Will Changing to a 16T Front Sprocket Cause Chain Slap on the KTM 1390 Super Duke Swingarm?

When contemplating a gearing change on the 1390—like dropping to a 16T front sprocket or increasing the rear to a 39T, 40T, or 41T—riders often worry about altering the anti-squat geometry and causing the chain to slap the bottom of the swingarm or chain guard under heavy compression.

When I designed the Superduked Shark Guard, the goal was to eliminate any chance of contact. I figured making the guard the same height as the OEM rubber guide, but positioning it even farther back—closer to the axle, and therefore farther away from the front sprocket—would solve the issue. To verify this, I track-tested it extensively at Laguna Seca using stock gearing, which I calculated was the closest the chain would get to the bottom of the swingarm.

I use a lot of suspension travel landing off the Corkscrew, and I ran that bike hard. The result was zero contact anywhere. Even on the rubber guide itself, there were no marks anywhere near that area. If you are somehow putting chain marks on your swingarm or guard with a stock 525 chain and stock geometry, you must ride loose and wild, and bottom out the suspension frequently.

If you do decide to change your gearing, keep in mind that a larger rear sprocket will change the chain line and reduce anti-squat. Always double-check your clearances by running the suspension through its full stroke.