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Which Half is the Back-Half? |
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| What exactly is a “back-half” car? Here is what it used to be - a drag car with a 2”x 3” square tube frame, starting behind the driver's seat and going to the rear bumper. The original purpose of the back-half modification was to permit the installation of wider tires. Another reason was to permit a more efficient suspension system, like coil-over shocks and possibly ladder bars or a 4-link set-up. Yet, many of the early back-half cars maintained their original leaf springs, moved in-board for tire clearance, and in fact, still remained mostly stock in almost every other area of the chassis. One other thing on the “used to be” list was that most of the engines only had about 600 to 900 horsepower. Now let's fast forward to 2004. The back-half car of today is a different beast. A good back-half car has basically a full tube chassis from the firewall back. A primary reason for this is the mandatory SFI chassis Spec requirements. And some of this new chassis technology is a requirement in order to handle the vastly increased horsepower of today's engines. Can you imagine how a 1970s era back-half chassis would handle with 1500 to 2000 horsepower? Not too well, probably. In fact, “Wipeout” would not just be the name of an old song about surfing. And yet, there are many racers running in back-half classes that are still running 30-year old technology. However, the problem is not behind the firewall - it's in front of the firewall. And who is to blame for this? In many cases it's the sanctioning bodies putting on the events. The typical rules for a back-half class usually call for stock firewalls and stock front frames (or sub-frames). This in itself is not the problem. The front frame area is usually reinforced and tied in to the rest of the chassis with tubing routed through the firewall and connecting solidly to the cage. This creates a sturdy chassis from front to rear. The weak link is the front suspension systems. Many sanctioning bodies still require stock (or mostly stock) front suspension. The rules makers may permit the use of better shocks or struts and even tubular “replacement” A-arms, but the real problem is the requirement to maintain the “original” attachment point geometry for the front suspension. In my opinion, this requirement is not only short sighted but it's also dangerous. For instance, does anyone really think that the stock double A-arm geometry built into a '55 Chevy is correct for a 3000 pound, 200 MPH doorslammer? If the car always went straight, a solid axle from a '32 Ford and a cross-mounted leaf spring would probably suffice. This obviously worked in the old 140 MPH AA/GS Willys with an 800 HP Oldsmobile engine, but how would you like to drive a race car with a twin turbo, 2000 HP combination, and decades-old front suspension technology? It would be like watching a reincarnation of Wild Willie Borsch. While everything may work OK with the stock '67 Camaro front suspension when the car is going straight, what happens when the car gets a out of shape in the lights? You could be in for big trouble. And don't forget that there is usually someone in the other lane, too. Sanctioning bodies that are promoting back-half doorslammer sportsman racing need to take a close look at some of their requirements, and determine if their own class rules are causing potential safety issues and added risks for the drivers (their paying customers). Is it really going to screw up the “integrity of the class” if a back-half car is fitted with a front suspension system designed for racing, when you know that the car has the potential of running 200+ MPH? Isn't it about time the sanctioning bodies gave the drivers a little more to work with? It's not 1970 and we're not in Kansas anymore.
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