If there is no surface on which the brake block can apply force to the rim. Fail.
If you mean braking on a unmachined rim then don't worry. Unmachined rims are new and only really made to stop brake squeak on new bikes. Google it.
@TheBrick(Tommy) started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
If there is no surface on which the brake block can apply force to the rim. Fail.
If you mean braking on a unmachined rim then don't worry. Unmachined rims are new and only really made to stop brake squeak on new bikes. Google it.