Can anyone with a Sasquatch Bronco measure their scrub radius?

[MillerAndCheeto]

Hi Bronco6G forum, I'm hoping someone who has a Sasq package can check some measurements (that may require a bit of trig). A few have asked about scrub radius before, with no answers. I'm hoping a thread definitively asking with instructions will at least get me some measurements and I can calculate it myself.

Can someone crawl under their rig and draw a line from upper to lower ball joint and imagine if that line continues down to the ground, where in relation to the center of the tire does that line reach the ground (measured typically in mm or 1/16th inches).

The Bronco should have a positive scrub radius - center of the tire is slightly farther out from the wheel well than the imaginary line that reaches the ground.


If that imaginary line is too hard to figure out with the wheel and the other suspension parts in the way let me know and I'll give you some other measurements to grab and we can do some trig.

Thanks in advance, this question has been raised a few times but there has been absolutely zero answers, so if you have time to crawl under your rig you can give some info that would be very helpful for everyone.

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[Werkedperformance]

But why?

Whats the end game? What are you trying to figure out?

And not scrub radius....thats just silly

you making long travel arms? spill it.

 

[MillerAndCheeto]

But why?

Whats the end game? What are you trying to figure out?

Would like a definite answer on the scrub radius of a Sasq Bronco that will better guide decisions on what wheel offsets are most appropriate. If the scrub radius is 0.5" then going from a 30mm offset rim to a 0mm is not a big deal. If the stock 30mm offset rims are already at a 2" scrub, pushing it out another 1.18" might not be a great idea for longevity of the components.

 

[MillerAndCheeto]

And not scrub radius....thats just silly

you making long travel arms? spill it.

Haha, sorry to burst your bubble, but just the scrub radius. I'm an engineer, I don't do anything without researching as much as possible before making a decision. I think scrub radius is a very overlooked aspect of people sticking 0 and even -18 offset wheels on their Broncos. I know I am going to change my rims and tires however I'm on the fence between an 18mm or 0mm offset and am compiling as much data as I can before making a decision. If the 0 offset pushes the scrub radius past my comfort zone I'll stick with the 18mm offset despite the better visual appeal the 0 offset gives it.

So yah, boring answer, but info would be helpful.

 

[The Bronze]

I like where you are headed with this research. Scrub radius changes affect the vehicle handling and even make changes that the automated driving systems can’t account for. There are alignment machines that can calculate scrub radius and then you compare as you swap rims, spacers and such. No matter how you determine your scrub radius and determine your offset choice, you can then find a competent alignment tech and they MAY be able to either make SAI adjustments to help correct for any remaining changes in wheel offset or help provide input on the use of spacers (if positive SR) to restore SR to near factory specs. If the shop’s equipment isn’t displaying the diagnostic angles (body shop or diagnostic angles), find another shop. Following to see what you find.

 

[PSUTE]

This is what your ass is for. Seat of the pants as to how to handle things trumps all else including/regardless of technology once you know the vehicle you're driving...

 

[clhman]

Hi Bronco6G forum, I'm hoping someone who has a Sasq package can check some measurements (that may require a bit of trig). A few have asked about scrub radius before, with no answers. I'm hoping a thread definitively asking with instructions will at least get me some measurements and I can calculate it myself.

Can someone crawl under their rig and draw a line from upper to lower ball joint and imagine if that line continues down to the ground, where in relation to the center of the tire does that line reach the ground (measured typically in mm or 1/16th inches).

The Bronco should have a positive scrub radius - center of the tire is slightly farther out from the wheel well than the imaginary line that reaches the ground.


If that imaginary line is too hard to figure out with the wheel and the other suspension parts in the way let me know and I'll give you some other measurements to grab and we can do some trig.

Thanks in advance, this question has been raised a few times but there has been absolutely zero answers, so if you have time to crawl under your rig you can give some info that would be very helpful for everyone.

Should be taking delivery within two weeks. If no one replies before then, I’d be happy to help. Message me to remind me. I understand where you are coming from.

 

[North7]

This is what your ass is for. Seat of the pants as to how to handle things trumps all else including/regardless of technology once you know the vehicle you're driving...

Us engineers don't design products fully by the seat of our pants, we operate off of data.

I'm not sure which seat of the pants calculator will help the OP purchase new wheels and tires?

 

[North7]

Haha, sorry to burst your bubble, but just the scrub radius. I'm an engineer, I don't do anything without researching as much as possible before making a decision. I think scrub radius is a very overlooked aspect of people sticking 0 and even -18 offset wheels on their Broncos. I know I am going to change my rims and tires however I'm on the fence between an 18mm or 0mm offset and am compiling as much data as I can before making a decision. If the 0 offset pushes the scrub radius past my comfort zone I'll stick with the 18mm offset despite the better visual appeal the 0 offset gives it.

So yah, boring answer, but info would be helpful.

I like where you are headed as well, looking forward to your results.

