Alignment Question

[mscot]

A bit over a year ago I had a 2.25" lift on my truck and at the ~500 mile mark I had the alignment re-done. They were only able to get the caster to 1.9.
I drove it like this for almost a year and last weekend upgraded to JBA UCAs.
I just took it in for an alignment and they were able to get caster to 4.0/3.8. Terrific.

What was odd is that the report shows the before on the caster as 3.9/4.7.

How could that be?

Here's the report

 

[Daikon]

Aftermarket UCA's are designed to increase caster by default. The 'before' number is what the JBA's achieved once you put them on. The alignment 'fine tuned' it

A bit over a year ago I had a 2.25" lift on my truck and at the ~500 mile mark I had the alignment re-done. They were only able to get the caster to 1.9.
I drove it like this for almost a year and last weekend upgraded to JBA UCAs.
I just took it in for an alignment and they were able to get caster to 4.0/3.8. Terrific.

What was odd is that the report shows the before on the caster as 3.9/4.7.

How could that be?

Here's the report

 

[plasticsnaks]

The JBA’s are built with an added ~2* caster....so you were at +1.9* with stock uca’s then the JBA’s added ~2*....that’s where you got the increase on the “before” reading.

Edit...
Daikon beat me to it ����

 

[mscot]

Thanks for the quick replies.

I thought alignment adjustments were done at the LCA.
if the LCA was locked into place (alignment-wise) wouldn't new UCAs not have an affect until they're adjusted?

 

[TEujunga]

Thanks for the quick replies.

I thought alignment adjustments were done at the LCA.
if the LCA was locked into place (alignment-wise) wouldn't new UCAs not have an affect until they're adjusted?

Caster angle is determined by the geometric relationship between the ball joint locations on the lower and upper control arms. Lifting the truck changes this relationship and reduces the caster angle. Adjusting the lower control arm eccentric cam bolts can regain some, but not all, of what was lost by moving the lower control arm ball joint slightly forward.

Aftermarket upper control arms move the upper ball joint location rearward compared to stock. This results in increased caster angle -- usually about 2 degrees, as pointed out above -- even if the LCA adjusting bolt settings aren't touched.

 

[Daikon]

Thanks. I needed this explanation too!

Caster angle is determined by the geometric relationship between the ball joint locations on the lower and upper control arms. Lifting the truck changes this relationship and reduces the caster angle. Adjusting the lower control arm eccentric cam bolts can regain some, but not all, of what was lost by moving the lower control arm ball joint slightly forward.

Aftermarket upper control arms move the upper ball joint location rearward compared to stock. This results in increased caster angle -- usually about 2 degrees, as pointed out above -- even if the LCA adjusting bolt settings aren't touched.

 

[mscot]

Ok. Next question. I've noticed I still get a bit of rub on the body mount on passenger side. I plan to crayon it and see how bad it is.
But, is there a way to avoid doing a BMC? Would moving Caster higher affect anything negatively? Would that even solve the issue?
Would going up another 3/4" on the lift help? (I'm at 2.25" now)
Would spacers work? I believe that would make it worse but it doesn't hurt to ask.
Wheels are 17x8.5 with -6 backspacing

 

[plasticsnaks]

Ok. Next question. I've noticed I still get a bit of rub on the body mount on passenger side. I plan to crayon it and see how bad it is.
But, is there a way to avoid doing a BMC? Would moving Caster higher affect anything negatively? Would that even solve the issue?
Would going up another 3/4" on the lift help? (I'm at 2.25" now)
Would spacers work? I believe that would make it worse but it doesn't hurt to ask.
Wheels are 17x8.5 with -6 backspacing

Yes go higher on the caster if it’s not maxed out already. Go as high as you need to clear the body mount if possible. Higher caster should have no negative effects as long as you get the camber and toe in spec. Lifting more will not help as when you compress the suspension it’ll still rub....and your -6 wheel backspace is fine. Wheel spacers will also most likely make your tire rub worse.

Just went through this with a friends t4r...2.5” lift with JBA uca’s....-10 backspace 8.5” wide wheels with 285 toyos. Maxed out the caster on drivers side but still just barely rubs the body mount. Passenger side has more adjustment left....he didn’t want to chop the body mounts so he’s going with 265’s.

 

[mscot]

[MENTION=156276]plasticsnaks[/MENTION] or anyone else

I just dropped the truck off at the alignment place. The tech I spoke with warned me against going higher on the caster saying it could cause issues with the drive train and how it handles on and Offroad. I understand that the turning radius will be affected somewhat but would going from 4 to 5 degree of caster really affect the drivetrain and how it acts when 4x4 is engaged?

I told him lets see what they can get out of moving it forward a bit. It doesn't rub at all when moving the tires to and fro while standing still, only when in motion and at a sharp turn.

He was really pushing doing the BMC which I just don't want to do.

 

[plasticsnaks]

Hey mscot, I really don’t think going higher in caster (4.5-5) is going to affect your drivetrain nor have effects on road and off road driving....especially with 2.25” lift. The tech may not be factoring in that your JBA’s moved the upper ball joint towards the rear. It’s definitely worth trying to move you caster up to get the tire off of the body mount...if that doesnt move the wheel foward enough, then you’ll be facing the BMC or smaller tires.

Hope you get it to your liking!

 

[mscot]

Thanks.

 

[mscot]

Luckily they got caster to 4.5 and no rubbing now.
Camber is at -1 and -1.3 which isn't great but I'll take it for now.

 

[Run Forrest Run]

Similar situation and could use experienced eyes and feedback.
Installed Ironman Nitro lift (3”/2.5”) and Ironman UCA’s w/ 4* built in caster.
Went to local shop for alignment assuming it should be simple. Currently running stock wheels/tires with plans to size up to 285’s. I requested caster above 4 to avoid future rubbing with stock wheel. Tech worked diligently for 2.5 hours but it was obvious he didn’t have experience. I should have asked more questions before taking it in- my bad. End result is that all is in spec, but couldn’t get Caster above 3.0 on drivers side and 2.8 on passenger. It drives great, but could use some advise. Should I find a more experienced shop before buying new tires or am I being OCD that my Caster is in the low end of spec?
Before and After alignment specs and photos of L and R rear LCA below.
Does it look like the LCA was even adjusted or is it still in the neutral position?
I see signs of adjustment but don’t know how to read what was done.
Thanks for any experience or advice you can offer!