For an explanation of this design, see my wheelbuilding article.
With half-step gearing, the larger shifts are made with the rear derailer, and the front is for fine tuning. This allows an 8- or 10-speed set up to have a reasonable range with fairly close spacing of the gears. One downside of half-step is that it uses all possible combinations, including those that run the chain at a fairly severe angle. This is not a big deal in an 8-speed rig, but is kind of marginal for 10-speeds. Another serious disadvantage is that every other shift in the normal sequence is a double shift (front and rear derailers simultaneously).
Half-step gearing is most suitable for riding in flat terrain, where shifting is rare. For bicycles with few speeds, it does allow finer gradations to get as close to the "ideal" gear for the particular wind conditions as possible.
Modern shift patterns use larger jumps on the chainwheels to select general ranges of gears, and fairly closely-spaced 7-or-more-speed clusters for the fine tuning. This greatly simplifies the shifting pattern, allowing constant adjustment to different grades in rolling terrain, with only occasional need for double shift.
See my Article on Gear Theory .
Conventional handlebars are divided broadly into two styles: "drop" and "upright"
|22.2 mm||7/8"||22.2 mm||7/8"||Steel bars. Mainly BMX, older Mountain bike bars.|
|23.8 mm||15/16"||22.2 mm||7/8"||Obsolete British size for steel handlebars, common on older 3-speeds.|
This size was also used for older British steel drop bars.
|25 mm||23.5 mm||Obsolete French size.|
|25.4 mm||1"||22.2 mm||7/8"||Standard I.S.O. size, used on the vast majority of newer bicycles with upright handlebars.|
This size was formerly common for steel drop bars.
|25.4 mm||1"||23.8 mm||15/16"||Standard I.S.O. size, used on most bicycles with drop handlebars.|
Also used on older British aluminium upright handlebars.
|25.8 mm||23.8 mm||15/16"||Unofficial in-between size used by some Italian handlebar makers for handlebars designed to be usable in either ISO (25.4) or Italian (26.0) size stems.|
|26.0 mm||23.8 mm||15/16"||Italian standard for drop bars, other bars made to fit Italian stems and some high-end aftermarket drop bars.|
This is sometimes incorrectly called "road" size.
|26.4 mm||23.8 mm||15/16"||Older Cinelli and Cinelli copies. Cinelli changed over to 26.0 mm in 1998.|
|27 mm||23.8 mm||15/16"||Titan (obsolete).|
|31.8 mm||1 1/4"||23.8 mm||15/16"||Road oversized.|
Sometimes incorrectly referred to as "handlebar ribbon." This mistake results from a translation error. (in French and Italian, there is no distinction between "ribbon" and "tape.")
|Dropout with built-in hanger||Plain dropout||Plain dropout with adpator claw|
This is a very complicated technology, with very ancient roots. For many applications, such as sprockets and bearings you want a very hard surface to the part, but the inside of the part should be treated to a lesser hardness so as to avoid excessive brittleness and breakage.
A conventional threaded headset consists of four races plus associated parts:
The adjustable race is secured by either a:
Threaded HeadsetNote wrench flats on locknut and top threaded race.
Threadless HeadsetNote pinch bolts on stem.
This type of headset must be used with a special handlebar stem that clamps on to the outside of the steerer, either with one or more pinch bolts (a.k.a. binder bolts), or other means. The stem is further secured by a plastic or metal cap which is bolted to the star nut.
To adjust an "Aheadset"-type headset, the stem binder must be loosened, then the bolt that runs through the cap to the starnut is tightened, usually with a 5 mm Allen wrench. This presses the stem down against the tapered bushing that fits inside the adjustable cup. and takes up the slack in the system. The stem is then aligned with the front wheel and tightened with its binder bolts. (Once the stem binder bolts have been tightened, the adjusting bolt that goes to the star nut is under no significant stress, and may even be removed.)
The upper collar has a gap at one point, with a pinch bolt to squeeze the gap together. (This upper collar may also include a cable stop for the front brake, if the bicycle has a rigid fork and conventional cantilever brakes.)
The handlebar stem is clamped tightly to the steerer, preventing the upper collar from moving upward. As the upper collar is compressed by the binder bolt it squeezes lower collar downward, taking up any slack in the headset bearings.
