How's my numbers?

[Fawth]

Hi Guys,
New builder here, building a westcoast crawler with my dad and son and looking for a little insight on our numbers. Its a back halfed JK with an LS th400 and Atlas t-case and dana 60 axles, 41.5" tires, 117.5 wheelbase 37" COG. The axle mounts cant move but I can move the front frame mounts around to suit better numbers if required. The upper link range to work with at the frame can be between X=33-36" Y=16.75" Z=25-27.5" and the lower link range at the frame is X=37-41" Y=15.75 Z=21-22.5". As for the rear I'm fixed with the upper frame mount X and Y value but have two options for Z=25" or 29.25" and I'd like to leave the axle end alone, the lowers at the axle are welded already but at the frame I have some movement, X=42.5-47" Y=16.5" Z=21-22.75".
If anyone has some input on what to change it would be greatly appreciated.

 

[Treefrog]

Hi Guys,
New builder here, building a westcoast crawler with my dad and son and looking for a little insight on our numbers. Its a back halfed JK with an LS th400 and Atlas t-case and dana 60 axles, 41.5" tires, 117.5 wheelbase 37" COG. The axle mounts cant move but I can move the front frame mounts around to suit better numbers if required. The upper link range to work with at the frame can be between X=33-36" Y=16.75" Z=25-27.5" and the lower link range at the frame is X=37-41" Y=15.75 Z=21-22.5". As for the rear I'm fixed with the upper frame mount X and Y value but have two options for Z=25" or 29.25" and I'd like to leave the axle end alone, the lowers at the axle are welded already but at the frame I have some movement, X=42.5-47" Y=16.5" Z=21-22.75".
If anyone has some input on what to change it would be greatly appreciated.

Most eye catching things are the front AD being high, front pinion travel is rather high. Your ICs are not that long. Usually its better if they are a bit longer. Roll slopes seem fine, especially for a crawler.

Just guessing that raising the frame uppers will help a bit.

A side note, your overall vehicle weight seems like it may be on the lower side of what would be typical. It is generally best practice to do the math with the vehicle as it would be on the trail, or a bit over that, not unloaded in the garage.

It is also a bit odd that your front and rear unsprung weights are the same. Disregard if it is rear steer and no water in the front tires.

In the front you may need to watch for engine clearance with the upper axle Y being somewhat small.

The newer versions of the calculator have additional features that may come in handy if you are able to use them.

 

[Fawth]

Thanks Treefrog, I’m assuming the ICs you’re referring to are the Instant Center? Or is it the lower control arms? I’ll mess with some more numbers tomorrow and try and get it a little more dialed. As for roll centre is it bad to have that below my COG? If it’s undesirable I suppose I could always add a sway bar after she gets some use.

 

[Treefrog]

Thanks Treefrog, I’m assuming the ICs you’re referring to are the Instant Center? Or is it the lower control arms?

Instant center.

I’ll mess with some more numbers tomorrow and try and get it a little more dialed. As for roll centre is it bad to have that below my COG? If it’s undesirable I suppose I could always add a sway bar after she gets some use.

Roll centers are normally below the COG. I don't know of any rigs outside of maybe a moon buggy that would anywhere close to having the sprung cg below the roll center.

 

[Fawth]

I made a few changes to lengthen the IC and wondering if this looks like an overall better setup than previous? Also forgot to mention it is going to be a 4WS rig. Thanks again for taking the time to check out my specs

 

[Treefrog]

I made a few changes to lengthen the IC and wondering if this looks like an overall better setup than previous? Also forgot to mention it is going to be a 4WS rig. Thanks again for taking the time to check out my specs

From a quick glance, not seeing anything that stands out in a bad way.

