How's my numbers?

[Treefrog]

Looks like its time we need this, I was hoping it would take a bit longer, but I guess its a sign that builds are being done.

So, for those asking about how their suspension numbers check out, throw it here. Preferably in the form of a screenshot of the calculator. Just trying to keep the bible and calculator threads less cluttered.


Link to the linked suspension bible: December's Bible Build: Linked Suspensions

Link to the link calculator thread: New Version of the 4 Link Calculator

Link to link calculator download: https://irate4x4.com/resources

 

[Sterlingfire]

Can anyone say sticky?

 

[Lil'John]

I'll bite. This is for a low profile FJ55 Land Cruiser(think first gen s10 blazer in size):

This is front link for maybe 1-2" of lift for 35" tires with 60" WMS axles. I think the weight is probably a bit over estimated.

Intended use is driving to Rubicon on Wentworth and playing in the rocks. No high speed wheeling.

 

[Treefrog]

I'll bite. This is for a low profile FJ55 Land Cruiser(think first gen s10 blazer in size):

This is front link for maybe 1-2" of lift for 35" tires with 60" WMS axles. I think the weight is probably a bit over estimated.

Intended use is driving to Rubicon on Wentworth and playing in the rocks. No high speed wheeling.

Yeah, the weight may be a bit high. The sprung CG also seems very high. Looking at the geometry, it seems that they panhard may have the axle and frame ends reversed, not that it makes much difference at ride height. And I'm assuming you have the upper link on the passenger side?

Getting to the results, Triaged's 3-link calculator is set up for the rear, so the roll slope signs are inverted when used for the front, so you are looking at slight oversteer. Also, since front wheel, the antisquat is actually antidive, and after accounting for brake bias, your looking at more like 30%. And when the CG ends up being lower antidive will be higher.

Getting into how it will behave, with the numbers given, the front may want to wander a bit, and its gonna have body roll like a drunk on a tightrope. Also, its likely to have lots of bump steer. I haven't crunched the numbers yet, so I can't give a definite answer, but non parallel lower links are going to change the axle heading as it travels. As far as the ride goes, it will be pretty smooth, but will have a tendency to pitch a fair bit when braking and will want to lift a little when climbing.

Sorry if I am typing stuff you already know, someone who doesn't know will eventually see this and I don't want to make them walk away confused.

 

[Lil'John]

Yeah, the weight may be a bit high. The sprung CG also seems very high. Looking at the geometry, it seems that they panhard may have the axle and frame ends reversed, not that it makes much difference at ride height. And I'm assuming you have the upper link on the passenger side?

Getting to the results, Triaged's 3-link calculator is set up for the rear, so the roll slope signs are inverted when used for the front, so you are looking at slight oversteer. Also, since front wheel, the antisquat is actually antidive, and after accounting for brake bias, your looking at more like 30%. And when the CG ends up being lower antidive will be higher.

Getting into how it will behave, with the numbers given, the front may want to wander a bit, and its gonna have body roll like a drunk on a tightrope. Also, its likely to have lots of bump steer. I haven't crunched the numbers yet, so I can't give a definite answer, but non parallel lower links are going to change the axle heading as it travels. As far as the ride goes, it will be pretty smooth, but will have a tendency to pitch a fair bit when braking and will want to lift a little when climbing.

Sorry if I am typing stuff you already know, someone who doesn't know will eventually see this and I don't want to make them walk away confused.

My best guestimate is the weight is somewhere in the 500 to 1000lbs too much... I lost a lot of body/glass as well as engine weight... but I gained ~400lbs in axle weight. The CG was a "educated" guestimate... the general rule of thumb I was given was to use the cam button for height. I pulled that number off an existing rig.

For the panhard bar, the way it was explained is the Z height was "critical" in the middle of the bar while the angle and length should be the same as the tie rod. Frame mount is on the driverside. The explanation on bump steer was that the shorter the panhard bar compared to the tie rod, the worse the bump steer would be.

