I have a kids' 18" bike with a fixed gear and a coaster-brake. I would like to replace the rear hub with a (preferably 3-)geared hub with a coaster brake as it is the kind of brake my kid is most comfortable with.
The problem I am facing is that it is an aluminium frame bike and it only would take a hub with 110mm OLD. Yet, all the hubs I am able to find are 116-120 (Sturmey Archer S2, SRAM T3, Shimano Nexus SG3C-41) or even 130mm (SRAM i-Motion) in width.
Is there any chance of modifying the Shimano Nexus or the Sturmey Archer hubs to fit a 110mm frame (e.g. by replacing the outer screw/lock nuts with narrower variants)?