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This guide is designed to help you understand how bicycles are measured and help you choose the correct bike size that fits your body and riding style.
For many people bike fitting is seen as something to be afraid of, it is seen as something that they can not understand and only the bearded guru in the bike shop understands it. Luckily I am a bearded guru and have spent many years in a bike shop doing bike fits, from doing it the old school way with plum lines and spirit levels to today's fancy laser-guided computer systems, I have seen all the ways to complete an essentially easy task.
To be honest, it is not really difficult, particularly if you can measure yourself and be honest about your height. I have met a lot of 178cm (5ft10) guys who could swear blind that they were 180cm (6ft) tall, by the way, it is always guys that go for this kind of adding a centimeter or two to their height, take from that what you may.
The first big thing that everyone seems to get wrong is that they believe their bike fit is a fixed measurement, it is not. In fact, it changes during the week, which is why hanging on to a 5-year-old bike fit report and wanting your bike to fit those measurements is wrong.
I want you to think about your work week. Do you sit at a desk Monday to Friday, 9 till 5? If the answer is yes, imagine you went out and rode 50 miles on a Saturday and the Sunday. Your bike fit on a Monday morning will now be different to your bike fit on a Friday evening. Your muscles will be more relaxed and more in tune with being on a bike after the weekend as opposed to being stuck in an office chair all day.
This does not mean a bike fit is wrong. It is just not a rigid set of numbers. Your bike fit is actually a fit window. You can fit a range of lengths and angles, some will be more suited to comfort and some will be more suited to racing.
So we have now got this far and we have not even talked about how to know if you fit a bike. Most bike fit guides will presume you have a bike and you are going to be using that for working out your fit. This is not ideal if you do not have a bike, how can you buy your first one and get it right. Well with a buddy we will help you get it correct by taking one initial measurement, this will get the basics down. To start we will need to measure your inseam.
To measure your inseam, stand with your back a wall, without your shoes on. Take a hardback book and place it between your legs, raise it to the point you are about to do yourself a mischief. Get your buddy to mark where the top of the book meets the wall. Do this 3 times to get a good average and eliminate any risk of making a mistake. Fairly simple is it not?
We can then use the Greg LeMond or the 109% method, both are pretty much the same idea, to plot out a basic idea of the bike size you will need. I have found this chart to be fairly accurate over the years. Remember though, no bike company will make frames that only go up in 1cm jumps so pick the closest to your size.
The second images shows you the measurement to make to sure your saddle is at the correct height. If you are using a tape measure you can generally catch the hook of the tape on your crank arm bolt and then pull the tape up the way to help you set the correct height.
If the chart puts you between two sizes and you can not decide which way to go, think about your “ape index”. You will need to bring your buddy back for this as you need to two measurements here. Stand with your arms outstretched, get your buddy to measure from fingertip to fingertip, if this comes out larger than your height get the bigger model, if it comes out smaller, get the smaller bike.
You will obviously need to know your height to know this. So get your buddy, book, and the wall again. Stand with your back against the wall, put the book on your head and get your buddy to mark where the bottom of the book touches the wall. Easy. Hopefully, you will have kept your shoes off.
Now you have a good idea of your bike size, everything else is just tying down the small details. We will cover them in more depth in another article, if you are only planning on riding with flat pedals, this guide should be good enough for you. The most important thing is if you do not feel confident being on a bike and want to get your feet down have your saddle low for a couple of journeys and then put it up to around where the LeMond mark is, this is for the long term benefit of your knees. Keeping your saddle too low to enable getting your feet flat on the ground will not work out well for your body in the long run.