What Size Bike Should I Get? Avoid These Common Mistakes!

There’s no better day than the one where you purchase a new bicycle, but during this process, you may be struggling with the question of "what size bike should I get?". Ending up with a machine that doesn’t fit you properly is a frustrating and expensive mistake so we’ve put together the advice below to make sure it doesn’t happen to you!

Where to Start - Match the Bike to the Riding you Intend to do

The first thing you should ask yourself is what type of riding you plan on doing. For racing, it’s likely you’ll want to achieve an aerodynamic position so a long top tube and short head tube will help, but for endurance riding or touring a more upright position with less reach will be more suitable.

If you don’t know which style of bike is suitable for where and when you ride, have a look at the guide below detailing some different styles of bike and their intended use:

  • Road Race Bikes - Racing geometry giving a long, low and aerodynamic position. Quick handling and focus on bottom bracket stiffness and translation of power to the road. Best suited to tarmac/asphalt roads only and for competitive events such as criteriums.
  • Endurance Road Bikes - More upright geometry with shorter reach, aimed at providing improved comfort compared to a racing bike during sportive and gran fondo events.
  • Touring Bikes - These feature the same drop handlebars as an endurance road bike but have greater clearances for wide tyres (28-30mm), mudguards and mounts for panniers etc. Often have v-brakes for better stopping power when fully laden with bags.
  • Hybrid Bikes - A crossover between MTB and road bike. Flat bars, upright position, slick road tyres and powerful brakes. Ideally suited to city riding on tarmac and footpaths.
  • Mountain Bikes - Designed to tackle off road conditions, generally feature front suspension and many models offer rear suspension as well. Disc brakes for maximum stopping force. Great off road but noticeably heavier and slower on tarmac than other styles.
  • Cyclocross Bikes - Road race geometry, knobbly tyres (typically 35mm) and smaller gearing. Faster alternative to a MTB in light off road conditions. Many models now feature disc brakes.
  • Triathlon/Time Trial Bikes -Designed specifically for maximum speed on tarmac roads. Forward aerodynamic geometry, aero bars and deep profile tubing. Great on fast open roads but can be less versatile and have poorer handling in built up areas.
  • Single speed/Fixed Gear Bikes - As the name suggests these bikes have only one gear and may or may not have a freewheel. Because of this they are best suited to flat or undulating areas. Low maintenance makes them great for commuting.

If you are unsure what type of riding you plan to do or are just starting out then the best approach is not to buy anything too extreme in either direction and with as much adjustability as possible; avoid integrated seat-posts and stems for example.

Review What you’re Riding Now

It may seem obvious but this is an approach many people never consider. If you already have a bike then take some time to consider how well it fits you and use the results to help guide your new purchase. Not confident to analyze your current riding position? There are a multitude of bike shops and independent business offering bike fit analysis and improvement and if you’re planning to spend a large amount on your new bike, the cost of this service can be a savvy investment.

If you are confident enough to do your own bike fit then apps such as Hudl Technique and Bike Fast Fit are really helpful.

All these Bike Companies use Different Measurements, What do They Mean?

Spend any time reading bike brochures or scrolling through websites to find a new ride and you will notice that bike companies all have their own, unique way of measuring bike sizes. As a customer, this can make your job very confusing!

If you are struggling then the best measurement to use when comparing different brands is effective top tube, this is the horizontal distance between the top of the seat tube (not including seatpost) and the center of the stem cap. Typically you have much more adjustment available with saddle height than reach (determined by stem length) so getting the effective top tube measurement as close to optimum as possible is of great importance. If you want to learn more about the different measurements bike companies quote, then the video below covers the most common ones:

Another great way of comparing different bike sizes is by using the stack and reach method. This gives you an indication of where the handlebars will be relative to the bottom bracket and is comparable across all brands so long as they publish the measurements.

How it Feels is the Best Test of All

You can spend hours and hours carefully studying size guides and geometry diagrams but the best test of whether a bike fits you is to simply jump on and see how it feels to go for a ride. If you have lot’s of cycling buddies then ask to try out their bikes in an exchange for a beer and see how you get on. If you have a bike shop nearby then go and explain that you are unsure what size bike to go for. Most shops have demonstration models and will be happy for you to try them out, even for a couple of days in some cases, especially if it might result in a sale.

I Seem to be Between Two Sizes, What Shall I Do?

Unless you’re having a completely custom frame made for you, there is always a chance you will fall right between two sizes from a manufacturer. If this is the case then the general rule of thumb is to plump for the smaller of the two. The handling of a bike will be affected less by lengthening the saddle height and stem length, as opposed to reducing them.

Follow the tips above and you can avoid the enviable situation of having a brand new bike that just doesn’t quite feel right, and remember:

  • Think about the type of riding you’re going to be doing before deciding on a bike
  • Consider how well your current bike fits as a starting point
  • Standardise bike measurements using stack and reach if possible
  • Try out as many bikes as you can and listen to your body when doing so
  • If in doubt, slightly small is preferable to slightly too large

If you have any other tips you have used to find the right size bike then please let us know.

Robert Parker

I am Robert, the founder of cyclistchallenge.com. As any true cyclist, I love my bike and like to get out on it with any spare time I have.When I'm not riding, I like to write reliable and fully independent articles on cycling tips, bike and equipment reviews, as well as general cycling news.Welcome to Cyclist Challenge.