I recently bought a Kryptonite Evolution series 4 Standard U-lock for my bicycle. While I have been quite happy with the lock itself, I had issues with the bracket. The supplied bracket mounts on the bicycle tube by a strap that gets tightened with a bolt. That is generally a good idea because this type of bracket fits several different tube diameters. However, over the course of a few days the bracket would always come loose as the the strap slipped. At least that is what happened on my bicycle with its 28.6 mm tube and the lock being mounted vertically.

As I didn’t see an obvious way to fix the existing bracket I designed my own bracket. This bracket mounts on the tube by pressing two haves together with four M4 stainless bolts. The socket part of the original bracket, that accepts the lock, then mounts onto the bracket using the original M4 stainless bolt.

I got the two parts manufactured from aluminium on a CNC mill. They turned out quite nice and both the socket for the lock and the bracket itself fit well.

The two halves of the new bracket

The new bracket with bolts and lock socket

I have to admit that the new bracket doesn’t look as elegant as the original one but the fit is rock-solid and I never had it come loose.

You can download a CAD model of the bracket in the STEP file format. Please note, that threads can not be represented in STEP. All five threads are M4.