How's my numbers?

[Toy4rnr]

Posting up my preliminary numbers for the rear 4 link I want to do, this is as close as I can get without having the brackets in hand. Mostly the only thing that might change is frame separation of the upper links by maybe an inch. The rest should be pretty spot on based off what I have been provided by Ruffstuff as I am going to be using their brackets and upper axle mount.

Vehicle 1997 Toyota 4runner, 3.4 v6, automatic, front 65" WMS, rear 63" wms with 15x8/3.75 backspace wheels on 12.5 wides. COG is as close to the top bellhousing bolt as I could get. Frame height is 21.5-22" depending on how much fuel is in the vehicle and what not.

Current link setup is stock lengths with a panhard correction. I drive this thing on the road often to and from local trails and camp spots, below is 50% drive bias.



If I make my uppers the same length:
Anti's go to 77% droop, 48% ride height, 36.7% bump.
Pinion goes to 10* droop, 0* ride, -2.66* bump
Roll slope stays the same. Body roll axis changes to -1.1* (oversteer loose)


Looking for some guidance, I always thought anti's in the 40-60 range was best at 50% bias and I know understeer is better, but I have been playing with this thing for days and cannot get it any lower than it is.

Oh one other question, when making the links the same length, even if I have the lowers 3" forward of axle, why are they placed in the same place on the frame in the diagram?

 

[Treefrog]

Posting up my preliminary numbers for the rear 4 link I want to do, this is as close as I can get without having the brackets in hand. Mostly the only thing that might change is frame separation of the upper links by maybe an inch. The rest should be pretty spot on based off what I have been provided by Ruffstuff as I am going to be using their brackets and upper axle mount.

Vehicle 1997 Toyota 4runner, 3.4 v6, automatic, front 65" WMS, rear 63" wms with 15x8/3.75 backspace wheels on 12.5 wides. COG is as close to the top bellhousing bolt as I could get. Frame height is 21.5-22" depending on how much fuel is in the vehicle and what not.

Current link setup is stock lengths with a panhard correction. I drive this thing on the road often to and from local trails and camp spots, below is 50% drive bias.



If I make my uppers the same length:
Anti's go to 77% droop, 48% ride height, 36.7% bump.
Pinion goes to 10* droop, 0* ride, -2.66* bump
Roll slope stays the same. Body roll axis changes to -1.1* (oversteer loose)


Looking for some guidance, I always thought anti's in the 40-60 range was best at 50% bias and I know understeer is better, but I have been playing with this thing for days and cannot get it any lower than it is.

For 50% bias and antisquat, the target for a vehicle like yours is probably in the 35-45 range. You are probably fine with a little bit of oversteer. If you want it lower, you could try raising the lower axle a little bit. With the split in up vs down travel, roll slope is probably not going to be a big factor in handling.

There is no requirement to have equal length links. Are the pictures of what you are thinking of making? And you are also considering an option that uses equal uppers and lowers?

Oh one other question, when making the links the same length, even if I have the lowers 3" forward of axle, why are they placed in the same place on the frame in the diagram?

I am not sure what you mean by this.

 

[Toy4rnr]

For 50% bias and antisquat, the target for a vehicle like yours is probably in the 35-45 range. You are probably fine with a little bit of oversteer. If you want it lower, you could try raising the lower axle a little bit. With the split in up vs down travel, roll slope is probably not going to be a big factor in handling.

There is no requirement to have equal length links. Are the pictures of what you are thinking of making? And you are also considering an option that uses equal uppers and lowers?


I am not sure what you mean by this.

Thank you for the response and guidance. Would the 35-45 range be at ride height or should I try to maintain that all throughout the travel? I am at 48% currently so just a little over the higher number. As for oversteer, if -1.0 isn't bad then I am fine with it and will leave my lowers centered on the tube. I just don't have a frame of reference when looking at that number. I am sure my current numbers are horrid, the rear suspension is stock length links with a panhard drop and it has crazy axle steer at full droop.

The pictures are what I was thinking of making. I added equal length link numbers as I hear it frequently when people are building theirs. From what I remember over the last two years reading up on this stuff is the uppers can be as short as 70% the length of the lowers as a general rule of thumb. Not really, there is a mounting solution, but its too tight of a fit on my vehicle.


It is just something I noticed on the Side View and Top View seen here. Shouldn't the uppers technically be around 3" more rearward? Unrelated to my numbers, just something I noticed is all.

 

[Treefrog]

Thank you for the response and guidance. Would the 35-45 range be at ride height or should I try to maintain that all throughout the travel? I am at 48% currently so just a little over the higher number. As for oversteer, if -1.0 isn't bad then I am fine with it and will leave my lowers centered on the tube. I just don't have a frame of reference when looking at that number. I am sure my current numbers are horrid, the rear suspension is stock length links with a panhard drop and it has crazy axle steer at full droop.

Your numbers are pretty normal for a multipurpose rig. It may be a good idea to keep antis within that range in the 2-3 inches of compression. It may be worth checking to see what raising them does. Much easier in the calc than with a welder.

The pictures are what I was thinking of making. I added equal length link numbers as I hear it frequently when people are building theirs. From what I remember over the last two years reading up on this stuff is the uppers can be as short as 70% the length of the lowers as a general rule of thumb. Not really, there is a mounting solution, but its too tight of a fit on my vehicle.

Keeping the links within 30% of each other in 2d is a good rule of thumb. But it does not matter which is longer.

It is just something I noticed on the Side View and Top View seen here. Shouldn't the uppers technically be around 3" more rearward? Unrelated to my numbers, just something I noticed is all.

It looks like it is working correctly. You have 37 for the frame X for the upper and lowers. The coordinates are the location of the point relative to the ground at the center of the rear axle. They values are not relative to each other.

 

[Toy4rnr]

Your numbers are pretty normal for a multipurpose rig. It may be a good idea to keep antis within that range in the 2-3 inches of compression. It may be worth checking to see what raising them does. Much easier in the calc than with a welder.

Keeping the links within 30% of each other in 2d is a good rule of thumb. But it does not matter which is longer.

It looks like it is working correctly. You have 37 for the frame X for the upper and lowers. The coordinates are the location of the point relative to the ground at the center of the rear axle. They values are not relative to each other.

I will see what happens if I move them up a tad and report back. I think I did that earlier but it didn't have much effect and being at center line already I didn't want to sacrifice too much vertical separation. The amount I have should be plenty for 37s down the road which is the biggest tire I ever plan to go.

Ahh ok thanks for the insight.

Oh that makes sense then, I was wondering how a link 3 inches forward could land in the same place as a link on axle center line .

But if it looks pretty normal and nothing looks bad then I think I have a game plan pending the antis cant be tamed anymore. Thank you very much for the help.

 

[Toy4rnr]

Moving it up 1 inch on the axle side helped quite a bit with anti's actually. I think I will run this. There is 7.75" of vertical separation with the new axle side location. I know less separation means more stress on the brackets and what not, but that it is also better to package something that works as the 25% of tire rule is more of an ideal practice rather than a requirement.

 

[gt1guy]

Keeping the links within 30% of each other in 2d is a good rule of thumb. But it does not matter which is longer.

What you can do with link lengths is use it to fine tune your pinion angle changes, or reduce axle steer.

Everything effects everything else. So while you can make your pinion angle always perfect, you may have shitty axle steer as a result. The trick is to find a happy place for everything even though nothing will be perfect.

 

[Treefrog]

What you can do with link lengths is use it to fine tune your pinion angle changes, or reduce axle steer.

Everything effects everything else. So while you can make your pinion angle always perfect, you may have shitty axle steer as a result. The trick is to find a happy place for everything even though nothing will be perfect.

Lengths can also be used to find tune other behavior in travel, like antis.

 

[mpaine]

hello everyone, this is how my jeep is currently set up and i went wheeling with it for the first time since the build was finished. as it sits my only real complaint is the the excessive amount of body roll it has on off chamber situations. otherwise for the first time out i think it handled much better than i would have expected.

it would be great to get some feedback on my setup/numbers. i think my first change should be to widen my frame side rear lowers but after that im not sure what else i can do to fix the tipsiness.

 

[Treefrog]

hello everyone, this is how my jeep is currently set up and i went wheeling with it for the first time since the build was finished. as it sits my only real complaint is the the excessive amount of body roll it has on off chamber situations. otherwise for the first time out i think it handled much better than i would have expected.

it would be great to get some feedback on my setup/numbers. i think my first change should be to widen my frame side rear lowers but after that im not sure what else i can do to fix the tipsiness.

Do you have an anti-roll bar? Is it an issue when it's sitting off camber or is it only an issue when you start to load the drivetrain?

From a quick glance, widening the frame side lowers will not have a big affect.

There is nothing in the numbers that scream for attention for a crawler.

What follows is with the assumption that it is an issue with leaning, not drivetrain loading. You have a larger distance between the vehicle roll axis and the sprung CG. This is going to cause it to want to lean. There are only three ways to reduce the lean. Lower CG. Higher roll centers. Anti-roll bars. CG is the preferred method. Followed by anti-roll bars. And lastly by higher roll centers.

