Pre 2006 American Classic 9mm disc hubs used 15267 bearings and are said to be not convertible to 15mm thru axle. This isn't strictly true. I have converted one of these hubs to 15mm thru as follows:
- remove 15267 bearings;
- machine bearing pockets 0.8mm deeper on either side;
- install 6803 bearings;
- install Tune thru axle (fine tune bearing preload using Tune supplied bearing preload shims).
One added benefit of this conversion is that you end up using a stiffer 17mm axle and loose some weight. Replacing the 15267 bearings, bearing spacer and AC 9mm end caps with a 6803 bearings, a Tune 17mm axle and Tune 9mm end caps saves about 14g.