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How's my numbers?

Treefrog said:
Overall, not bad. Cg seems a bit high, that will change the antis some. Also the body all three roll axis are oversteer or neutral. Not necessarily a bad thing, but can be a problem if an unaware drive gets behind the wheel.
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Thank you for the input. Im able to bring my frame side lowers in and get both the rear roll slope, and the body roll axis to understeer, would this behave better to an unaware driver? I also did lower the center of gravity, kinda hard to tell but it will be a pretty tall Jeep.

JK link data 1.5.png
JK link data 2.5.png
 
I noticed a big change in the roll oversteer numbers when I changed to the new version of the spreadsheet. I had scary roll oversteer, made some pretty invasive changes to lower the frame ends of the lower links, and it drives better, but the new spreadsheet doesn't really show that.

I'm not sure where to go from here.
 

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mano002 said:
I noticed a big change in the roll oversteer numbers when I changed to the new version of the spreadsheet. I had scary roll oversteer, made some pretty invasive changes to lower the frame ends of the lower links, and it drives better, but the new spreadsheet doesn't really show that.

I'm not sure where to go from here.
Click to expand...
Which version were you using? A few versions ago, I caught a mistake in the front roll center math that would affect the body roll slope.

It is possible that a little change in the value had a large effect, it is also possible that lowering the links affected other aspects as well.
 
I started using 4.0, and updated to 6.1, and then to 7.6. The change I was talking about was between 6.1 to 7.6.
 
mano002 said:
I started using 4.0, and updated to 6.1, and then to 7.6. The change I was talking about was between 6.1 to 7.6.
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Which roll slope changed? Body or front? The fix was implemented in 6.1, so all three versions should have the same output for the same inputs. I'll double check it with the 3 link setup this weekend. I did not spend much time checking the values for 3 link roll stuff.
 
Treefrog said:
Which roll slope changed? Body or front? The fix was implemented in 6.1, so all three versions should have the same output for the same inputs. I'll double check it with the 3 link setup this weekend. I did not spend much time checking the values for 3 link roll stuff.
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Looks like it was a data entry issue on my end. I had the frame end of the pan-hard bar below the axle end.
 
First go at rear 4 link numbers. Truck is a trail rig, mostly rock crawling in the southeast. 1981 Toyota, dual transfer cases, leaf sprung (RUFs) in the front. I'm thinking I need to drop the frame side lowers down some to get them flatter. I've got plenty of room to move things around, especially the uppers.

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TSG said:
First go at rear 4 link numbers. Truck is a trail rig, mostly rock crawling in the southeast. 1981 Toyota, dual transfer cases, leaf sprung (RUFs) in the front. I'm thinking I need to drop the frame side lowers down some to get them flatter. I've got plenty of room to move things around, especially the uppers.
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You are probably right about needing to drop the frame side lowers. It may be beneficial to widen the upper axle and lower frame points. The total combined angle only needs to be about 40*, having less angle will help with keeping the axle pointing in the right direction when the suspension is articulated. As for the upper frames, you may want to move them up, closer to parallel with the lowers. It would keep you from having to drop the lowers some.
 
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Where on the newest version do I see the the roll steer through wheel travel? I'm probably just being stupid.

Oh, and how does my junk look? Just started adding my numbers to the new version. Haven't got to the drive shafts or shocks yet.


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gt1guy said:
Where on the newest version do I see the the roll steer through wheel travel? I'm probably just being stupid.

Oh, and how does my junk look? Just started adding my numbers to the new version. Haven't got to the drive shafts or shocks yet.


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Roll steer isn't calculated. I'm not about to touch the math involved in solving in 3d space. 2d was hard enough to wrap my head around. For now.

If you are after the roll axis, it is the plots for Roll Slope (Front and Rear) and the value feed back Body Roll Axis. The former are located under the anti plots; the latter is above the center column of plots. If you are after Body Roll Axis at travel values other than ride, head to the Vehicle Pitch page.

Looks pretty good. Might benefit some from raising the rear upper frame. May be able to get away with less angling of the links in top view.
 
Here's what I was thinking of. It was in the 4barlink V3.1d, from many moons ago.

In the "travel " tab, you had two buttons you could hit for bump or droop. Then under the side view info, you could see the "x" of the tire change.

I guess "roll steer" was the wrong term to use, since what it's giving you is in two wheel bump "or" droop. But it is nice to see and by getting the full droop number, then getting the full bump number, you can figure that your fully articulated "steer" will be an exaggerated version of those two numbers.

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My vehicle currently has a 3 link front and leaf springs in the rear (chevy 63’s). The numbers for the front suspension can be seen in attached images below, and these front values will be constant/constrained for the sake of this post (as i dont want to change this currently).

