Intro to fitting 35s (< 3" Lifts for those that wheel and love alignments)

So, then the front cam bolt does what exactly?

 

The front will change the camber and the caster, same with the rear. Mine is currently all the way out in the rear. And almost all the way I’m up front. I have 0 camber and 3.4 caster

 

The picture is a bit deceiving. The SPC logo is angled slightly back 20° or so .. not straight and parallel with truck. The picture almost looks straight on but it’s not

 

Okay. Cool. Looked like position D from the pic.

 

Nice truck!! And video!! What did you repaint it??

 

It’s wrapped Avery Dark Grey!

 

It’s purdy

 

Just got refunded for the 1st CMC..

 

@Arcticelf
I figure this may come in handy.

 

Nice video, one small correction. Talking about wheel Offset is not in degrees, it’s in millimeters. I think it’s a little miss leading because back space and offset are dependent on wheel width. You brought up 16” vs 17” wheels as far as difference in sidewall, which is important for off-roading. But as far as clearing 35s, width of rim and tire in combination with backspace and offset are gonna be the big factors, besides getting the caster set to move the wheel forward.

 

Most people here don’t air down low enough to ride their side walls.

 

Very true. I realized I messed up the degrees part - Do you mind if I grab your comment and pin it to the comment section of the video?

There’s so much that goes into fitting them, tires/rim width, etc. that I was trying to remember everything off the top of my head. I should’ve broke it down more.

 

Yes. Especially in this crowd. Otherwise true beadlocks would be much more common. I used to have 35x12.5 r 15 mud terrains on narrow steelies. I never lost a bead but I am sure I was very close

 

Yes please feel free to add. There is a lot of things that play a part in fitting 35s. It doesn’t help that small differences in individual trucks and setups, and how much flex happens to determine whether or not something runs and how bad. A tiny bit more frame/body flex can help or hurt. Also the farther out the wheel/tire combo you will run more on the fender side and less on the body mount. I would also recommend painting/lining the inside of the fender well after cut and hammer of the pinch weld. It loves to collect dirt/mud and will rust. In your video it looks like you are starting to get some surface oxidation. Another trade of of cutting so much and removing the plastic wheels liners is the amount of mud/dirt/debris that gets kicked up into the gaps between the panels. The front side of the doors take a beating, and I shoot out the area under the bed rails regularly.

 

What does increasing caster at the UCA (via aftermarket parts) have to do with fitting 35s?

 

Move tire forward away from cab mount

 

I was up 10 hours today working on my turd gen, so some of this may be fucked up, but seeing all the misinformation about how all this works has motivated me to try to educate some folks. Anything wrong let me know and I'll correct it. Also since its impossible for me to explain this stuff just typing it out, I'm going to provide photos of actual Tacoma parts and explanations. I'm sure some folks know all this stuff already, but based on the things I see around TW they are few and far between so we're going to dumb it wayyyyyyyy down.

TLDR response:
No they don't. Aftermarket UCAs technically edge the tire closer to the cab mount/fire wall (albeit negligibly) by moving the upper ball joint backwards. Aftermarket UCAs have caster built in to compensate for the loss of caster when lifting our trucks. Due to the geometry of the A-Arms, as they go down to the bottom of their range of travel they start to lose caster, when you lift your truck you set its ride height closer to the bottom of that range where there isn't much caster. A lot of folks don't like the handling and "feel" (can be dangerous as well) of having low positive caster so fab shops designed their UCAs with extra caster built in to compensate for the loss due to the geometry after lifting.

Long response:
We'll just start with the basics....

Caster in its most simple terms is the relationship between the upper and lower ball joint. I just copied this from a PDF since this post is going to take long enough to type out and explain.




OK, how does this apply to our trucks? Lets see some Tacoma parts. I happen to be working on my 3rd gen currently and have my front end completely disassembled. I have a set of stock length Total Chaos Heimed UCAs to replace the OEM set. I placed the TC on top of the OEM. These are the driver side UCAs. Notice how the aftermarket UCA ball joint is just a little bit further back? That helps increase positive caster, it also negligibly moves the tire closer to the firewall.




