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Caster 3.3 after lift. But handles great

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Greg H

Greg H

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I there weren't any longer LCAs included w/ that lift than that 3.3 is probably just about what it should be after raising 2".
Maybe OPs previous Jeeps were also lifted w/out new LCAs (or UCAs) and is just used to low caster.

But FWIW @Greg H I would HIGHLY RECOMMEND those Mopar lift LCAs at a minimum, but adjustable LCAs FTW! Getting that caster in the 6s I bet you'll be quite happy, those Mopar LCAs will get you to about 4.5 to maybe 5.
One of my previous Jeeps was stock. The last one a 14 2 door sport was stock for 1.5 years before I put a BDS 3.5" lift on it. That lift didn't have new LCA's but had Octo Cam Washers to correct caster. That jeep felt like the wind was blowing it around on the Interstate when there was no wind. My wife didn't like driving it on the highway after the lift. She said after driving my JLUR after installing the lift that she didn't notice any difference except the steering wheel was off center slightly to the left. The alignment fixed that. She doesn't mind driving it.

I Read something interesting about the effect of lifts and tire sizes on caster. It says;

" Installing a suspension lift with stock fixed length control arms does two things... 1) It very slightly pulls your axles closer together, shorting your wheelbase a tad. 2) It very slightly decreases your front axle's caster angle by rotating the axle a tad. That slight reduction in caster angle is actually a good thing for larger tires since you don't want quite as much caster angle for a larger tire like you'll be running with your new suspension lift."

That explains why a Sport, Sahara, and Rubicon have different caster specs as below;
Model tire size recommended castor
Sport 245/75R18 31.5" 5.35
Sahara 255/70R18 32.0" 5.05
Rubicon 285/70R17 33.0" 4.80

So my thinking is running 315/70R17 (35.0") tire the castor should be slightly lower maybe offsetting the slight reduction in caster of a true 2" Lift like my Dynatrac Endurosport. But I don't believe it should have dropped to 3.3. I'm thinking the tech at Big O Tires did something wrong reading the castor on the alignment. My neighbor has an 18 JLUR with the same lift. The dealer did his alignment. His castor is 4.0 left and 4.20 right. His wife thinks his drives better after the lift. He thinks it is effected by the crown in the road more.

But back to my original question. If the Jeep drives good is there any reason to change the LCA's to increase castor? Doesn't increasing castor cause increased pinion angle causing it to wear faster?
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One of my previous Jeeps was stock. The last one a 14 2 door sport was stock for 1.5 years before I put a BDS 3.5" lift on it. That lift didn't have new LCA's but had Octo Cam Washers to correct caster. That jeep felt like the wind was blowing it around on the Interstate when there was no wind. My wife didn't like driving it on the highway after the lift. She said after driving my JLUR after installing the lift that she didn't notice any difference except the steering wheel was off center slightly to the left. The alignment fixed that. She doesn't mind driving it.

I Read something interesting about the effect of lifts and tire sizes on caster. It says;

" Installing a suspension lift with stock fixed length control arms does two things... 1) It very slightly pulls your axles closer together, shorting your wheelbase a tad. 2) It very slightly decreases your front axle's caster angle by rotating the axle a tad. That slight reduction in caster angle is actually a good thing for larger tires since you don't want quite as much caster angle for a larger tire like you'll be running with your new suspension lift."

That explains why a Sport, Sahara, and Rubicon have different caster specs as below;
Model tire size recommended castor
Sport 245/75R18 31.5" 5.35
Sahara 255/70R18 32.0" 5.05
Rubicon 285/70R17 33.0" 4.80

So my thinking is running 315/70R17 (35.0") tire the castor should be slightly lower maybe offsetting the slight reduction in caster of a true 2" Lift like my Dynatrac Endurosport. But I don't believe it should have dropped to 3.3. I'm thinking the tech at Big O Tires did something wrong reading the castor on the alignment. My neighbor has an 18 JLUR with the same lift. The dealer did his alignment. His castor is 4.0 left and 4.20 right. His wife thinks his drives better after the lift. He thinks it is effected by the crown in the road more.

But back to my original question. If the Jeep drives good is there any reason to change the LCA's to increase castor? Doesn't increasing castor cause increased pinion angle causing it to wear faster?
Actually since all the JLs, JLUs, JLUSs, JLRs, and JLURs all use the same LCAs they have to have a wide range caster spec just to cover their tails.

IMO you'll have a Jeep with better road manners w/ the caster in the 6 range, but you are the one behind the wheel and if you like the way it rolls down the road then it's all good! And yeah, increased caster can effect pinion angle to the point of causing issues, but 6 to 6.5 is not in that area.
 

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I there weren't any longer LCAs included w/ that lift than that 3.3 is probably just about what it should be after raising 2".
Maybe OPs previous Jeeps were also lifted w/out new LCAs (or UCAs) and is just used to low caster.

But FWIW @Greg H I would HIGHLY RECOMMEND those Mopar lift LCAs at a minimum, but adjustable LCAs FTW! Getting that caster in the 6s I bet you'll be quite happy, those Mopar LCAs will get you to about 4.5 to maybe 5.
FWIW, I just had an alignment done on my 21 JLUR with the longer molar LCAs. My front caster came back surprisingly at 7.3d
 
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FWIW, I just had an alignment done on my 21 JLUR with the longer molar LCAs. My front caster came back surprisingly at 7.3d
Is your JLUR lifted? If so how much? I've heard you shouldn't go over 6.
 

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Let's not forget by raising the vehicle, you are changing the pinion angle so having the adjustable LCA/UCA allows you to change the caster, which also will change that pinion angle.
 