With the leaf springs, the rear roll center height was measured at about 32.5” (front is about 28.125”), and this would lead to an oversteer setup.

To that point, I have been driving the vehicle to and from the trail and the truck handles incredibly well at speeds in 2 wheel drive (no unwanted or unpredictable handling characteristics at highway speeds). However, I haven’t driven many linked rear suspension vehicles and if there is room for improvement, I’m all ears (I just don’t want to link the rear, and have something that handles horribly which is my biggest fear and unknown).

During my trip to the Rubicon this summer, I noticed the rear suspension wanting to wrap and hop while on the trail (very slow speeds and in low-low 4 wheel drive), so I figured I would begin my next phase in the build which would be to 4-link the rear suspension.

My overall goals with the truck still revolve around driving to the trail, wheel the trail and then drive home. To that point, my focus of this post will initially be around the trip to and from the trail in 2 wheel drive at highway speeds, and then evolve the conversation as to what impacts the desired outcome would have on the truck in a rock crawling scenario.

When manipulating the newest 4 link calculator my focus has been primarily on the values for the roll axes. Where I’m getting torn and looking to develop a better understanding is which is more desirable for rear 2 wheel drive power transmission at highway speeds; is it more desirable to focus on the vehicle body roll and keeping this value tight (roll axis slopes upward towards the front suspension) or would it be preferred to target a very negative rear roll axis height, but develops a loose body roll axis (slopes downward towards the front suspension)?


Option 1:

A rear roll center height of 28.125” and a rear roll slope of -0.3° (Body Roll Axis = 0.02° Roll Understeer – tight)
Rear Instant Center coordinates:
x = 121.54"
z = 34.18"

Option 2:

A rear roll center height of 31.36” and a rear roll slope of -3.1° (Body Roll Axis = -1.4° Roll Oversteer – loose)
Rear Instant Center coordinates:
x = 108.38"
z = 31.43"

For these two options, the anti-squat values in a 2wd scenario is 93% and 96% respectively.
 

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Vhd44 said:
My vehicle currently has a 3 link front and leaf springs in the rear (chevy 63’s). The numbers for the front suspension can be seen in attached images below, and these front values will be constant/constrained for the sake of this post (as i dont want to change this currently).

With the leaf springs, the rear roll center height was measured at about 32.5” (front is about 28.125”), and this would lead to an oversteer setup.

To that point, I have been driving the vehicle to and from the trail and the truck handles incredibly well at speeds in 2 wheel drive (no unwanted or unpredictable handling characteristics at highway speeds). However, I haven’t driven many linked rear suspension vehicles and if there is room for improvement, I’m all ears (I just don’t want to link the rear, and have something that handles horribly which is my biggest fear and unknown).

During my trip to the Rubicon this summer, I noticed the rear suspension wanting to wrap and hop while on the trail (very slow speeds and in low-low 4 wheel drive), so I figured I would begin my next phase in the build which would be to 4-link the rear suspension.

My overall goals with the truck still revolve around driving to the trail, wheel the trail and then drive home. To that point, my focus of this post will initially be around the trip to and from the trail in 2 wheel drive at highway speeds, and then evolve the conversation as to what impacts the desired outcome would have on the truck in a rock crawling scenario.

When manipulating the newest 4 link calculator my focus has been primarily on the values for the roll axes. Where I’m getting torn and looking to develop a better understanding is which is more desirable for rear 2 wheel drive power transmission at highway speeds; is it more desirable to focus on the vehicle body roll and keeping this value tight (roll axis slopes upward towards the front suspension) or would it be preferred to target a very negative rear roll axis height, but develops a loose body roll axis (slopes downward towards the front suspension)?


Option 1:

A rear roll center height of 28.125” and a rear roll slope of -0.3° (Body Roll Axis = 0.02° Roll Understeer – tight)
Rear Instant Center coordinates:
x = 121.54"
z = 34.18"

Option 2:

A rear roll center height of 31.36” and a rear roll slope of -3.1° (Body Roll Axis = -1.4° Roll Oversteer – loose)
Rear Instant Center coordinates:
x = 108.38"
z = 31.43"

For these two options, the anti-squat values in a 2wd scenario is 93% and 96% respectively.
Click to expand...
So, I have no idea where "loose" and "tight" came from on the body roll axis. I'm guessing its because they describe the general feeling. It is far better to use the terms oversteer and understeer.

Regarding the leaf sprung rear suspension, which way does the rear roll slope slant, does it climb up going from the rear to the front or descend? And what is the left right spacing of the leafs on the axle?

