'Get used to hearing the term "systems approach." Car crafters are an independent bunch, and we rarely purchase all the components for a trick engine or bitchin' suspension all at once. The time-honored piecemeal approach is much easier on the wallet. Since drag racers and quarter-mile street masters are more horsepower junkies than suspension innovators, chassis parts are often ignored in the quest for that elusive low e.t. If you consider yourself enlightened, think about planting the power your engine already makes. It might be easier than you think.
We've dismembered the front and rear suspension systems into smaller chunks of more easily digestible information. Keep in mind that the systems approach is your ultimate goal. Integrate the front and rear suspensions so the front half works as hard as the rear and you will experience a car that leaves harder than it has a right to.
Weighty IssuesWe met Jimmy Byrne at the Cordova, Illinois, NMCA race running an '88 Mustang in Xtreme Street. Byrne was runner-up based on consistent 8.30s on almost every pass that weekend with just he and his wife Lee Ann running the whole operation.
We grilled Byrne on his thoughts on improving traction. His ideas are grounded in hundreds of dragstrip passes with several stock-suspended Mustangs: "The theory says a lighter car is faster. But the fastest I ever went in my Mustang was when it was the heaviest. Most cars are nose heavy. If I take all the ballast out of my car, it will measure 55 to 58 percent of the weight on the nose. So that means you gotta put weight in the back."
That sounds counterintuitive, but the Byrne plan has merit. "For a street car, you want to make it look stock, so you're not gonna move the battery to the trunk. So you gotta add weight back there. There's a guy down the street from me who was pulling the interior out of his car to go quicker. I told him to put all the stuff back in and add 100 pounds of weight in the trunk. You also want it as far back in the rear as you can put it." This guy was running nitrous and had more power than tire, which is the focus of Byrne's suggestions. Horsepower is easy to make now, but there are fewer guys who have a handle on traction.
To give you an idea of how much difference 50 pounds can make, Byrne said on one pass he put 25 pounds of ballast directly over each rear shock and his Mustang spun the tires. He moved the weight 6 inches farther back in the trunk and the car planted the back bumper on the starting line. This ballast change represented roughly 3 percent of the car's rear weight, yet it had a drastic effect on traction. Granted, this is on an 8-second, 160-mph car, but this is no ladder-bar or four-link drag race rear suspension. Byrne's Mustang still uses stock upper- and lower-control-arm mounting points. Makes you think, doesn't it?
ShocksOne of the easiest and quickest ways to tune the suspension on a street/strip car is with shock absorbers. For normal street driving, a shock is used to dampen the oscillations of the springs. This is accomplished with hydraulic damping. That same style of damping can be used to help tune both the front and rear suspensions to perform exactly the way you and the traction gods intend for maximum bite.
For the front suspension, the old racer trick was to use "dead" stock shocks. Some racers even went so far as to drain the hydraulic fluid by drilling holes in their shocks. Then came 90/10 shocks. This generic term describes shocks with 90 percent of the control on compression (called bump) and 10 percent on extension (rebound), making it very easy to extend and difficult to compress. These shocks work to allow front-end rise to shift weight to the back for traction, but also hold the front end up through the traps, causing aerodynamic drag. A better solution is a single-adjustable shock that allows you to tune the shock to extend at a given rate. A car with lots of power tends to want a slower front-end rise than a slower car with less power.