How's my numbers?

essentially the front will body roll less than the rear due to the roll center % compared to COG. High roll center less need for sway bar, low roll center more need for sway bar.

Having a sway bar on a race car is good regardless, you will probably have a lighter one up front is guess
 
06h3 said:
essentially the front will body roll less than the rear due to the roll center % compared to COG. High roll center less need for sway bar, low roll center more need for sway bar.

Having a sway bar on a race car is good regardless, you will probably have a lighter one up front is guess
Click to expand...
So the closer the roll center number is to the cog, the less body roll?

In my case the cog I estimated is 36 and front roll axis is 31.5 and rear roll axis is 26.3? When moving link locations what changes roll axis?
 
Malburg114 said:
Would moving the frame end and a lower roll slope be a bad thing? I had plans to run the rear upper link mount with an adjustable mount to be able to move it up or down an inch or so.
Click to expand...
Probably not. Adjustability is a good idea.
Malburg114 said:
Does link length play a role into any of this? I have the option to shorten or length them some but will change the pivot point and my understanding is cause the need for more slip in the driveshaft as the pivot point changes

I watched the video from busted knuckle you sent me last night. While some of it I need to go back and rewatch but seems the front roll center can be corrected with a front sway bar which I was already planning on running and one in the rear.
Click to expand...
Link length's role is to limit how much everything changes as the suspension moves.

I won't say how it will change driveshaft plunge. I will say that the maximum and minimum lengths from the calculators driveshaft tab is the longest and shortest it can reach for almost every setup.
Malburg114 said:
So the closer the roll center number is to the cog, the less body roll?
Click to expand...
The closer to the CG the smaller the rolling torque. Overall body roll also depends on stuff like where the springs are.

The downside to a higher CG is that the axle swings farther to the side.
Malburg114 said:
In my case the cog I estimated is 36 and front roll axis is 31.5 and rear roll axis is 26.3? When moving link locations what changes roll axis?
Click to expand...
The line between the convergence points of the upper links and the lower links is the roll axis. The roll center, the height you are asking about, is where that line crosses over where the wheels touch the ground. For a track bar, it's the center of the track bar instead of the upper link
 
Ok, after 2 years of not being able to do this project, I double checked all my measurements with my brackets in hand and came up with the following for my rear 4 link. This will be a street/trail vehicle. My old measurements had some oversteer, I am now seeing 2.7* understeer which I hear is preferable. Hoping to get some feedback before I bust out the plasma and get to work. New calc is very nice also! Thanks for any input! This is a 1997 Toyota 4runner on 35s currently, will eventually go up to 37s (maybe).
1747504419462.png
 
Toy4rnr said:
Ok, after 2 years of not being able to do this project, I double checked all my measurements with my brackets in hand and came up with the following for my rear 4 link. This will be a street/trail vehicle. My old measurements had some oversteer, I am now seeing 2.7* understeer which I hear is preferable. Hoping to get some feedback before I bust out the plasma and get to work. New calc is very nice also! Thanks for any input! This is a 1997 Toyota 4runner on 35s currently, will eventually go up to 37s (maybe).
1747504419462.png
Click to expand...
The 2.7* is for the vehicle's slope, not the rear suspension's. The text placement is needs reworked, but the rear suspension roll slope is the upper right of the 4 smaller plots. It is 2.6 degrees as designed. I would recommend lowering the antis as well. In theory it is pro-lift at the moment. Generally, your use case should be targeting 30-40% and below 50% throughout travel with the drive bias set to 50%.

I would suggest seeing if you can raise the uppers at the frame and make them wider at the axle.

What is the front suspension? IFS?
 
Treefrog said:
The 2.7* is for the vehicle's slope, not the rear suspension's. The text placement is needs reworked, but the rear suspension roll slope is the upper right of the 4 smaller plots. It is 2.6 degrees as designed. I would recommend lowering the antis as well. In theory it is pro-lift at the moment. Generally, your use case should be targeting 30-40% and below 50% throughout travel with the drive bias set to 50%.

I would suggest seeing if you can raise the uppers at the frame and make them wider at the axle.

What is the front suspension? IFS?
Click to expand...
Thanks for the input I forgot with 50% bias I want below 50% AS. I raised the lower axle side mount to adjust AS. Thanks for pointing me to the roll slope chart. It is still in positive territory through about 1" of up travel which I think is what I want for driving on the road (less darty). I raised the axle side lower bracket up one inch to fix the AS.

I cannot widen the lower axle mounts any more, its a toyota axle and they're basically on the very limit of how wide i can go, I'll have about 1" for a nut in their current configuration. The upper frame side cannot go much higher either, I would not be able to weld the top side of the bracket if I went any higher so they must stay.

