+1 to a warm pair of sleeping socks for in camp or when really cold, a pair of down booties or down socks.  For sleeping socks, find some nice fluffy, thick merino wool socks (maybe check out NZ possum down socks, order up a size, shrink them a little and enjoy super thick, warm but very light socks).  If you want to go the down sock/bootie route, consider Goosefeet down socks.  Super light (~2 oz.) yet super warm.

If your shoes are wet in camp you can use some cheap plastic produce bags worn over your socks (with rubberbands to help keep them up) inside your shoes.  You can also bags like this as a vapor barrier liner which can help keep your feet warm as long as you don't mind a little clamminess.

Also make sure you've got good insulation under you and on all of your extremities.  A warm pad will add a lot of warmth to your sleeping set-up and we all lose lots of heat from our head, hands and feet.  There's some truth to putting on a warm hat if your hands or feet are cold.

While on the go, thin (0.5mm) neoprene socks worn over a merino sock help keep my feet warm (enough) while hiking in wet, snowy conditions in trailrunners.  Haven't tried it while biking but it seems like it would translate over.  Goretex socks could probably work for this too.

Hey there, the name's Nico. 

I finally bought my first mountain bike a little over a year ago.  The original impetus for the bike was to use to access remote parts of my local national forest that are seasonally (or in some cases permanently) closed to vehicles.  Mostly ride old fire roads, abandoned double tracks and the occasional stretch of single track.  In recent years, the FS has just left a lot of the access roads gated and locked all year for lack of funds to do any upkeep; the bike has been a great tool to maintain access to some of these otherwise out of the way spots.

I'm an avid and long time UL hiker and have recently become interested in the idea of combining my love for camping and backpacking with my newfound interest in riding a mountain bike around the backcountry.  My camping kit is pretty dialed (~6-7 lb base weight), so now I'm putting together a rackless carry system for my bike and looking forward to putting it to good use.

I most ride and hike in the Los Padres National Forest behind Santa Barbara and Ojai, CA with occasional forays a little farther north toward Big Sur or inland to the Sierra to go see my brother.

Looking forward to learning more about bikepacking here.  Cheers.