Mid-Travel: Too much caster?

Hi all,

I'm running a 2.5" lift with aftermarket UCAs (Icon Delta Joint). I've driven my truck with low (~2.5°) caster and know first-hand how squirrelly the front end feels due to angle of the wheels (another thread referenced "shopping cart wheels" and that's an accurate analogy). I am running 4.5° of caster to push the wheel forward from the cab mount and so the truck tracks straight on the highway.

However, there is now a "dead zone" when my steering wheel is centered (about 15 degrees in either direction). This is due to my wheels being brought forward - think like a mountain bike with slack fork, it requires more input at the handlebars to turn. The bump steer in my truck is quite bad due to the dead zone.

Now for my question: Is 4.5 degrees of caster too much for a mid-travel setup? Is 3.5° a more reasonable target?

Appreciate any input.

 

It’s not clear to me that ride height has any effect on the optimal caster. I would just keep it in factory specs.

Personally, my caster is about 4 degrees, but that is only because the 4x4 shop set it up that way after I asked them to move the wheels forward to solve a rubbing issue.

 

A stock Tacoma with no lift should have a factory spec caster of 1.8-2.5 (or around that range). A lifted truck often requires more caster (and aftermarket UCAs to achieve that higher caster).

@gudujarlson you're happy with the 4 degrees of caster? No bump steer or "dead" feeling in when the steering wheel is centered?

 

I would certainly bump it down a degree and see where that gets you. My Tacoma is stock but I’ve run nearly 6° in my mid/long travel GX without any weird return to center issues.

 

https://accutuneoffroad.com/tacoma-4runner-wheel-alignment/

 

Following....

 

I think you might be misunderstanding what aftermarket UCAs are used for. When a taco is lifted, it loses caster and must be re-aligned to get it back into spec. If the truck is lifted high enough, it becomes impossible to align it back into spec. This is where aftermarket UCAs are needed. Many have 2 degrees of caster built in so that aligning into spec is possible again.

My truck handles fine with 4 degrees of caster. When I first had it aligned I subjectively felt it took slightly more force to steer, but it was subtle. Now I never think about it. If I get it aligned again, I will tell them to try to keep it within spec while moving the wheel forward for clearance. I’m not sure the tech understood how to adjust SPC UCAs.

 

I understand what you're saying, but aftermarket UCA forces caster to become 3.5-4.5 degrees with the build in caster from the component design. In my mind, "spec" is what's recommended from Toyota, which is around 2.5 degrees.

I digress, it sounds like I should shoot for 3.7ish-4ish degrees on next alignment. 4.5 is pretty dang high and produces bump steer for me.

 

Accutune always publishes great tech articles. I replaced my LCAs prior to alignment and slammed them as far forward as they could go. The alignment tech ended with 4.5 degrees of caster. I always thought more caster is better, but am learning there is a sweet spot. Possible to go too high on caster at 4.5 degrees.

 

im on 2.5 caster and it feels awesome to me, accutune lift with kings here. steering is tight and rail straight going 63.

 

My caster is around that number as well drives so nice accutune kings lift over here as well

 

Post the numbers from the alignment and has any other work been done other than the UCA's? What wheels (back spacing/offset), tires etc. 4.5 degrees of caster should not be causing what you describe. I would be looking for something else. Depending on your tire size this may be of interest to you. HOWE TC Pump Steering Kit – JD Fabrication Looking at your profile. Are you running 285/70/17 KO2's and the ProComp 7069 wheels? Icon recommends a max of 4.75" back spacing the pro comps have 5.25". I would make sure the tire and or wheel is rubbing any where, especially the UCA. I would also make sure you don't have a tight ball joint.

 

This thread seems to be bang-on with my current thought process: https://www.tacomaworld.com/threads/caster-recommendations.730180/

A member commented that 4.5 was too high and he was much more happy with 3.5.

@AusBerg @71tattooguy when you say Accutune lift do you have the Icon Delta Joint UCA? I have the Accutune lift package with that as well.....

@01_dhrracer you are correct with my wheel and tire setup. The wheels do not contact the UCA, I have double checked in the past. LCA ball joint is brand new, I grease the upper ball joint occasionally. I'll get photos of previous alignments uploaded. I still think that remove a degree of caster and setting my alignment at 3.5 might be the golden ticket.

 

Pro Comp wheels have 4.75 backspace: https://www.procompusa.com/product-...h-6-on-5-5-bolt-pattern-flat-black-7069-7983/

 

I’m running dirt king UCA’s

 

For mid travel 2” lift or higher, 3-4* caster with 3.8* being ideal.

 

I have the accutune UCA's

 

Aftermarket UCAs do not force caster to 4 degrees. Caster can still be adjusted without a range of values. Case in point, with my SPC’s I have had 2 alignments, one with 2 degrees and one with 4.

I had some tire rubbing with the first alignment, so I took it to a 4x4 shop and told them explicitly to move the wheel forward. I think they did that but then didn’t set the SPC into the neutral caster position, so now my caster is out of spec.

 

While I may be wrong please take with a grain of salt, I too agree with gudujarlaon. My thoughts is the aftermarket UCA's allow for greater caster range, not 'forced'. And I thought the biggest advantage for a large caster # is to allow a larger wheel to fit with less cutting, as well as to avoid feeling squirrelly on the road. Which I do not experience at 2.5 degrees. I know I have the ability to go more, but I liked how it felt pre lift at 1.5 degrees so I wanted small incremental changes until I felt it was comfortable to drive.

Sounds to me you may have some luck dialing the caster back a degree or two, then just see which you like better and go from there.

 

@AusBerg @gudujarlson you both are correct, I misspoke when I said aftermarket UCAs "force" caster. They simply open the door to higher caster being achieved.

Yes, I've made up my mind that ~3.5-3.8° degrees is what I should go with next. 4.5 seems much too high.

Thanks all!