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The cycling retail worker’s raison d’etre - to answer this question. Despite the seemingly universal approach to sizing when it comes to bikes, measured in centimetres, inches, or simply ‘Small, Medium, etc’, believe it or not there is no universal science or standard applied to bike sizing.
Every bike brand approaches sizing slightly differently, thus producing a liquid and sometimes difficult environment to approach as a potential buyer. This creates a problem as it often works out that you can be a 52cm in one brand but a 50cm in another. This happens because the basis of that number comes from where exactly on the frame the bike is being measured.
For example, the majority of brands will base that measurement off of the top tube length. But there are brands such as Pinarello that take their measurement from the length of the seat tube. This creates scenarios where it isn’t as simple as working out what size you are and shopping around, it’s important to be aware of the way different manufactures size up their bikes. Let alone the difference in geometry between the different types of bike; aero, endurance, etc.
So to come back to the original question, what size bike do you need? The answer is really, it depends. The only sure-fire way to know if a bike fits you is to try it, take time to understand the geometry chart, or simply ask your local bike shop to help you out.
To find the right size bike for you it is important to know your height. Then you should take a look at the manufacturer you are interested in and their size guides. Every brand will have its own size guide available for all their models.
Frame Size (cm)
|XXS||5'0 and below||47 and below|
|XS||5'0 - 5'3||47 - 50|
|S||5'3 - 5'6||51 - 53|
|M||5'6 - 5'11||54 - 56|
|L||5'10 - 6'2||57 - 59|
|XL||6'0 - 6'3||60 - 63|
|XXL||6'3 and above||63 and above|
It is important to note that size guides are generally quite rough and are to be used as a starting point when it comes to sizing. Just because your height corresponds to a size on the guide, do not get attached to that size as quite often you will straddle a couple of sizes.
The quick answer – yes, absolutely. There is often a temptation to grab a bargain when it comes to bikes at the expense of sizing and fit. And although this may work out fine for a very few choice exceptions, generally speaking the sizing of the bike should be the leading factor in your purchase.
The cost of a bad fit outweighs the benefits of any money saved on buying a bike in the wrong size. The list of places where injury will come up is pretty extensive; neck, shoulder, wrist, elbow, lower back, upper back, ankle, knees and so on and so forth. A bike that doesn’t fit you well is going to at best cause discomfort on the bike and at worst cause actual harm to your body.
If you’re unfortunate enough to have a bike that doesn’t fit then there are some things you can do to help make the bike fit. However, this really does boil down to how badly the bike fits as there is only so much room for improvement.
For the vast majority of cases a bad fit usually means the reach is off in some way. The reach represents the distance between the handlebars and shifters with your body via your arms. This reach can either be too short or too long. If the bike is too big you will feel very stretched out, with your arms locked out and your body hunched over uncomfortably. If the reach is too short then you will feel like you are putting too much pressure on your hands, and again, feel like you’re leaning too far forward over the handlebars.
This can be counteracted by putting on a shorter or longer stem. We generally treat 100mm length stems as the starting point as this is pretty much slap bang in the middle of available stem sizes. If the bike is too long, try out an 80mm stem. If it is too short then put a longer, 120mm stem on there. Stems go all the way down to 30mm and all the way up to 150mm but the further away from 100mm you get, generally speaking, the more extreme your correction is and the more apparent it is that the bike frame size is simply wrong.
Generally speaking we would expect a stem size of between 80mm and 120mm to be fine for most people on the correct size frame. If the fit requires a shorter or longer stem than that, then we would probably look at sizing the frame up or down.
Another big factor that will greatly increase or decrease comfort on the bike is your handlebar height. Almost all bikes will come with an uncut steerer tube that has at least some level of adjustability on this front. You can see this with the amount of spacers that are above and below the stem. Naturally, the more spacers on top the lower the riding position, and vice versa.
Despite the temptation to #slamthatstem and go for the pro look, having handlebars that are too low is going to cause neck pain and pain in the wrists and hands. It will make those longer rides very uncomfortable once you’re around an hour in. So it is important to take the height of the handlebars into consideration when looking at your position on the bike.
There are two easy ways of fixing issues with handlebar height. You can simply move the spacers around so that you get to your desired and comfortable height. Or you can look at positive and negative rise stems which use the angle of the stem to lower or raise the bars.
In most cases, a simple adjustment in the reach and handlebar height normally sorts out little niggles and pains that can appear from a bad bike fit. But there are other contact points on the bike that are just as important and worth checking out.
You saddle has a few different things that can affect your position. The angle of the saddle will increase and decrease pressure on your hands. The position of the saddle rails in the clamp will affect your reach as well as your legs relationship to the bottom bracket and the general motion of cycling. And saddle height will mainly influence your comfort on the bike as well as how effective your riding technique is. So it is worth taking into account your saddle when you’re having issues with the fit.
If you’ve had a play with these various contact points on the bike and found that you’re still having issues with the bike. Then the only other thing to consider is a bike fit or a new bike.
Bike fits for a long time were only available to the pros and those serious cyclists that were willing to spend the cash to get a perfect position. However, over the past couple of years there has been a democratisation of bike fitting in a sense as more and more fitters have opened shop and more and more regular cyclists look to them to get a good position on the bike.
There can be no denying that the scientific and thorough approach to bike sizing that comes with a professional bike fit is the best way of nailing your position on a bike. They do know what they’re talking about and it is the only sure-fire way of absolutely perfecting that position or scientifically ironing out any issues with your fit. So if you’re having actual bodily pain consistently then we would absolutely recommend a bike fit.
For many people though bike fits are just too expensive. You can expect to pay between £150 and £300 dependent on where you are and who you see, which is an expense that a lot of people can’t afford. We understand that and so hope this guide has helped show you the points on the bike that are adjustable and might be able to help you work out any issues yourself. But if you’re feeling real pain and worried about lasting damage, then a bike fit might be the right choice for you.
So to wrap this all up here are our top tips for you to nail bike sizing: