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

[AVGeek99]

Keep in mind that with a lifted JL you can get away with minimal side effects running a higher caster angle (6-7) if your JL has a FAD and you don't use 4WD at higher than 45mph. When running a caster of 6-7, depending on your front drive shaft you may get some vibration at higher speeds when it is spinning. If you ever go 45+ mph in 4wd you may want to test to see if you get vibration.

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[Kum4224]

That's what I'm currently using with the stock lca's but was wondering if another hole would be used with the longer ones.

No, the top hole is what you should be using regardless of if youre using extended mopar arms or factory. Caster will be pushed way too far if you use the other holes. Steering might become way too heavy and damage to the pinion.

 

[Wraith]

Hey everyone, been following this thread trying to get my Jeep dialed in. I have the AEV geometry correction brackets and RT 2.5". I swapped the keyed caster blocks from the 2.5-3" setting to the 3.5-4" to see what the improvement would be like. Steering is heavy but it had stopped any and all wandering. Trying to get an idea of what my actual caster reading is. Here is what I have. Did I calculate this correctly?

Garage floor slopes uphill towards front of Jeep. Jeep facing uphill.

Passenger floor slope 0.5 (centerline of axle)
Driver floor slope 0.5 (centerline of axle)

Passenger axle diff reading 89.3 (0.7)
Driver axle diff reading 89.1 (0.9)

Passenger reading corrected 88.8 (+1.2)
Driver reading corrected 88.6 (+1.4)

+6.0 factory axle C specification

Final caster passenger +7.2
Final caster driver +7.4

Final average +7.3

I am going to dial the caster back to the middle hole on the keys I think if I did my calculations correctly. Steering is heavy and seems to be slow to respond then snappy all the sudden. Wandering is gone though.

Did I do this correctly or since the garage floor slope uphill 0.5 and the Jeep is pointed uphill I should have subtracted versus adding? I am not certain on this part.

 

[BDinTX]

@Wraith I think you want to subtract the .5* you're getting from the floor slope. That will appear as additional caster which needs to be removed from the final number.

Edit: You may also be able to zero your gauge on the floor to eliminate it

Edit2: For reference w/ angle finder zero'd on floor before measurement
6.1* on '21 EcoDiesel JLU w/ factory CAs and AEV Geo brackets set for the most caster:

5.4* on '20 2.0T Etorque JLU w/ factory CAs and AEV Geo brackets set for the most caster:

 

[Wraith]

@Wraith I think you want to subtract the .5* you're getting from the floor slope. That will appear as additional caster which needs to be removed from the final number.

Edit: You may also be able to zero your gauge on the floor to eliminate it

I think you are right. If I take the uphill slope of 0.5 degrees out of the mix and zero at the floor I am getting the following

Passenger diff reading 89.7
Driver diff reading 89.6-89.7

Caster passenger +6.3
Passenger caster +6.3 - +6.4

I spoke to AEV and they said the holes aren't an exact caste degree difference as weight and all that plays a part. They did say if it feels tighter and more planted at the higher setting run it. There's no downside.

 

[BDinTX]

Passenger diff reading 89.7
Driver diff reading 89.6-89.7

Caster passenger +6.3
Passenger caster +6.3 - +6.4

I think you're mathing the wrong direction still.
Caster passenger 89.7+6-90=5.7*

Edit: disregard, I was mathing wrong

 

[BDinTX]

it shouldn't but any little bump in the surface can throw it off and these angle finders are probably only accurate to 1/10* at best anyway. Did you turn it around, re-zero on the floor before turning the gauge around?

 

[Wraith]

I just had a moment lol. If I zero the gauge at the floor then rotate it 90 to get 90 degrees and place it in that orientation on the diff at the passenger side its reading a consistent 89.7 and driver 89.6 - 89.7

 

[Wraith]

@BDinTX so

I think you're mathing the wrong direction still.
Caster passenger 89.7+6-90=5.7*

I think my order of operations are clearly off lol. By what you posted im getting the same give or take 1/10.

So with those readings closer to the higher end of whats recommended for tight steering. This makes sense if the caster keys are 1 degree of offset, which would make the middle hole at 4.7-4.8 at the higher end of factory spec. Yes?

 

[BDinTX]

@BDinTX so
...This makes sense if the caster keys are 1 degree of offset, which would make the middle hole at 4.7-4.8 at the higher end of factory spec. Yes?

My mathing skills start falling off after the plussing and minusing BUT I have a good working relationship with our AI overlords.

 

[Wraith]

I ate lunch and I'm able to clearly think now ha! Makes sense as the C's are set at +6.0 degrees of caster at 90 so if the axle is tilted slightly backwards as in my readings I am subtracting caster from the overall +6.0 giving me the +5.6-5.7 degrees? I have always added to the degree as the axle is titled further backward further increasing the caster?

I was going crazy until I realized I wasn't orientating my gauge properly after zeroing. Once I did so the 0.5 that was pulled out went back in and gave the same consistent reading of 89.6-89.7 at the diff. When I check the pinion I am getting 0.3-0.4 so slightly over the neutral 0 for the +6.0 spec. Seems to all check out unless I am missing something. I appreciate the assist.

 

[THAW]

I think you're mathing the wrong direction still.
Caster passenger 89.7+6-90=5.7*

Looks to me like @Wraith had it correct; his gauge is reading backward from 90.

6.3°

 

[THAW]

...the axle is tilted slightly forward as in my readings...

I believe that gauge shows the top of the axle rotated back from 90°, in other words +0.9° positive caster (or +0.4° without the floor).

 

[Wraith]

I didn't do these correctly initially. I just redid it. Here are the passenger side readings.

 

[THAW]

@Wraith I believe your gauge is in 0-90° mode, you have to read the inclination icon, or change it to 0-180° mode.

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