Performance Trends, Inc.

Producing Quality Computer Tools for Racers and Engine Builders since 1986

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4-Link Calculator v2.0 (std and Plus version) for Windows XP/Vista/Win 7/Win 8/Win 10/Win 11

Computer Program to Simulate and Analyze Rear Suspension 4-Link Setups for Instant Center, Pinion Angle and Driveshaft Angle Change, Anti-Squat %, and More for Drag Racing

Click here for new Plus Version's features.

 

Overview:

The 4-Link Calculator lets you input, view, save, analyze and compare your 4-Link rear suspension geometry. You enter heights above the ground and distance ahead of the front axle for up to 6 holes for all 4 brackets for your car, or any number of cars.  (Plus version allows for up to 15 holes.) All these measurements are saved in the library for retrieval, analysis or modification in the future. You can also enter other measurements like Wheelbase, Pinion Angle, etc. for more detailed calculations performed by the program.

Once entered, the program will display calculated parameters like Instant Center Length and Height, Anti-Squat %, and changes in Pinion Angle, Driveshaft Angle and Yoke Movement (splines sliding into or out of the transmission yoke) if you have the suspension go through some dynamic changes.

Making changes is just 1 click of the mouse. Click on a bracket hole to change the attachment point, or click on an Instant Center and the program draws the 4-Link setup which produces that instant center.

 

What is Anti-Squat?

Anti-Squat is an engineering term which describes the 4-Links likely performance under acceleration. 4-Link settings with less than 100% Anti-Squat are likely to squat under hard acceleration (rear of car drops), and "hit the tires more softly". Conversely, settings with more that 100% Anti-Squat tend to raise the rear of the car when accelerating and "hit the tires harder".

 

Options:

The program has several options, including:

  • You can ask the program to suggest a good starting location for the Instant Center.  See picture below.  These are based on noted drag racing authority Dave Morgan, who wrote the box "Door Slammers, The Chassis Book".  These suggestions are based on your car's potential ET and vehicle weight.  Our feedback shows several racers have had major improvements in their 60 ft times by following these suggestions.

  • Either work with Dynamics, where the static and dynamic conditions are calculated and drawn, or mapping all instant center locations.

  • Draw in the imaginary "neutral line", the line of 100% Anti-Squat. Theoretically, instant centers which lie on this line will not "pitch rotate" up or down as the car accelerates. Pitch rotate means have the front or rear of the car rise or fall with respect to the other end of the car.

  • Draw in imaginary "extension" lines to show how the Instant Center is arrived at.

  • Produce tables of all possible 4-Link combinations. This table can be ranked by Anti-Squat %, Instant Center Height or Instant Center Length so you can quickly find combinations which will produce minor or major changes in launch.  See table below.

  • Option for Ladder Bars. 

  • Option for changing the colors and line thickness of the line drawings.

  • Option for working with "% Rise" instead of "% Anti-Squat".

 

The program is compatible with Windows XP,  Vista, Win 7, Win 8, Win 10, which means it is easy to use and you will be able to print the results on most any printer, usually in color if your printer supports it.

 

Plus Version:

The Plus version adds several features to your 4 Link Calculator, including:

  • Allows for up to 15 holes on each bracket
  • Allows for generating several holes between 2 other holes on either a straight line or on an arc that you specify.
  • Allows for limits to be specified, to eliminate combinations you are not interested in, like instant centers below ground.
  • Allows for an 'Animate' mode where the program simulates some vehicle dynamics (squat and rise). This is to illustrate how the instant center location, % anti-squat, pinion angle, yoke slip CAN change as you go down the track. This animation may NOT be the same as what your car produces. It also does NOT change if you change the 4 link settings. Our Suspension Analyzer lets you import actual shock travel data to simulate what your car is doing.
  • Option lets you display the Static Bar Angles (at ride height).  In 2019 this feature expanded to also showing Static Bar Length and Bar Length Changes with a new option.
  • Torque Arm rear suspension type (like 3rd and 4th generation Camaros).  See picture below.
  • You can add absolute Pinion Yoke angle to be displayed, which basically tracks the twist put on the axle during dynamics.  The standard Pinion Angle shown below is the angle between the pinion yoke and the driveshaft and is useful for tracking changes in the U joint angle.
  • Choose (click on) a combination from the Table and you can choose to load those conditions back to the main screen.
  • You can have the program draw the car's outline higher or lower.  This does not change any calculated results.
  • Powerful "Adjust Bars" option lets you adjust the length of either or both bars and see the effect on pinion angle, driveshaft yoke movement, anti-squat, and all other calculated parameters.  to see picture below for more details.

Check the pictures below for more information.

 

 

 

Torque Arm Rear Suspension Type

 

Powerful Adjust Bars Feature:  Click on Measurements, then Adjust Bars for the "Adjust Bars" screen shown in middle of screen.  Make adjustments to the bar lengths, either in inches, or turns of a particular thread pitch, and program shows how everything will change.  If you like the new settings, click on "Keep Changes" and all new properties are installed to the current 4 Link File.  In addition, wheelbase length, and all the new hole locations on the top and bottom axle bracket are re-calculated and installed also.

 

 

What You Need:

Computer with Windows XP, Vista, Windows 7, Windows 8, Windows 10, Windows 11.

 

More Information, Download Demo:

to go to our Demo Downloading page to download a FREE 4 Link Demo.

 

More Information, Watch Demo Movies:

to go to our Demo Movie page to watch 4 Link Demo Movies .

NOTE:  If you buy the standard version and later decide to go to the Plus version, it is more expensive to do it in 2 steps rather than just buying the Plus version first.

To Order:

4 Link Standard: Our DOWNLOAD ONLY option. If you only want the unlocking code and DO NOT want a CD shipped, click on Add to Cart below. You will not be charged shipping.
$99.95
4 Link Standard: If you want a CD shipped to you, click on Add to Cart below. There will be shipping charges added to your order. You can still download the demo and get your unlock code sooner with this option.
$99.95 plus shipping
4 Link Plus: Our DOWNLOAD ONLY option. If you only want the unlocking code and DO NOT want a CD shipped, click on Add to Cart below. You will not be charged shipping.
$149.95
4 Link Plus: If you want a CD shipped to you, click on Add to Cart below. There will be shipping charges added to your order. You can still download the demo and get your unlock code sooner with this option.

$149.95 plus shipping

Call 248-473-9230. Visa and Mastercard accepted.  Performance Trends can provide you an "unlocking code" number to activate all features (bring it out of demo mode). When newer versions are released, you can download the latest demo and activate all features with this same "unlocking code".

The "on screen" help explains all features, inputs and outputs. This program does not come with a user’s manual.