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How to choose the right size bike

Posted by Michael Tarr on

Buying a bike online doesn't have to be a daunting process, especially when buying a single speed bike. If you are new to cycling it is completely normal if you feel absolutely clueless about what size bike to go for. Choosing the right size single speed bike is not as hard as you think and in this guide I hope to make the idea of buying a bike online more positive.

If you plan on using your bike with flat pedals and normal shoes then sizing can afford to be a bit more relaxed. This simply means you can choose a bike that is either one size larger or smaller than your ideal size. Sizing becomes very important when you start riding with a clip in pedal system because you become fixed into position. Having the incorrect bike size when riding clipless can cause discomfort, pain or even injury.

Symptoms of incorrect bike size

If you have a bike that is too big you will be feel very stretched out. In an extreme case you may not even be able to touch the pedals when at their lowest position. If a bike is too small then you are likely to feel cramped and may not be able to raise the saddle high enough to allow for an efficient pedalling action.

How to find your correct bike size

Here are some tips to help you find the correct size bike.

1. Find out your height

It is surprising how many people don't know their own height. Knowing your exact height will help you make a more accurate decision about bike size.

2. Consult our bike size chart >> BIKE SIZE CHART

Once you know your height you can look at our bike size guide page which has a few charts from various brands which will give you a rough idea of what size you need. You can afford to be out by a couple of centimetres if your desired bike is not available in your exact size.

3. Measure your inner seam

Your inner seam measurement is taken from your crotch area where the saddle would be all the way down to the floor. Take this measurement in centimetres and multiply it by 0.67. For example if your inner seam measured 85cm (85 x 0.67 = 56.95). The value 56.95cm is your ideal top tube length so you should be looking for a 57cm bike or a size nearest that.

What parts of the bike determine it's size?

A bike gets it's size based on it's top tube length (A) and it's seat tube (B)

Traditionally bikes have always had near identical top tube and seat tube lengths. Most single speed bikes seem to keep the retro vintage feature of having zero slope in the top tube. With this style frame it is safe to take the size measurement from the seat tube (B).

Some bike designs have a sloping top tube. A sloping top tube is a feature of compact frame geometry most often found on road bikes. Bikes with compact geometry are sized by their 'effective top tube length'. This is the measurement taken from centre of the head tube to the centre of the seat post. Most brands provide a sizing table for their frames.  A good example of this compact frame geometry is given to us by Cinelli.

In the diagram above the red column has all the available frame sizes of the 2015 Cinelli Mystic Bike. It has a sloping top tube so it's frame size should be determined by it's 'effective top tube' length (T1).

When it comes to choosing the correct frame size firstly check the style of frame. Ask yourself if the top tube has slope or not. If the top tube is horizontal then you can choose a bike based on the seat tube measurement. If the bike has a sloping top tube then try to find out it's 'effective top tube' measurement.

If you have any more questions about bike size please email us or contact us on live chat.

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