 

[DangerNoodle]

Hey, new guy to this forum, looking for some advice on numbers. Currently working dual triang 4-linking the of my FJ40, 37s-39s, 100" WB, FJ80 axles, TT LF4, 8l90, atlas. I brive this thing a lot on the road, and handling hasn't been too much of an issue. I go slow-moderate pace on trails. Front is currently 3-linked and i'm looking to make some changes there as well, as I need to adjust my upper for more engine clearance with this new swap. I'm hoping to not move much on the front, but it has been giving me a lot of unloading issues on the front with big climbs. It basically completely unloads and I get no traction on the fronts. I'm currently on a 70/30 lowers-upper. No idea how to fix this issue with geometry, would love some help there.

Rear is a fresh start from SOA. Frame side lowers are about 14" apart, and I can't really change that. Everything else is fair game. I'm shooting for good road manners if possible, but I would perfer it to better offroad.

Thanks in andvance!

 

[Treefrog]

Hey, new guy to this forum, looking for some advice on numbers. Currently working dual triang 4-linking the of my FJ40, 37s-39s, 100" WB, FJ80 axles, TT LF4, 8l90, atlas. I brive this thing a lot on the road, and handling hasn't been too much of an issue. I go slow-moderate pace on trails. Front is currently 3-linked and i'm looking to make some changes there as well, as I need to adjust my upper for more engine clearance with this new swap. I'm hoping to not move much on the front, but it has been giving me a lot of unloading issues on the front with big climbs. It basically completely unloads and I get no traction on the fronts. I'm currently on a 70/30 lowers-upper. No idea how to fix this issue with geometry, would love some help there.

Rear is a fresh start from SOA. Frame side lowers are about 14" apart, and I can't really change that. Everything else is fair game. I'm shooting for good road manners if possible, but I would perfer it to better offroad.

Thanks in andvance!

That is not a common engine.

Before I comment on the numbers, The unloading is a spring/shock issue more than a geometry issue. A suck down winch is probably going to be the answer.

If you can move the front upper link, there are ways to reduce or negate torque roll in a 3-link. There are some details on it in the linked suspension bible. Check post 1 of this thread for the link.

Most of the numbers look ok. It switching between vehicle oversteer and understeer may not be the most desirable, but may be hard to avoid. For a street going rig, its generally better to have roll understeer than oversteer. But you are still pretty close to neutral.

Front Pinion changes angle a bunch. Not in the bad direction, but it is still quite a bit for the front.

You can relax the triangulation in the rear if you need to.

 

[DangerNoodle]

That is not a common engine.

Before I comment on the numbers, The unloading is a spring/shock issue more than a geometry issue. A suck down winch is probably going to be the answer.

If you can move the front upper link, there are ways to reduce or negate torque roll in a 3-link. There are some details on it in the linked suspension bible. Check post 1 of this thread for the link.

Most of the numbers look ok. It switching between vehicle oversteer and understeer may not be the most desirable, but may be hard to avoid. For a street going rig, its generally better to have roll understeer than oversteer. But you are still pretty close to neutral.

Front Pinion changes angle a bunch. Not in the bad direction, but it is still quite a bit for the front.

You can relax the triangulation in the rear if you need to.

Hey Frog, thanks a ton for the input! Do you have any good readings for info about mitigating the effects of the unloading with springs / shocks. I'm running some king 2.0s valved and sprung by Ben at filthy motorsports. They ride super well, but the unloading kills me on climbs. I watch a lot of guys walk stuff that I cant in similar rigs.

I wanted something pretty unique for this build, and the LF was the way it seemed, lol. Fun little engine for sure, but I don't think I've ever heard of anyone else running it in a 4x4 swap.

I'm planning on lengthening the upper front,so that should help with pinion angle, I think. I dug through the link bible, but i didn't see a bunch on upper placement. I'll dig again and see if I can find any more. Is vertical seperation on the frame side of things necessary, or is it better to keep it closer to the same?

I have a ton of space in the rear, so I think I'll keep the extra triangulation unless you think there is a reason not to.

Again, thanks so much for taking the time to look though this and help. I really appreciate it!