The upper link is probably going to end up on the driver side... the axle is passenger side drop and there was going to be packaging issues with upper link on the passenger side.

For the body roll, the style of rig already has a bad case without a sway bar when using a soft suspension. I found that out with my leaf sprung version of same rig Crap your pants death sway when going 50mph+ and hit a bump in the road.

The follow up question I would have is: what happens if I shorten the links but maintain the Geometry Summary numbers?

 

[Treefrog]

My best guestimate is the weight is somewhere in the 500 to 1000lbs too much... I lost a lot of body/glass as well as engine weight... but I gained ~400lbs in axle weight. The CG was a "educated" guestimate... the general rule of thumb I was given was to use the cam button for height. I pulled that number off an existing rig.

For the panhard bar, the way it was explained is the Z height was "critical" in the middle of the bar while the angle and length should be the same as the tie rod. Frame mount is on the driverside. The explanation on bump steer was that the shorter the panhard bar compared to the tie rod, the worse the bump steer would be.

The upper link is probably going to end up on the driver side... the axle is passenger side drop and there was going to be packaging issues with upper link on the passenger side.

For the body roll, the style of rig already has a bad case without a sway bar when using a soft suspension. I found that out with my leaf sprung version of same rig Crap your pants death sway when going 50mph+ and hit a bump in the road.

The follow up question I would have is: what happens if I shorten the links but maintain the Geometry Summary numbers?

Taking the CG as is then. And 500 lbs adds up real quick when you start carrying gear,

I would recommend raising the panhard up, packaging allowing, to try to get the roll down.

Any difference in length or angle will cause bump steer.

Try to get the upper to the passenger side if at all possible. My understanding is that when on the drivers side it adds to body roll.

I would suggest outboarding springs and shocks as much as possible to help with roll as well.

Shortening the links results in more drastic changes to the geometry throughout travel.

 

[vetteboy79]

Try to get the upper to the passenger side if at all possible. My understanding is that when on the drivers side it adds to body roll.

This gets into something that usually is overlooked when just playing the numbers game.

When the front axle has traction, the upper link is in compression (think: the pinion wants to wrap down, and the upper link keeps that from happening). Usually due to packaging the upper link ends up having a bit of upward angle toward the chassis, so the net effect is that there's an upwards vector pushing on the chassis, generating that lift.

What also happens when the vehicle has traction is the chassis generally wants to lift the driver side as a reaction to the driveshaft torque (driver side motor mount is in tension/passenger side in compression). So an upper link on the driver side will add to this; an upper link on the passenger side will counteract it. (note - this only applies when the front axle is being powered and has traction)

Keeping the upper link as flat as possible will minimize that contribution, likewise if you have a way to package the link on the driver side with a downward angle to the chassis, it can be helpful.

The same is true for the rear, although in the opposite way. The pinion wants to rotate up under power so the upper link(s) are in tension. It's more common for the rear to be a 4/5 link so that force usually ends up being symmetrical.

My old XJ had a good example of what ends up happening with the upper being on the driver side. It mostly worked well, but in some cases you could really feel it - here are two pictures:

What happened here is it really got bound up trying to climb the front passenger tire over that rock. It was already leaning off-camber to that side to begin with, and when you're applying torque and the vehicle isn't moving, it rotates the chassis more to the passenger side, and then now with the driver side drooped out the upper link has even more of an angle to push on the chassis to rotate it even more. Felt sketchy as shit.

That kind of behavior isn't really quantified in the AS/AD numbers because the vehicle isn't accelerating, there isn't weight transfer happening. It's just a result of static torque being applied to the system.

 

[vetteboy79]

For comparison, here's what that one looked like:

Like mentioned above, I'd try to get the roll axis angle to a positive number. From a 2WD/street driving standpoint this setup worked excellent and had very little roll and no perceivable bumpsteer.

