Racers often take pride in the longevity that their racecar components questionably endure over the years. “My transmission has lived for almost a decade, and my slicks are working great after three seasons,” you might hear them say.
That’s all well and good, but some maintenance practices are crucial when it comes to preventing failure that can result in catastrophe. If you have been at the dragstrip for any reasonable amount of time, chances are you’ve probably seen a rear differential want to leave, or had success leaving, out from under a racecar due to failure of some sort.
When we snagged our 1968 Camaro last year, the backstory goes that it has been a Texas Super Stocker and subsequently a bracket car since 1972 — intended as an opportunity to “teach an old dog new tricks” hence, the name for our Project Rover.
One of the critical inspection recommendations are the rod ends and spherical joints used with a ladder bar or 4-link rear suspension. Not only did we want to continually upgrade the car with new technology in the go-fast department, but it was also time to make some updates in the aged suspension components for safety’s sake.
We spoke to Curt Perry at Chassis Engineering about his recommendations for updating the rear suspension.
“People should check everything out when it comes to all chassis and suspension components,” Perry explains. “I would recommend detailed inspection of each of the suspension bars, rod ends, and spherical joints annually, at very least.”
Perry also explains that many racers will begin racing with a smaller engine, but then may step up to more horsepower or even a boosted combination, yet neglect to check the suspension hardware as their horsepower increases.
Before dismantling, we carefully measured and logged the dimensional layout of our old rod ends before they came off the ladder bars. With those dimensions carefully duplicated with the new rod ends, we retained our proper rearend pinion angle in relationship to our driveshaft.
We continued the recommended inspection by checking all of the rod end mounting threads in each of the ladder bars. We used a new bolt with unmolested threads to gauge thread mesh. Though our ladder bars appear in good shape, we could detect a slight bend in one of our front spherical rod ends when we applied a straight edge.
We would also have similarly inspected whatever track-locating device is used, whether it be a wishbone or diagonal link, but that is an entirely new issue for us to address. The Camaro’s dated suspension is equipped with a very short-in-length Panhard bar above the differential. That is a personal red flag for me.
Chassis companies do still sell Panhard bars as a means to keep the rear differential centered during suspension movement. That side-to-side arching motion is okay for a hot rod or performance street application. However, many chassis experts claim for reliable launches at the dragstrip, that old-school design is not the best way to go. That motion that a Panhard bar creates during launch can cause a lack of repeatability in today’s high-tech shocks. When we specified the replacement rod ends for our ladder bars, we also ordered a diagonal link from Chassis Engineering.
Perry also recommended we inspect for any out-of-shape mounting holes caused by years of launching and suspension movement. Though our bolt holes were undamaged, we could see indications of wear in many of the 5/8- and 3/4-inch bolts.
When we were on the topic of fasteners, Perry discussed the use of National Aerospace Standard (NAS) Bolts or high-quality grade-8 fasteners.
“One of the most critical factors is the use of bolts that have a shoulder across the entire width between your housing and chassis brackets,” he explains. “If you allow a bolt’s thread within that shear area, your bolt is only going to be as strong as the inside diameter of the thread.”
With our ladder bars apart, we wire-brushed away all of the previous paint; this was not only to refinish our ladder bars, but more importantly to inspect each and every weld that made up the bars. If you look at the suspension components of many of today’s Pro Stock and Pro Modified cars, the 4-link bars and related components are left uncoated to allow for easier inspection of welds and tube damage.
“A lot of racers don’t pay a lot of attention to the jam nuts,” Perry elaborates. “The jam nut (or check nut) can cause problems as much as anything else. Not only does the jam nut prevent a thread from backing out, the thread contact between the ladder bar and rod ends needs to be held tight to prevent thread contact wear from stress and suspension movement.
With our ladder bar system, it is relatively straightforward to install a diagonal link kit in replacement of our Panhard bar. These diagonal links, such as those offered by Chassis Engineering, install diagonally between the front ladder bar bracket and a rearend housing bracket. The diagonal design allows the suspension to stay centered while also permitting each side of the ladder bar and sprung suspension to operate independently. This helps the shocks perform their duties with a true vertical motion of the overall suspension.
Most pre-fabricated diagonal links are designed for a standard 24-inch width spacing of the ladder bars. With our bars constructed at only 22.5-inches of spacing, we ordered an unwelded kit so we could customize the diagonal length to match accordingly.
Chassis Engineering offers multiple diagonal link options. Its standard link setup can handle the typical tube chassis car and is constructed of 3/4-inch x .156-inch mild-steel tubing. The optional heavy-duty and Top Gun diagonal links are designed with larger 1-inch tubing. We ordered the more substantial 1-inch unit kit for our heavier back-half Camaro compared to a lighter tube chassis car.
Perry practices what he preaches on his own vehicles — he is currently applying the same suggested maintenance to the chassis of his personal racecar.
He noted that he has been so busy in his job at Chassis Engineering that he hadn’t really raced his own car for a few years. “Just yesterday, we took my car out and make a few laps in it for fun,” He says. “Following our track day, my son and I made the decision to update the tires and a few other pieces, but we’re also going to put it up in the air, remove all of the tires, brakes, and go through all of the front and rear suspension hardware piece by piece to make sure everything is right.”
If you can imagine the stress your chassis undergoes to get down the track in quick fashion, lap after lap, weekend after weekend, it just makes sense that examining all the components in a hard-working suspension is a matter of performance and safety.