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Bicycle Sizing Guide
What to measure?

In order to size a bike correctly you should consider your height and inside leg measurement along with your riding style and the style of the bike itself.

Measuring your height is best done by standing upright against a wall with your legs together (shoes off) and shoulders back. Place a pencil on top of your head, holding it parallel to the floor and mark the wall. You can now measure your height easily against the wall.

Your inside leg measurement is taken from the floor (again, no shoes) to your crotch. Stand with your legs roughly shoulder width apart against a wall, then take your inside leg measurement. It is probably easier to get someone to do this for you.

It's about clearance not contact

The distance between you, specifically your crotch and your bike's top tube (a.k.a. crossbar) is known as clearance. Clearance is indicated by standing over the bike, forward of the saddle and measuring the distance from your crotch to the top tube.

It is important to be able to stand safely over the bike when stopped. Therefore, a clearance of at least two inches should exist on all the bikes you ride. It can be thought of as a safety net to prevent injuring yourself if you need to jump forward of the saddle suddenly.

How are bikes sized?

All adults' bikes are measured by their frame size. This is typically the length of the seat tube: the near-vertical tube that the saddle and seat post slide into. Manufacturers will measure these slightly differently. However, the rule of thumb is to measure from the centre of the bolt which fastens the crank arms, all the way up the frame, to the top of the seat tube. Some brands (especially American) stop short of the top, only measuring to the point where the top tube meets the seat tube.

Personal choice is a factor

Bikes are designed to have their saddles raised. That is to have some of the seat post showing (e.g. as the above illustration). The amount riders wish to raise or lower their saddles is a matter of personal choice. Some riders like the saddle to be higher than the handle bars which means their hands are low when riding, giving them an aerodynamic position. Others may prefer a more comfortable ride with their hands level or even higher than the saddle height, giving a more upright position (a.k.a. sit up and beg).

This is where style will play a factor: a grandmother riding a hybrid to the shop 1 kilometre away is likely to want comfort not aerodynamics; whereas the off-road speed demon is more likely to size for optimum efficiency and not care about straining his lower back.

For an example of choice, lets highlight two riders in the Tredz office. One is 6'1" and rides a 17" Kona hardtail with an extra long seat post which is raised to its maximum. This is a very small frame for his height providing him with a huge amount of clearance and plenty of maneuverbility as he can easily throw the bike around. Another chap is 5'8" and rides an 18" Specialized hardtail. Chap 2 also has lots of seat post showing, perhaps 7", and also feels he can maneuver the bike easily. Both are correct because both are comfortable with their frames and their style of riding.

Your measurements, confidence, riding style, previous bikes, model choice et cetera will all play a part in sizing correctly for you. For a general guide follow our chart below. Please remember that these are only guidelines and personal opinions may differ. We are always happy to discuss frame sizes with you, please call customer services on 01792 560651.

What can you adjust on the bike?

Saddle height Riding a bike efficiently requires pedalling, not standing idly at the curb. In order to create sufficient distance between the saddle and pedals it is possible that your saddle will be raised too high for you to sit on and touch the floor with both feet. Even on tiptoe. This is perfectly safe for adults only, providing you have allowed sufficient clearance.

To get the best out of each pedal stroke, your saddle should be high enough that your leg almost fully extends at the bottom of each pedal stroke. To check this put one crank arm in line with the seat tube (at approximately the 5 o'clock position for the right hand pedal and 7 o'clock for the left). Place the heel of your shoe on the pedal. Your leg should now be straight. This now means that when riding, using the balls of your feet, your legs will extend sufficiently to allow their muscles to work efficiently.

Though this is the best for efficiency and comfort it will not suit all styles. Jump, BMX and DH bikes are just a few exceptions. A lower seat position allows a greater ease of movement over the frame. This is especially important for tricks and steep technical terrain.

Saddle angle The saddle nose can be tilted upwards or pointed downwards. This will vary your weight distribution on the saddle. Most commonly, the saddle is set parallel with the floor. The saddle can also be moved forwards and backwards, moving your backside and you, nearer to or further from the handlebars. Personal choice is all important, so have a play around to see what you prefer.

Handlebar height Some bikes have easily adjustable handlebar heights thanks to the classic quill type stem. The more modern a-head type of stem (arguably lighter) is a bit more difficult to adjust but usually possible. The higher the handlebar in relation to the saddle, the more comfortable the ride position will become as you are less stretched out and bent over. The lower the handlebar, the more aerodynamic the rider becomes - usually at the cost of backache.

Shifter/brake angle Brake levers and gear shifters can be angled to suit your preference. In order to get the most power from your hands it is felt that your fingers should form a straight line with your arms when applying the brakes. This should also be the most comfortable position. The brake lever reach (distance from the handlebar) can also be adjusted in some cases. This is especially useful for those with smaller hands.

Information supplied courtesy of www.tredz.co.uk