 

[No way]

I built the rear link on my Zuk within the limits of stock wheelbase etc. It transformed that car completely.

Now, building a buggy by less class rules I want to fit 4-links both ends. It'll crawl most of the time and likely never run faster than 35mph.
Front is just playing with numbers at this stage as I don't yet know ho much space I'll need for the engine and all.
I want this thing to be compact and low which on Mogs and 40"s will be a challenge. My goal is to not make it any taller than my Zuk on 35"s
Guesstimating a lot of things at this stage and the chassis will largely be built around the axles and tires.

 

[Lil'John]

I guess I should have included the graphic

The low/no lift puts the lower links almost flat while the upper is actually at a downward angle

vetteboy79, from your graphic, it looks like your upper is angled same direction as your lower. I'm not sure if my upper angled "opposite" will produce a different effect.

As someone noted, packaging is an issue for me on the upper. If I wanted it on the passenger side, it ends up about 2-3 inches inbound of the center of the diff. I'd have to double check but I believe that the upper bracket also ends up at the trasfercase output.

 

[Treefrog]

vetteboy79, from your graphic, it looks like your upper is angled same direction as your lower. I'm not sure if my upper angled "opposite" will produce a different effect.

As someone noted, packaging is an issue for me on the upper. If I wanted it on the passenger side, it ends up about 2-3 inches inbound of the center of the diff. I'd have to double check but I believe that the upper bracket also ends up at the trasfercase output

It will attempt to move the side of the frame that has the panhard. This will result in more side to side movement of the axle. Mounting it on the other side dulls this effect. Are you sure that you are unable to package it on the passenger side? Perhaps on top of the diff or outboard of the frame.

 

[Treefrog]

I built the rear link on my Zuk within the limits of stock wheelbase etc. It transformed that car completely.



Now, building a buggy by less class rules I want to fit 4-links both ends. It'll crawl most of the time and likely never run faster than 35mph.
Front is just playing with numbers at this stage as I don't yet know ho much space I'll need for the engine and all.
I want this thing to be compact and low which on Mogs and 40"s will be a challenge. My goal is to not make it any taller than my Zuk on 35"s
Guesstimating a lot of things at this stage and the chassis will largely be built around the axles and tires.

What imediatly sticks out is that your lower links will be snag happy at the axle end. Don't be afraid of having higher axle side mounts than frame side mounts. The frame side links also seem rather close, but that just means they need to be sturdy. The only thing I can suggest is shortening the uppers to try and get better travel behavior, but for slow speed it will work. It will have a tendency to squat less when climbing, which may not be bad.

Mind if I ask which version you are using? There are some issues with travel in 4.0 to 5.2.

 

[Lil'John]

It will attempt to move the side of the frame that has the panhard. This will result in more side to side movement of the axle. Mounting it on the other side dulls this effect. Are you sure that you are unable to package it on the passenger side? Perhaps on top of the diff or outboard of the frame.

I was set to do passenger side but ran into issues:

Sadly, nobody makes a mini-truss for the Dodge D60. I was also unsure how to reinforce it. But as noted, part of the issue is engine placement(oil filter) I'm going to stuff the axle under the rig and see how things line up before I fully decide drive/pass for upper link.

 

[No way]

What imediatly sticks out is that your lower links will be snag happy at the axle end. Don't be afraid of having higher axle side mounts than frame side mounts. The frame side links also seem rather close, but that just means they need to be sturdy. The only thing I can suggest is shortening the uppers to try and get better travel behavior, but for slow speed it will work. It will have a tendency to squat less when climbing, which may not be bad.

Mind if I ask which version you are using? There are some issues with travel in 4.0 to 5.2.

Lowers are getting bolted to the flange on the Mog housing so I'm actually expecting them to help prevent snag at that spot, at least going forward.

You mean the f.s.are too close on vertical separation? I can probably fix that.

The posted pic was from v. 5.2.


