Looking at Badlands vs Sasquatch Wheel/Steering Geometry

[zuke]

If I were to guess, I'd expect it was a way more complex start...

Here's a guess at how the meeting went but with totally made up numbers;

"We expect to sell 40,000 non-sasquatch units and 60,000 sasqutch ones, let's set the center at 60% of the distance between the two ideal settings biased toward the higher sales model"

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[5GENIDN]

Well that's interesting. I thought the 3.0 was clearly beefier, but that's not what seems to show (?). I wonder if the way that shows the racks is ignoring where the 3.0 is actually beefier and kinda makes the 74W option appear clearly better (but is a different material with different specs).

When I look at this picture, I see a HOSS 3 as clearly beefier.... It is the "fins" or stiffening ribs that dynamically make the housing significantly more ridged... If you notice the orientation of the "ribs" they appear to be designed to add rigidity where the housing would need the increase the most, 90 degrees to the rack bar and pinion interface. Both the HOSS 2 and HOSS 3 are cast aluminum where as the 74 weld is milled from billet, actually more accurately a length of very thick plate. The HOSS 3 housing does not appear to be a "thicker casting but if you look closely at some of the flanging It does appear to be more robust. look closely at the bolting flanges at the bottom. There is a distinct differance.

 

[userdude]

When I look at this picture, I see a HOSS 3 as clearly beefier.... It is the "fins" or stiffening ribs that dynamically make the housing significantly more ridged... If you notice the orientation of the "ribs" they appear to be designed to add rigidity where the housing would need the increase the most, 90 degrees to the rack bar and pinion interface. Both the HOSS 2 and HOSS 3 are cast aluminum where as the 74 weld is milled from billet, actually more accurately a length of very thick plate. The HOSS 3 housing does not appear to be a "thicker casting but if you look closely at some of the flanging It does appear to be more robust. look closely at the bolting flanges at the bottom. There is a distinct differance.

Well, I see an attempt to cut off most of the obvious fins you're talking about; the middle one is certainly missing the most of what you're talking about and needs more closer eyeballing to even see it (even given a more trained eye). Just just my opinion, I guess. Call me "skeptical" of how some of that turned out with that vendor.

And also I thought it was a bit thicker, which I was wrong.

 

[87-Z28]

Hey! I'm hoping to understand the difference between the non-sasquatch and sasquatch (HOSS 3.0) wheel placement and suspension setup:

Known: the non-Sas runs +55 offset wheels, and the Sas runs +30 offset *with upgraded components.

What I would like to know is: Did the engineers at Ford change the steering axis placement/orientation when moving to a +30 offset in order to keep the same scrub radius as the non-sasquatch models? Or did they just move the wheels out and then put on a "heavy duty steering rack" to compensate for the increased leverage on the suspension?

I'm asking because I'd like to know what my wheel options are on my Sasquatch. If they really did modify the steering axis for a +30 offset, I would not want to go to +35 or higher wheels and get a zero or possibly negative scrub radius. Now if the setup is the same as a non-sas, then that would mean moving to +0 wheels would actually be a 55mm shift away from how the steering was designed, not a 30mm shift. Generally I wouldn't want to move more than an inch away from the centerline the vehicle was designed with.

I'm aware that many people run +0 without significant issue, but I am: 1. planning to run technical offroading, 2. planning on keeping to 200k+ miles, 3. in love with the green paint and want to protect it, and 4. an obsessive mechanical engineer

If anyone has looked into this before, please let me know!

*Not sure if this should go under the suspension or wheels category, admins feel free to place where fit*

the steering axis (kingpin axis) does NOT change between models, since all models use the same double wishbone geometry (LCA, UCA, knuckle, and frame hard points). Given the same coilover geometry (compressed and extended length), the kinematics of the double wishbone dictates the kingpin axis throughout a full suspension cycle (see first plot).

scrub radius is the lateral distance between steering axis intersection with road surface and the tire contact patch centroid. Hence scrub radius is dependent on tire/wheel geometry. A more comprehensive metric of steering resistance is the total moment arm (scrub radius and mechanical trail). Not just scrub radius.

Some plots of total steering moment arms for oem tire/wheel configurations are shown.

 

[zyglyrox]

i was just about to tag @87-Z28 as they have gone into the technical detail on this. sure enough they have appeared

 

[Hyperbolic_Tangent]

the steering axis (kingpin axis) does NOT change between models, since all models use the same double wishbone geometry (LCA, UCA, knuckle, and frame hard points). Given the same coilover geometry (compressed and extended length), the kinematics of the double wishbone dictates the kingpin axis throughout a full suspension cycle (see first plot).

scrub radius is the lateral distance between steering axis intersection with road surface and the tire contact patch centroid. Hence scrub radius is dependent on tire/wheel geometry. A more comprehensive metric of steering resistance is the total moment arm (scrub radius and mechanical trail). Not just scrub radius.

Some plots of total steering moment arms for oem tire/wheel configurations are shown.

Wow, super helpful, thank you.

So my 34.5” tires on my +55 offset wheels are yielding a ~30mm net lever arm. Is this a big deal? Should I change to +30 wheels?

 

[razehound]

the steering axis (kingpin axis) does NOT change between models, since all models use the same double wishbone geometry (LCA, UCA, knuckle, and frame hard points). Given the same coilover geometry (compressed and extended length), the kinematics of the double wishbone dictates the kingpin axis throughout a full suspension cycle (see first plot).

scrub radius is the lateral distance between steering axis intersection with road surface and the tire contact patch centroid. Hence scrub radius is dependent on tire/wheel geometry. A more comprehensive metric of steering resistance is the total moment arm (scrub radius and mechanical trail). Not just scrub radius.

Some plots of total steering moment arms for oem tire/wheel configurations are shown.

Thank you, this is incredible.

So then keeping a "closer" offset with larger tires is not necessarily better than otherwise. It looks like the 30mm offset is actually better suited for tires 34-37" (its almost like Ford knows what they're doing haha).

It appears that 33" tires are about the break even, where either wheel offset yields similar moment.

The only other thing I'd like to see is the plot for a 0 offset wheel. I can already understand how it would look, but it would be nice to include in the thread since its such a popular option people run.

Would be interested to see exactly where 37" falls on either plot, since it seems to be well optimized for already in the +30mm range.

Much appreciated!!

 

[87-Z28]

My post was just trying to clarify the whole scrub radius thing. Not trying to spread fear about steering and scrub radius. The hoss 3 rack likely has very good factors of safety.

I wouldn’t over think the wheel offset. OEM will be very conservative for increased steering rack factors of safety. At the end of day we are all trying to increase clearance with larger tires. So whatever offset helps to keep tires from rubbing as needed. Personally I would not go to a negative offset wheel. I doubt it is necessary anyway.

some additional plots for typical wheels. 0 and 18 mm offsets. The 18mm is a nice sweet spot for 37s wrt steering moment arm. I don’t have that combo but I think it is also good wrt rubbing issues during full suspension cycling. Others that run similarly can confirm. Small suspension lift (-2-3”) using decent coilovers. And small body lift (-1”) would be my choice for 37s.

link to kinematics

https://www.bronco6g.com/forum/threads/kinematic-model-of-oem-sas-front-suspension.108300/

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