* UCAs improve Caster but reduce clearance at the rear fender.
* You can reduce the amount of space lost by setting the alignment optimally
* Daily driveability is much better after adding UCAs.
So, last October I lifted my 4 cyl std cab Tacoma with OME 885 springs and Dakar Leaf pack. See http://www.tacomaworld.com/forum/sus...ines-pics.html. This gave me a full 3" of lift. I did not install any upper control arms. Here are my final post-lift alignment numbers:
Left Right Factory Range Camber: 0.5 0.3 0.2-1.3 Caster: -0.1 -0.2 1.0-2.5 Toe: 0.05 0.05 0.0-0.11
My wife noticed right away that the truck felt "skittish" and didn't like driving it. After six months, including a long road-trip to Moab, I decided I was ready to get some caster back, so I purchased some Light-Racing Upper Control Arms from wheelers.
I installed them last weekend. I didn't bother with an install thread for them because of the most excellent TW UCA install thread here: http://www.tacomaworld.com/forum/sus...w-install.html and the excellent video produced by SPC, maker of the control arms, here: http://spc-tv.com/install/lt-suv/69-...trol-arms.html
Using the instructions I pre-set the caster at the "+3" position (+2 is "neutral")
Yesterday, took the truck in to get it aligned at my local shop I've been using for years. Here are the alignment numbers from that. Check out the huge 3.7 caster before they started!
BEFORE: Left Right Factory Range Camber: 0.2 0.2 0.2-1.3 Caster: 3.9 3.7 1.0-2.5 Toe: -1.23 -0.63 0.0-0.11 and AFTER: Left Right Factory Range Camber: 0.5 0.4 0.2-1.3 Caster: 2.4 2.4 1.0-2.5 Toe: 0.05 0.07 0.0-0.11
I talked to the shop and rang up PRS 2 TiFJ. He gave the following observations and instructions.
* If you increase caster AT THE TOP of the spindle, you decrease clearance, because that moves the spindle hub back.
* If you increase caster AT THE BOTTOM of the spindle, you increase clearance, because that moves the spindle hub forward.
* On the stock truck, caster and camber must be played off against each other, because the combination of eccentric cams on the lower-control-arm affects both caster and camber.
* But the adjustability on the Light-Racings means you can set Camber at the top of the spindle, in addition to setting caster there.
* Toe is adjusted by the tie-rod ends, and is a completely separate adjustment.
So, to maximize clearance:
1. First, Maximize caster using the eccentrics on the lower control arm. Do not worry about camber at this time.
2. Reset the caster cams on the UCAs to the minimum value to bring Caster to an acceptable value. I decided to trade off a little less caster for a little more clearance here, and moved the UCA cams to the "+1" position (One degree LESS than neutral, and two degrees less than I started)
3. Set the camber using the UCA adjustment slide.
4. Finish off toe normally.
So I met with the alignment technician this morning, and stood in the shop while he worked. Pretty much my only contribution to the effort was showing how to turn the caster-adjustment cams on the UCAs. To get maximum "2.5" caster on my truck, the UCAs would have to be set at the neutral "+2" position. I deliberately traded off to get a little more CLEARANCE at the expense of a little less caster and ended up with the following final alignment numbers:
Left Right Factory Range Camber: 0.5 0.5 0.2-1.3 Caster: 1.7 2.0 1.0-2.5 Toe: 0.05 0.06 0.0-0.11
I'm now on the fence about getting a cab-mount-chop, because I hate tire rub in all its forms, and I like having the option to run chains on all four wheels.
The bonus to having waited this long to install UCAs is that I'm now qualified to talk "before and after" about driving the truck with and without upper-control-arms.
1: As expected, the truck now tracks better. On my short drive to the shop with the 3.7 degrees of caster, the truck was *very* stable and I kinda liked that. But even at 1.7, it's much more directionally stable, self-corrects easily to the zero position after the tiny variances in the road, and takes a lighter hand on the wheel. Truck no longer feels skittish or twitchy. I'm pleased.
2: The factory UCA ball joint, rather than OME shock length, seems to have been the limiting factor in droop. When I jack up the front end I now raise the whole thing two full inches (at the fender) before the tires finally leave the ground.
The amount of droop IS telling as I go over our various highway bridge joints that are a regular feature of my commute. Before, with the lift and the factory UCAs, the front would drop and the truck would lurch forward, forcing the headrest into the back of my head on some of these joints. Now, I glide easily over these small drops. This is an unexpected bonus, and I'm *very* pleased.
bjmoose gives a hearty "ThumbsUp" to Light Racing upper control arms.
Much later EDIT: - you may find this pic helpful in aligning the SPC control arms: