My back brakes don't lock the wheel (skid): feature or a bug? When I apply rear brakes only (I know this isn't the proper way to stop), it slows me down but never locks the wheel to the point of skidding (on dry pavement anyway). This is a new 'cyclocross' style bike with disc brakes. It has both regular road bike levers and auxiliary brake levers, if that matters. I am exerting quite a bit of force on the lever and they do not touch the handlebars (bottom out). It seems like a defect to me because that's not what I'm used to from my old hybrid bike with V-brakes, but having had it in the shop a couple of times, I'm starting to wonder -- are these brakes ineffective or is this a design feature to prevent skidding? 

If this is a flaw, what is wrong - the brakes, the pads, the cables/adjustment or something else? 

If it's a feature, how does it work?
Disc brakes should be capable of locking the rear wheel.

If this is a new bike I would suggest it's a set up/ breaking in issue rather than a fault.

I'm not sure of the brakes you are running, but guessing they're cable discs due to having axillary levers. I'd ensure :


the brake pads are bedded in
the disc brake rotor alignment is good
the pad contact point is correct (refer to your brakes manual)


Check out this question, Disc brake break-in?

If that didn't help I'd check that the auxiliary levers aren't impeding the full cable pull.