Edit: It's solid axle up front with radius arms.
1747576163046.png
 
Toy4rnr said:
Thanks for the input I forgot with 50% bias I want below 50% AS. I raised the lower axle side mount to adjust AS. Thanks for pointing me to the roll slope chart. It is still in positive territory through about 1" of up travel which I think is what I want for driving on the road (less darty). I raised the axle side lower bracket up one inch to fix the AS.

I cannot widen the lower axle mounts any more, its a toyota axle and they're basically on the very limit of how wide i can go, I'll have about 1" for a nut in their current configuration. The upper frame side cannot go much higher either, I would not be able to weld the top side of the bracket if I went any higher so they must stay.

Edit: It's solid axle up front with radius arms.
Click to expand...
I would put the info for the front in so that the vehicle roll slope is accurate.

Positive oversteer is not the end of the world, and 1* is likely to be very tolerable.

I would recommended widening the axle uppers. As it is you have more convergence angle than needed, and straighter uppers tend to have less flex steer. You may want to consider lowering the axle uppers to get flat links as well. It will help with antis, roll center, and roll slope.
 
Treefrog said:
I would put the info for the front in so that the vehicle roll slope is accurate.

Positive oversteer is not the end of the world, and 1* is likely to be very tolerable.

I would recommended widening the axle uppers. As it is you have more convergence angle than needed, and straighter uppers tend to have less flex steer. You may want to consider lowering the axle uppers to get flat links as well. It will help with antis, roll center, and roll slope.
Click to expand...
Here is the front also, the calculator gets a little weird sometimes and stops changing values after filling in some fields so I had to do it a couple times. I think it might be I am filling in values too fast without having it update. I double checked my upper axle side bracket and fixed that, it helped a little, I also moved the frame side lower brackets in a half inch per side. I also lengthened the rear links out a bit which helped everywhere.
1747585729398.png




If I move the lower axle side mount up to the axle center line my as goes to 43%, 41.4%, 42.4% (compressed, ride, droop) and my roll slope goes down to 0.7. I don't really have many other options. This will have 6.25" of separation as opposed to 6.75" above. I can always beef up the brackets. I will be using 9/16" Grade 8 bolts.
1747585965334.png
 
Toy4rnr said:
Here is the front also, the calculator gets a little weird sometimes and stops changing values after filling in some fields so I had to do it a couple times. I think it might be I am filling in values too fast without having it update. I double checked my upper axle side bracket and fixed that, it helped a little, I also moved the frame side lower brackets in a half inch per side. I also lengthened the rear links out a bit which helped everywhere.


If I move the lower axle side mount up to the axle center line my as goes to 43%, 41.4%, 42.4% (compressed, ride, droop) and my roll slope goes down to 0.7. I don't really have many other options. This will have 6.25" of separation as opposed to 6.75" above. I can always beef up the brackets. I will be using 9/16" Grade 8 bolts.
Click to expand...
Either one should do well for the intended use. I would lean towards the one with more spacing.
 
Treefrog On the link sizing stuff, how biblical is it? I'm getting a value of 5.03 for my front upper link stretching with a 2x.250 tube and 1.25" heims. Reccommended value is 15, so it seems that being at 33% of the recommended value is sketchy.
 
DocRamsay said:
Treefrog On the link sizing stuff, how biblical is it? I'm getting a value of 5.03 for my front upper link stretching with a 2x.250 tube and 1.25" heims. Reccommended value is 15, so it seems that being at 33% of the recommended value is sketchy.
Click to expand...
It's hard to say, but my gut says that it is probably fine. I got the default values from another 4x4 forum and I think they may be meant for forces at ride. I seem to remember the calculator uses most extreme force across the travel range. How much force does it say is going through the link?
 
Treefrog said:
It's hard to say, but my gut says that it is probably fine. I got the default values from another 4x4 forum and I think they may be meant for forces at ride. I seem to remember the calculator uses most extreme force across the travel range. How much force does it say is going through the link?
Click to expand...
14,667lbs of maximum force.
 
06h3 said:
Correct. so your best case to get 10in of separation and keep your AS in the 80s is to lower your frame side lowers.

Also to get less Antisquat change through travel is to make your uppers shorter than your lowers.

If you can’t lower your frame side lower mounts then you live with high AS OR low separation.

I’ve tried em all but ballistic joints. Johnny joints, flex joints from parts Mike, Barnes joints, ruffstuff heims, Barnes heims, I kill em all. The only ones that stay in good shape is FK JMX16T. Pricey but they are good.

