Bump Steer/steering wheel goes nuts

[TwizzleStix]

Like I said earlier, hindsight is 20/20.

I attached the wrong specs in the OP. This is before and after when the suspension was stock with the KO2's.View attachment 163483
This is after with the Geisers, Deavers, and KO2's
View attachment 163484
Stock forged wheels. They were generally about 38/36 F/R. As you can see on the sheet the psi would swing wildly.

Ok, I see a specific problem that will indeed result in "skittish" steering. On practically EVERY vehicle, the more front caster you can run, the better the on-center steering and feel.

Your original before alignment shows plenty of toe-out which indeed makes a vehicle follow every crack and line in the road. A slight amount of toe-in is best for road use unless you're a dedicated racer. The corrected specs look pretty standard for the Raptor, so there should be no problems with the new alignment AND new tires.

The final after mods specs show you REDUCED caster by a 1/2 degree, which is bad, bad, bad. When the caster is high(positive), the steering tends to want to stay straight ahead because the contact patch is behind the steering axis. The more you reduce caster, the contact patch moves closer to the steering axis, so the steering tends to follow road irregularities easier.

I assume the alignment shop couldn't get the camber within spec without reducing the caster. I would take it back and tell them to maximize caster as long as the camber stays negative, up to zero camber, or at least no positive camber. This will give the truck more straight line stability for SURE. I've seen some lifted trucks REQUIRE adjustable upper control arms so they can maximize caster with the lower control arm adjustments and still get enough negative camber (about -1deg is best for front turning traction) with the upper arm.

If the steering STILL doesn't settle down, then you have some mechanical issues OR the alignment equipment is out of calibration.

 

[ssj4sadie]

Ok, I see a specific problem that will indeed result in "skittish" steering. On practically EVERY vehicle, the more front caster you can run, the better the on-center steering and feel.

Your original before alignment shows plenty of toe-out which indeed makes a vehicle follow every crack and line in the road. A slight amount of toe-in is best for road use unless you're a dedicated racer. The corrected specs look pretty standard for the Raptor, so there should be no problems with the new alignment AND new tires.

The final after mods specs show you REDUCED caster by a 1/2 degree, which is bad, bad, bad. When the caster is high(positive), the steering tends to want to stay straight ahead because the contact patch is behind the steering axis. The more you reduce caster, the contact patch moves closer to the steering axis, so the steering tends to follow road irregularities easier.

I assume the alignment shop couldn't get the camber within spec without reducing the caster. I would take it back and tell them to maximize caster as long as the camber stays negative, up to zero camber, or at least no positive camber. This will give the truck more straight line stability for SURE. I've seen some lifted trucks REQUIRE adjustable upper control arms so they can maximize caster with the lower control arm adjustments and still get enough negative camber (about -1deg is best for front turning traction) with the upper arm.

If the steering STILL doesn't settle down, then you have some mechanical issues OR the alignment equipment is out of calibration.

Awesome thanks! Do you think the added preload from the Geisers is what would cause them not to get the right balance?

 

[TwizzleStix]

Awesome thanks! Do you think the added preload from the Geisers is what would cause them not to get the right balance?

Can’t say for SURE, but it sure could be.

If the suspension is fully extended just sitting there all the specs will be hard to set for correct function. The suspension and specs are designed to be about mid-travel, (the original mid-travel not some lifted height mid-travel) so that when the suspension articulates with steering and operation the alignment will be within the best specs for handling/control.

When you alter the static height without moving the pivot points to match the original geometry, all the suspension/steering engineering goes out the window.

If the truck (or any vehicle) needs more ground clearance while keeping the original geometry, then larger diameter tires/wheels are the quick answer. “Lift kits” are an aberration to the suspension operation.

 

[Deleted member 12951]

This seems to be an issue with EPAS on some raptors. All we can do is hope that Ford has a program update for it.

 

[smurfslayer]

@TwizzleStix brought some class to the thread here. I’d like to add a little bit on tire psi. Those pressures are too high for even tire wear on the KO2’s based on superficial observations of users here, who didn’t shag them in the first 20k miles and my own personal usage. I ran high-ish psi too for the first year to 18 months, gradually stepping down after Raptor Assault and a few more months of driving the truck. I’m not worried about rolling over the tire like on a decent sports car in the Rap but I still want some balance to it. Even so, I’ve been 34/32 and not had any issues on the street even pushing things a bit. I like around 35/33 right now, without any meaningful load.

The center of my KO2s are much, much more worn than the edges and that’s a bit surprising to me for how I drive.

Good luck and I hope you get the skittish steering corrected.

 

[rightway]

I think the steering deficiency being described has a name, at least before all the upgrades. It's called "Tramlining"

I hope I don't offend any Raptor members by adding information from other sources.

These are my notes taken from past post readings and they may have come from the Raptor and for sure the F-150 Forums

Tramlining = Vehicle that’s wondering and following imperfections (for example ruts, groves) in the road.

This describes many causes https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=47
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One of the excited successful F-150 fixes that I noted was, re-calibrating the electronic steering system and also the comments from members after they saw the fix. They were indicating because of their unsolved steering problem, they had already traded in their vehicles, I assume dealer's not knowing of the fix.


This is another reference from my notes, may not be really helpful.

Originally Posted by tmcolegr --again probably from the F-150 Forum

SSM 47589 - 2016-2018 F-150 - Steering System Pull, Drift, And/Or Wander - Diagnostic Update

Some 2016-2018 F-150 vehicles may exhibit a steering drift, pull, and/or wander. To diagnose these conditions refer to Pinpoint Test (PPT) H - Steering System Pull, Drift, Wander or Steering Wheel is Off Center in Workshop Manual (WSM) Section, 211-00. Do not use PPT I - Poor Returnability Sticky Steering or Binding to diagnose drift, pull, and/or wander symptoms. These Pinpoint Tests are in the process of being updated.
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Good luck, hope this helps

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[smurfslayer]

Tramlining. Word up @rightay. bringing knowledge to the masses.