When & How to Back Half
A lot of us will build an engine that is so strong it will over power the car and the tires on the car. So at some point a back half is needed. You cant get wider tires on the car and the cars chassis cant take any more power. Between flex and tire width the car will simply over power the track and become dangerous to you and the person your racing against.
The tires need to be as wide as will fit under the car and as tall as the engine and available gearing will support. this gives the best contact patch that can get under the car. No regular street car can support large wrinkle wall slicks. Even if they could fit the cars chassis would not allow them to work as they should.
Wrinkle wall or street radials
Many hot rods and other performance cars can use larger rear tires. When it comes to racing the big tires can be the advantage that makes wining ride. Lots of power to find its way to the ground can come without much work. A mild big block with a large shot of NOS in a few stages can give more power than any standard tire can handle.
Now even with not racing many cars today can make a lot of power. The modern turbo setups and LS and LSX engines on the market today 1000 hp cars are not so uncommon. With this kind of power running around on the street many serious pro street cars will end up with a back half at some point. They will run large treaded street radial tires on large 12″ or bigger rims.
Frame rails and roll cages
When you do a back half the essence of the build is to chop out all the factory frame behind the passenger compartment and install a large bar that would allow a much narrower set of frame rails to be welded to the car. Then the rear is shortened or replaced with smaller one. so the larger tires will fit just closer together under the car. Many will at this point build a roll cage on top of the frame rails and around the driver. This lets you make the entire car stronger and keep that big hp from ripping the car apart. Connecting the rear bumper all the way to the front making a much stronger car over all. This also helps with stiffness.
Body, trunk, seats and fender lips
The inside body structure of the car is replaced with the heavy steel frame rails that support everything from that point on to the rear bumper. With most of the trunk removed to make room for the larger tires. It also takes a bit of interior space from most cars where the tires are now sitting. Often the rear seats are lost. In some cars the only option is to move the rear end back and lengthen the wheel base. Not a bad thing in most cases. Longer wheel base is often very useful when building a fast drag car. This requires moving the fender wheel openings back some so the wheel opening can fit the big tires.
Plans for the future…
My plans for the future are to back half my current c4 project. We plan to do some pretty major upgrades to the vette so it will keep up and run with the most modern cars and dead hook at the track like an all out race car. I will be trying to make room for some pretty large tires in the rear. Hopefully this will happen with enough time to get the project on the web for all to see. Its one of those cars that the back half is not normally done and takes a lot of work to make right and also requires a lot of measuring and figuring. To not end up with the tires sticking into the drivers seat or have the tires hanging out the back. Since i will be basically sitting with the tire at my back. I will also want to take some steps to keep an exploding tire from ripping into the car and into the drivers seat.
More to come…..