If it were only when braking I'd say your rim has a dent in it.
If it were only when braking I'd say your rim has a dent in it.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett
Check to be sure that your front and back quick releases are tight. If your wheel falls off, it won't be pretty.
If the quick release is tight, see if the wheel has any side-to-side movement in the fork. If that's the case the cones are probably loose. That can cause pretty noticeable wobbliness on a descent.
Handy Sheldon Brown advice: http://www.sheldonbrown.com/cone-adjustment.html