Alignment, Caster, Clearance, and Driving Report with Light Racing UCAs

Camber measurements need to be made with the weight on the suspension. With the weight off the suspension the top of the tire will camber in, because the uca is shorter than the lca.

 

Perfect - that was my assumption, but I appreciate the help!

 

Nvm....I figured it out.

 

Adding my experience with SPC UCAs here:

'18 Tacoma Off-Road, 315/75/16, Pro Comp 7032 (4.5 BS), 1.25" Spidertrax Spacers

Alignment 1: Had 33s on at the time. Caster set to 3.6 driver and passenger. Did a cab mount chop and cut some plastic, but had plenty of clearance. Later added the spacers for a wider stance and needed to cut a little extra plastic, as well as perform a pinch weld fold. Wheels with spacers fit with zero rubbing issues. Used 3M professional rubberized coating for all cuts in the wheel wells.

Alignment 2: Switched to 35s. Occasional rubbing when reversing. Assumed caster was still set to 3.6, so I asked a guy at a small shop to adjust the alignment to allow for more room behind the wheel. Turns out it was at 4.0 driver and passenger. Guy adjusted it to 3.2 and 3.5. Rubbed like CRAZY. No idea what he was thinking. In any case, I cut every shred of the cab mount that could possibly be removed and took a sledge to the firewall to make some room (note: have yet to plate it). Still wasn't enough, and I wasn't willing to axe the spacers.

Alignment 3: Went to 4 Wheel Parts, talked to their tech manager, and made a specific request for more room behind the front tires. He set them to 2.8 and 3.3 and stated that he had the LCAs pushed all the way forward. Rubbing decreased slightly, but was still significant at full lock and when reversing.

Alignment 4: I was concerned about the manager saying they "pushed the LCAs all the way forward" but not saying a word about adjustments to the UCAs. My assumption was that they hadn't adjusted them (because it's "complicated"). I returned to 4WP, brought in the SPC spec sheet and said that I'd like the LCAs all the way forward and the UCAs set to at least F, if not G. No cost for the change.

With that very specific request, they set the UCAs to G and LCAs all the way forward for passenger but slightly back on the driver's side to keep the split for road crowd (Colorado). Originally I said I would happily go without this split, but it turns out that with setting G, there was ample room for a split. Final caster readings were 1.7 and 2.4. Drives great, tracks straight, camber is <0.5, and the tires have a full inch of room between the tire and cab in places it used to rub.

What I Learned:

• 95% of techs either aren't skilled enough to properly align with SPC UCAs or they're too lazy to do it.
• When getting an alignment, be very, very specific about what you want. LCAs all the way forward, and specify the setting you want on the UCAs (hand them the sheet describing the positions).
• I already knew this, but spacers complicate clearance (as do 35s). However, with proper alignment settings and some clearance work in the wheel wells, they can fit comfortably.
• With 285s (as of most of you likely have), a CMC, and a proper alignment, you will never, ever rub.

I think this mostly echos others' posts, but hopefully it's helpful to someone.

 

@drewkillsit
Appreciate you sharing your experiences, feedback along with lessons learned. I’ve recently made the jump to 35’s myself and have had to make those significant clearance changes as well. Along with that I also have had 4 alignments done in the past 3 weeks to try and get this front end dialed in.

 

Successfully got rid of my rubbing today with the tips in the OP. 33s with -25 offset. Setting caster to maximum on the LCA gave me enough clearance!

 

OK.

Ive read over this thread a few times and have a pretty good grasp on how all this works. Just wanna double check though.


My current set up -

-265/70s on stock Sport wheels w/ 1.25" spacers
- 5100 @ .85
- Eibach springs
- 1/4" top plates
- UCAs set at position D (+2*)

The lower control arms were set at a "neutral position" when the truck was aligned previously.

The camber and toe are on point. The caster is set at roughly 2.5*ish. Truck drives great, tracks straight. The 265s do occasionally rub the mudflaps since all of the caster was achieved at the upper ball joint and the tire is sitting towards the back side of the wheel well.

I plan on upgrading wheels and tires here soon, so Id like to get the truck realigned.

Upgrading to 285/75/16s on 16x8 et-10s wheels, so Im gonna need all the room I can get.

