What's new

New Version of the 4 Link Calculator

Treefrog

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Current Version: 6.9

All versions I have access to can be found on the Resources Page.


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

Link to the Check My Numbers thread: How's my numbers?


With the changes to the board, a goal was set of generating more current and up to date technical information. To this end, it is time for another update to the 4 Link calculator, which had its last major update done in 2016. The goal of this update is to assist in coilover placement and the selection of springs. This is done by adding portions of BillaVista's Preliminary Spring Rate Calculator, which was made in 2004.

Despite the discussion around the accuracy of some of his recommendations in The Coilover Bible, the equations he presented are correct, except for one which is partially correct. Both approaches towards determining the ideal spring rate present in Primary Spring Rate Calculator are accounted for, as is the approach presented by ZukIzzy.

The partially accurate equation presented by BillaVista is the equation for the install ratio (ratio between spring rate and wheel rate), "IR = DR * ACF = (d1/d2) * cos(alpha)." This equation is good enough for most applications, but does not account for all factors., such as the true rotation point of the axle, and the angle between the tangent of the wheel travel arc and vertical. It also has limitations when trying to determine wheel rate during travel.

As per usual, the numbers in the Current Version are for testing purposes.



Going forward. I plan to add support for a second shock, and possibly driveshaft length and angles.

Feedback, suggestions, and math/error checking are all appreciated.

At the very least, can we keep this from becoming a check my numbers thread?

Edit: 7/27/2020 Updated current version to 5.1.

Edit: 8/9/2020 Updated current version to 5.2.

Edit: 12/9/2020 Updated current version to 5.3.

Edit: 12/23/2020 Updated current version to 5.4.

Edit: 12/28/2020 Updated current version to 5.5.

Edit: 2/18/2021 Updated current version to 6.0.

Edit: 3/7/2021 Updated current version to 6.1.

Edit: 4/12/2021 Updated current version to 6.2. Fixed all links from forum backend change.

Edit: 4/30/2021 Updated current version to 6.3.

Edit: 4/30/2021 Updated current version to 6.4.

Edit: 5/5/2021 Updated current version to 6.5.

Edit: 5/6/2021 Updated current version to 6.6.

Edit: 5/11/2021 Updated current version to 6.7.

Edit: 4/13/2022 Updated current version to 6.9.

Edit: 1/30/2022 Updated current version to 6.8.
 
Last edited:

Rob50lx

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Thanks for sharing.
Is there a there a thread that gives examples of stock suspension values or a good explanation on how to map/measure values?
 

Treefrog

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Thanks for sharing.
Is there a there a thread that gives examples of stock suspension values or a good explanation on how to map/measure values?

I don't know of a thread for stock values. As for measuring, a plumb bob and chalk might be the easiest way. Mark the points and tire centers on the ground, record the heights, move vehicle, and measure.
 

gt1guy

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Yes, thanks for taking time and for sharing. Austin This needs to be added to the resources page.

I know, I'm on a boat i a lake .... 100% will add it when I can


Ok, so I didn't type that part about being on a lake...................I assume that was Austin. Or this site has scary ghosts already
 

Treefrog

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Just updated to 5.1. Updated the links in the first post.

Caught a big error in the calculation of the wheel rate when using the suspension height approach. This effect of the error is more pronounced the less equal up and down travel are. Also caught some errors in the link sizing that should not effect the values much. I forgot to check the factor of safety equations from when I changed them from force at ride height to maximum force. And, since I was working on the link sizing page, added some presentation of data from both ends. Also changed how the lookups for the material and rod ends work to make them more user friendly.

Austin Would you mind adding the newest version to the resource page?
 

Austin

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Just updated to 5.1. Updated the links in the first post.

Caught a big error in the calculation of the wheel rate when using the suspension height approach. This effect of the error is more pronounced the less equal up and down travel are. Also caught some errors in the link sizing that should not effect the values much. I forgot to check the factor of safety equations from when I changed them from force at ride height to maximum force. And, since I was working on the link sizing page, added some presentation of data from both ends. Also changed how the lookups for the material and rod ends work to make them more user friendly.

Austin Would you mind adding the newest version to the resource page?

Done :smokin:
 

azdirt3.0

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Awesome, thanks!! Any chance there would be 3 link possibility added to this in the future?