With that said, I’m 7k lbs, on 43s, have a 110:1 crawl ratio through an auto trans so my joints see load. I broke 9/16 bolts in the bracket. Going 5/8 has been problem free. Less separation will put more load on everything
Click to expand...
Hey. its been a few months since I have visited this build. Spent some time in the garage this weekend. I worked the numbers to get the AS to 90 (assuming a 36" Instant Center) and decreased the load on the rear lowers from 10.8 to 8.5k However, my vertical separation for the rear is only 8.5.

I have plenty of leeway to lower the rear lower link mounts to increase separation, but as I understand, that hurts my AS. I have attached the new and old version of the 4 link calculator for your review. ( I don't know how to see the static AS in the new calc.- its prob right in front of my face somewhere )

Thank you for all of your help thus far.

Mike
 

Attachments

If you are at 8.5in of separation with a 4 link I’m sure it’s fine. It’s more of a concern with 1 upper link.

I’d try to get your AS a tad lower then 90 though
 
06h3 said:
If you are at 8.5in of separation with a 4 link I’m sure it’s fine. It’s more of a concern with 1 upper link.

I’d try to get your AS a tad lower then 90 though
Click to expand...
Moving my axle side lowers up from 19" to 19.5" moves the AS down from 90 - 85. This would be 8" of separation. moving from 19-20" makes 78 AS and 7.5" of separation.
 
SolidKM said:
Moving my axle side lowers up from 19" to 19.5" moves the AS down from 90 - 85. This would be 8" of separation. moving from 19-20" makes 78 AS and 7.5" of separation.
Click to expand...
I agree with 06h3 about lowering AS some. Probably by moving the rear frame points. You may want to shorten the links some as well.
 
Treefrog said:
I agree with 06h3 about lowering AS some. Probably by moving the rear frame points. You may want to shorten the links some as well.
Click to expand...
Treefrog 06h3 So I am running the RK belly pan that was ever so popular with the TJs and LJs. I just discovered that the frame side uppers are not 2 5/8 mounting for joints but rather like 2 3/8. I could weld new frame side uppers maintaining the same height from the ground but shortening the upper link. This seemed to bring down the AS a little more, and generally you want the uppers to be shorter than the lowers, correct? Or, I could find a joint the replicates the original RK upper mounting width. Thoughts? Thank you both for the help. (v3 sheets attached show the upper link length from 45" to 38")
 

Attachments

SolidKM said:
Treefrog 06h3 So I am running the RK belly pan that was ever so popular with the TJs and LJs. I just discovered that the frame side uppers are not 2 5/8 mounting for joints but rather like 2 3/8. I could weld new frame side uppers maintaining the same height from the ground but shortening the upper link. This seemed to bring down the AS a little more, and generally you want the uppers to be shorter than the lowers, correct? Or, I could find a joint the replicates the original RK upper mounting width. Thoughts? Thank you both for the help. (v3 sheets attached show the upper link length from 45" to 38")
Click to expand...
Is lowering the rear lower frame points an option? The lengths look a bit better. They were starting to get a bit long.

Upper vs lower length depends on geometry and travel. Generally, pinion angle change tends to benefit from the longer side view link being on the side with less travel. In your case that would mean a slightly longer upper link would result in better pinion angle change.
 
Malburg114 said:
Thoughts? Newb to rear 4 links. Front 3 link is pretty well in place and can't change to much besides the frame side upper link length and height and even then, it's pretty minimal.

Rear 4 link its pretty wide open. The numbers I listed are the ideal places, but I can narrow or widen the lower links at the frame more and move them up. The upper link at the rear frame can go up and down some but not much more inboard without some crazy braces.

Car is a 4500 car for koh/ultra4 series that will see a bit of regular crawling at sand hollow/rubicon/jv and street driven on occasion. The numbers are how i currently have it set up but overall ride height will probably come down 1.25 inches to even out the front travel, I wont know that till I get it off table/stand I have it on when i turn it around though.

Sorry for the multiple pictures, the calculator loads with the numbers super small at the top for me and only way to zoom in was with the magnifier in the settings on the computer.

rear
link calculator v2.1.PNG


front-i forgot to change the up travel number back to 8.75 which is what its setup for now on the stands
link calculator v2.2.PNG
link calculator v2.3.PNG
Rear antisquat/roll center

link calculator v2.4.PNG


front anti dive/roll center
link calculator v2.5.PNG
link calculator v2.PNG
Click to expand...
Following up on this as I got the truck turned around and started on the rear. The frame side upper link mount is adjustable in 1 in increments and theres 3 holes. Full calculator screen shot is with the link in the upper hole.

option 1
My anti squat options with the holes are:
13.3%=26.6%
22.7%=45.4
32.2%=64.4

option 2
i can lower the mount another 1/4 in to get:
15.6%=31.2
25.1%=50.2
34.6%=69.2

Option 3
Or I can raise it to the original height i had which is up 1/2" from the calculator screen shot. Options are:
8.5%=17
18%=36
27.5%=55

Im leaning towards leaving them at option 1 figuring ill run it in the top or middle hole and the bottom hole is just another option. Based off frogtree and 06h3, im shooting for antisquat options of 30-50% unless someone says otherwise And option 1 keeps most the holes numbers somewhat realistic/useable.