I know for a fact they will not fit with the alignment set where its current set, the 265s come within 3/4" of the cab mount.

I understand the caster needs to be set via the lower control arms to achieve more clearance between the back side of the tire and the fender. The lower control arm/spindle needs to be set at far forward as possible.

To achieve this, the front cam bolt needs to be pushed all the way in (towards the center of the truck) and the rear cam bolt needs to be pushed all the way out, correct? This should pull the wheel as far forward in the wheel well as possible if Im understanding correct, correct?

Another question...

For you guys running low offset wheels with 285s, what seem to be a good compromise between caster and tire clearance? Id love to keep the caster at 2.5*ish, but if I can get a little more clearance by bumping the caster down to 2* and have it still track properly, Im not opposed to this.

What seems to be a good compromise between the 2?


Thanks

 

Your description of the cam adjustment is correct except camber will also need to be taken into account. Also by moving the lower control arm forward you will increase the positive caster. I would then have them increase the positive caster as much as they can. This will give more clearance at the rear of the wheel well.

Another option is to set the upper control arm to position E (which will move the top of the spindle forward). Then have them align it to ~3 deg of positive caster. This should give even more clearance at the rear of the fender. This is what I have my '17 set at. I am running 285/75/16 tires with 16x8 0 offset wheels and do not rub my body mount. Your offset will increase the chance of rubbing the body mount.

 

Attached is a diagram that I put together. Hopefully this is helpful. Basically the idea is set the UCA to the lowest caster correcting setting while being able to get enough positive caster using the LCA. By doing this it will move the tire forward in the wheel well and increase clearance at the rear of the tire.

 

Thanks!

Glad what I thought made sense did.

My alignment guy is pretty good at doing what you want as long as I can tell him what you want.

1. Pull control arms the whole way forward to create as much rear clearance.

2. Set caster via upper ball joint

3. Set toe


What seems to be the best compromise between clearance and caster and keeping the wheels centered in the wheel wells?

 

If you keep the UCA's at position D I would try to get 3.5 degree of caster.

 

Gotcha.

Thanks for the input

 

Just got my alignment done, my numbers came out to be 0, 2.9, 0
I run 265/75-16 KO2s and as I was backing out of the parking spot I heard it rubbing. I turned around and walked back in and told them I’ve got more rubbing than I’ve ever had, and give them the keys back.
As they’re finishing up another car I go outside and look at my truck and come to realize I still have my front mud flaps, and my wheels have never been this far forward.
I asked them to remove my front mud flaps and no more rubbing.

 

Thanks for the post.. however I’m a bit confused.. wouldn’t you want your caster to be closer to 4 to allow enough clearance off the cab mount rather than 3.5, 1.7 and 2.4?? Isn’t the higher number more positive caster?? Increasing clearance off the cab mount?? I only ask because I’m dropping my truck off tomorrow (295s 3.5backspace -38)and i want to be able to give the tech viable info.. I’ve read some of the thread and am bit more confused now then i was from the OP

 

The space between the cab mount and the tire increases or decreases depending on where the caster adjustment is made. Adding caster on the factory LCA cams moves the tire further away from the cab mount. Adding caster on the spc uca moves the tire closer to the cab mount. You have to play with both the uca and LCA adjustments to get your desired results.

In his case, setting the uca to the lowest setting for caster and adding max caster at the LCA allowed his 35s to clear the cab mount and reduce or eliminate rubbing. His caster numbers may seem low and not what everyone suggests it should be, but all that matters is that it steers well and tracks straight.

 

Gotcha!! I have just been reading that somewhere between 3 and 4 degrees of positive caster (spec sheet) is the sweet spot. I do understand that caster can be also set on the UCA to compensate (maybe that was the 1.7 setting he was referring to). I just printed out a build sheet for the shop doing the instal for me and i said the caster should be adjusted forward from LCA between 3-4 and then adjusted from UCA.. i don’t want to give bad info

 

I just had my Tacoma aligned & rub with 285/70/17...all I see is red:

 

So just a general question.. if an alignment is done after lifted with factory tires will it be affected with larger tires? (No change in lift)

 

No

 

Thanks i didn’t think so