To answer your questions about roll axis, the farther from flat (0°) it is, the more prominent the oversteer or understeer behavior will be. But if you are happy with how it is now, you can make it so that the linked setup has the same roll axis and center. Body and axle roll axis slopes can be targeted relatively independently of each other. Understeer is generally preferred and regarded as safer, since the car will tend to point the correct direction after it breaks traction and the steering is more predictable.

Highway manners such as lower body roll and comfortable ride stem more from the spring and shock placements and tuning and if/how a roll bar is used/needed. Roll axis and how close it is to the CG do play a big roll in how much roll is possible. IC height plays into the ride some too.

The anti-squats are on the high side, but don't seem to bad; maybe try to get it so that it never crosses over 100%, as that can make it a little odd, but since that's on the droop side of things isn't to big of a deal.

Take a look at the "Vehicle Pitch" sheet. The points of interest for rear suspension are 50% rear (hard on the gas), and 100% rear (steep climb). Try to keep these from crossing 100% as that will tend towards hop.
 
Thank you very much for the in-depth reply Treefrog. At the risk of diluting the "How's my numbers" with leaf spring talk, i try and keep that at a minimum.

Regarding the leaf sprung rear suspension, which way does the rear roll slope slant, does it climb up going from the rear to the front or descend? And what is the left right spacing of the leafs on the axle?
Click to expand...

I'm not sure how to analytically figure out the rear roll slope, but during a climb, the wrap/hop wants to push the rig up and forward
(seen in this video at about the 1:00 mark)

The spacing of the leaf springs are 40.25" on center (currently directly under the frame rails)

To answer your questions about roll axis, the farther from flat (0°) it is, the more prominent the oversteer or understeer behavior will be. But if you are happy with how it is now, you can make it so that the linked setup has the same roll axis and center. Body and axle roll axis slopes can be targeted relatively independently of each other. Understeer is generally preferred and regarded as safer, since the car will tend to point the correct direction after it breaks traction and the steering is more predictable.
Click to expand...

What impacts will it have if i focus solely on individual roll axis slopes versus the body slope? For example, if i have a rear roll slope of -3.1° which would indicate a high understeer scenario, but the overall body roll axis is -1.4° indicating a oversteer scenario and I'm not which would govern the suspension handling characteristics more?

Highway manners such as lower body roll and comfortable ride stem more from the spring and shock placements and tuning and if/how a roll bar is used/needed. Roll axis and how close it is to the CG do play a big roll in how much roll is possible. IC height plays into the ride some too.
Click to expand...

Unfortunately I have yet to identify this level of detail for the rear shock placement and i can pull details pertaining to the front later this weekend and report back.

I'm currently running Fox Factory Series DSC remote resi 12" coilovers up front with 14" 225 #/in lower coil and a 12" 150#/in upper coil. As for the rear, they are a basic 12" travel monotube IFP shock. I also do not have a front or rear anti-roll bar at this time. Packaging one in the front would be rather difficult but i wouldnt be opposed to adding one in the rear if it adds benefits to the overall suspension system performance. If there is room for improvement from a handling perspective, then I'm all ears as well, but i'm sure that would require more details from me.

Take a look at the "Vehicle Pitch" sheet. The points of interest for rear suspension are 50% rear (hard on the gas), and 100% rear (steep climb). Try to keep these from crossing 100% as that will tend towards hop.
Click to expand...

This is a cool component of the tool and one that i will become more familiar with. It looks like i would need to modify my front lower axle mounts to dictate the values to drop below the 100% suggestion of the rear performance. Hypothetically speaking, if i did not want to change the front mounts, how could i combat the affects of hopping/wrapping or to lower the values below the 100% suggested value in these graphs (whether it would be added hardware such as a rear anti-roll bar or various other points to manipulate within the calculator).

Thanks again for taking the time to help out Treefrog - I truly appreciate your input.
 
Vhd44 said:
Thank you very much for the in-depth reply Treefrog. At the risk of diluting the "How's my numbers" with leaf spring talk, i try and keep that at a minimum.



I'm not sure how to analytically figure out the rear roll slope, but during a climb, the wrap/hop wants to push the rig up and forward
(seen in this video at about the 1:00 mark)

The spacing of the leaf springs are 40.25" on center (currently directly under the frame rails)
Click to expand...

1627694355339.png

It is the slope of the 3/8L link that is equivalent to a control arm.
Vhd44 said:
What impacts will it have if i focus solely on individual roll axis slopes versus the body slope? For example, if i have a rear roll slope of -3.1° which would indicate a high understeer scenario, but the overall body roll axis is -1.4° indicating a oversteer scenario and I'm not which would govern the suspension handling characteristics more?
Click to expand...
So, 3.1° is still pretty low, if you are looking at 10 or so it is getting a little high. It should be noted that there are cars that have higher from the factory. The body axis governs what the body wants to do. The front and rear ones govern what that axle wants to do. As for what impacts focusing on individual vs body has, I'm not exactly sure. I would think that body has more to do with which end wants to hit the wall when you loose traction and that the individual dictates more how that end reacts to steering, i.e. if the axle wants to turn more than is being asked of it.
Vhd44 said:
Unfortunately I have yet to identify this level of detail for the rear shock placement and i can pull details pertaining to the front later this weekend and report back.