Here is a calculator that will help once you get some data:

Rim & Tire Size Calculator

 

[Werkedperformance]

SAI is non adjustable, without changing things that "can't" be changed.

Changes in tire size affect SR. So that comes Into play.

OP are you keeping 315s? What size are you going to?

FWIW, the Bronco suspension was originally designed around the 33 inch packaging. Thats why a Badlands non squatch has more travel. Id suspect the best geometry would be found on the less offset badlands wheels with the sassy wheels being a compromise.

Back to my first post, whats the end game?
Big tires? Stance? Trying to do both without driving like shit?.... Lift?
I'll help when I have time to measure, but it could be a few days

 

[hellahella]

SAI is non adjustable, without changing things that "can't" be changed.

Changes in tire size affect SR. So that comes Into play.

OP are you keeping 315s? What size are you going to?

FWIW, the Bronco suspension was originally designed around the 33 inch packaging. Thats why a Badlands non squatch has more travel. Id suspect the best geometry would be found on the less offset badlands wheels with the sassy wheels being a compromise.

Back to my first post, whats the end game?
Big tires? Stance? Trying to do both without driving like shit?.... Lift?
I'll help when I have time to measure, but it could be a few days

Is it safe to say that whatever the findings we get from this is also applicable to 33s? I’m getting a nonSAS and the wheels I’m looking at are +18 offset so I’m def watching.

 

[MillerAndCheeto]

Is it safe to say that whatever the findings we get from this is also applicable to 33s? I’m getting a nonSAS and the wheels I’m looking at are +18 offset so I’m def watching.

I would say it is likely going to be similar. If the Sasquatch has a, say, 10mm positive scrub I would imagine the non-Sasq is in a similar situation. That being said, without getting the measurements this is purely speculation on my part at this time.

 

[MillerAndCheeto]

SAI is non adjustable, without changing things that "can't" be changed.

Changes in tire size affect SR. So that comes Into play.

OP are you keeping 315s? What size are you going to?

FWIW, the Bronco suspension was originally designed around the 33 inch packaging. Thats why a Badlands non squatch has more travel. Id suspect the best geometry would be found on the less offset badlands wheels with the sassy wheels being a compromise.

Back to my first post, whats the end game?
Big tires? Stance? Trying to do both without driving like shit?.... Lift?
I'll help when I have time to measure, but it could be a few days

End-game is having the confidence that changing tire offset won't move the scrub radius outside of my comfort zone for adding unnecessary wear and tear on the suspension components. Because we're talking about ~88 lb tires, the moment-arm applied to the components is not insignificant. Maybe I'm overanalyzing it, but I'm also genuinely curious and no one has provided this information on this forum.

I will be changing to 315 KO2's.

Between the Sasq and Non-Sas there is also a slight lift difference (0.5" or so?) so that combined with any changes to any suspension component + different tyres would alter the SR between Sas and Non-Sas, so it's not quite as easy to say badlands non-sas has the "best" geometry as it's not an apples to apples comparison. Best articulation - yes, agreed Badlands non-Sas as they don't have to limit the travel.

 

[Ares]

for a measurement of potentially 10mm... Im trying to fathom how anyone would ever accurately approximate a lines intersection with the ground through a tire... when your looking for accuracy within a half of an inch of absolute measurement...

It would be completely made up, and theres no possible way you wouldnt get garbage results for something you only do if you are seeking absolute precision.

assuming the arms and knuckles are the same, wouldnt you just measure the tire track width and divide by 2? wouldnt that tell you the offset of the tread between tire packages?

 

[MillerAndCheeto]

for a measurement of potentially 10mm... Im trying to fathom how anyone would ever accurately approximate a lines intersection with the ground through a tire... when your looking for accuracy within a half of an inch of absolute measurement...

It would be completely made up, and theres no possible way you wouldnt get garbage results for something you only do if you are seeking absolute precision.

assuming the arms and knuckles are the same, wouldnt you just measure the tire track width and divide by 2? wouldnt that tell you the offset of the tread between tire packages?

That's a fair question, however that is where a little bit of trigonometry would be required and potentially require taking the tire off. Taking tire off is slightly more prep so I'll just over the tire-on scenario measurements:

1. Without Tire Off:
a. Distance from ground to upper steering axis point
b. Distance from ground to lower steering axis point
c. Distance between upper and lower steering points on the horizontal plane (could require a small level depending on how much room there is, or drawing imaginary lines down to the ground and measuring the distance between)
d. Distance from inner tire width to an imaginary line straight down from the upper steering axis point
e. Width of tire on the ground
f. Calculated interception point on the ground measured from the upper steering axis point
g. Middle of tire measured from upper steering axis point
h. Scrub Radius


Here's the calculation:

(a - b) / c = the negative slope of the steering axis (rise over run)

f = (b / slope) + c

g = (e/2) + d

h (Scrub Radius) = g - f

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