There are no changes to our rear bumper rules, but with the number of questions we have received about them since our reminder that the “Gold Cup” style bodywork is no longer permitted, we thought it a good idea to remind everybody what is legal for a rear bumper! There is also a clarification on how this is tech’d.
So here’s the CKNA Rules on rear bumpers:
Rear Bumpers
All karts must have either a CIK plastic rear bumper, or a “full width” steel bar style bumper consisting of at least 2 horizontal bars between the frame rails (additionally, see “Metal Double Bar Bumper below). Single bar bumpers are not allowed. Bumper must be at least 1” rearward of the rear tires. All rear bumpers must be wide enough to cover at least half the width of each rear tire, and may not extend past them unless a rain race has been declared.
Metal Double bar rear bumpers
Tubing must be a minimum of .630” diameter. Bumper must be attached to each of the main frame rails. Top bar must be 6.5” to 12” from the ground with the driver seated in the kart. Bottom bar may not be any lower than the frame rails of the chassis, or higher than the top plane of the rear axle. An interrupted bar design is acceptable between the frame rails so long as there is a rear cross bar present. Slip joints between the frame rails are also acceptable. The top and rear bars may be connected, but no 90 degree joints may be at the outer edges of the upper bar. Additional reinforcement bars are optional. Bumper may be mounted at an angle of 0 – 45 degrees tilted rearward.
Additionally, many bumper/kart manufactures are now making these bumpers slide side to side much more. Therefore, while checking if the rear bumper covers at least half the tire, tech officials will slide the bumper inward on each side. This means that to be legal, at least half the tire must be covered no matter the position of the rear bumper on the slides.
So yes, metal rear bumpers are still legal. They must cover at least half the rear tire AT ALL TIMES and must have an upper and lower bar as described above.
The plastic CIK style ones are OK too, but many times people have them hanging out past their rear tires. You will be told to correct that at Grands in pre-tech with the bumper wider than the rear tires! It’s much easier to fix that at home:
