World Library  
Flag as Inappropriate
Email this Article

Shifter (bicycle part)

Article Id: WHEBN0002564375
Reproduction Date:

Title: Shifter (bicycle part)  
Author: World Heritage Encyclopedia
Language: English
Subject: Derailleur gears, Electronic gear-shifting system, Hub gear, Bicycle gearing, Bicycle drivetrain systems
Collection: Bicycle Parts
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Shifter (bicycle part)

A twist-style seven-speed indexed shifter made by SRAM
A pair of Suntour down tube shifters.
A right (rear) Shimano 7-speed below-the-bar shifter with integrated brake lever.
A pair of stem mounted shifters.
A 3-speed shifter on a Triumph.
A bar-end shifter.
Shimano 9-speed STI levers
Shimano above-the-bar levers.

A bicycle shifter or gear control or gear levers is a component used to control the gearing mechanisms and select the desired gear ratio. Typically, they operate either a derailleur mechanism or an internal hub gear mechanism. In either case, the control is operated by moving a cable that connects the shifter to the gear mechanism. Shifters are mounted on the down tube of the frame, stem, or various locations on the handlebars. Manufacturers of shifters include Shimano, Campagnolo, Microshift, Sturmey Archer, and SRAM.

Shifter controls are mounted so that the right shifter controls the rear derailleur and the left shifter controls the front derailleur. For hub gears, the control is also mounted on the right.

Various shifters designs have included friction shifters and index shifters, which do not require fine-tuning during a gear change, as well as shifters integrated with the brake controls.

Contents

  • Friction shifting 1
  • Index shifting 2
  • Shifter designs 3
  • Combined brake and shift levers 4
    • Advantages 4.1
    • Disadvantages 4.2
  • Variations 5

Friction shifting

Originally, gear control levers consisted of a simple lever. Changing gears required pushing or pulling the lever so that the derailleur would move the chain to a different sprocket on the rear hub. The cyclist would need to adjust the lever to center the chain on the sprocket.

This system started out with 2 or 3 sprockets, and by the 1970s had developed to 5 and 6 sprockets. Many inexperienced cyclists, especially those who started in the US 1970s bike boom, found it difficult to change gear accurately. Typical difficulties included gear changes that left the chain in between two sprockets, which causes noisy rattles, or undesired and unexpected gear changes. However, many experienced cyclists still prefer friction gears for their simplicity and long-term reliability, as well as the ability to mix and match components from different manufacturers without the compatibility issues of indexing systems. Another benefit of friction shifting is the ability to shift from the lowest to highest gear in one simple motion. In addition, the introduction of ramped freewheel sprockets (such as Shimano's Hyperglide system) and derailleurs with floating jockey wheels has made accurate gear changes much easier than previously. Friction or ratcheting shifters remain popular for front derailleurs, since only two or three chainrings are used, and allow trimming of the front derailleur.

Index shifting

Index shifting is a system where the control has discrete stops. Hub gears by design are indexed, but for derailleur systems, indexing was an innovation. Each stop corresponds to one position of the derailleur. This allows the cyclist to change gear without having to adjust each time, as in friction shifting.

The first successful indexed shifting system was the Shimano Index Shifting or SIS, introduced in 1984 on the 6-speed Dura-Ace racing groupset. This made it near impossible to misshift, but at the expense of having more difficult initial adjustment. Most modern bikes made today are equipped with index shifting. Prior to this, Shimano had sold a system called Positron, in which the indexing mechanism was placed in the derailleur; however this system was only targeted at cheaper bicycles and gained a bad reputation. In all modern indexed shifting systems, the indexing mechanism is placed in the shifters.

Index shifter styles include twist shifters, trigger shifters (such as Shimano's Rapidfire design), shifters integrated with brake levers, levers mounted on the downtube, and bar-end controls. A twist shifter is mounted in line with the handlebar grips. Shifting is controlled by rotating the grip of the shifter. Trigger shifters have separate levers that change gears to the next gear up or down. Early indexed shifters could be used in friction mode for backwards compatibility, but this feature is no longer common.

New mountain bicycles use either twist shifters or trigger shifters. Older mountain bicycles may have thumb shifters, often indexed for the rear derailleur and friction for the front. Shimano's Deore, LX, XT, and XTR mountain groupsets include combined brake/shift controls, called Dual-control. Moving the brake lever perpendicular to the direction to control the brakes operates the shift mechanism.

Given that friction shifters were compatible with almost any derailleur, index shifting systems have been criticized for their non-interchangeability. For example, Shimano indexing components are often incompatible with SRAM or Campagnolo components, because the amount of cable pulled between each "click" is different in each system. For example, a typical Shimano (2:1), 7-speed shifter changes the cable length by 2.9mm between each gear, while a similar 7-speed SRAM (1:1) shifter changes the cable length by 4.5mm; some other SRAM units, (that differ only by an MRX designator), are compatible with Shimano units. In addition, newer components are often not backward compatible with older systems from the same manufacturer, so finding spares for older systems is often difficult, and stocking all of the possible combinations (shifters, derailleurs, chainrings, freewheels, and cassettes) is a challenge for the local bike shop. Some components can be mixed and matched between systems, but it can be a bit of a kludge to do so. Component manufacturers have been accused of planned obsolescence for introducing more and more complicated shifting systems—and withdrawing support for older systems—to a riding public which generally doesn't need so many gears for basic transport, utility, or recreational cycling.

One notable exception to the lack of compatibility in modern shifters is the fact that none of Campagnolo's front shifters are indexed, so they are compatible with all double or triple cranksets, even those of different manufacturers. Campagnolo rear shifters are also partially backwards compatible because a mechanic can upgrade them for use with a different number of rear sprockets by replacing a small part, the shift disc.

Shifter designs

Older road bike shifters may be down tube gear levers, mounted on the down tube of the frame. These have been available both non-indexed (friction) and indexed. If the levers are not mounted on the handlebar, the rider would have to move a hand from the handlebars to the gear lever to change gears. This made changing gears difficult while turning, going up hill, maneuvering in traffic, or during a race, as the rider would lose some stability from having only one hand on the handle bar, while adjusting the lever. Friction shifters have the added disadvantage of having to be trimmed every time the gear was changed, which might take a few moments. This led riders to usually stay in one gear, unless they were about to rapidly change their speed. Indexed shifters addressed the trimming issue, but the stability issue remained.

Thumb shifters are simple shifters which used to be common on mountain bikes, essentially being a downtube shifter mounted on top of the handlebars. Stem-mounted shifters are also similar. These gave way to twist-grip shifters as developed by SRAM, which remain common on flat handlebars. 'Rapidfire' or trigger shifters use two triggers below the handlebar, one to change up and another to change down.

Combined brake and shift levers

Campagnolo Veloce 9-speed Ergopower lever

With the introduction of systems such as Shimano Total Integration, Campagnolo ErgoPower, and the more recent SRAM Double Tap systems, the majority of these issues have been addressed. These systems combine a trigger shifter into each brake lever, and were sometimes referred to as brake/shift levers (or brifters), for their ability to combine the brake and shift functions into a single unit for use with one hand. However, in recent times, the term brake has been dropped, and the levers are referred to simply as shifters or integrated shifters. These integrated shifters, when combined with gear ramps and teeth shaping on the cassette, address most of the issues with friction and index shifters.

Advantages

Integrated shifters allow for rapid and precise shifting, without removing the hands from the handlebars. This system has been combined with gear ramps and tooth shaping on the cassette to allow for the chain to transfer power while shifting. This allows more frequent shifting to allow the desired cadence, an especially useful capability in traffic or during a race. The cyclist can accelerate more rapidly (thanks to rapid up shifting while pedaling), maintain a straighter line while accelerating (such as while riding along a curb in traffic, or during a race), and downshift while approaching an intersection or a hill. The ability to rapidly shift allows a cyclist to better maintain a good cadence and therefore cycle faster with less effort.

For touring cyclists and recreational riders who use drop bars, integrated shifters may make riding easier and more comfortable, as they allow the rider to use more hand positions and also retain access to both the brakes and gear shifters at the same time.

In general, the additional weight, expense, and occasional maintenance of shifters on a road bicycle is far outweighed by the performance advantages in a racing context.

Disadvantages

Integrated shifters are not without their disadvantages; the system is more complicated and subject to greater wear and tear than previous systems, especially friction shifters. Due to their greater number of parts, index shifters are more expensive and less reliable than friction shifters. Index shifters rely on uniform cable tension, but over time the derailleur cable will stretch, causing the system to slowly drift to the right of the gear. In addition integrated shifters need a considerable amount of additional gear cable and housing compared to downtube mounted shifters, this leads to more friction and so less responsive shifting. Periodic adjustments are required.

Variations

[[Image:Raleigh Chopper-001.jpg|thumb|US Raleigh Chopper Mk1 with top tube

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.