So now I've said twice that increasing caster at the UCA actually decreases clearance at the firewall. How is that?....This would be easier to show with a photo that is straight on from the side instead of at an angle, however I don't have one, so I'll use this photo of my 2013 with a TC+2 kit. Obviously the hub is mounted on the spindle between the upper and lower ball joint, however notice that the hub is much closer to the lower ball joint than the upper. Making alignment adjustments at the LCA has a much larger impact on tire position than the UCA simply due to that relationship.
Now, why do I say "negligibly"? Because the hub isn't mounted right on the lower ball joint (if it were, upper ball joint position wouldn't influence the tire/firewall relationship at all), its located a couple inches above the lower ball joint, so when you install aftermarket UCAs the upper ball joint is shifted further back, angling the spindle back more which moves the hub, wheel and tire back a tiny bit closer to the firewall. The spindle sits on the line that is formed between the upper and lower ball joint, changing that angle changes the position of the tire.



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Ready for a mind fuck?

"Caster" doesn't really matter for fitting tires. More positive caster is a byproduct of having to move the tire away from the firewall. Everybody just seemed to fall in line saying "MOAR CASTER" instead of what everyone should be saying which is "MOVE THE TIRE FORWARD AWAY FROM THE FIREWALL" You can increase positive caster by doing 2 things, moving the upper ball joint backwards, or moving the lower forwards. We do the latter and indirectly increase caster while making room for 35s.

If you want to fit 35s the laziest way possible, you do it at the LCA. The only other way is to tub the firewall, and moving a cam is a lot easier than tubbing. Here is another image to help understand this. This is a top down view of my 2019 OEM driver side LCA. Notice how the ball joint is biased towards the front cam, and the cams and ball joint make the points of a scalene triangle? This relationship allows each cam to influence caster and camber to different magnitudes. (On the LCA both cams will have an effect on both caster and camber due to their relationship with the ball joint, however you'll frequently see the rear cam called the "caster cam" since it primarily affects caster) So when you want to get your 35 away from the firewall you adjust the rear cam outboard and that pushes the ball joint forward in a small arc. So now your camber is all fucked up....but notice how the front cam is closer to the ball joint? Yep, just adjust that in or out to set your camber to your preference. If you wanted to get the absolute maximum space between your tire and firewall you would need to set the caster cam all the way outboard, and the camber cam all the way inboard, that would shift the tire as far forward as it could go, however you would likely have fucked up camber, so you have to find a balance between firewall/tire clearance and where you want your camber.



How big of a difference does this actually make? Its dramatic. I took 35s off my 2013, put them on my stock 2019 with 1000miles, cut the fenders, cut the flares, CMC and was still rubbing like a mofo. I couldn't drive straight without the tire rubbing on the fire wall....but after adjusting the rear cam outboard, pushing the lower ball joint forward it stopped 85% of the rubbing. I drove with 35's on a bone stock suspension for 800miles with it only rubbing when I bottomed out what little bump travel it had, and on the stock UCA in reverse

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Lets get a little more complicated and move onto talk about UCAs and more triangle bullshit...See how the heim joints and the uniball form somewhat of a "right triangle"? I think Heimed UCAs are kind of cool because they have a more direct influence on camber and caster. Since the ball joint is straight out from the rear heim when you thread the heim in or out it has a more direct effect on camber, and the same goes for caster since the ball joint is so far away. If you noticed, the adjustment points are backwards from the LCA. What I mean by that, is on the LCA, the rear cam is for caster but on the UCA its the forward heim and vice versa. The same direct adjust-ability goes for the SPC UCAs, they also have a direct effect on alignment specifications by moving the upper ball joint in its seat/positions.





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Now are you ready for an even bigger mind fuck? Remember where I said that "caster" doesn't matter for fitting 35s? I can increase firewall/tire clearance by reducing caster.........at least using the UCA. How? Lets take a look at another look at the second photo in this post. This is the passenger side and if I take the front UCA heim and thread it in, the upper ball joint will be pulled forward. Now with the upper ball joint pulled forward, the angle of the spindle comes back closer to "0" caster, actually reducing caster. However as the spindle changes angle, the hub is brought farther away from the firewall increasing clearance............albeit negligibly Interestingly, the change in caster wouldn't be negligible, you could reduce it back closer to "0" caster and still clear 35s at the firewall perfectly fine because now both ball joints are pushed forward as far as they can be.

 

Awesome post! Adding this to the first.

 

I just got mind fucked in so many ways