SPC UCA

I need to get in to the negative numbers so the tire will go more forward

 

Not necessarily.

 

Negative caster on UCA, tire goes forward.
Positive caster on LCA, tire goes forward.

 

The top axis moves forward. Remember if you move the top forward the bottom goes backwards and vice versa. Caster is a vertical line that pivots thru the hub as it’s center point. So if you move the top forward 2* the bottom moves back 2*. Just keep that in mind as the alignment adjustments are made.

 

I already had that in mind. That’s why I said I need to get in to the negative numbers to move my tire forward. The subject is UCA.

Again,
Negative caster on UCA, tire goes forward.
Positive caster on LCA, tire goes forward.

We are saying the same thing.

 

The position on the UCA has very minimal affect on the tire position. I did the experiment with my SPC's and an alignment tech. If you can't get your tire far enough forward by maxing the caster on the you LCA then the UCA adjustment won't help.

Also, I thought the Icon UCA had 2* of negative caster built in, to allow you to max out the positive caster at the LCA. But I don't have them so I don't know that for sure. That's just what would make sense to me.

 

Caster SPC

 

UCAs with built in caster (almost all aftermarket UCAs) have built in positive caster which pushes the tire back toward cab mount. This improves articulation and droop when the front is lifted higher than OEM.

Yes, the caster adjustments done to a UCA will not move the tire nearly as much as caster on a LCA. But it does help.
From what I’ve found on the inter webs, the secret is to adjust the LCA cam bolts in opposite directions to get the most caster. Point the rear cam bolt to 90* and the front cam bolt to 270* (drivers side, and opposite for passenger side). After that, you then adjust the UCA to do final adjustments for caster and camber.
An Adjustable UCA won’t help tremendously, but it will help.

 

you can not gain more positive caster by putting negative caster into the uca and it doesn’t matter if you set the uca first then make the additional adjustments with lca.

 

No, you have to set the LCA cam bolts first and then make the final adjustments for caster/camber with the UCA.
You’re the first person I’ve heard say that they didn’t gain any forward caster with these UCAs. That’s the whole point of SPC making them.
Everyone on this forum that I’ve read about says they were successful with attaining more forward caster with the SPC UCA. SPC and AccuTune Offroad also claims the same in their experience with them on Tacoma’s . I’ve had phone conversations with both of them.
I’ll have mine installed next week, so I’ll report back about my experience with them

 

I've had the SPCs, Icon Delta Joints, and JBA ucas. The SPCs do in fact allow for more fine tuning in getting your tires away from the back of the wheel well as long as you are not looking for big positive caster numbers.

"D" position will give you +2 degrees of caster over stock.
"E" position will give you +1 degree over stock.

By utilizing the "E" setting and maxing out your lower control arms to max positive caster while adjusting your camber at the UCA you will get good caster numbers and keep your tires further away from the back of the wheel well. Just make sure you cycle your suspension afterwards to make sure the UCA ball joint does not make contact with the coils.

 

Yep, this is what I’ve been hearing from everyone else that has the SPCs. Good to hear it from another person.
What are your wheel and tire specs and which setting did you put your SPCs at?

I have 285/70/17 tires and 17x9 -12mm offset with 4.5” of backspacing.
I don’t need much for clearance. Another .5” of additional clearance should keep me far away from the cab mount.

Thank you for your input!

 

I ran 34x10.5r17 tires on 17x8.5" -10 wheels. I had the ball joint in the E position. I have the cab mount chopped as well so clearance was a non issue.

 

Alright, so I got my SPCs installed today. It fixed all the rubbing. My tires are now about 1” further forward in the wheel well. I used setting “D”. The tech set the LCA camber bolts to get the most caster first, then set camber as close as possible at the UCA. He then fine tuned camber at the LCA.
It drives and steers like a dream and I’m way further away from the CM.

So in short, yes SPC UCAs will most definitely help move your tire forward in the wheel well.

Thanks to all that gave feedback. I appreciate it!!

 

Getting ready to Install these this weekend. Does this look correct for setting E? I placed the control arms like they would be on the vehicle with the instructions in the middle just want to confirm.

 

That's how I run mine

 

Yep, looks right.
SPC also encourages you to go no further than “D” unless it’s necessary. They told me that the tracking and steering will be affected if you use E or F. I’m not sure how much, but the SPC tech told me a couple times to try D before going any further.

 

it's true in my case that when we went above D and took caster to 5.7 & 5.9 it did not have an even and consistent steering feel. did not like. back down to D, went to 5.0° both sides at the time and it was perfect.

 

Thank you for the quick replies. I found an old thread on here from trident904, apparently had same size/offset wheels as I do (17x9 -38 ray10) utilizing E setting to clear CM with strong chop. I do have a body mount relocate sitting here if need be. I will play around with it and see what I can get away with. Trying to run 315/70/r17.

 

Not sure I follow that logic. It all depends on where you caster ends up with your LCA maxed out and every truck is a little different. I've got mine at D on the passenger side and G on the driver side. With my LCA maxed positive that got me to ~3deg positive driver and ~3.5deg positive passenger, which keeps it driving straight with the crown of the road. No tracking or steering issues, as expected. I suppose I could go down on both but I don't see any advantages to having more positive caster when the LCA are already max forward.