What Size of Bike and Frame Do I Need?

Do you want to try out biking? Whether it's for recreation or competition, riding a bike can be a fun and rewarding experience. The first thing you'd want is to look for the best bike for you, but with so many bikes to choose from, how do you know which one to get?

Many people new to biking assume that getting a highly-recommended bike is good enough, but you need to make sure that you're riding one that "fits" you. Instead of asking what's the best-selling bike, you should be asking "What Size Bike Frame Do I Need?".

The Importance of Getting the Right Size

If you ride two bikes of the same brand and model but with different frame sizes, you'll immediately notice the difference in terms of how they handle. The one with the right frame size will feel much more comfortable to ride.

However, comfort is just one of the many benefits you can get from getting a properly-sized bike frame. A properly-sized bike will let you have better control over it and reduce the chances of slip-ups and ​injuries. This is very important in more technical kinds of biking, like mountain biking or trail riding.

On the other hand, riding a bike with the wrong frame size can be a dangerous (and tiring) experience. Just steering with the handlebars will feel awkward or you may not have enough elbow room to make tight turns or pedal properly. This may seem like a minor bother at first, but it will be a big issue over time.

bad back cycling

Via keyassets.timeincuk.net

To make matters worse, riding on a poorly-fitted bike can also have long-term effects on your body. Some of these include back and joint problems and muscle pain for straining to compensate for the awkward frame size. That means frame size is more important than other factors when choosing a bike.

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.

How to Check For the Right Frame Size

If you check out bikes for sale, you'll notice that most of them list their frame sizes as S,M,L, and even the occasional XS/L. However, it isn't a reliable factor since different bike vendors have various ways to categorize their bike frames. An S-sized frame on one brand may be an XS for another.

A more reliable indicator would be showing the measurements of the seat tube and the top tube since you have exact figures to let you compare it to your body measurements. If you want more accurate estimates, short of actually trying the bike, look for the seat tube length and the top tube length.

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:

Getting the Right Bike Height

The seat tube is the vertical tube that also holds the seat. The longer the seat tube length, the "taller" your bike is. Have it too high and getting on and off the bike will be difficult. Have it too low, and you have a bike that may feel too cramped.

spew cycling

Via surlybikes.com

With a proper tube length, you'll have enough room ​to not feel cramped, but close enough that you can steer as much as possible while keeping both hands comfortably on the handles all the time. This is vital for managing trails with sharp curves, where you need all the maneuverability you can get.

Making the Choice

Once you determine the ideal measurements, check out the bikes size chart. Look for the right frame size that's closest to your ideal measurements. It's normal to find frame sizes that only get one measurement right; fortunately, you can compensate for it by making adjustments to the saddle.

making the choice cycling

Via proteusbicycles.com

If you're still having trouble figuring out the right frame size, you can always try asking for a test ride. Try out two or three different frame sizes (the ones closest to your ideal measurements) and see which one gives you the most amount of comfort and control and make the adjustments later.

Speaking of adjustments, you should always go for a slightly smaller bike frame if there's no exact fit; making adjustments for a smaller bike may require nothing more than adjusting your saddle, but a larger frame could have the lowest saddle height and still feel too big.

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.

More than Size

To make sure your bike fits you better, you can also consider upgrading the saddle, handlebars, and pedals for better comfort:

  • The saddle should be broad enough to provide support but not too wide that it would cause chafing on your inner thighs.
  • The handlebars should be comfortable and let you keep a firm grip at all times, especially when turning.
  • The pedals should turn smoothly and grip your shoes properly without being too large or too heavy.
cycling swallow boltsm

Via sheldonbrown.com

​Final Word

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

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!