The Whys And Hows Of The 4-Link Rear Suspension
Introduction
- Purpose: To understand the functions and mechanics of the 4-link rear suspension system.
- Significance: Used in drag racing, especially in Pro Stocks, to manage high horsepower and ensure effective launch and acceleration.
Basic Mechanics of Rear Suspension
- Rear suspensions do more than support car weight; they propel the car forward.
- Standard car suspensions cannot handle drag-style launches without additional traction devices.
- Aftermarket traction helpers include traction bars, leaf links, ladder bars, and the 4-link system.
History and Development
- 4-link system developed by Ron Butler, essential in Pro Stocks.
- Requires precise tuning for effective performance.
Understanding Torque and Launch Dynamics
- Torque Reaction: When power is applied, the rearend pinion tries to climb the ring gear.
- Housing Rotation: Causes lifting of the car's front and weight transfer to the rear.
- Impact on Traction: Correctly tuned suspension improves tire planting and acceleration.
Common Traction Devices
- Traction Bars
- Used in street and mild performance cars.
- Works by preventing upward rotation of the rearend housing.
- Leaf Links
- Older system, phased out due to limitations like suspension binding.
- Ladder Bars
- Forces the rearend to travel in an arc.
- Good for straight-line racing but can bind in turns.
- 4-Link System
- Most advanced, offering adjustability and control.
- Requires understanding of geometry and physics for tuning.
4-Link System Details
- Composed of four links with different angles affecting chassis lift and rearend separation.
- Adjustment Factors:
- Upper bar angle affects leverage and chassis lift.
- Lower bars adjust for more or less chassis lift.
- Adjustments are dynamic, changing as the car moves.
Hot Tips for Drag Racing
- Automatic cars need level positioning for better weight transfer.
- Unequal-length links can enhance suspension response.
- Equal-length 4-links help manage manual cars' reactions.
Preload and Street Usage
- Preload Adjustment: Lengthen top left link to counteract engine torque and ensure stable launch.
- Street Adjustments: Bars should be parallel for lateral movement without binding.
- Avoid preload/jacking on the street to prevent oversteer.
Conclusion
- 4-link systems are complex but provide significant benefits for drag racing and performance tuning.
- Proper understanding and adjustments are crucial to harnessing their full potential.
- Street setups require a different approach to avoid handling issues.
Article presented as originally published, reflecting historical context and values.