 

[Treefrog]

Hey Frog, thanks a ton for the input! Do you have any good readings for info about mitigating the effects of the unloading with springs / shocks. I'm running some king 2.0s valved and sprung by Ben at filthy motorsports. They ride super well, but the unloading kills me on climbs. I watch a lot of guys walk stuff that I cant in similar rigs.

I do not. I know that as the hill gets steeper, the less weight on the front. You may need to go with a suck down winch.

I wanted something pretty unique for this build, and the LF was the way it seemed, lol. Fun little engine for sure, but I don't think I've ever heard of anyone else running it in a 4x4 swap.

Given the narrow range of production, probably a reason they aren't common.

I'm planning on lengthening the upper front,so that should help with pinion angle, I think. I dug through the link bible, but i didn't see a bunch on upper placement. I'll dig again and see if I can find any more. Is vertical seperation on the frame side of things necessary, or is it better to keep it closer to the same?

Just looked through the bible, and I didn't see it at quick glance. My bad. I guess I had wanted to do more reading on it before I posted about it.

I have a ton of space in the rear, so I think I'll keep the extra triangulation unless you think there is a reason not to.

Again, thanks so much for taking the time to look though this and help. I really appreciate it!

There is some stuff in the Bible about roll steer, post 116. There is some other stuff before that, but I doubt the validity of how I went about gathering the data.

 

[broken4_racing]

Hey Guys, Looking for some tips on my numbers. Planning out a new build, will be an Ultra4 4500 car. No streets. WB is 114 and I think the rest of the numbers are in there. Biggest issue I am finding is that to raise my AL/AD I am reducing the frame vertical link separation. On my last car I followed the 75% of the axle separation rule. So with 9.5" at the axle, I should be around 7". But at 7" the AL/AD is just too low. For this type of car I am shooting for 40-50 with a 50% Drive Bias. Thanks for any and all help!

 

[Treefrog]

Hey Guys, Looking for some tips on my numbers. Planning out a new build, will be an Ultra4 4500 car. No streets. WB is 114 and I think the rest of the numbers are in there. Biggest issue I am finding is that to raise my AL/AD I am reducing the frame vertical link separation. On my last car I followed the 75% of the axle separation rule. So with 9.5" at the axle, I should be around 7". But at 7" the AL/AD is just too low. For this type of car I am shooting for 40-50 with a 50% Drive Bias. Thanks for any and all help!

That's a real flat AS curve. Not often someone manages to do that.

It is highly recommended to design front and rear at the same time. Maybe keep an eye on the front pinion angle change since that is the same as caster change.

For 4500, the calculator can do panhard suspensions.

 

[broken4_racing]

That's a real flat AS curve. Not often someone manages to do that.

It is highly recommended to design front and rear at the same time. Maybe keep an eye on the front pinion angle change since that is the same as caster change.

For 4500, the calculator can do panhard suspensions.

Thanks Treefrog. Definitely a guideline, just dropping all the way to a 5" separation seems like alot.

Thats what i have been shooting for. Real flat and around 40-50. Any suggestions on keeping that but increasing the frame separation? Just worried the forces will get too high with such little separation.

The front is the correct draft design. I am doing a 4 link front. Ill either run cables or a bellcrank steering system to meet the rules for 4500.

 

[Treefrog]

Thanks Treefrog. Definitely a guideline, just dropping all the way to a 5" separation seems like alot.

Thats what i have been shooting for. Real flat and around 40-50. Any suggestions on keeping that but increasing the frame separation? Just worried the forces will get too high with such little separation.

You can move it down to where you want the geometry and then move the point up the link. Though that will affect travel. Its up to you if you want to increase separation in exchange for less desirable geometry during travel. There is an argument to be made that you have very little traction at down travel and will spend very little time at full bump. That said, pay attention to the white line in the side view. The IC is where the forces go. The effective separation changes during travel. The calculator also reports the max force in each link for the given acceleration.