 

[mpaine]

Do you have an anti-roll bar? Is it an issue when it's sitting off camber or is it only an issue when you start to load the drivetrain?

From a quick glance, widening the frame side lowers will not have a big affect.

There is nothing in the numbers that scream for attention for a crawler.

What follows is with the assumption that it is an issue with leaning, not drivetrain loading. You have a larger distance between the vehicle roll axis and the sprung CG. This is going to cause it to want to lean. There are only three ways to reduce the lean. Lower CG. Higher roll centers. Anti-roll bars. CG is the preferred method. Followed by anti-roll bars. And lastly by higher roll centers.

Thank for the quick reply!

I do have a anti-roll bar, but it is a stock heavy duty cj bar. Which is great on road but dramatically reduces my suspension travel when flexing.

You are right with your assumption it is an issue with leaning and can be slightly better or worse when loading the drivetrain depending on which side I'm leaning on.

I was hoping the solution wouldn't be to lower the CG because that is obviously the more time consuming/more difficult thing to change

 

[Treefrog]

Thank for the quick reply!

I do have a anti-roll bar, but it is a stock heavy duty cj bar. Which is great on road but dramatically reduces my suspension travel when flexing.

You are right with your assumption it is an issue with leaning and can be slightly better or worse when loading the drivetrain depending on which side I'm leaning on.

I was hoping the solution wouldn't be to lower the CG because that is obviously the more time consuming/more difficult thing to change

It may be worth considering one or two lighter bars and leaving them connected offroad.

 

[mpaine]

It may be worth considering one or two lighter bars and leaving them connected offroad.

I have considered looking for a lighter bar. I just have very limited space, definitely no room for a front anti-roll bar and little space behind the rear axel. so I'm not sure yet how many options I have. I will probably try a bar before I start trying to lower my motor to help my CG

 

[06h3]

Here is a question that doesn't seem to be talked about much here, but force/load given at 1G. It seems super useful on the new calculator that Treefrog built. I understand that load/force is infinite. If I drive up to a wall and floor it, I can load it up till something breaks. If I lawn dart it, I will break my shit. It seems load is only calculated via weight and link design. Tire size does not play a role. Either way, it gives me an idea of the load my 3 link sees compared to others.

What is a comfortable load/force number?

I am a heavy rig (7k) and my rig sees higher loads due to weight and usually being the "broken rig" hauler when other people's shit breaks.

My 3 link broke once. It sucked and it was 100% my fault. I had my rig down and had to throw my rig together last minute for a trip and in the rush I misplaced my upper 3rd link. It was angled far too back at ride height and when drooping out it would lessen the separation. it ripped the mount off the frame, we then plated it to hell to get me through the trip, then it was breaking 9/16 grade 8 bolts and sheering 1/4in plate. I ran those numbers and it spit out 27k lbs of force given at 1G.

I redid my 3 link and prioritized seperation and strength to the max. It got the load at 1G down to 14k lbs. Significantly less than the 27k it saw when it broke.

I run 5/8 bolts now, the best of the best 1 1/4 FK rod ends. The components can handle more, and the load is less. I am confident in it now.

A friend with a lightweight 3500lb rig which is half the weight of mine, and it sees 15k of load at 1G, which is more than me, which is not surprising. Very little separation. It would 100% break if it was on my rig.

The rear usually sees more load than the front but how much more? I guess it's all subjective.


So with all that said, we are playing with imaginary numbers since load is so variable and infinite but what do you guys think is a safe number for load at 1G wth 5/8 bolts and quality 1 1/4 heims. 20k? 10K? 25k?

 

[Treefrog]

Here is a question that doesn't seem to be talked about much here, but force/load given at 1G. It seems super useful on the new calculator that Treefrog built. I understand that load/force is infinite.

Static load is finite. And is normally not the issue.

If I drive up to a wall and floor it, I can load it up till something breaks. If I lawn dart it, I will break my shit.

Send it and get send it results. FAFO and all that.

It seems load is only calculated via weight and link design. Tire size does not play a role.

That sounds right, but it might take into account bias; I haven't looked at it in a bit and can't remember. I think it does it as if a 1g acceleration is done via tire contact patch. 1g being convenient because it is easy to scale and change to negative. I believe it takes the most extreme value across all of the travel and reports/uses that for link sizing. So if you have links that are steep when the suspension extends the load goes up significantly.

Either way, it gives me an idea of the load my 3 link sees compared to others.

What is a comfortable load/force number?

I would caution against comparing forces outright. It may be better to use force/weight or to look at link factor of safeties.

