SWAY BAR SIZING
Any recommendations on a new sway bar for my 1969 Mustang? How does it work and why not just install the biggest one available?
Which one you use is generally dependent on what type of driving you want to do in your car. You didn’t mention what engine/drivetrain combination you have, so I will give the generic lowdown.
The front sway bar (I prefer the term antiroll bar) is nothing more than a big torsion spring to keep the body from rolling over in a turn. The bar, when twisted down its length, acts like a big spring. When the car is rolling along and the wheels are moving together, the bar rotates around the frame mount points. In a turn, one side is compressing and one side is rebounding, and the force on the rollbar gets twisted. This transfers the energy over to the other side of the car, reducing the “roll” of the vehicle.
How the bar does this is by the material used, the radius of the bar ( bigger means stiffer), and the length of the arm from the mount point (shorter arm is stiffer). The stiffer the bar, the harder it is to twist, and the less the car rolls in a turn. However, the stiffer the bar, the harsher the ride, and the car can bounce around on rough surfaces. There are ways to get around this, but the stiffer the bar, the harsher the ride.
Ford generally stuck with a 7-inch bar on base Mustangs, and some “GT” handling packages were around 15/16 inch in diameter. Most aftermarket bars start at 1 inch and they can get to 11/4 inches for a bar that uses the stock location. Any bigger than that and you start having fitment problems with the stock mounting location. Length of the arms is also limited by the original suspension envelope.
If you think you need to improve the rollover of your car, the good news is that the aftermarket bars have been made to really work well with the original suspension. Unless you are seeing serious track time, the Addco (addco.net) 1-inch sway bar is engineered right and will help with whatever suspension you decide to use. Good luck with the ’69!
The stock bar below measures out at 0.685 inch, while the Addco bar (PN 715 shown) is a 1-inch bar. The bigger the radius of the bar, the harder it is to twist.