Take a look at the first part of this post. It doesn't directly help, but the concepts should. December's Bible Build: Linked Suspensions

The front is the correct draft design. I am doing a 4 link front. Ill either run cables or a bellcrank steering system to meet the rules for 4500.

Hopefully there will be a build thread.

 

[broken4_racing]

You can move it down to where you want the geometry and then move the point up the link. Though that will affect travel. Its up to you if you want to increase separation in exchange for less desirable geometry during travel. There is an argument to be made that you have very little traction at down travel and will spend very little time at full bump. That said, pay attention to the white line in the side view. The IC is where the forces go. The effective separation changes during travel. The calculator also reports the max force in each link for the given acceleration.

Take a look at the first part of this post. It doesn't directly help, but the concepts should. December's Bible Build: Linked Suspensions

Hopefully there will be a build thread.

Ah, ok i think i follow that. So basically if i shorten the upper links along the designed line (once I am happy), I can increase separation without effecting the design. My only concern with that is that I will end up with some pretty short links haha

My only thing about the acceleration, I that I really have no idea the range of acceleration that will be seen. Especially with racing.

Yup, there will definitely be a build thread.

For an Ultra4 car, what should I be shooting for in regards to AS? Since it see's desert, rock crawling etc. My thoughts are closer to the rock crawling of 80-100 and then the desert wont be quite as good, but better than bad in the rocks.

 

[Treefrog]

Ah, ok i think i follow that. So basically if i shorten the upper links along the designed line (once I am happy), I can increase separation without effecting the design. My only concern with that is that I will end up with some pretty short links haha

Correct. And you can adjust upper and lower links at both ends.

My only thing about the acceleration, I that I really have no idea the range of acceleration that will be seen. Especially with racing.

Generally best to leave it at 1. Makes it easy to scale and keep track of when look at stuff link link sizing.

Yup, there will definitely be a build thread.

Looking forward to it.

For an Ultra4 car, what should I be shooting for in regards to AS? Since it see's desert, rock crawling etc. My thoughts are closer to the rock crawling of 80-100 and then the desert wont be quite as good, but better than bad in the rocks.

I think around 30-50 is preferred. Most cars seem to try to have flatter links. Better in the desert and not bad in the rocks.

 

[broken4_racing]

Correct. And you can adjust upper and lower links at both ends.

Generally best to leave it at 1. Makes it easy to scale and keep track of when look at stuff link link sizing.

Looking forward to it.

I think around 30-50 is preferred. Most cars seem to try to have flatter links. Better in the desert and not bad in the rocks.

Leaving it 1 will really only allow me to compare different setups correct? Not actually analyze what the car will see in a race.

Sorry, I was talking back in the 100% rear bias days lol. Yes 30-50 with the 50% front bias.

 

[Treefrog]

Leaving it 1 will really only allow me to compare different setups correct? Not actually analyze what the car will see in a race.

Pretty much. It scales the forces on the links, but that's all.

Sorry, I was talking back in the 100% rear bias days lol. Yes 30-50 with the 50% front bias.

I'm thinking that the trend is probably 20-40 or lower accounting for bias. Most still talk like bias isn't accounted for.

 

[93blackxj]

Leaving it 1 will really only allow me to compare different setups correct? Not actually analyze what the car will see in a race.

Sorry, I was talking back in the 100% rear bias days lol. Yes 30-50 with the 50% front bias.

I wouldn't sacrifice that much separation or upper link length to gain a little AS/AD. As tree said, I think the 20-40 range with 50/50 bias is a good baseline. Your pinion angle change is already pretty extreme and shortening the uppers is only going to make that worse unless you take them further back on the axle. I think a little more separation at the frame would help this some too.

 

[broken4_racing]

I wouldn't sacrifice that much separation or upper link length to gain a little AS/AD. As tree said, I think the 20-40 range with 50/50 bias is a good baseline. Your pinion angle change is already pretty extreme and shortening the uppers is only going to make that worse unless you take them further back on the axle. I think a little more separation at the frame would help this some too.

