Clive Forth's A-Z of Mountain Biking: G for Gears

Words: Clive Forth
Photos: Frazer Waller

Welcome to the A-Z of skills and technique, a bi weekly look into the language around skills tuition with some useful riding tips thrown in for good measure. We are slowly but surely working our way through the alphabet and this week we hit the G spot and get orgasmic about Gears.

gear |gi(ə)r|

noun

1 (often gears) one of a set of toothed wheels that work together to alter the relation between the speed of a driving mechanism (such as the engine of a vehicle or the crank of a bicycle) and the speed of the driven parts (the wheels).

Who out there remembers having a five-speed racer or a three-speed Sturmey Archer? Hands up if you had the early over bar seven-speed set up on your MTB.

I recall them all and I like many of you have seen the crazy developments that have taken place over the years, internal gear hubs now running fourteen speed and the old thread-on cassette incorporating free-hub has gone, replaced with new light weight CNC machined units boasting up to eleven sprockets allowing the rider to use a single chainring while maintaining a wide range of ratios.

Forgive me if this technical jargon bamboozles you, for those of you who are new to this or less technically minded here are some images that should help you identify just what the hell I’m rambling on about:

With the pretty pictures done, let’s look at how this wide range of gears can be used to good effect on the trail. The basic concept of having such a broad spread and wide selection of gears is to enable you to maintain a consistent cadence (rpm or leg speed) while pedalling up and down Dale. Inevitably (especially if you ride down here where I’m based in the Alps) at some point you run out of them and either continue to grind uphill with nose to stem or spin your legs round flat-out like a Lamborghini on the rev limiter.

All too often I see people using a less savoury ratio for the job, the aim of the game is to be energy efficient and maximize the use of those gears. In order to do so, gear changes should be frequent when tackling undulating terrain; if gravity offers some assistance, take it.

Energy is burned in large quantities when we do one of the following.

  • Spin like the clappers
  • Grind as if towing a truck
  • Turn the cranks from zero rpm, i.e. when you start to pedal

Every time you start off, exit a corner and start to pedal or start to pedal from coasting along you have a big drain on your energy. Learning to match the gear to your road/trail speed will help you save energy and make smooth, fast progress along the trail. When making a shift between chainrings try and balance the gear ratio by dropping down a sprocket if shifting into a small ring or shifting up a sprocket if shifting onto a larger ring.

You will find that many of the ratios you have available on a multi ring set up are actually the same, in a 3×9 set up approximately 35% of the possible gear combinations (ratios) are the same, this means your old 27 speed bike actually has 17-18 gears. Coincidentally a new 2×10 set up (20 speed) has approximately 10% overlap (same ratio combinations), giving you 18 speeds.

Torque (pushing a large ratio) can be used to help keep the bike planted on the floor through rough sections; it’s easy to remember, “Torque equals traction”. However, the added leverage will require more power and this will drain your precious energy resources, so a period of recovery (easy pedalling) may be required before the next effort.

I find there are many sections of technical trail that can be cleaned with ease if you either accelerate into them and carry some speed or select a larger gear and torque your way through, if you’re sitting and spinning then you’re not suspended and it’s harder to absorb the rough ground and move the bike around below you – standing and using a larger gear in these situations can be beneficial.

I appreciate that we humans differ slightly, we provide the engine and suspension in this vehicle, some of us will be big capacity diesels with lots of torque while revving low and others may be that 1000cc turbo unit that just loves to scream along on the red line. So next time you’re out on the trail have a play and feel the difference for yourself, experimentation is key to finding that sweet ratio for the job.

Until next time, keep it upright.

Clive Forth. MTBSkills, Transition Bikes.

www.mtbskills.co.uk

Follow Clive on twitter - twitter.com/cliveforth

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