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Bicycle computer

What is a bicycle computer?

A bicycle computer is a small unit that attaches to your handlebars and provides you with information about your ride.

A basic computer will provide you with your speed (current, maximum and average), how far you have cycled and how long you have been cycling.  More complicated models will provide you with your pedal rate (cadence), heart rate, power output, calorie consumption, the gradient of hills, your rate of climb and the temperature.  And if it is a GPX unit it will provide you with mapping, route directions and compass headings as well.  

Why would I want one?

Even a basic bike computer can add a whole extra dimension to your cycling.  For instance, if you ride a route regularly, say a commute, it is fun to see if you can beat your best time (whilst keeping safe!).  Or to see if the five coffees (or the three beers) you drank in the afternoon make a difference to your performance on your cycle home.

Recording your times over a set course is a simple way of seeing if your fitness is improving and can be achieved with a basic computer.  The more complicated computers can take this to a higher level using heart rate and power output information to track fitness progression.  Some allow a download of information to a PC where you can use supplied software to crunch all the data to give you useful information with charts and graphics of your ride.

A basic computer can tell you how far you have cycled, which is vital if you are following written directions of the - turn right at T junction after 1.5 miles - sort.  A computer with GPX will be able to provide you with a map and navigate you through a preset route, much like a car satellite navigation unit.

How do they work?

Most bike computers work their calculations based on the functions of wheel rotations and time.  For instance, if a 700mm diameter wheel (approx 2.2 m circumference) rotates 100 times in one minute the computer can calculate the speed as (2.2 x 100)  220 metres per minute or (220 x 60 / 1000) 13.2 kph (about 8mph).  Of course you don’t really need to know any of that or do the calculation yourself.  The computer will do it for you - often several times a second.

To count the wheel rotations a small magnet is fixed to the spokes of one of the wheels and a sensor attached to the frame sends a signal to the computer unit on the handlebars every time the magnet flashes past.  Cheaper bicycle computers use a wire to connect the sensor to the computer whilst more expensive models are wireless. 

What should I look for when selecting a bicycle computer?

  1. Range of functions – think about what you really want and what you can do without if price is a factor.
  2. Ease of use - how much information is on the screen?  Can you read it?  Can you scroll to other information easily?  Is the navigation through the information logical? How many buttons are there?  Are they easy to operate?  With gloves on?  Is there a backlight for poor light conditions?  Are there just too many functions? – sometimes less is more!
  3. Ease of initial set up – this includes attaching the mounting and the sensors etc. to the bike and setting up your personal and bike data on the computer (basic models will probably just require a wheel size).
  4. Wired or wireless – wireless is easier to set up, looks tidier and there are no wires to accidentally snap.  However, some models can be affected by things like overhead powercables. 
  5. Cost – you get what you pay for but, as ever, prices tend to rise exponentially towards the upper end.   A very basic bicycle computer can be bought for under £10 whilst a top end GPX will set you back over £400.
  6. Mounting – should be easy to fit, allow for quick removal of the computer unit at cafe stops etc. and should hold the computer firmly to the handlebar with no wobble.  An extra  mounting (and sensor) to allow the computer to be attached to a second bike might be a bonus to look for.
  7. Ability to download data to a PC – if you are looking for a multi functional computer to help you with your training then this feature will allow for much greater analysis of the data and an easy way of storing ride information.