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Let's not forget by raising the vehicle, you are changing the pinion angle so having the adjustable LCA/UCA allows you to change the caster, which also will change that pinion angle.
Increasing the castor increases the pinion angle in addition to the increase you get when you do the lift.
 
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Increasing caster decreases pinion angle, the opposite of lifting without using longer arms.
When you add positive caster it tilts the top of the axle toward the back of the vehicle. That increases the pinion angle. When you lift your jeep it makes the axle lower than the transfer case which also increases the pinion angle.
 

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When you add positive caster it tilts the top of the axle toward the back of the vehicle. That increases the pinion angle. When you lift your jeep it makes the axle lower than the transfer case which also increases the pinion angle.
When you tilt the pinion down, that would be less angle. Adding longer lowers tilts the pinion down. When you lift the vehicle with the stock length arms, it angles the pinion up increasing the pinion angle (and decreasing the caster angle), therefore the need for longer lowers. I think you are confusing driveshaft angle and pinion angle. With a low pinion front axle, you often have to sacrifice caster as you cannot run enough pinion angle to avoid driveline vibrations. Optimally the pinion should point at the output shaft of the transfer case, but that is much less critical with the FAD.
 

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...That slight reduction in caster angle is actually a good thing for larger tires since you don't want quite as much caster angle for a larger tire...

That explains why a Sport, Sahara, and Rubicon have different caster specs as below;
Model tire size recommended castor
Sport 245/75R18 31.5" 5.35
Sahara 255/70R18 32.0" 5.05
Rubicon 285/70R17 33.0" 4.80
I suggest that this is not the reason why the three Wrangler trims use the same control arms, but rather it is the reason that Jeep knows that using the same controls arms will work out ok most of the time.

Caster angle is a measurement that is relatively easy to measure relatively accurately, but it needs to be contextualized to have real value when making comparisons.

Caster angle implies the "trail" parameter of the steering system, so when it is discussed in the abstract as a specific value it is serving as a proxy for the actual and meaningful parameter which is the trail that results for the combination of caster angle and tire diameter.

The information you referenced may have mentioned trail and how it relates to caster.

With regards to caster angle discussion; trail is the actual factor that influences the impression of self centering stability that the driver senses at the steering wheel.

If you take a detailed look at the Caster Angle specifications you can see that the Rubicon spec with the steeper caster angle actually results in more trail than the Sport does with the noticeably shallower caster angle. The differences are not great, but tend towards what is probably the opposite direction that many casual observers presume when they simply look at statements based solely on caster angle.

Here is an illustration using generalized round tire measurements that demonstrates how differing tire sizes tend to relate to the trail parameter.

Jeep Wrangler JL Caster 3.3 after lift. But handles great Caster and Trail_01A
 
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I suggest that this is not the reason why the three Wrangler trims use the same control arms, but rather it is the reason that Jeep knows that using the same controls arms will work out ok most of the time.

Caster angle is a measurement that is relatively easy to measure relatively accurately, but it needs to be contextualized to have real value when making comparisons.

Caster angle implies the "trail" parameter of the steering system, so when it is discussed in the abstract as a specific value it is serving as a proxy for the actual and meaningful parameter which is the trail that results for the combination of caster angle and tire diameter.

The information you referenced may have mentioned trail and how it relates to caster.

With regards to caster angle discussion; trail is the actual factor that influences the impression of self centering stability that the driver senses at the steering wheel.

If you take a detailed look at the Caster Angle specifications you can see that the Rubicon spec with the steeper caster angle actually results in more trail than the Sport does with the noticeably shallower caster angle. The differences are not great, but tend towards what is probably the opposite direction that many casual observers presume when they simply look at statements based solely on caster angle.

Here is an illustration using generalized round tire measurements that demonstrates how differing tire sizes tend to relate to the trail parameter.

Jeep Wrangler JL Caster 3.3 after lift. But handles great Caster and Trail_01A
To be honest, I'm not completely understanding what your saying. But it sounds like you are saying because the trail is farther back with larger diameter tires you need less caster to get a good handling vehicle. Is that correct?
 

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To be honest, I'm not completely understanding what your saying. But it sounds like you are saying because the trail is farther back with larger diameter tires you need less caster to get a good handling vehicle. Is that correct?
Yes, but you do not want to just focus on the self centering and stability provided by trail. The caster angle also affects the camber of each of the two front wheels when you are purposefully cornering. Traction is increased when you have the caster setting integrated in balance with all the other parameters for optimum movement.

So, the 4.8* caster found on the stick Rubicon provides (above) adequate trail for stabilizing self centering, but the 5.35* caster found on the stock Sport has a beneficial affect on the the wheel camber when pushing the front end through a corner at speed.

The caster settings shown in the OEM chart are the result of increasing spring/lift height without providing matched control arms. It works out ok, but many Jeep owners find that there is opportunity for improvement.

Adding lift without making change to the control arm length decreases caster and decreases the stabilizing self centering. If you added the lift so you can install larger tires the trail will increase with the new tires and this increase in trail will decrease the impact of decreasing the caster.

If you use that fact as a reason to accept a steeper caster angle you are going to be sacrificing another beneficial characteristic so keep that in mind.

The caster on my Jeep with 37" tires is 5.5* driver - 5.7* passenger. It seems to work pretty good.
 
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Just an update. I replaced my LCA's with Rough Country adjustable LCA. I set them at 24 3/8". Measuring off the circles on the side of the differential I'm now at 6.3 degrees. I'm surprised 3/8" gained 3.0 degrees caster. It does handle better. The main time I notice a difference is on paved County roads. I'm not having to correct the steering with the dips and uneven spots in the road like I used too. Don't really notice a difference in town or on the interstate.
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