I am a heavy rig (7k) and my rig sees higher loads due to weight and usually being the "broken rig" hauler when other people's shit breaks.

My 3 link broke once. It sucked and it was 100% my fault. I had my rig down and had to throw my rig together last minute for a trip and in the rush I misplaced my upper 3rd link. It was angled far too back at ride height and when drooping out it would lessen the separation. it ripped the mount off the frame, we then plated it to hell to get me through the trip, then it was breaking 9/16 grade 8 bolts and sheering 1/4in plate. I ran those numbers and it spit out 27k lbs of force given at 1G.

I redid my 3 link and prioritized seperation and strength to the max. It got the load at 1G down to 14k lbs. Significantly less than the 27k it saw when it broke.

I run 5/8 bolts now, the best of the best 1 1/4 FK rod ends. The components can handle more, and the load is less. I am confident in it now.

A friend with a lightweight 3500lb rig which is half the weight of mine, and it sees 15k of load at 1G, which is more than me, which is not surprising. Very little separation. It would 100% break if it was on my rig.

1g is 22 mph/s. Hit that rock doing 10mph and you might see 4+g. That force goes from 27k to 108k+ fast.

The rear usually sees more load than the front but how much more? I guess it's all subjective.

I would not make that assumption. The rear doesn't often take an impact.

So with all that said, we are playing with imaginary numbers since load is so variable and infinite but what do you guys think is a safe number for load at 1G wth 5/8 bolts and quality 1 1/4 heims. 20k? 10K? 25k?

That requires looking at the bolt shear strength.

 

[snivilous]

I had asked on dezert rangers a long time ago what design accelerations to use for an IFS long travel setup, and one dude recommended 10G frontal, 5G vertical, 3G lateral. Different use case and take it with a grain of salt, but food for thought.

 

[06h3]

Static load is finite. And is normally not the issue.

Send it and get send it results. FAFO and all that.

That sounds right, but it might take into account bias; I haven't looked at it in a bit and can't remember. I think it does it as if a 1g acceleration is done via tire contact patch. 1g being convenient because it is easy to scale and change to negative. I believe it takes the most extreme value across all of the travel and reports/uses that for link sizing. So if you have links that are steep when the suspension extends the load goes up significantly.


I would caution against comparing forces outright. It may be better to use force/weight or to look at link factor of safeties.

1g is 22 mph/s. Hit that rock doing 10mph and you might see 4+g. That force goes from 27k to 108k+ fast.

I would not make that assumption. The rear doesn't often take an impact.

That requires looking at the bolt shear strength.

I saw on one of your calculators that there was a load at travel # but I cant find that file. Was it in an older one and you took it away?

I can see the case of the rear seeing less load due to the control arm angles reacting in favor of the load path (naturally wants to push the bars up to less angle) where the front wants to push against the links and can cause them to push down and make the angle steeper. Or maybe I am looking at it wrong.

I had asked on dezert rangers a long time ago what design accelerations to use for an IFS long travel setup, and one dude recommended 10G frontal, 5G vertical, 3G lateral. Different use case and take it with a grain of salt, but food for thought.

Thanks for that, so far I have used, well my friends #'s at 1G hasnt fallen apart yet so I think mine will be fine comparsion

 

[Treefrog]

I saw on one of your calculators that there was a load at travel # but I cant find that file. Was it in an older one and you took it away?

It should still be available. Check the history tab on the resource. I don't remember if 5.x had separate or if you will have to go with 4.x. You may want to check the change log for whatever version you are using, there were some changes to how some stuff was calculated, but I don't know what off the top of my head.

I can see the case of the rear seeing less load due to the control arm angles reacting in favor of the load path (naturally wants to push the bars up to less angle) where the front wants to push against the links and can cause them to push down and make the angle steeper. Or maybe I am looking at it wrong.

I want to say half wrong. Typically the rear sees more acceleration force, while the front will see more impact forces over the vehicle life. As for how it pushes the links, it depends on the IC. And up may not be less angle. I think it's best to think that the forces on a link are direction independent, at least off-road.

Thanks for that, so far I have used, well my friends #'s at 1G hasnt fallen apart yet so I think mine will be fine comparsion

The default FOS values on the link sizing tab were sourced from another forum. I cited it somewhere but I think it was NC4x4. A FOS of 6 at 1g is the same as a FOS of 1 at 6 g. And that's for the max force.

 

[06h3]

Anyone want to flame me on link #'s. The front has been the same for about 2 years. It works, its a big heavy full bodied rig and I think for being its size and weight it works awesome.

