The clincher rim is the most common type rim type with raised edges (rim shoulder) where a wire is sandwiched between by pumping up the tube.
Cross-section of a clincher rim.
1=rim bed of the rim
3=rim edge of the wheel
4=bead wire in the tire
5=inflated inner tube
7=tread of the tire casing
Most bicycle tires are clincher for use with a clincher rim. These tires have a steel wire or Kevlar fiber bead that interlocks with flanges in the rim. A separate airtight inner tube enclosed by the rim supports the tire carcass and maintains the bead lock. An advantage of this system is that the inner tube can be easily accessed in the case of a leak to be patched or replaced.
The ISO 5775-2 standard defines designations for bicycle rims. It distinguishes between
- Straight-side (SS) rims
- Crochet-type (C) rims
- Hooked-bead (HB) rims
Traditional wired-on rims were straight-sided. Various “hook” (also called “crochet”) designs re-emerged in the 1970s to hold the bead of the tire in place, resulting in the modern clincher design. This allows higher (80–150 psi or 6–10 bar) air pressures than older wired-on tires. In these designs, it is the interlocking of the bead with the rim, not the tight fit or resistance to stretching of the bead, that keeps the tire on the rim and contains the air pressure.