FORGOTTEN MOTOCROSS TECH: KTM’S ADJUSTABLE HEAD ANGLE TEST FRAME

On Jul 3, 2022 Last updated Jul 3, 2022

By making an over-sized and ovalized head tube, KTM was able to build a test frame that allows them to change the head angle at the track to test the effect of different angles on the bikes handling.

Motocross history is filled with examples of creative ideas that were heralded as groundbreaking, but, because of the rapid rate of change in development, sank into the swamp of forgotten technology. Although some ideas are best left abandoned, others were truly innovative (if not ultimately successful). MXA loves to reveal motocross’ tech trivia. Do you remember this idea? KTM’s adjustable head angle test frame.

KTM had many different eccentric CNC-machined inserts that could be inserted into the top and bottom of the head tube to alter the frame’s head angle. Note the clamps on the top and bottom races that held the inserts in place. This 2015 test program was stopped when it was determined that the stiffness of the new head tube altered the shareability of the data to the stock frame.

Back in 2015, KTM was looking for a way to confirm the best head angle. This required the engineers to design a series of frames with different head angles and build them up as complete bikes so the test riders could analyze the changes. It was time consuming. To speed up testing, KTM decided to build one frame with a head angle that could be changed within the confines of an oversized head tube. This allowed the KTM engineers to take one bike to the test track and change the head angle at will.

To achieve this, the head tube was ovalized on the longitudinal plane and CNC-machined inserts were clamped into the head tube. By varying the inserts’ orientation, the frame’s head angle could be altered. With a bundle of inserts, it was possible to test tiny head angle changes at the track. Was it a brilliant idea? Yes and no. In the end, KTM abandoned the idea because the overly beefy head tube stiffened up the chassis so much that the head angle results were not repeatable on a conventional frame.