To harvest the kinetic energy from the vehicle suspension system, a tubular generator, which is composed of a single permanent magnet layer coreless model, was proposed in the previous study. Despite the excessive volume of the generator, both output power and power density are significantly lower than other conventional machines. This paper examines different designs of the tubular generator with the goal to enhance the performance, including a double permanent magnet layers coreless model and a cored model. By using a commercial finite element method (FEM) software, two proposed generators are theoretically analyzed and compared with the conventional generator. Analyzed results reveal that under the same operating conditions, the cored model can regenerate the largest amount of the power density. These results indicate that cored model can be considered as a promising candidate for the application to the electromagnetic shock absorber in sport utility vehicle (SUV).