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Fork end
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Fork end
A fork end, fork-end, or forkend is a slot in a bicycle frame or bicycle fork where the axle of a bicycle wheel is attached. A dropout is a type of fork end that allows the rear wheel to be removed without first derailing the chain.
Track bicycle frames have track fork ends, on which the opening faces rearwards. Because they do not have dropouts, the chain must be derailed from the sprocket before the rear wheel can be removed from a typical track bike. Some single-speed bicycles intended for street or trail use are also equipped with track fork ends instead of dropouts.
On bicycles that do not have a derailleur or other chain tensioning device, rear horizontal dropouts allow adjustment of chain tension, and can accommodate a range of chain lengths or cog sizes. They were standard on most older derailleur bicycles from before the 1990s. An older derailleur-equipped bicycle with horizontal dropouts can be readily converted into singlespeed, fixed gear or to use an internally geared hub.
Rear vertical dropouts have the slot facing downwards. The advantage is that the wheel axle cannot slip forward compared with horizontal dropouts. The disadvantage is that on a bicycle without a rear derailleur but with vertical dropouts, the chain tension cannot be adjusted by moving the wheel forwards or backwards, and needs another means of chain-tensioning, by a derailleur, chain tensioner, or eccentric bottom bracket or rear hub. Fixed wheel bicycles cannot use any form of chain tensioning device, because the lower run of chain is pulled very tight when using the transmission as a brake.
In general, a modern bicycle frame intended for derailleur gears will have a vertical dropout, while one designed for singlespeed or hub gears will have horizontal dropouts or track fork ends.
Lawyer lips or lawyer tabs (a type of positive retention device) are tabs fitted to the fork ends on the front fork of bicycles to prevent a wheel from leaving the fork if the quick release skewer comes undone. Lawyer lips were introduced in the 1970s and are designed to compensate for user error in the operation of quick release skewers .
A side effect is that the quick release, which was developed to allow the wheel to be removed without having to unscrew any components, no longer works as designed: the skewer must be unscrewed in order to remove the wheel (although tools do remain unnecessary). This means that the tension on refitting must be adjusted again. Some cyclists file off the lawyer tabs, so the quick release works as originally intended.
A correctly secured quick release is unlikely to be ejected from the fork end in normal use where rim brakes are in use, although the moments in disc brake systems can cause quick-release front wheels to be ejected past the lawyer tabs. A solution to ejection risk would involve mounting the front disc brake calliper in front of the fork blade rather than behind, as the reaction force on the disc would then be into, rather than out of, the fork-end. The widespread adoption of through-axles in modern bikes was partly driven by the transition to disc brakes.
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Fork end
A fork end, fork-end, or forkend is a slot in a bicycle frame or bicycle fork where the axle of a bicycle wheel is attached. A dropout is a type of fork end that allows the rear wheel to be removed without first derailing the chain.
Track bicycle frames have track fork ends, on which the opening faces rearwards. Because they do not have dropouts, the chain must be derailed from the sprocket before the rear wheel can be removed from a typical track bike. Some single-speed bicycles intended for street or trail use are also equipped with track fork ends instead of dropouts.
On bicycles that do not have a derailleur or other chain tensioning device, rear horizontal dropouts allow adjustment of chain tension, and can accommodate a range of chain lengths or cog sizes. They were standard on most older derailleur bicycles from before the 1990s. An older derailleur-equipped bicycle with horizontal dropouts can be readily converted into singlespeed, fixed gear or to use an internally geared hub.
Rear vertical dropouts have the slot facing downwards. The advantage is that the wheel axle cannot slip forward compared with horizontal dropouts. The disadvantage is that on a bicycle without a rear derailleur but with vertical dropouts, the chain tension cannot be adjusted by moving the wheel forwards or backwards, and needs another means of chain-tensioning, by a derailleur, chain tensioner, or eccentric bottom bracket or rear hub. Fixed wheel bicycles cannot use any form of chain tensioning device, because the lower run of chain is pulled very tight when using the transmission as a brake.
In general, a modern bicycle frame intended for derailleur gears will have a vertical dropout, while one designed for singlespeed or hub gears will have horizontal dropouts or track fork ends.
Lawyer lips or lawyer tabs (a type of positive retention device) are tabs fitted to the fork ends on the front fork of bicycles to prevent a wheel from leaving the fork if the quick release skewer comes undone. Lawyer lips were introduced in the 1970s and are designed to compensate for user error in the operation of quick release skewers .
A side effect is that the quick release, which was developed to allow the wheel to be removed without having to unscrew any components, no longer works as designed: the skewer must be unscrewed in order to remove the wheel (although tools do remain unnecessary). This means that the tension on refitting must be adjusted again. Some cyclists file off the lawyer tabs, so the quick release works as originally intended.
A correctly secured quick release is unlikely to be ejected from the fork end in normal use where rim brakes are in use, although the moments in disc brake systems can cause quick-release front wheels to be ejected past the lawyer tabs. A solution to ejection risk would involve mounting the front disc brake calliper in front of the fork blade rather than behind, as the reaction force on the disc would then be into, rather than out of, the fork-end. The widespread adoption of through-axles in modern bikes was partly driven by the transition to disc brakes.
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