Appreciate your input, thanks

 

[Treefrog]

Lowers are getting bolted to the flange on the Mog housing so I'm actually expecting them to help prevent snag at that spot, at least going forward.



You mean the f.s.are too close on vertical separation? I can probably fix that.

The posted pic was from v. 5.2.


Appreciate your input, thanks

It's not that they are too close, it's just that they are close.

Are you locating the axle housing centerline at 20 inches from the ground? One of the current limitations of the calc. is that it can't show an offer housing. Easiest way around that is too add 2x the portal height to the tire diameter and the portal height to the rolling radius. Doing this will provide a better visual of the links in regards to the axle tubes.

 

[No way]

It's not that they are too close, it's just that they are close.

Are you locating the axle housing centerline at 20 inches from the ground? One of the current limitations of the calc. is that it can't show an offer housing. Easiest way around that is too add 2x the portal height to the tire diameter and the portal height to the rolling radius. Doing this will provide a better visual of the links in regards to the axle tubes.

Yeah, I just remember reading somewhere that the calculator would not be able to account for portals and to just add numbers as if it were for a straight axle.

The portals provide a 4" lift. Should I set tire diameter to 48" and rolling radius to 24" ?

 

[Treefrog]

Yeah, I just remember reading somewhere that the calculator would not be able to account for portals and to just add numbers as if it were for a straight axle.

The portals provide a 4" lift. Should I set tire diameter to 48" and rolling radius to 24" ?

Yeah, at least to make it visually correct. The portals reduction boxes affect the results some, and unfortunately I don't have an answer as to how much.

 

[No way]

Yeah, at least to make it visually correct. The portals reduction boxes affect the results some, and unfortunately I don't have an answer as to how much.

They do add another element to the equation

Plus, just to fawk things up even more, I'm setting about 5 degrees of rake to the portals. I'm just gonna ignore all that and get my numbers acceptable as if the portals weren't there.

 

[Treefrog]

They do add another element to the equation

Plus, just to fawk things up even more, I'm setting about 5 degrees of rake to the portals. I'm just gonna ignore all that and get my numbers acceptable as if the portals weren't there.

5* changes the height less than 0.5%. That's not a bad approach.

 

[Vhd44]

Here is my current project. The build is a 2001 Tacoma with 63" Chevy leaf springs in the rear, and a 3-link and panhard up front. The front coilovers are 12" travel, 2.5" Fox. The up-travel is currently set for about 5" of up travel and the static frame height below the front body mount is currently 28". The goal of this rig is to be able to drive to the Rubicon, wheel the Rubicon, and drive home (mountain drive with speed limits up to 65 MPH, covering about about 120 road miles round trip). The numbers are currently what is set up (Guesstimation for the COG and Weight).

 

[Treefrog]

Here is my current project. The build is a 2001 Tacoma with 63" Chevy leaf springs in the rear, and a 3-link and panhard up front. The front coilovers are 12" travel, 2.5" Fox. The up-travel is currently set for about 5" of up travel and the static frame height below the front body mount is currently 28". The goal of this rig is to be able to drive to the Rubicon, wheel the Rubicon, and drive home (mountain drive with speed limits up to 65 MPH, covering about about 120 road miles round trip). The numbers are currently what is set up (Guesstimation for the COG and Weight).

Numbers look fine. It would probably be a good idea to figure out the rear roll center height and make sure that the front roll center is higher. Roll center is probably the only value that isn't difficult to calculate.

 

[Wilson]

I guess I should have included the graphic


The low/no lift puts the lower links almost flat while the upper is actually at a downward angle

vetteboy79, from your graphic, it looks like your upper is angled same direction as your lower. I'm not sure if my upper angled "opposite" will produce a different effect.

