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Trials Terminology

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This topic is a work in progress and will be expanded on, if you want anything added or see something I've missed or got wrong let me know and I'll get it added/edited!

Do you know where to find your TPA?

Why your modified bike is classed as a stock?

Why your stock spec bike is classed as a mod?

Look no further for your bike trials definitions!

Types Of Riding

  • TGS or tap, gap and sidehop is generally performed on the streets and is usually made up of single moves generally where the rider is looking to perform the biggest taps, gaps and sidehops to their ability or of a spectacular nature such as over water features or onto Post boxes. Good examples of this style are videos by Neil Tunnicliffe or Damon Watson.
  • Street is generally, but not solely, performed on 24" bikes setup with low bottom brackets, high front ends and short chainstays. More of a flowy style of riding linking up traditional moves like gaps and hopping up and off objects with BMX type spins and manuals. Mostly ridden on the street but this style of riding can be done on natural, generally rocky areas. Good examples of this style are videos featuring Ali C or Danny Macaskill.
  • Natural is usually associated with comp style riding on rocks, tree stumps or any non man made obstacles. A lot of natural riding is made of the basics of TGS though it is made more difficult by the general lack of flat smooth takeoffs/landings and the fact the riders have to adapt to their surroundings to pick lines and make the most of what little space they have. Good examples of this style are Jack Carthy and the Tartybikes videos of Stan Shaw.

Types Of Bikes

  • Mod - A 20" wheeled bike. Most mods nowadays are fitted with 19" rear wheels as standard allowing fatter tyres to be used.
  • Stock - 26" wheeled bikes.
  • Modstock - 26" wheeled bike which uses a 116mm width rear hub usually found on mods.
  • 24 - Funnily enough a 24" wheeled bike.

All of these different types come in styles suited to the disciplines listed above and if you cannot find a frame to your liking there are companies who specialise in custom building trials frames to the geometry of your choice.


  • Bashplate/bashring - Bashplates are found on mods and are bolted to the frame beneath the bottom bracket. Bashrings are used on all trials bikes and are usually fitted to the cranks though can be fitted onto the bottom bracket. Used to protect the sprocket or FFW from damage.
  • Bottom bracket - Centre axle which the cranks are mounted to. Either square taper or ISIS drive fitting.
  • Brake Booster - Device used to link up the mounting bolts of a set of rim brakes to prevent the frame from being forced apart when braking heavily.
  • Cranks - Arms connecting the bottom bracket to the pedals. Available in square taper or ISIS drive fitting.
  • Disc brake - A powerful brake which uses a disc mounted to the hub of a wheel to slow down. Generally more suited to mods and 24" street bikes.
  • FFW or front freewheel - a single speed freewheel generally mounted on the cranks though can be fitted to fixed rear hubs.
  • Hydraulic rim brake/HS33/HS11 - A powerful brake which uses the rim sidewalls to slow down. Generally more suited to stock bikes.
  • ISIS drive - Splined interface between the bottom bracket and crank arms. Generally stronger and longer lasting than square taper.
  • Snailcams - Chain tensioners fitted to the axle of the rear hub.
  • Starnut - A nut which is fitted to the inside of the steerer tube on a set of forks which is used to tension the headset.
  • TPA - Turbo pad adjuster as found on hydraulic rim brakes and Echo disc brakes. Used to move the pads closer in to the rim when your out and about riding to make up for pad wear.

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