I agree. I wont be shortening the uppers. My latest revision puts the AS at 28% with 50% bias or 55% with 0% bias. and this was only by increasing my separation to 7". This helped my pinion angle too.

 

[93blackxj]

I agree. I wont be shortening the uppers. My latest revision puts the AS at 28% with 50% bias or 55% with 0% bias. and this was only by increasing my separation to 7". This helped my pinion angle too.

You could also add some adjustment at the uppers with a hole 1" lower if you want the option to increase the AS to see what works better. Like tree said, the 75% of axle separation is just a guide line to get you close.

 

[broken4_racing]

You could also add some adjustment at the uppers with a hole 1" lower if you want the option to increase the AS to see what works better. Like tree said, the 75% of axle separation is just a guide line to get you close.

That's the plan lol. I am going 1.5" lower though. With 3/4" bolts, 1/4" of meat between the holes just isn't enough. Thinking I am going to do 26" and 27.5". That gives me 41% and 28% AS respectively with 50% Bias.

 

[RustyC]

Thanks to everyone that keeps the calculator progressing. This is my first build using the calculator.
Jeep LJ, intended for street and trail use. Main focus is keeping the on road negative performance to a minimum.
Looking for input on antis and roll center / slope and torque roll being the front upper link is on the left side. AC compressor and exhaust prevent it from being on the right side. I tried to move things around a bit to get to this point.
Is the positive to negative swing of the roll slope through the travel a big issue?

 

[Treefrog]

Thanks to everyone that keeps the calculator progressing. This is my first build using the calculator.
Jeep LJ, intended for street and trail use. Main focus is keeping the on road negative performance to a minimum.
Looking for input on antis and roll center / slope and torque roll being the front upper link is on the left side. AC compressor and exhaust prevent it from being on the right side. I tried to move things around a bit to get to this point.
Is the positive to negative swing of the roll slope through the travel a big issue?

The positive-negative swing is pretty normal, and practically unavoidable.

The torque roll is up to you. If you're fine with it, it's not a huge concern. With how flat your upper link is, it shouldn't be over exaggerated. If you want to reduce it some, you can try to get the upper link lower at the axle than at the frame.

 

[06h3]

Amazing work you have done here Treefrog

I have estimates of my front 3 link and a projected rear 3 link but will confirm when I get home from a work trip then post it.

With that said, is there a way to calculate load on the front upper link under acceleration in 4x4? I am concerned about the load my rear upper link would see and as of right now it says the front upper link would see more load but that’s under braking, I know my new 3 link is strong and isn’t braking under forward movement when rock crawling but I don’t think I have done any sudden panic stops to mimic max load

 

[Treefrog]

Amazing work you have done here Treefrog

I have estimates of my front 3 link and a projected rear 3 link but will confirm when I get home from a work trip then post it.

With that said, is there a way to calculate load on the front upper link under acceleration in 4x4? I am concerned about the load my rear upper link would see and as of right now it says the front upper link would see more load but that’s under braking, I know my new 3 link is strong and isn’t braking under forward movement when rock crawling but I don’t think I have done any sudden panic stops to mimic max load

It should be the same force, just different direction.

 

[06h3]

Ok, here’s what I have on my front 3 link and what I have “projected” for a rear 3 link. I have a story with it.

So, critique away. When you read the front and have a critique read my essay first. I may have answered it lol a lot of time and effort went into trying to maximize a number of factors in an extremely confined space. Anyways, I think my front roll axis is too high. Not sure I can do much about it but I’ll take any and all critiques. A few notes on my front. I have just over 48k miles on my SAS, it was a daily driver for a few years, it’s been through a few 3 link renditions, it’s been well over 80 mph in its current form on the freeway for an hour or more at a time and feels fine. My last rendition was axle end separation, I have a ton of separation for a SAS H3. There’s about 20 of us and I doubt any have more than 8in of separation and I have over 10 and a lot of work went into that. I needed it because the load of 43s were breaking bolts and cracking 1/4in plate.

