#### Treefrog

##### Book Wheeler

Current Version: 6.10

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: 1/30/2022 Updated current version to 6.8.

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

Edit: 11/8/2022 Updated current version to 6.10.

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: 1/30/2022 Updated current version to 6.8.

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

Edit: 11/8/2022 Updated current version to 6.10.

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