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Mountain Bike Transmission & Gears

  1. Mountain Bike Gear Levers

    Mountain Bike Gear Levers
  2. Mountain Bike Rear Derailleurs

    Mountain Bike Front Derailleurs
  3. Mountain Bike Front Derailleurs

    Mountain Bike Front Derailleurs
  4. Mountain Bike Chains

    Mountain Bike Chains
  5. Mountain Bike Cassettes

    Mountain Bike Cassettes
  6. Mountain Bike Chainsets

    Mountain Bike Chainsets
  7. Mountain Bike Bottom Brackets

    Mountain Bike Bottom Brackets
  8. Mountain Bike Pedals

    Mountain Bike Pedals
  9. Chain Guides

    Chain Guides
  10. Mountain Bike Chainrings

    Mountain Bike Chainrings
  11. Chainset Bash Guards

    Chainset Bash Guards
  12. Mountain Bike Groupsets

    Mountain Bike Groupsets
  13. Single Speed Section

    Single Speed Section
  14. Jockey Wheels

    Derailleur Jockey Wheels
Transmission & Gears Information

Mountain bike gear levers are cable operated levers which move the front or rear mech moving the chain to a different cog changing the gears.  The three types of mountain bike gear lever are trigger, twist and thumb shifter and each off-road groupset manufacturer has a slightly different method of shifting so please check compatibility with current set up before purchase.  Merlin Cycles stock mountain bike gear levers from Shimano, SRAM and microSHIFT.


Mountain Bike Rear Derailleurs The rear derailleur, or rear mech, is the device on the bottom rear right hand side of the of the bike frame which moves the chain up and down the cassette on the back wheel changing the rear gears.  They are available in three lengths of cage: short, medium or long with traditional hanger or Direct Mount attachment. Merlin Cycles stocks mountain bike rear mechs from major component manufacturers Shimano and SRAM.

Mountain Bike Front Derailleurs The front derailleur, or front mech, is the device just above the chainset which moves the chain to change gear on the front. They are available in several different seat tube clamp sizes but more important is the type of mech which is determined by cable routing and frame shape. Merlin Cycles stock Conventional, Top swing, E-Type, Shimano Direct Fit, Top pull and Dual pull type front mechs from major component manufacturers SRAM and Shimano.


Mountain bike chains may all look the same but care must be taken to choose the correct one. Make sure it is compatible with your current transmission system brand and amount of gears, eg 9 or 10 speed, as chains become thinner with increasing amounts of gears. All chains are supplied a standard length which needs shortened to suit current set up. Merlin Cycles stock mountain bike chains from manufacturers Izumi, YBN, SRAM, Shimano and KMC.

Mountain Bike Cassettes the cluster of sprockets on the axle of the rear wheel, are available in many different amounts and ratios. They are supplied with a set amount of sprockets, or speeds, with differing amounts of teeth which determine how easy or difficult it is to pedal. The number of sprockets must correspond with current gear levers as different speeds cannot be mixed. Merlin Cycles stock mountain bike cassettes from SRAM and Shimano which are compatible with each other’s systems.



Mountain Bike Chainsets The chainset, or crankset, is the front set of chainrings and crank arms which rotates round the bottom bracket shell of the bike. They are available with either one (single), two (double) or three (triple) chainrings with varying amounts of teeth and crank arm length is either 170 or 175mm. Merlin Cycles stock mountain bike chainsets from major brands including Race Face, SRAM, Shimano and Truvativ.


Mountain bike bottom brackets are available in several types. Traditional axle types which pass through the bottom bracket shell and are attached to either square taper, ISIS or Octalink cranks. External cup types are a set of bearing cups which sit outside the bottom bracket shell and the chainset axle passes through. Press fit systems are a simple bearing race which pushes into the frame without any threading. Merlin Cycles stock mountain bike bottom brackets from manufacturers Hope, Shimano and Race Face.



Mountain bike pedals are available in flat, traditional type, and clipless where the shoe is clipped into the pedal just like ski bindings. Flats are great if you want to use normal shoes while clipless are better for longer rides or racing but the cost of cycling shoes must also be factored in when purchasing. Merlin Cycles stock mountain bike pedals from DMR, e-thirteen, Shimano, Look, Crank Brothers and Time.


Mountain Bike Chainguides Chain guides are devices which keep the chain tensioned preventing chain slap or the chain coming off the front chainring. Previously only used on DH and dirt jump bikes, the advent of single ring cross country chainsets and double chainring compatibility of new chain guides means they are becoming a lot more common.  Merlin Cycles stock mountain bike chainguides in ICSG and BB Mount formats from the best in the business, e-thirteen.


Mountain Bike Chainrings The chainring is the toothed ring on the chainset with the number of teeth determining how much effort is needed to pedal. Chainrings are attached to the crank arms by 3, 4 or 5 bolts and are designed as either inner (small), middle or outer (large) depending on their position on the chainset. Dedicated single chainrings for DH or trail are also available and are chain guide or bash guard compatible. Merlin Cycles stock mountain bike chainrings and spares from A2Z, SRAM, Shimano and Hope.


Chainset Bash Guards A chainset bash guard is a hardened plastic protective ring around the outside of the largest chainring which is slightly larger and protects the teeth and chain from impacts. They bolt directly on to the chainset via the chainring bolts and generally used on larger travel bikes where there is more chance of the chainrings hitting obstacles. Merlin Cycles stock chainset bash guards from brands including DMR, Shimano, Hope and e-thirteen.


Mountain Bike Groupsets Groupset is the name for the collective group of parts on the bike covering transmission, gearing and braking. Each groupset is created to suit a certain style of riding and grouped into a range with matching components including; bottom bracket, brake callipers, brake discs, brake levers, cables, cassette, chain, chainset, gear levers and front and rear mechs (derailleurs). Merlin Cycles stock mountain bike groupsets from the two biggest component manufacturers Shimano and SRAM.


Single Speed Section Single speed mountain biking is often described as the simplest form of mountain biking as there are no gears to go wrong. Converting your geared bike to single speed is relatively easy with a few basic parts; single speed chain tensioner, spacers for rear cassette to keep the single sprocket in the correct chain line position and a thicker single speed chain. Merlin Cycles stock single speed mountain bike parts from brands including SRAM, YBN and DMR

Jockey Wheels are the two small plastic wheels on the bottom of the rear mech which control the tension of the chain and ensure that it doesn’t rub on the frame. They are easily replaced if damaged or for marginal gains you can get titanium or carbon jockey wheels with ceramic bearings which will probably outlast your mech. Merlin Cycles stock jockey wheels from major brands including BBB, Hope, Shimano and Tacx.

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