I have been on leafs in the rear for well over 10 years. Factory H3 leafs, sprung over, with an anti wrap bar. I just finished linking it. I will admit, I had limitations, I wasnt willing to go through the cab to place coilovers and I wasnt willing to lose the factory tank at the moment (that may change after I use this setup) I was very confined to the spaces I had.

So with all that said, its still a little ways away from driving but do you think this setup will work worse or better then a set of leafs? Or how will it act differently than a set of leafs? I know it will deflect way less becasue the leafs would still wrap even with an anti wrap bar if I loaded up the rear while not being squared up on ledges. IIgnore the anti squat numbers, I forgot to put the upper frame side link back to what it was, I just looked and changing the frame side upper link value ONLY changes anti squat, not roll center or slope. I was messing with frame side upper link placement and have adjustability with multiple holes. Thoughts on where to go? I can be over 100% or in the 60% range. It’s a rock crawler that still does desert stuff and goes on the highway but prioritizing rock crawling and ledges.

I assume the consensus will be, get your axle side track bar mount higher. What does that net me? Stability? I know it’s top heavy compared to Jeeps but my roll center to COG ratio is 62% is that something to look at and how does that compare to a rig at any height

 

[Treefrog]

Anyone want to flame me on link #'s. The front has been the same for about 2 years. It works, its a big heavy full bodied rig and I think for being its size and weight it works awesome.

I have been on leafs in the rear for well over 10 years. Factory H3 leafs, sprung over, with an anti wrap bar. I just finished linking it. I will admit, I had limitations, I wasnt willing to go through the cab to place coilovers and I wasnt willing to lose the factory tank at the moment (that may change after I use this setup) I was very confined to the spaces I had.

So with all that said, its still a little ways away from driving but do you think this setup will work worse or better then a set of leafs? Or how will it act differently than a set of leafs? I know it will deflect way less becasue the leafs would still wrap even with an anti wrap bar if I loaded up the rear while not being squared up on ledges.

It is hard to say how it will do compared to the leafs. There are so many variables involved for that comparison.

IIgnore the anti squat numbers, I forgot to put the upper frame side link back to what it was, I just looked and changing the frame side upper link value ONLY changes anti squat, not roll center or slope.

That would be correct for a 3 link.

I was messing with frame side upper link placement and have adjustability with multiple holes. Thoughts on where to go? I can be over 100% or in the 60% range. It’s a rock crawler that still does desert stuff and goes on the highway but prioritizing rock crawling and ledges.

Generally, less than 50% is what I recommend when drive bias is 50%. Lower is better for desert, closer to 50% can accelerate faster and will stay flatter.

I assume the consensus will be, get your axle side track bar mount higher. What does that net me? Stability? I know it’s top heavy compared to Jeeps but my roll center to COG ratio is 62% is that something to look at and how does that compare to a rig at any height

A high roll center will lean less, but will give less warning for a roll. A higher roll center will be less stable since there is a higher force pointing away from the surface.

 

[06h3]

It is hard to say how it will do compared to the leafs. There are so many variables involved for that comparison.

That would be correct for a 3 link.

Generally, less than 50% is what I recommend when drive bias is 50%. Lower is better for desert, closer to 50% can accelerate faster and will stay flatter.

A high roll center will lean less, but will give less warning for a roll. A higher roll center will be less stable since there is a higher force pointing away from the surface.

Any suggestions for change in my setup?

 

['84 Bronco II]

Any suggestions for change in my setup?

I didn't say anything when I read your build thread because it looked like you had everything finalized, buuut since you're asking here...

I understand that you have a lot of packaging contraints, but you rear anti-squat is too high, mostly because of the angle on your lower links; that's why you had to get so much separation at the frame to get back to a reasonablish anti-squat number. As Treefrog mentioned, for a crawler, under 50% antisquat is a good place to be, but that number is going to depend a ton on your CG height input.

I realize your Hummer is tall, but I think your 45" COG estimate is way too high which is lowering the Anti squat values the calculator is outputting (EDIT: My "way too high" statement was based on you mentioning 79% in your thread, obviously your calculator numbers posted here are way lower because of your frame side separation and your unrealistically high COG input). In reality, your antisquat numbers are probably much higher. What your steep lower link angles and high anti-squat are going to do is cause the rear end to jack and hop on steep climbs whereas a lower anti-squat will stay planted and put down traction. It will also ride a lot harsher than flatter links with lower anti-squat values.

