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BIKE SIZING ADVICE

Buying a bike which is the right size is probably the most important part of choosing your new cycle. But how do you work out what size to get? A good shop should be able to advise you and let you try different sizes, but there are a few guidelines which help:

Childrens Bikes...

If the bike is for a child, they generally fall into age categories based on the average size of a child of a specific age. There is no hard and fast rule that says that you must buy a bike of a particular size for a child of a specific age. If the child is comfortable and not too stretched on the bike, and they can manage all the controls ie turn the handlebars safely, reach the brake levers and operate them AND touch the floor with the ball of their foot, then there is nothing to prevent you from selecting a bike in a bigger age category.
  • 12" Wheel Cycles - Suitable for ages 2 to 4
  • 14" Wheel Cycles - Suitable for ages 3 to 5
  • 16" Wheel Cycles - Suitable for ages 5 to 7
  • 20" Wheel Cycles - Suitable for ages 7 to 9
  • 24" Wheel Cycles - Suitable for ages 9 to 11
  • 26"+ Wheel Cycles - Suitable for ages 11+ (These are classed as adult cycles.)
First Bikes; 12" & 14" wheels, suitable for average ages 2 up to 5. Larger and slightly older children should benefit from the 14" wheel bicycles.
When buying 12" & 14" wheel bikes there are many many "pretenders" out there - essentially many of these "bikes" are no more than toys.
It is worth looking for bikes which feature ball bearings in the hubs and main cog assembly.
Many of these bikes have plastic bushes instead of steel bearings and whilst some manufacturers make a very good job using plastic bushes AND provide a back up of spare parts, many more do not.
Without naming names, many of the cartoon and character branded bikes bought from supermarkets and catalogues are the worst offenders.
Be cautious and ask of the seller whether you can get spare parts, as the plastic bushes commonly wear out very quickly.


Once a child has learnt to ride without stabilisers (generally about age 5) they will move up to a 16" wheel cycle. These do not normally come fitted with stabilisers but they can be added to virtually all 16" wheel bikes if required.

Once you get into the realms of 20" wheel bikes and above, you may be offered multiple frame sizes. This has the benefit of being able to fit a younger child onto a bigger wheeled bike if they are confident riders. Although you will find that size options are generally not offered on a particular model, rather that different models have different frame sizes.
It is a very tempting thing to do, but don't buy a bike which is too big for your child in the hope that they will grow into it. They will, but in the meantime they will be riding a bike which is not easy for them to control, which can be very dangerous. It does not really save money anyway, because if you change bikes more often, the outgrown ones will have a higher resale value.

Adult Bikes...

Once you are into 26" wheel bicycles (road bikes typically have have 700c, 27" or 28" wheels), then size is only determined by Frame Size. The size of the frame is measured from the top of the frame at the point where the seat post is inserted, down to the centre of the axle carrying the pedal arms (bottom bracket). In the UK and USA this is measured in inches, in Europe it is often in centimetres. Unfortunately some manufacturers measure their models to the centre of the intersection of the top tube and the seat tube, which can throw some of the sizings out a little. If in doubt, ask the shop and they should be able to tell you which way a particular bike is measured - or bring a tape measure!

The following rules of thumb should be applied when you try a bike for size:

Racing Bikes: Standing flat footed on the ground, you should have a minimum of 1" clearance between yourself and the top tube of the frame

Mountain Bikes: Standing flat footed on the ground, you should have a minimum of 3" clearance between yourself and the top tube of the frame.

A simple calculation can be used to estimate your required frame size if you are not able to sit astride a bike to measure:

Measure your inside leg measurement to the floor, subtract 3" (for mountain bikes, or 1" for road bikes) then subtract 10" (the average distance from the bottom bracket to the ground). This will give you the maximum frame size that you will need.

But buying a bike of the correct size is not just about the height from the ground. As bikes get bigger height-wise, they also get longer. The distance from the saddle to the handle bars increases by on average 1" for every 2" increment in frame size. So you must also make sure that though you may be able to stand astride a bigger framed bike, that you can still comfortably reach the handlebars and manage all the controls. Remember that the saddles on all bikes are adjustable by between 4" and 10" so any bike can be tailored to fit you perfectly.

The main thing to remember is that a bike which is too big can be difficult to control - this can be very dangerous.


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