I'm currently running Fox Factory Series DSC remote resi 12" coilovers up front with 14" 225 #/in lower coil and a 12" 150#/in upper coil. As for the rear, they are a basic 12" travel monotube IFP shock. I also do not have a front or rear anti-roll bar at this time. Packaging one in the front would be rather difficult but i wouldnt be opposed to adding one in the rear if it adds benefits to the overall suspension system performance. If there is room for improvement from a handling perspective, then I'm all ears as well, but i'm sure that would require more details from me.
Click to expand...
Its not really needed to go after that part now. It was more about link placement is not the only factor in how it rides.
Vhd44 said:
This is a cool component of the tool and one that i will become more familiar with. It looks like i would need to modify my front lower axle mounts to dictate the values to drop below the 100% suggestion of the rear performance. Hypothetically speaking, if i did not want to change the front mounts, how could i combat the affects of hopping/wrapping or to lower the values below the 100% suggested value in these graphs (whether it would be added hardware such as a rear anti-roll bar or various other points to manipulate within the calculator).

Thanks again for taking the time to help out Treefrog - I truly appreciate your input.
Click to expand...
The front link geometry should not play that big of a roll in how the rear behaves, at least on that particular analysis. Suck down winch is one way, but from a link standpoint, it probably isn't something to target all that much. What happens is that as the slope of a climb increases, the front becomes unloaded, as the force on the spring gets lowered and shifted rearward. In the rear it gets a little more complex, as the weight comes off the front it wants to go to the rear, but at the same time, the load on the rear is also being reduced. This means that the rear may not change its loading all that much, it just appears to since the front may droop out 6+ inches. So a more accurate data point is front all the way drooped and the rear at ride. The 100% travel is just a quick thing to look at and see if something is really far off.
 
brainstorming on a project. want a 4-link but cant move the gas tank, so straight uppers outside the frame, triangulated lowers. 60% street, 30% dezert/exploration, 10% rocks.

seems like it should work alright, might have to add a sway bar to help keep things level when throwing it into a turn but on paper if the packaging works out there shouldnt be a problem. open to suggestions/input.
rearsuspension.jpg
 
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mobil1syn said:
brainstorming on a project. want a 4-link but cant move the gas tank, so straight uppers outside the frame, triangulated lowers. 60% street, 30% dezert/exploration, 10% rocks.

seems like it should work alright, might have to add a sway bar to help keep things level when throwing it into a turn but on paper if the packaging works out there shouldnt be a problem. open to suggestions/input.
Click to expand...
Looks like it should work. Only things of note are the links below the axle and that those are extremely long links. Also be aware of inward movement in articulation with the uppers.
 
Treefrog said:
Looks like it should work. Only things of note are the links below the axle and that those are extremely long links. Also be aware of inward movement in articulation with the uppers.
Click to expand...

limited by the body, so dropping the lowers made things a lot nicer. it will see very little rocks, so the link length and them being lower isnt a huge concern but you observation is noted.
 
That layout is what's called a Satchell link in certain circles. Terry Satchell was a suspension engineer at Ford for years and worked with their road racing programs.

So if you're thinking that you're off in left field with the design, it has been used successfully before. Albeit it was road racing but, with the usage you say it will see, it should be pretty sweet.

You do need to pay attention with the convergence on the lowers. There's nothing else helping with restricting the axle from lateral movement. So, the closer you can possibly be to 45* the better.
 
gt1guy said:
So if you're thinking that you're off in left field with the design, it has been used successfully before. Albeit it was road racing but, with the usage you say it will see, it should be pretty sweet.
Click to expand...

by no way is it unique, there are a handful of U4 cars out there with this setup. in a straight line, im not concerned. my concern is coming into a corner and getting some body roll and the lowers trying 'push' the car over. i will just have to make provisions for a sway bar.
 
so i just saw this thread.

here are mine. one thing i will say is it feels stable, up down left right. it just feels good for the most part.
1636051277529.png


1636051310652.png


1636051336049.png
 
chaplinfj60 said:
so i just saw this thread.

here are mine. one thing i will say is it feels stable, up down left right. it just feels good for the most part.
Click to expand...
Good to see you got it working. Since you have a driving rig, you may want to fill in some of the stuff on the "Shocks" page and see how that looks.
 
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