I know you are concerned about separation and the forces the links are putting on the mounts, but I would raise the axle-side lower link mount to at least the axle centerline. This will help flatten the lower link, improve your flex steer, lower your antisquat, and give you more ground clearance. This still probably wont be enough though and I would make your lowers a bit longer. It looks like you could extend the lowers and inboard them to the crossmember just ahead of where you have them mounted on the frame now. In addition to getting them flatter from the additional length, inboarding the lower frame mounts will improve clearance and help reduce flex steer. Your ~10° lower link angle sucks, try to get it as close to zero as you can without making your frame side lower mounts rock anchors. I mentioned flex steer a few times because your current design has a lot, giving it a tendancy towards oversteer which can feel squirrely.

Obviously changes you make to your lowers are going to affect what you need to do with your upper link to maintain a good pinion angle through travel and get your anti squat where you want it. If you know someone with corner scales that can handle the weight of your rig, getting an accurate COG height will help you out a lot, otherwise keep a good bit of adjustability in your upper mounts. I understand your upper is probably where it is due to space constraints, but there is no need for any triangulation in the upper and the closer you can get the frame and axle mounts to the center of the vehicle, the better to avoid asymmetric forces on the chassis which can cause suspension performance quirks.

Your rear panhard is another big issue. The angle is very steep which is going to transmit more force into the chassis (suspension harshness) and result in a lot of lateral axle movement which can cause clearance/binding issues for driveshafts, shocks, and tires. The lateral movement can also make it feel unsettled at speed with large suspension movements. You have your ride height modeled at mid travel which means you want your tack bar flat at ride height. You need to raise the axle side mount, lower the frame mount, or a combination of the two. The easiest move looking at your setup at this point would be to lower the frame side mount, but that will lower you roll center; however, a sway bar can easily fix that issue. You would have to relocate your bumps and/or upper link mount, but if you could get the track bar on the back side of the axle so that you are not trying to go under your upper link, you could potentially raise your axle-side mount quite a bit and extend the track bar as close to the passenger rear wheel as you can which will also help the static angle as well as the angle change/lateral shift through travel.

One last thought not related to the calculator, but still related to your new rear suspension setup, is there any way you could get your coilovers outboard on the frame? This has a few advantages: you could tuck them up in your wheel well so the don't have to hang down so low (presuming your tires will clear), the lower mount could get a lot closer to the wheel which helps clearance if you do have to hang them below the axle, and lastly it will improve stability and reduce body roll and torque twist significantly over your inboarded setup.

 

[06h3]

Between your post and mine it exceeded the max characters.

It was quiet over there, so I figured some were biting their tongue, but I have thick skin. I can take a flaming about how I am a fucking idiot who can't build suspensions, but at the same time, give the reason so when someone else reads my build thread in 10 years from now, they can learn. I spent too much time reading 15 year old threads wading through "OP doesnt know shit" to find the 2-3 solid answers on WHY OP doesn't know shit.

I will go comment by comment but first start off by saying that I appreciate the input, am willing to make changes (at this point after I drive it) and am committed to this rig so I will make the changes as I see fit. I have redone my 3 link front a couple times, gone through numerous coil spring, shocks/shock tuning and ultimately to coilovers, axle swaps, changing link locations etc. so I just want people to know the advice won't fall on deaf ears and is a waste of time as people type stuff out to give me advice. With all that said, any changes won't be immediate since it is brand new. I will also say, building a link suspension in a weekend has its pros and cons, pros: its done fast! Cons: hindsight is 20/20 so I may see things differently after. I had a friend fly out, we worked our asses off and accomplished a lot but in order to do that we couldn't ponder much. So anyways, thank you for the solid input, I do truly appreciate it.

Ok, on to business.

Lower link angle. In reality I could have gone further back and use a shorter link bracket, but link angle is 7* at ride height, I thought it wasn't terrible. Jake Burkey on busted knuckle rock rods tech videos says keep it under 10*. I thought that was under 10* at ride height, maybe he meant at its steepest angle? Either way, it is something I can change in the future if it is problematic. I can say that I CANT inboard my links unless I ditch the factory tank and if I ditch the factory tank then I will go with a 4 link. While all the pics were on the pass side, the factory tank is on the driver side and is right up against the frame rail so inboarding is a no go, and trust me, if I could, I would have, I saw benefits to inboarding my lower links up front when I did that. I wish I could.

I will touch base on a few topics here. Anti squat, upper link placement, and COG. One of the few things I had going for me in this build is that the H3 has a metric fuck ton of room for frame side upper link placement. I could place (2) 4 hole brackets on top of each other and still have room to cut up a 3rd one and have a total of 10 holes so the adjustability is basically infinite in my opinion. I threw in my COG all the way down to 30 for reference (which I highly doubt it is) and I can still get it under 100% with my current layout. I would be willing to put in the work to find my true COG. Heres some info on COG, think thats the correct formula?





