The 4-link suspension is the most common and proven setup among the many different classes in drag racing, but it also has its own limitations — namely in regards to adjustability. That’s where Rick Jones Race Cars and Quarter-Max come to the table.
A 4-link is designed to locate the rear axle with four links, two on each side. Besides these links controlling and transmitting the loads placed on the axle during acceleration and braking, the bottom links also control the axle placement front to rear. The upper links keep the axle from rotating and keep the pinion angle consistent. A 4-link uses a Panhard bar or Watt’s link (also used on other rear suspension set-ups) to laterally locate the rear end. The Panhard rod is used on many production vehicles that use a solid rear axle because it’s simple yet effective, although a Watt’s link is more adjustable/tunable than a Panhard bar.
This design was created so racers could make adjustments on the fly without changing the ride height of the car. – Rickie Jones
The Extreme Adjustable Billet 4-Link
Much like other sports, drag racing is highly competitive — racers are always looking for ways to improve their own skills as well as the performance of their race cars. More than a decade ago, RJ Race Cars created an alternative design to the traditional 4-link that enhances flexibility and adjustability, providing racers with the ability to fine-tune their 4-link to a much greater degree than the standard, age-old 4-link bracket.
The Extreme Adjustable Billet 4-Link bracket system was designed by Rick Jones and has been installed on RJ Race Cars for over 15 years. This 4-link system features billet weld-on chassis brackets that utilize a unique bolt-on 4-link plate system with a keyway that allows both top and bottom 4-link plates to move up and down in increments of 1/8-inch, allowing fine tune adjustments to be made to the instant center of the 4-link. With the adjustability on tap in this design, it was an obvious choice for our new BlownZ06 C7 Corvette drag radial car — we’ll be pairing it with JRi Shocks and a host of internals from Strange Engineering and US Gear in the center section to guide the car into (hopefully) the three-second zone at 200 mph.
“We came up with this design to help our customers adjust to the different track conditions they may encounter. This design was created so racers could make adjustments on the fly without changing the ride height of the car,” says Rickie Jones of RJ Race Cars.
The zinc plated bolt-on upper and lower plates are CNC-machined from billet 4140, and are heat-treated for added strength to stop hole elongation to provide years of consistency on even the most extreme applications. The weld-on chassis brackets are CNC machined from billet 4140 with all holes drilled and reamed for an exact fit.
The Extreme 4-link uses a unique keyway system for extra strength, which is an industry-first. The bolt-on plates each have six 1/2-inch holes that have a .625-inch spacing and are available in steel or the titanium upgrade option.
Depending on your specific application, the Extreme 4-link offers a vast array of different adjustments at your disposal. Each kit comes with separate upper and lower plates offering fine-tuning adjustments down to 1/8-inch increments. Each plate has a total of 21 holes (six holes for the big bolts and 15 for the 3/8-inch bolts) on the 4-link side in addition to the adjustments on the particular rear-end housing. Tuning a car with traditional one piece 4-link brackets the smallest change you can make to the spread is typically 5/8-inch or more, although some can be as much 3/4- or 1-inch spacing.
“When you make a change with a traditional 4-link with that kind of spacing, it’s a big move, and a lot of times, we’d try two holes and wish we could be in the middle. That’s what started us down to the path to designing this 4-link system, so you can go every 1/8-inch.
Jones explains that while you could get the instant center “in the neighborhood” with non-adjustable brackets, fine-tuning it to its best performance was rarely possible, forcing one to compensate elsewhere to get into that window, like adjusting the shocks to get it right where you wanted it. You also don’t have to adjust the ride height as a result of getting the 4-link where you want it to be, which is paramount to our radial tire Corvette.
“With this 4-link, you can put the 4-link essentially anywhere you want — there’s no longer that compromise. You can put the 4-link where you need it to be. You can build the shock how you want it and put the 4-link where it needs to be to match the shock.”
Instant center length adjustments, Jones explains, are typically around 1.5-inch with each hole re-positioning on the Extreme 4-link at 1/8-inch, while the traditional 5/8-inch holes moves the instant center about 8-inches … giving the Extreme system five times finer adjustment over conventional configurations.
The Extreme Adjustable Billet 4-link Kit comes in four different styles of weld-on billet chassis brackets. The chassis brackets are available in different heights/configurations to fit any chassis crossmember setup:
With traditional 4-links, you often ran into wishing you had more slots for adjustments because you needed that in-between space to find that centerline. – Rickie Jones
• 15-inch center-to-center, 1-5/8-inch round tube notches (2-inch raised top crossmember).
• Tall, no top notch, 1-5/8-inch lower round tube notch (fit your own top crossmember, lower is preset).
• Tall, blank, no notches top or bottom, universal fit, able to be fit to square tube chassis or any notch desired for round tubes.
(All versions of the weld-on brackets use the same bolt-on 4-link plates)
The kit comes complete with NAS bolts and ARP 12-point nuts for added strength.
“The word extreme is an understatement when describing this system,” Rickie states. “There are dozens of different combinations you can run. With traditional 4-links, you often ran into wishing you had more slots for adjustments because you needed that in-between space to find that centerline. With the Extreme Adjustable 4-link kit, we have eliminated those issues.”
During installation, while mocking up and welding, RJ insists the use of grade 8 bolts. After all the welding is complete, RJ recommends reaming the holes and using the NAS 4-link bolt kit during final assembly for even less bolt movement. As an important note to this step, Rickie adds, “definitely don’t use a drill bit.”
RJ Race Cars has been equipping its Pro Stock, Pro Mod, and Top Sportsman-style cars with the Extreme 4-Link for over a decade — virtually every car coming out of the RJ Race Cars shop has also been outfitted with this kit. Rickie tells us, “we want to market this to sportsman racers as well as professionals.” Some big names such as Jeg Coughlin, Steve Jackson, and Jason Scruggs are just a few who racers that have been running and winning with the Extreme Adjustable 4-link Suspension. Rickie also mentions, “the only reason a racer may choose to go with a traditional 4-link over the Extreme 4-link is cost. But we always recommend them to go with a stronger component with more adjustability that will save them time and money in the long run.”
Rickie adds in closing that, “the Extreme Adjustable Billet 4-Link Suspension System provides the ultimate range of adjustability and performance advantages on the race track while maintaining the highest strength and consistency for even the most extreme high-powered combinations.”