As someone noted, packaging is an issue for me on the upper. If I wanted it on the passenger side, it ends up about 2-3 inches inbound of the center of the diff. I'd have to double check but I believe that the upper bracket also ends up at the trasfercase output.

if you can actually build that, I think that it will be decent. I moved away from crunching numbers, to design parameters (which you hit) curiosity always got me and I plugged numbers, once built. Unfortunately I have never gotten the opportunity to test my designs.

My critique would be to make the upper a few inches longer than the lower as it helps keep the pinion and caster in check. The negative roll axis is good. Triangulating the lowers is the easiest way to do it as the pan hard is co-dependent upon the steering box.

 

[Treefrog]

if you can actually build that, I think that it will be decent. I moved away from crunching numbers, to design parameters (which you hit) curiosity always got me and I plugged numbers, once built. Unfortunately I have never gotten the opportunity to test my designs.

My critique would be to make the upper a few inches longer than the lower as it helps keep the pinion and caster in check. The negative roll axis is good. Triangulating the lowers is the easiest way to do it as the pan hard is co-dependent upon the steering box.

You can keep pinion in check with a longer lower too. Lowers that are longer than uppers keep antis in check as well

 

[Vhd44]

Numbers look fine. It would probably be a good idea to figure out the rear roll center height and make sure that the front roll center is higher. Roll center is probably the only value that isn't difficult to calculate.

Thank you for the reply! I measured out the roll center of the rear based on the diagram that you provided, and it looks like my rear roll center height is about 4" higher than the front roll center height (rear measured about 32.5" from ground). I'll be courious to see how this feels when driving the rig (i'm assuming that with the rear roll center height being higher than the front roll center height, it will have some oversteer effects on the handling of the truck).

 

[Treefrog]

Thank you for the reply! I measured out the roll center of the rear based on the diagram that you provided, and it looks like my rear roll center height is about 4" higher than the front roll center height (rear measured about 32.5" from ground). I'll be courious to see how this feels when driving the rig (i'm assuming that with the rear roll center height being higher than the front roll center height, it will have some oversteer effects on the handling of the truck).

You assume correctly. It will have a bit of oversteer

 

[Lil'John]

if you can actually build that, I think that it will be decent. I moved away from crunching numbers, to design parameters (which you hit) curiosity always got me and I plugged numbers, once built. Unfortunately I have never gotten the opportunity to test my designs.

My critique would be to make the upper a few inches longer than the lower as it helps keep the pinion and caster in check. The negative roll axis is good. Triangulating the lowers is the easiest way to do it as the pan hard is co-dependent upon the steering box.

I've checked upper link placement and it is doable.

My friend who gave me the numbers has done at least two front linked on same style rig... this one is #3 and I've got long term project that will be #4 ;) He's also done numerous FJ40s. I trust his numbers and the feedback I got here confirmed my expectations.

 

[Wilson]

I've checked upper link placement and it is doable.

My friend who gave me the numbers has done at least two front linked on same style rig... this one is #3 and I've got long term project that will be #4 ;) He's also done numerous FJ40s. I trust his numbers and the feedback I got here confirmed my expectations.

Don, right?

 

['84 Bronco II]

Numbers look fine. It would probably be a good idea to figure out the rear roll center height and make sure that the front roll center is higher. Roll center is probably the only value that isn't difficult to calculate.

Stupid question, but I assume that the line determining the roll center height between the forward mounting point of the leaf and the frame mounting point of the shackle would be in the same spot for an inverted shackle setup since the spring and shackle are still "swinging" about the same axis?

 

[Treefrog]

Stupid question, but I assume that the line determining the roll center height between the forward mounting point of the leaf and the frame mounting point of the shackle would be in the same spot for an inverted shackle setup since the spring and shackle are still "swinging" about the same axis?

I believe so. I'm not very knowledgeable when it comes to leaf setup.

 

[Snowracer]

looking for second opinion on this for my current buggy set up. Front and rear are almost the same numbers so not sure if having my anti squat/anti dive numbers in the mid 40s is good as was always under the impression closer to 100 was better. so flame away as it is tuesday