So, I am not concerned on Anti Squat, I am very confident I can get it right, I just need to know what my true COG is so I can accurately place the link on the frame side. As for axle side upper link placement it wasnt really for anti-squat, it was a priority that I am placing this upper link bracket as high as I can to reduce load off the upper link, I would figure out anti squat later and it just so happens that going up that much helped my anti squat.

As for track bar, yeah. I agree 100%, of course I wish it was flatter. I would have to go back and look; I can't remember if I could put it over the upper link. I may have room for it. I was stoked that I was having a 41in long track bar, I asked a few others with 3 link rears and it was longer than anyone else, but I guess it doesn't matter because it sits at 13* angle at ride height. I vividly remember having it longer then it was and it ran into the upper link because they travelled at different planes. The quick answer was shorten it a few inches, if we had more time, maybe we would have chosen other options. Anyways, I can't lower my frame side in its current position because it would hit the 3rd member at full bump. I could potentially bring my axle side over the upper link. The reason I didnt go behind the axle is because the coilovers were there. I see that 4WU puts their track bar behind the axle and the coilovers behind the axle. From pics it looks like to do that they put GIANT coilover mounts to space the coilovers far off the axle tube. I didn't want that kind of leverage on something that holds my vehicle up, especially because I weigh quite a bit more than a toyota. So thats why the track bar went behind the axle. Admittedly I am nervous about rock crawling performance with the coilovers and links in big boulder canyons. In the canyons my leafs were sprung over, the mount was short and tucked up way higher on the frame side then the links, I had nothing below the axle tubes. Leafs worked awesome there but then on ledges, even with an anti wrap bar, I felt the power wouldnt hit the ground immediately, the springs wanted to wrap in certain situations and loads. So this brings me to the next topic of outboarding. I was concerned that outboarding would cause clearance issues. My framerail is very wide. Off of memory it is 43in wide. My axle WMS (with spacers) is 69in wide. It is something I will consider though. I felt like we just wrote it off because of how wide my axle is. Id be curious if my coilovers are mounted wider then a TJ just because my frame is that much wider compared to a TJ with outboarded coilovers. Probably not apples to apples but I would be curious. They are angled back and inboard compared to the axle so I hope the inboard frame side does provide some stability because of the direction they are going.

Readers digest version: Maybe I could put the axle side track bar up above the upper link, or get it back behind the axle and live with giant pain in the ass hanging 12in behind the axle tube coilover mounts or go behind the axle, put coilovers outboard and in the cab and on top of the axle tube but dont really wanna go in the cab.

One last question, my COG to roll center, I want predictability and stability, is there a percentage between the two for that? It seems the higher the roll center, the more stable it is but the less predictable it is?

I think I covered it all. I really do appreciate all the insight and would be interested in any other opinions from others or comments from you on this.

 

[Treefrog]

but I think your 45" COG estimate is way too high

For an H3 on 43s, it seems pretty reasonable. If not slightly low. Though I haven't looked at the build thread to be more sure.

Your ~10° lower link angle sucks, try to get it as close to zero as you can without making your frame side lower mounts rock anchors. I mentioned flex steer a few times because your current design has a lot

10 is pretty reasonable for a trail rig. Flatter is better, but belly height matters too.

there is no need for any triangulation in the upper and the closer you can get the frame and axle mounts to the center of the vehicle, the better to avoid asymmetric forces on the chassis which can cause suspension performance quirks.

Agreed on no triangulation, but properly out-boarded is better. IF, and it's a big if, done properly you can cancel out torque rolling.

 

[Treefrog]

I thought that was under 10* at ride height, maybe he meant at its steepest angle?

I'm pretty sure all of his advice except for pinion angle is at ride height.

I can still get it under 100% with my current layout

100% anti with what drive bias? Because with the 50% drive bias you currently have in the calculator, you would want the anti squat below 50%. The older advice of below 100% is for the older calculator that bias 100% to the rear.

Heres some info on COG, think thats the correct formula

I think it looks right but don't have time to dig into it. There is an easier way. Measure weight split flat, use tape to mark a vertical line on the vehicle at the balance point. Elevate one end, weigh and mark balance line again. Where they cross is the CG.

One last question, my COG to roll center, I want predictability and stability, is there a percentage between the two for that? It seems the higher the roll center, the more stable it is but the less predictable it is?

Higher percentage is going to lean less off camber, but a higher roll center has handling downsides and it's better to use an anti-roll bar to reduce leaning.

 

[06h3]

So you think its better to lower the frame side mount then raise the axle side?