The Ge Force is the only threadless headset which doesn't use the handlebar stem as part of the adjustment. These headsets may be used with any stem, either external clamping or internal expander/wedge type.
|BMX/ O.P.C. bikes||.833"|
|26.4 mm||32.7 mm||24||Used mainly on bicycles with one-piece cranks, also some early mountain bikes.|
|French 25 mm||22 mm||26.5 mm,|
|30.2 mm||25.4 |
|Obsolete. French steerers usually have a flat filed on the back, rather than a grooved keyway as with other threaded systems.||Interchangeability note:|
These 5 sizes of forks
since the head tube
|1" ISO Standard |
|7/8"(22.2 mm)||26.4 mm||30.2 mm||24||This is the standard 1" size.|
|1" Italian (25.4 mm)||7/8"(22.2 mm)||26.5 mm,|
|30.2 mm||24||Obsolete. Threads are cut at 55 degrees, but ISO or J.I.S. headsets can be used.|
|7/8"(22.2 mm)||27.0 mm||30.0 mm||24||Older or lower-quality bicycles from Asia|
|1" Raleigh |
|7/8"(22.2 mm)||26.4 mm||30.2 mm||26||Proprietary size used on Raleighs made in Nottingham, England|
|22 mm||26.7 mm||30.8 mm||25.4 |
|Higher quality Austrian bikes use English/ISO|
|French Tandem 28 mm||22 mm||25.4 |
|Obsolete and rare.|
|1 1/8" (28.6 mm)||1" (25.4 mm)||30.0 mm||34.0 mm||26||"Oversized" (This size is more often used for threadless systems.)|
|1 1/4" (31.8 mm)||1 1/8" (28.6 mm)||33.0 mm||37.0 mm||26||Mainly used on tandems|
||BMX/||26.4 mm||32.7 mm||Used mainly on bicycles with one-piece cranks.
||1" ISO Standard (25.4 mm)||26.4 mm||30.2 mm||This is the standard 1" size.
||1 1/8" (28.6 mm)||30.0 mm||34.0 mm||Most newer mountain bikes use this size.
||1 1/4" (31.8 mm)||33.0 mm||37.0 mm||Mainly used on tandems
(38.1 mm)||39.8 mm||49.6 mm||Proposed OnePointFive standard
for downhill and freeride applications.
If you want to replace one headset with another, you must take into account the stack height of the new headset.
Both hub flanges were 1mm farther to the left than those of a normal hub, causing increased dish in the rear wheel, and persistent spoke breaage problems. Many loyal Helicomatic fans tout the ease with which the cassette may be removed for spoke replacement as a great virtue, but if the hub were better designed, it wouldn't break so many spokes!
These hubs were prone to bearing problems as well. Due to clearance requirements, they couldn't fit the normal 9 1/4" bearing balls, so they used 13 5/32 balls on the right side. These didn't hold up well. The cones tended to wear rapidly, and replacement cones are no longer available to fit these hubs.
Hellenic stays were introduced by (and named for) the British frame builder Fred Hellens in 1923, and have been used off-and-on since by frame builders who wish to make their frames visually distinctive. It is of no practical value, and often causes un-necessary complication to brake cable routing, luggage rack attachment and installation of frame pumps. It is also slightly heavier than normal frame construction.
Recent users of this design include GT, Huffy and Nashbar.
He also did a lot of pioneering work on suspension designs for bicycles, and deveoped a bicycle seat that was based on an upside-down dropped handlebar with furniture webbing wrapped between the two straight sections.
He was also known for roller demonstrations where he would perform a strip-tease while riding on the rollers. A very cool guy.
High gears are for going fast, when the terrain permits. The rider must push much harder on the pedals in a high gear, so high gears are not suitable for lower-speed riding, due to the great strain that hard, slow pedaling puts on the joints.
Before the use of chain drive, bicycles had direct drive. The cranks were directly attached to the hub of the drive wheel. The larger the wheel, the farther the bicycle would move with each turn of the pedals. The diameter of the drive wheel determined the gear of the bicycle. The larger the wheel, the higher the gear.
With a chain-driven "safety" bicycle, you can have any gear you want by selecting appropriate sprockets. With a high-wheel bicycle, the limiting factor is how long your legs are, because you can only pedal a wheel that is small enough for your legs to straddle and reach the pedals throughout the pedal revolution.
The safety bike was first introduced on a commercial scale in 1885, and by 1893 high-wheelers were out of production.
|Articles by Sheldon Brown and others|
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