Mopar LCA swap

[AnnDee4444]

The fact is, when you rotate the axle 2 degrees, you’re loosing about 2% of your effective toe, not really much to worry about.

I bet it's not even 2%, and it varies depending on how much toe you start with:

• If you have 0 degrees of toe, rotating the axle (a.k.a. adding caster) won't effect toe at all.
• If you have 1 degree of toe, rotating the axle 90 degrees would result in the same geometry as 0.5 degrees of camber.

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[Odyssey USA]

I bet it's not even 2%, and it varies depending on how much toe you start with:

• If you have 0 degrees of toe, rotating the axle (a.k.a. adding caster) won't effect toe at all.
• If you have 1 degree of toe, rotating the axle 90 degrees would result in the same geometry as 0.5 degrees of camber.

Now I can visualize why. Thanks

 

[Roky]

If you can’t see the difference with a tape measure it’s not worth worrying over imo.

 

[AnnDee4444]

If you can’t see the difference with a tape measure it’s not worth worrying over imo.

When it comes to this, I totally agree.

But that didn't stop me from attempting to calculate it. With the axle's camber at 0° and the toe set to 1°, rotating the axle from 4° of caster to 6° results in 0.003° of toe change (if my math is correct). Keep in mind that the OEM toe specifications are only 0.2°, so the changes are even more negligible.

Caster	Resulting Camber	Resulting Toe
0°	0.000°	1.000°
1°	0.009°	1.000°
2°	0.017°	0.999°
3°	0.026°	0.999°
4°	0.035°	0.998°
5°	0.044°	0.996°
6°	0.052°	0.995°
7°	0.061°	0.993°
8°	0.070°	0.990°
9°	0.078°	0.988°
10°	0.087°	0.985°
15°	0.129°	0.966°
30°	0.250°	0.866°
45°	0.354°	0.707°
60°	0.433°	0.500°
75°	0.483°	0.259°
90°	0.500°	0.000°

 

[Roky]

When it comes to this, I totally agree.

But that didn't stop me from attempting to calculate it. With the axle's camber at 0° and the toe set to 1°, rotating the axle from 4° of caster to 6° results in 0.003° of toe change (if my math is correct). Keep in mind that the OEM toe specifications are only 0.2°, so the changes are even more negligible.

Caster	Resulting Camber	Resulting Toe
0°	0.000°	1.000°
1°	0.009°	1.000°
2°	0.017°	0.999°
3°	0.026°	0.999°
4°	0.035°	0.998°
5°	0.044°	0.996°
6°	0.052°	0.995°
7°	0.061°	0.993°
8°	0.070°	0.990°
9°	0.078°	0.988°
10°	0.087°	0.985°
15°	0.129°	0.966°
30°	0.250°	0.866°
45°	0.354°	0.707°
60°	0.433°	0.500°
75°	0.483°	0.259°
90°	0.500°	0.000°

I freakin love it ! You math dudes are great, I wish I paid more attention in school, and less time chasing the girls........?

 

[Odyssey USA]

When it comes to this, I totally agree.

But that didn't stop me from attempting to calculate it. With the axle's camber at 0° and the toe set to 1°, rotating the axle from 4° of caster to 6° results in 0.003° of toe change (if my math is correct). Keep in mind that the OEM toe specifications are only 0.2°, so the changes are even more negligible.

Caster	Resulting Camber	Resulting Toe
0°	0.000°	1.000°
1°	0.009°	1.000°
2°	0.017°	0.999°
3°	0.026°	0.999°
4°	0.035°	0.998°
5°	0.044°	0.996°
6°	0.052°	0.995°
7°	0.061°	0.993°
8°	0.070°	0.990°
9°	0.078°	0.988°
10°	0.087°	0.985°
15°	0.129°	0.966°
30°	0.250°	0.866°
45°	0.354°	0.707°
60°	0.433°	0.500°
75°	0.483°	0.259°
90°	0.500°	0.000°

Bam! lol

 

[blnewt]

@AnnDee4444
You da man!
That'll justify the guys saying toe is affected (even though it's so minimal as to not amount to more than zip), so lets get that $150 alignment ordered up!