I've used it to run numbers for my front 3-link. You just adjust the number of uppers to 1 and panhard to 1. This constrains the axle as a standard 3 link, with your numbers for the upper link y location determining the side (positive for left side and negative for right side upper).
 

azdirt3.0

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Just updated to 5.1. Updated the links in the first post.

Caught a big error in the calculation of the wheel rate when using the suspension height approach. This effect of the error is more pronounced the less equal up and down travel are. Also caught some errors in the link sizing that should not effect the values much. I forgot to check the factor of safety equations from when I changed them from force at ride height to maximum force. And, since I was working on the link sizing page, added some presentation of data from both ends. Also changed how the lookups for the material and rod ends work to make them more user friendly.

Austin Would you mind adding the newest version to the resource page?

Just one thing of note that I found when putting my numbers in the new 5.1 version. The travel numbers under the Front Upper Links, Front Lower Links, Front Panhard Bar, Front Roll Center Height are linked the travel input from the rear suspension (Cells C9 and C10) rather than the front travel (Cells P9 and P10). This does not affect anything other than the displayed travel numbers but figured I would let you know.

Thanks for adding all the additional features to the calculator! This is a great resource tool.
 

Treefrog

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Just one thing of note that I found when putting my numbers in the new 5.1 version. The travel numbers under the Front Upper Links, Front Lower Links, Front Panhard Bar, Front Roll Center Height are linked the travel input from the rear suspension (Cells C9 and C10) rather than the front travel (Cells P9 and P10). This does not affect anything other than the displayed travel numbers but figured I would let you know.

Thanks for adding all the additional features to the calculator! This is a great resource tool.

Thanks for letting me know. I have updated them for the next version.
 

Treefrog

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What about adding the CG bias front to rear as discussed in the "ThinAir" thread?

Adding it to the calculations for what?

Weight distribution is there, it is used for the springs. Correct me if I am wrong, but it is my understanding that front rear balance does not affect squat and anti squat.
 

Treefrog

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Just updated to 5.2. Updated the links in the first post.

Found some more errors in the front shock movement and install ratio calculations, should only change things if you did not have the front set to axle. Missed a few values when copy pasting it seems. Fixed the stuff azdirt pointed out. Also fixed the initial wheel rate not accounting for preload when using the shaft showing approach. Should have been paying a little closer attention when fixing that for 5.1.

Oh, and I added bypass shocks to it. Doesn't have the ability to help with valving, but at least it has install ratio and stuff regarding length and travel usage.

Looked over a lot of the Shock math while setting it up for copy pasting for the bypasses. All of the cell links should be fixed, so the math should be good now, unless it is inherently flawed.

With the removal of bypasses from the planned features list, I am adding sway bars to the list. No guarantee on when it or driveshaft lengths and angles are getting added.

Austin Mind throwing this one up on the Resources page?
 

No way

Viking Mothfukle
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Absolutely love this tool. Thank you for making and sharing it :beer::beer::beer:

My only bummer is I'm not excel-savvy enough to see a "simple" sollution to convert from imperial to metric. Takes a bunch of multiplying/dividing by 25,4 :laughing: :homer:
 

Treefrog

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Absolutely love this tool. Thank you for making and sharing it :beer::beer::beer:

My only bummer is I'm not excel-savvy enough to see a "simple" sollution to convert from imperial to metric. Takes a bunch of multiplying/dividing by 25,4 :laughing: :homer:

Will look into adding the ability to take metric inputs then. Shouldn't be too hard.
 

Treefrog

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I got bored again, and it is now 5.3. Links above updated.

Anti calculations account for wheel movement during travel now.

Changed some wording to match the terms in the Linked Suspension Bible.

Added some stuff for estimating dent resistance, its not a perfect approach, but it should be enough to give an estimate.

Changed it so that the FOS share a target by type instead of all types having the same target.

And added some stuff to help with locating shocks, namely compressed and extended lengths.

Austin Mind updating the resources tab again?
 

Treefrog

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I need to find other stuff to spend time on. 5.4 is now out.

Fixed an issue with the plots and track width. As well as some stuff to do with hiding bypass results when not using them.

Added portal height to the plots.

And the big feature of 5.4: Driveshafts. Lengths and u-joint angles throughout travel are now calculated. Portal heights are accounted for in these calculations.