I think with the COG and anti squat, I will just play with the holes I have see where it feels right, I have enough room and adjustability there that I know it can be dialed in perfectly by messing with it.

I think the bigger issues I will have to deal with is roll center, stability and track bar angles.

Edit: Under 100% with 0% drive bias or under 50% with 50% drive bias. I am confident I can keep it under those numbers with the amount of adjustability I have or changes Id have to make, I have a ton of room to play with there.

 

[mano002]

I have always heard that you can use the top bolt of your bellhousing as the COG for a truck. We used some scales and lifted 2 wheels with a hoist and calculated the height of the COG and it calculated out to.... the top bolt of the bellhousing. So I would go and measure that height and use that as a good guestimate of COG.

 

[06h3]

Funny how that worked out. I used the top of the bellhousing bolt. They say for aluminum blocks and aluminum heads use center of crankshaft and top of the bellhousing for iron blocks and iron heads. I have an aluminum block and heads but since I am a more top heavy rig naturally I went the top of the bellhousing

 

['84 Bronco II]

link angle is 7* at ride height, I thought it wasn't terrible. Jake Burkey on busted knuckle rock rods tech videos says keep it under 10*. I thought that was under 10* at ride height, maybe he meant at its steepest angle?

7-10° gets thrown around as a limit at ride height depending who you talk to, but really, those are rules of thumb. Flatter is better for suspension performance. I was calculating 10° based off the numbers in the spreadsheet you posted, but if you're actually at 7°, maybe it is not as bad as I thought, but still on the steep side.

One last question, my COG to roll center, I want predictability and stability, is there a percentage between the two for that? It seems the higher the roll center, the more stable it is but the less predictable it is?

As far as "predictability," that is totally driver preference. Having a higher roll center reduces body roll and gives more seat of the pants stability when off camber or cornering hard, but some drivers prefer more body roll because it gives more feedback as to how hard they are pushing the car. Reducing body roll does have the real performance benefit of reducing weight transfer to the outside/downhill tires, but without going to extreme ends of the spectrum, it isn't really going to change the cornering/sidehill performance of the vehicle significantly, just how stable the driver perceives the vehicle to be. Too much antiroll is less "predictable" because the driver gets less feedback via body roll before the vehicle falls over.

I seem to remember someone suggesting sub 40% anti roll for desert racing, 40-60% for general purpose rigs, and 60+% for crawlers, but again, what is right for you is going to be driver preference to a large extent as well as packaging constraints. You could build adjustment in your track bar mounts like your upper link mounts to tune it some if you have the space.

For an H3 on 43s, it seems pretty reasonable. If not slightly low. Though I haven't looked at the build thread to be more sure.

Maybe it is, but it's not a Florida mudtruck, so it seemed high to me. Most of the stuff I have measured has been in the 30-40" range.

but belly height matters too

Yes, but not as much as a lot of people think. Generally the perfomance benefits that come from the stability of lower belly heights outweigh the drawbacks of a low belly. Most modern buggies with 42/43" tires are being built with sub-20" belly heights, which is lower than my Bronco II on 37" tires. Obviously, it is hard to stay very low with big tires on a full-bodied rig.

done properly you can cancel out torque rolling.

And if done improperly can exacerbate it. Kind of like the old advice about putting the upper 3rd link on the passenger side instead of the driverside on a front axle, but that also depend on the upper link angle.

Higher percentage is going to lean less off camber, but a higher roll center has handling downsides and it's better to use an anti-roll bar to reduce leaning.

True, but in a pure crawler application, you want all the roll center height you can get, just look at the old 3-Link comp cars. For high-speed desert racing, you want a really low roll center so the axle isn't pivoting around the vehicle. For 06H3's purposes, I think his rig has more of a crawler bias.

So you think its better to lower the frame side mount then raise the axle side?

If you want a lower roll center, but I think a higher axle mount would work better for you, especially if you want to avoid packaging a sway bar too.

I have an aluminum block and heads but since I am a more top heavy rig naturally I went the top of the bellhousing

That is pretty reasonable then if that's how you came up with 45". It just seemed really tall to me.

 

[Ghetto Fab.]

True, but in a pure crawler application, you want all the roll center height you can get, just look at the old 3-Link comp cars. For high-speed desert racing, you want a really low roll center so the axle isn't pivoting around the vehicle. For 06H3's purposes, I think his rig has more of a crawler bias.

Seems like they are getting away from that. I haven't noticed a track bar on any recent buggy builds. No doubt they are the one group that wouldn't notice the drawbacks though. I think the current trend is only really tall because everyone of those guys is running portal housings. It would be interesting to pick someone like Jessie's brain on that though.