Ask These Questions to Dial in Your Bike Size

Peter Glassford
by Peter Glassford
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Ask These Questions to Dial in Your Bike Size

Figuring out what size bike you should ride seems like an easy question to answer; however, it is a question that gets debated and messed up frequently. New cyclists don’t have the experience to base their choice on and may not be sure what type of riding they want to do. While seasoned cyclists may have experience in one discipline, like road, they may struggle to choose an optimal size in another discipline, like gravel or mountain.

If you are looking for a new bike, it’s worth spending time checking or double checking, your best bicycle size and geometry for your goals, limiters and fitness.

Here are a few questions to answer to get you into the right bike:


If I asked you to describe yourself as an athlete what would you say? You would likely list some events you have done, what type of riding you like to do, perhaps some threshold power numbers, body proportions, flexibility and strength. These factors that make you the athlete you are will also be what helps you get sized and fit to your best bike.

If you have a bike, or a quiver of bikes, then you have some information you can use to guide your next bike purchase. If you struggle with saddle sores, numbness or poor performance, despite getting a bike-fit and/or changing saddles, stems and other components, then you have some indications your current bike size or geometry is not appropriate for you and your goals.

Take some measurements from your bike and record key details about the size, model, year of your bike and bring it into the shop or bike-fitting studio to help guide the choice they help you make.


Depending on your experience with cycling this may or may not be a tough question. If you are sure you are only doing one type of riding then this isn’t a big discussion! If you are new to cycling or looking for a new crazy goal, then get out and try a few types of bikes. You can use test-rides at shops, rental bikes, borrowed bikes and watch for demo-days at local resorts and trail-heads. Research what people like you are using in the events you are interested in. While it may be informative and neat to look at pro-bikes, be wary of sponsor bias and the differences elite-fitness and youth can make in geometry and bike choice.



Many bicycle brands and shops have sizing charts to help guide riders on the correct frame size for their given discipline and body size. There are rough methods that use height and riding type (e.g., Trek offers this table) to help riders get into the correct range of frame so that stem length and seat-post height are not excessive. There is going to be a crossover between these general suggestions and that is where a bike-fitter, or fitting service like Retuul, or experienced coach or bike shop employee, can be helpful. Your body proportions, flexibility and riding discipline help make these final decisions. I am 5-foot-10 and I am quite flexible and still race mountain bikes at a relatively high level. Going by the chart above I fall between an 18.5–19.5 mountain bike frame size and given my more aggressive racing and flexibility I have generally used a longer 19.5 mountain bike, but have also used 18.5 for my trail bikes.


Once you’re at the shop, sit on a variety of bikes and test ride a few to get a feel for different bikes and the control they offer. The classic standover test, where you stand over the top tube with your hips in front of the saddle isn’t worth a lot since we are most concerned about riding the bike not standing over it. Most bikes have a range in seat height but not nearly as much in stem length (reach), so picking a frame for reach is your main goal when selecting a frame. Many road riders think they want the lowest position they can get, but the reality is many of us will do better on a more relaxed geometry that doesn’t stress the low back and neck as much.

Taken together these methods can help you narrow your best-sized bike. Work together with your favorite local shop and perhaps an experienced bike-fitting specialist who can help make sure your new bike is going to be the fastest, safest and most comfortable for you given all the components that make you an athlete.

About the Author

Peter Glassford
Peter Glassford

Peter is a cycling coach and registered kinesiologist from Ontario, Canada. He travels frequently to work with athletes at races, camps and clinics. He also races mountain bikes for Trek Canada and pursues adventure in all types of movement. Follow @peterglassford on Twitter, or check out his online and in-person coaching at


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