Q: More and more forks seem to be coming with 20mm bolt thru axles, or with the option of having them, but are they worth the extra hassle, cost and weight?
Cam Tullio, Modena
A: It depends how hard you ride really. Depending on fork model a 20mm axle adds about 20-30% to steering stiffness, as well as increasing overall wheel security massively. You'll really notice this when trying to turn up off camber corners, holding a straight line through diagonal rooty/ rocky sections or generally trying to force your bike where it doesn't naturally want to go.
The downsides are that it takes longer to get the axle out on an old skool bolted design. RockShox Maxle and the Marzocchi equivalent are no slower than a conventional QR though. If you factor in the weight of the QR skewer they replace bolt thru forks aren't noticeably heavier either. But they can cost more and you'll need a 20mm compatible front hub to go with them.