There are significant differences between gundrilled, and solid torsion bars other than their weight. The hole in the center of gundrilled torsion bars creates two surfaces instead of one, allowing the bar to react differently than a solid bar to deflection. Gundrilled torsion bars have a faster spring rate than a solid torsion bar, which means they rebound, or spring back, quicker. The center diameter of a hollow torsion bar is adjusted to achieve the same spring rate as a solid bar. Therefore, no chassis adjustments need to be made when switching from solid to hollow bars. Schroeder gundrilled, and solid torsion bars all start the same way, as aircraft quality high alloy steel stock, and the gundrilled bars are drilled out using the same high performance equipment used to machine the barrels of fine rifles. Track conditions and chassis characteristics determine which type of bar is the best choice for your particular application.