Thoughts? Front cannot be changed as its already welded and I ran the numbers before and those are the best I can get. And maybe im looking at it wrong but first build ive used the calculator for.

The rear lower link frame side mounts can go farther inboard if that would benefit anything. Lower link length is as short as I can get it with the body/wheelbase but upper link length can go longer or shorter. Trying to have minimal driveshaft plunge/slip.
4 link calculator 5.2025 v2.PNG


rear only upper hole
4 link calculator 5.2025 v2 rear only 1.PNG


rear only middle hole
4 link calculator 5.2025 v2 rear only.PNG


rear only bottom hole
4 link calculator 5.2025 v2 rear only 2.PNG
 
Malburg114 said:
Following up on this as I got the truck turned around and started on the rear. The frame side upper link mount is adjustable in 1 in increments and theres 3 holes. Full calculator screen shot is with the link in the upper hole.

option 1
My anti squat options with the holes are:
13.3%=26.6%
22.7%=45.4
32.2%=64.4

option 2
i can lower the mount another 1/4 in to get:
15.6%=31.2
25.1%=50.2
34.6%=69.2

Option 3
Or I can raise it to the original height i had which is up 1/2" from the calculator screen shot. Options are:
8.5%=17
18%=36
27.5%=55

Im leaning towards leaving them at option 1 figuring ill run it in the top or middle hole and the bottom hole is just another option. Based off frogtree and 06h3, im shooting for antisquat options of 30-50% unless someone says otherwise And option 1 keeps most the holes numbers somewhat realistic/useable.

Thoughts? Front cannot be changed as its already welded and I ran the numbers before and those are the best I can get. And maybe im looking at it wrong but first build ive used the calculator for.

The rear lower link frame side mounts can go farther inboard if that would benefit anything. Lower link length is as short as I can get it with the body/wheelbase but upper link length can go longer or shorter. Trying to have minimal driveshaft plunge/slip.
Click to expand...
I would probably go with option 2.
 
Malburg114
Am I reading this correct, Your lower axle link is 3" behind your axle on the cover side of axle, not in front of your axle on the driveshaft side
Am I just confused as most times I see the lower axle link is a positive number not a negative number

Unsaved Image 1.jpg
 
Ovrez said:
Malburg114
Am I reading this correct, Your lower axle link is 3" behind your axle on the cover side of axle, not in front of your axle on the driveshaft side
Am I just confused as most times I see the lower axle link is a positive number not a negative number

Unsaved Image 1.jpg
Click to expand...
I must have typed it wrong. It should read with the link mount in front of the axle tube on the pinion side. I’ll update it to see if changes anything.
 
Working on buttoning the layout on my car. It's a 2 seat buggy, 5.3, TH400, Atlas 2 Speed, 14 bolt both front and rear, rear steer, 43s, and 16 ORIs. The goal is to crawl the technical stuff and be able to scoot across to the next obstacle in a hurry. The front axle is forward bias by about 2 inches for clearance between the diff and the hoop around the oil pan. Do these values support what I am looking to do?
1750051689966.png
 
dirtyrice said:
Working on buttoning the layout on my car. It's a 2 seat buggy, 5.3, TH400, Atlas 2 Speed, 14 bolt both front and rear, rear steer, 43s, and 16 ORIs. The goal is to crawl the technical stuff and be able to scoot across to the next obstacle in a hurry. The front axle is forward bias by about 2 inches for clearance between the diff and the hoop around the oil pan. Do these values support what I am looking to do?
1750051689966.png
Click to expand...
Looks pretty reasonable. You may want to add a little bit of AS in the rear to help with launch grip.
 
Changing the front to a 3-link with ORI's from leafs. 1999 Ram 2500 with unimog 419 portals, 5.9 gasser, 49" Baja Pro XS's, full hydro, rear will stay leafs. Mostly rock crawling and snow runs with some street cruising.

Thanks!

1000010717.png
 
Njt said:
Changing the front to a 3-link with ORI's from leafs. 1999 Ram 2500 with unimog 419 portals, 5.9 gasser, 49" Baja Pro XS's, full hydro, rear will stay leafs. Mostly rock crawling and snow runs with some street cruising.

Thanks!

1000010717.png
Click to expand...
Looks like it should be fine. Just watch out for strength on the upper link and maximum load on the ori struts.
 
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