 

[hurricanes99]

Well I didn't have time to put the control arms on myself so i dropped the jeep off at a local shop. I had the lowers pre measured just over 24 1/4". They called back and said they were on. I asked if they put it on the rack and what was my caster. He said they didn't, but would and charge me $30. I said go ahead no big deal. Called me back and said caster was 5.6 on both sides. That made no sense to me... I said did you all leave them at the pre measured amount? He stated no because they couldn't get them on.... omg. They dialed them back in to stock length. I'm gonna freak. I plan to do it myself now. What a pain in the ass. Now my question is will going from 5.6 to 6.3 be noticeable? Should I shoot for 6.5?

 

[Odyssey USA]

Well I didn't have time to put the control arms on myself so i dropped the jeep off at a local shop. I had the lowers pre measured just over 24 1/4". They called back and said they were on. I asked if they put it on the rack and what was my caster. He said they didn't, but would and charge me $30. I said go ahead no big deal. Called me back and said caster was 5.6 on both sides. That made no sense to me... I said did you all leave them at the pre measured amount? He stated no because they couldn't get them on.... omg. They dialed them back in to stock length. I'm gonna freak. I plan to do it myself now. What a pain in the ass. Now my question is will going from 5.6 to 6.3 be noticeable? Should I shoot for 6.5?

LOL there is no way I would pay for that shit. Especially checking the caster.

 

[Roky]

Well I didn't have time to put the control arms on myself so i dropped the jeep off at a local shop. I had the lowers pre measured just over 24 1/4". They called back and said they were on. I asked if they put it on the rack and what was my caster. He said they didn't, but would and charge me $30. I said go ahead no big deal. Called me back and said caster was 5.6 on both sides. That made no sense to me... I said did you all leave them at the pre measured amount? He stated no because they couldn't get them on.... omg. They dialed them back in to stock length. I'm gonna freak. I plan to do it myself now. What a pain in the ass. Now my question is will going from 5.6 to 6.3 be noticeable? Should I shoot for 6.5?

You will notice a big difference at 6.3

 

[hurricanes99]

My biggest thing is time.. I just need to make time to get them right. I called another place and they wanted to charge over $200 to take them back off and adjust...crazy. Gonna do it myself. I asked the shop today to pry the bracket off the brake line and they just cut it. So now the brackets for the old control arms are worthless. Not that i would be putting them back on, but thats not what i asked them to do. I also asked them to put the adjustable end towards the body and they did the opposite. All of this was written out.. not hard to follow.

 

[JT1]

tire size does not change the relative position of the axle.

It won't change measured caster, but it should change effective caster, right? Since both ball joints are now farther from the driving surface, the effective "steer ahead" should be greater.

 

[mwilk012]

It won't change measured caster, but it should change effective caster, right? Since both ball joints are now farther from the driving surface, the effective "steer ahead" should be greater.

That’s not measurable, though true.

while I’m sure it can be calculated, an alignment shop will just stare at you and point at the machine.

 

[blnewt]

My biggest thing is time.. I just need to make time to get them right. I called another place and they wanted to charge over $200 to take them back off and adjust...crazy. Gonna do it myself. I asked the shop today to pry the bracket off the brake line and they just cut it. So now the brackets for the old control arms are worthless. Not that i would be putting them back on, but thats not what i asked them to do. I also asked them to put the adjustable end towards the body and they did the opposite. All of this was written out.. not hard to follow.

I think a new shop is in order, that sucks!

 

[AnnDee4444]

It won't change measured caster, but it should change effective caster, right? Since both ball joints are now farther from the driving surface, the effective "steer ahead" should be greater.

That’s not measurable, though true.

What you're referring to is the 'mechanical trail'.

Increasing tire diameter should help, however an increased tire diameter usually also comes with other effects that make the increased mechanical trail negligible. I think a different pneumatic trail from different tire pressures or increased gyroscopic effect from the weight of the tire could have greater effects (and that's assuming you have the same tire make/model/load rating, and same wheel size/offset/weight). Also I believe wider and taller profile tires are more susceptible to tramlining anyway.

In short: Increasing tire diameter isn't a good way to make the steering better.

Somewhat related: https://www.jlwranglerforums.com/fo...-lowering-tire-pressure-helps-steering.33315/

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