengthen the LCAs, but at the time I thought it would be simpler to just lengthen the lowers. And I know some kits come with fixed uppers and adjustable lowers so I concluded it would be ok just to adjust the lowers.

The Jeep does handle much better at the current 6.2 degrees though I don't want to damage the driveshaft or transfer case if it is too steep.

Yeah, wheel looks good in the well…. I can’t believe how much lift you got…. You may want to consider some MC drop brackets….. you can drop your caster down until vibration goes away then use the drop brackets to level out the lcas to help with drivability…..

 

[AVGeek99]

Yeah, wheel looks good in the well…. I can’t believe how much lift you got…. You may want to consider some MC drop brackets….. you can drop your caster down until vibration goes away then use the drop brackets to level out the lcas to help with drivability…..

Yeah, I was surprised by the amount of lift I got too. I took 8 before measurements around the Jeep, and measured again after. The average of all 8 was a net 5.5". I have Rock Hard aluminum bumpers, that are super light, and I've not added anything that would weigh it down. I can't think of any other reason it would be so high. I'm just glad it fits in my garage and it is surprisingly easy to get up into. Next year I'm going to get the MC undercloak, maybe that will weigh it down a little.

So last Sunday I measured my caster on the bottom of the axle C on both ends. At the C my castor measured 7.4, still 6.2 on the axle next to the dff. I thought those should yield very similar measurements.? I lined my angle finder with the straight edge on the C to get an accurate reading. I dropped the caster to 5.1 at the Cs. Next to the diff it's now like 3.8, which seems too low. But it still drives very nice, no wandering or flightyness, and the vibration in the drive shaft is now gone. So I think I'll leave the caster at 5.1 for now.

I actually ordered the MC drop brackets a week and a half ago. They came on Tuesday. I did my ball joints today, which I think solved my shimmy and DW, knock on wood. I might wait a couple weeks to install the drop brackets. I think my wife is getting annoyed at all the time I'm spending out in the garage.

 

[Roky]

Yeah, I was surprised by the amount of lift I got too. I took 8 before measurements around the Jeep, and measured again after. The average of all 8 was a net 5.5". I have Rock Hard aluminum bumpers, that are super light, and I've not added anything that would weigh it down. I can't think of any other reason it would be so high. I'm just glad it fits in my garage and it is surprisingly easy to get up into. Next year I'm going to get the MC undercloak, maybe that will weigh it down a little.

So last Sunday I measured my caster on the bottom of the axle C on both ends. At the C my castor measured 7.4, still 6.2 on the axle next to the dff. I thought those should yield very similar measurements.? I lined my angle finder with the straight edge on the C to get an accurate reading. I dropped the caster to 5.1 at the Cs. Next to the diff it's now like 3.8, which seems too low. But it still drives very nice, no wandering or flightyness, and the vibration in the drive shaft is now gone. So I think I'll leave the caster at 5.1 for now.

I actually ordered the MC drop brackets a week and a half ago. They came on Tuesday. I did my ball joints today, which I think solved my shimmy and DW, knock on wood. I might wait a couple weeks to install the drop brackets. I think my wife is getting annoyed at all the time I'm spending out in the garage.

Sounds good brother……. Caster is not set in stone, run it wherever it best suits your situation…… We didn’t used to have this luxury of using higher caster to help remedy steering woes back before the FAD…… when you put on the drop brackets they will increase caster again by leveling out the arms, so you’ll have to fiddle with it again to get to your happy place…. Nice work, rig looks great……

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