Up travel, I am at 5in, I can get more but at the sacrifice of ride height. I can confidently say for up travel and ride height I have more uptravel then most SAS H3s, and/or a lower ride height. It can’t really change without crane modification. Track bar mods can probably be made. I can easily adjust frame side upper distance to ground.

Rear, my main concern is strength. I do not want to break and my fear is how much load will go through that upper link. I can basically move my upper frame side link another 5 in up or down for anti squat # I want.

I can do a triangulated 4 link and get any number I want, there’s so much space by removing the fuel tank and doing a fuel cell behind the rear axle between the frame rails. I do not like the hassle of doing a new fuel tank, the cost and the negative performance hs I f all that weight behind the rear axle but if my 3 link is so hindered I can figure out a fuel solution.

So is the rear 3 link a disaster waiting to happen? FWIW, my current setup is factory H3 leafs sprung over and an anti wrap bar, hopefully the performance is improved.

 

[Treefrog]

Front and rear roll slopes are a bit high, but not abnormal for a tall rig. Easiest way to get them down is to raise your trackbars or have the lower's converge more. Pros and cons to both options.

Your CG height seems a bit low for an H3 on 43s.

If you are worried about strength, why not do a 4 link with panhard? Only big thing to worry about is using bushings instead of heims. Or put the rig on a diet.

Antis are probably a bit high. But if the CG is higher than what you have, they will go down.

 

[06h3]

Front and rear roll slopes are a bit high, but not abnormal for a tall rig. Easiest way to get them down is to raise your trackbars or have the lower's converge more. Pros and cons to both options.

Your CG height seems a bit low for an H3 on 43s.

If you are worried about strength, why not do a 4 link with panhard? Only big thing to worry about is using bushings instead of heims. Or put the rig on a diet.

Antis are probably a bit high. But if the CG is higher than what you have, they will go down.

I thought my CG seemed low too. Doesn’t it auto calculate that on this calculator? If not I’ll adjust it.

Good point, my H3 may be low compared to other H3s but it’s still tall compared to all rigs, on the rear I have the ability to raise my track bar axle end, the front, I can get 1in up but I’ll have to notch the frame.

What’s the pro/con between converging lowers vs track bar? Is it strictly packaging or does it change other things?

The pro to the 3 link (or double triangulated 4 link) is that I have so much room for anti squat adjustment. I can basically have a bracket with 10 holes in it and get what I want. The 4 link with panhard I’d have to run the uppers on the outside of the framerail like the JKs have and I’d have very little adjustment. The anti squat would be what it is. Like typical JKs I have seen anti squat would be over 100% and I don’t want that.

So I was thinking 3 link and make sure I have it strong as hell so it can’t break or double triangulated 4 link and get the near perfect setup numbers wise (and strength) but at the expense of cost (new fuel tank behind the rear axle) departure angle (since it’s now behind the rear axle) and weight placement (for rocks I’ve seen the negative side effects of weight behind the rear axle) so ignoring cost, do I end up with a worse setup having a worse departure angle and weight placement even though I’m getting better numbers.

I have as much room as I need for separation to lessen load on the rear.

 

[Treefrog]

I thought my CG seemed low too. Doesn’t it auto calculate that on this calculator? If not I’ll adjust it.

The overall cg at ride is an input, it calculates the cgs that it needs from that.

Good point, my H3 may be low compared to other H3s but it’s still tall compared to all rigs, on the rear I have the ability to raise my track bar axle end, the front, I can get 1in up but I’ll have to notch the frame.

What’s the pro/con between converging lowers vs track bar? Is it strictly packaging or does it change other things?

In your case, the pros would be a flatter roll axis.
The general con would be the axle steering through travel. The more triangulated the lowers the more steering.