vegaken

Guys which torque arm is better for drag racing only, the long one or short one? What are the advantages and why is it better and what are some of the drawbacks? The car is going to be run under NMCA/NSCA Drag Radial rules. Thanks for the help guys.
Ken

IHI

iTrader: (1)

The torque arm set-up is basically a ladder bar suspension set-up so do some searching around for setting up ladder bar suspensions for a general oversite of what going on since suspension tuning is so critcal for hooking all the power. In a nut shell the factory mount has the instant center towards the front of the car and tranfers most of the power into the chasis so a good suspension set-up works great when using a long torque arm but be sure you get a unit that will allow you to adjust pinion angle. With a shorter torque arm you move the instant center back in the car and depending on what the angle is this puts alot of shock into the tire for a short amount of time, while a lower mount that moves the IC forward, but still low, doesnt shock the tires as hard, makes the chasis take more of the force and it will carry the force further away from the starting line so not to over power the rear tires and break traction.

RB83L69

Imagine a line on the ground that goes from the center of one tire contact patch to the other. Now imagine a line that goes from the centerline of that one, to the center of gravity of the car. Now imagine the point where that second line intersects the floor pan of the car.

In theory, for optimum torque transfer to the chassis, you'd want the torque arm mounted right at that point.

In reality, it's alot more complicated; because several things all happen at once when you launch. But, that should give you a general idea. The factory torque arm is somewhat too long by that standard. Most ladder bar and 4-link setups for street cars have a hard time getting long enough because of where they have to mount, if the floor pan is left unmolested.

I believe that in these cars with the stock engine weight and location you'll find that the theoretical optimum drag racing length is somewhere around 8 or 10 inches shorter than the stock one. That's only optimum in terms of force transfer though; it might or might not make your particular tires hook the hardest, which depends on how stiff the sidewalls are among other things like ssprings and shocks and how much the chassis flexes.