I've decided against adding sway bar calculations, at least for the time being. The closest I could get without having flex data is not all that close to reality.
Metric won't be added for now either. It would require an overall of most of the calculator to implement. And without a ground up rebuild, isn't going to be easily doable. Sorry everyone who doesn't live in the US. :usa:


Unless anyone has any requests, this will be the last one for quite a while.


Austin Mind adding one more? Should be a while before the next.
 

Treefrog

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I lied. Its only been 5 days and 5.5 is out. Caught some errors on the link sizing pages that are a result of me switching the way that users input new materials. Same issues were present for the rod ends. These errors do not affect the results. They only come into play if you try adding new materials or rod ends.



While I have the readers attention, what is the consensus on switching it to a macro enabled sheet? I would like to do this as it will allow me to use code to calculate the values instead of a bunch of linked cells. This will let me decrease the room needed on the calcs. page, but more importantly, allow for a higher travel resolution, among some other features. This would be an extensive rebuild allowing me to do some stuff like add support for those who live outside the U.S.:usa: I also believe it will open up the pathway for longer term ideas such as articulation.
 

Austin

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While I have the readers attention, what is the consensus on switching it to a macro enabled sheet?

Form the end users view, I'm sure most wouldn't know the difference. So initial thoughts are ... go for it.

Now that this is active development, moving forward, is there a way for users to to jump from one version to the next upgrade without copying cell by cell?

Should we have a email sign up list to alert people when there are updates?

I wonder if it would be better to make this in a webpage on here. That way people get updates automatically or could publicly share their specs for others.
 

Treefrog

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Form the end users view, I'm sure most wouldn't know the difference. So initial thoughts are ... go for it.

Now that this is active development, moving forward, is there a way for users to to jump from one version to the next upgrade without copying cell by cell?

Should we have a email sign up list to alert people when there are updates?

I wonder if it would be better to make this in a webpage on here. That way people get updates automatically or could publicly share their specs for others.

It prompts a warning about macros possibly being dangerous.

As far as I know, the only way is copying over. Outside a few versions, its not that important to upgrade. And even then, the bug fixes have yet to be extreme.

You say active development, its only really been active because of free time over the holidays. It could be this weekend or a year from now when the next version comes out. (Possible bug fixes aside, probably not happening this weekend).

Doesn't subscribing to this thread give notifications? Very few people need the calc so often that it would matter that they get the most recent updates. Its more of someone's building a buggy, looks for the calc, and finds it. Most of the people who have used it, probably never cared to monitor the updates and changes.

If you want to make it a webpage, feel free. Spreadsheet has worked for 17 years and 23 days. Apparently, there was a Java version at one point, but I have yet to find a copy. I'll provide help with some of the math if needed.
 

No way

Viking Mothfukle
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Treefrog.. you fawkin rock :smokin:

A web based sql type thing would certainly be cool but would require maintenance whereas the spreadsheet just flat out works, even offline.
So far I've needed the calculator twice in my life. Worst case scenario is maybe twice more, tops. I reckon most 4-link calc users build one or two buggys in their lifetime.
Still, there are thousands of people who would love to have access to it if they knew it existed.

I used the 3.0 version a couple of years ago and until you posted here I had no idea there were newer and better ones out there. I found that Jake Burkey had a version you could "buy for free" from the BKO website but I never got around to it.
Perhaps reach out to Jake and other web celebs informing them of the latest revisions being on here and ask them to mention the site and/or link to it in their YT and FB videos?
 

Treefrog

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Treefrog.. you fawkin rock :smokin:

A web based sql type thing would certainly be cool but would require maintenance whereas the spreadsheet just flat out works, even offline.
So far I've needed the calculator twice in my life. Worst case scenario is maybe twice more, tops. I reckon most 4-link calc users build one or two buggys in their lifetime.
Still, there are thousands of people who would love to have access to it if they knew it existed.

I used the 3.0 version a couple of years ago and until you posted here I had no idea there were newer and better ones out there. I found that Jake Burkey had a version you could "buy for free" from the BKO website but I never got around to it.
Perhaps reach out to Jake and other web celebs informing them of the latest revisions being on here and ask them to mention the site and/or link to it in their YT and FB videos?

Pretty sure that BKO's is just 3.0.
 
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