Choosing the best bike frame size: with examples from Trek and Basso

Finding a correctly-fitting bike frame is essential to your comfort while riding and getting the best performance out of your bike. Popular bike brands like Trek or Basso offer size guides to help you choose the right bike frame size. We also provide a generic bike size chart to help pair you with the right bike and frame. Follow our guide to find the best frame size for you.

Table of contents

• How are bike frames measured?
• Our bike frame size guide
• How to find the right Trek bike frame size
• How to find the right Basso bike frame size
• What if I’m in between sizes?
• The Swinnerton Bike Fit
• Find the right bike frame size at Swinnerton Cycles.

How are bike frames measured?

The bike frame size comes from the measurement of the seat tube. The seat tube length is the measurement from the top of the seat tube to the centre of the crank axle. However, road bike measurements come in centimetres, and mountain bike measurements come in inches and sizes are sometimes indicated by a range of sizes, for example, S (small), M (medium) and L (large), which can make finding the right size bike frame confusing. Luckily, we’re here to help!

To find the right bike frame size, measure your height and the inside of your leg length. Once you have these key measurements, you can find the right bike frame for your height.

Our bike frame size guide

You can access our frame size guide on each bike product page (look for the ruler icon) or visit our size guide page to find the right bike frame size. Match your measurements with the corresponding bike frame size. We have split the size guides into men’s, women’s and children’s sizing because men, women and children all have different anatomy, therefore, different geometry needs. 

For example, if you’re a man with an inseam measurement of 76cm and are between 170-175cm in height, you will need a 17-18″ or medium mountain bike or 54-55 or medium road bike. 

If you’re a woman with an inseam measurement of 76cm and are between 165-172cm high, you will need a 17-18″ or medium mountain bike or a 53-55 or medium road bike. 

Be aware that our size guide will only give you a rough indication of what bike size is right for you and that everybody has tiny differences in their body makeup. So it’s always a good idea to try before you buy.

Bike sizing will also differ from brand to brand. Here are some examples of our bike brands that offer specific sizing.

How to find the right Trek bike frame size

Whether you’re choosing a Trek bike or a Trek bike frame, here is how to select the right-sized bike. Trek road bike sizes have numbers to indicate sizes between 47 and 62. See the table below to find the perfect Trek road bike frame fit.

Size	Height	Inseam
47	152 – 158 cm	71 – 75 cm
50	158 – 163 cm	74 – 77 cm
52	163 – 168 cm	76 – 79 cm
54	168 – 174 cm	78 – 82 cm
56	174 – 180 cm	81 – 85 cm
58	180 – 185 cm	84 – 87 cm
60	185 – 190 cm	86 – 90 cm
62	190 – 195 cm	89 – 92 cm

For Trek mountain bikes, you can look at sizes between XXS and XXL. See the table below to find the right mountain bike size for you.

Size	Height	Inseam
S	155 – 165 cm	74 – 78 cm
M	165 – 176 cm	79 – 83 cm
L	177 – 188 cm	84 – 89 cm
XL	188 – 195 cm	89 – 91 cm

How to find the right Basso bike frame size

We are also a supplier of Basso bikes and Basso bike frames. Here is how to select the right size for you. We split our bike sizes between XS and XXL. Follow the table below to find your perfect bike frame size.

Basso Bike Size	Swinnerton Bike Size	Inseam
45	XS	60 – 65 cm
48	XS	65 – 75 cm
51	S	76 – 79 cm
53	M	80 – 83 cm
56	L	84 – 86 cm
58	XL	87 – 89 cm
61	XXL	90 – 95 cm
63	XXL	96 – 101 cm

What if I’m in between sizes?

If you fall between two sizes, the best way to decide whether to size up or down is to look at the reach length. The reach refers to the distance between the centre of the head tube to a line drawn vertically from the bottom bracket and indicates how long the bike is and how easy it is for you to reach the handlebars. If your reach is above average, we recommend a larger bike frame and vice versa.

It’s not just about the numbers

It’s not just about the numbers when choosing the right bike frame size; it will also come down to how the bike feels. Ask yourself, does the peddling feel comfortable? Do I feel cramped or overstretched? Can I reach and operate the breaks? That is why it’s crucial to come into a store and have a feel of the bikes before you purchase one.

The Swinnerton Bike Fit

Bike frame size is just the beginning of finding the right bike fit. There are many other factors to bike geometry. Whether you need a new bike, you’re experiencing discomfort on your current bike, or you’re looking to gain efficiency, at Swinnerton, we offer a bespoke service to help you find the perfect bike fit for you.

Our service includes various packages, including road bike, track bike, saddle and TRI bike fit. During these consultations, we use a combination of technology and our expertise to help you find the perfect heights and adjustments to your bike. 

We will ask questions like how often you use your bike and whether you are experiencing any discomfort. We’ll assess the flexibility of particular joints and muscles and then gather data on your riding style using a turbo trainer. We will then adjust bike aspects like the saddle height, cleat position and bar and stem where appropriate to correct your geometry.

To book your bespoke bike fit at Swinnerton Cycles, visit our bike fit online booking system.  

Find the right bike frame size at Swinnerton Cycles.

Bike geometry is not an exact science, and there are many contributing factors determining which bike frame is the right size for you. All our size guides cater for the average-sized and proportioned human. So if you need extra guidance on bike fit or bike frame size, don’t hesitate to contact us directly or come and visit us in our store, and we’ll help you find the perfect bike frame for your size.