What Size Road Bike Do I Need?

Road biking is an enjoyable way to boost your health, meet with new people, seek fresh air, and observe the environs at a slow pace. To really enjoy cycling, the last thing you want is to get the wrong bike for you. An ill-fitting bike can mess up your riding experience, including reducing your efficiency and putting you at risk of injuries.

Picking the right size road bike will ensure comfortable, safe, and effective riding. But how will you know the best size for you?

Whether you are new to biking or simply want to purchase a new bike, especially online, this article will help you get the perfect fit.

Road bikes

Road bikes are both streamlined and designed with lightweight frames, narrow, high-pressure tires, and drop handlebars for speed and distance. Their distance, speed, and efficiency come with a price; however, these bikes aren’t meant to withstand rough or rocky trails and are not durable or rugged like mountain bikes.

Choosing road bikes

Manufacturers’ guidelines of the road bike size

The simplest way to determine the bike size to buy is to use the typical guidelines provided by the manufacturers, which correlate different height ranges with various bike sizes.

Bicycle manufacturers have no standard sizes – every brand will have a specific approach to road bike design; thus, it’s important to have a general understanding of bike geometry. Don’t assume one brand is similar to another, even if the given sizes seem the same.

Most manufacturers size their road bicycles by top tube length, the distance from the seat tube to the head tube. Top tube length might differ because some bikes have horizontal top tubes while others slope downwards. Even so, this doesn’t increase or decrease the distance between the seat- and head tubes – the effective top tube length.

Many bikes manufacturers will also use the stack (distance between the centre of the head tube and the bottom bracket) and reach (horizontal distance from the bottom bracket to the top of the head tube) figures for their brands as they are an important way to compare road bike sizes and geometry. Using these figures is advantageous because they are independent of bike frame angles. Two bike frames might have two varying top tube lengths but similar reach, with different angles.

It’s even more crucial to get your size right if you plan to shop a road bike online. Most brands on the internet will suggest a road bike size based on your budget, height, and other measurements.

That might be great if your height and inside leg length match their suggestions. But if you are quite tall or short, we would highly recommend a road bike fit together with a test ride to ensure that you get the right size.

Road bike frame size

The frame is the bike’s metal or carbon-fiber body, and unlike the saddle (handlebars or seat), it’s not adjustable, making it the most important consideration in finding the right road bike fit. Even though there are varying bike frame geometries – traditional, compact, and semi-compact bike frames – the general bike shape and correct measurements help determine its primary function more often than not.

Most road bikes have traditional frame geometry or large isosceles (same length on all sides) triangles with a top tube or top bar parallel to the ground. Racing bikes have smaller frames, while commuter or touring bikes have larger frames.

Top tube length

The effective top tube length relates directly to your arm and torso length. For instance, if your road bike top tube is too long, you will be overreaching to the handlebars, which will cause a more aggressive riding position. It will be uncomfortable, especially on longer rides. Thus be sure to go for the right effective top tube length with perfect reach for a comfortable and fun ride.

Because women tend to have shorter upper bodies than men, their road bikes have shorter top tubes. Some manufacturers also change other aspects of frame anatomy on women-specific road bikes to offer women a better fit.

Height, inside leg length, and stand-over height

Your height, including the inseam (or inside leg length) and stand-over height, can be used to determine the right road bike frame size. Inseam is the measurement from the floor to the highest possible point of your crotch (where the legs meet the waist). It is usually measured in centimeters.

To measure your height, stand upright against the wall with your arms vertically on your body, legs together, and shoes off. Let your friend take the measurement in cm, feet, or inches.

To measure your inseam length, stand with your feet about 6 inches (15 cm) apart, then measure the distance from the inside of your foot to your crotch. It’s easier if your friend helps.

Stand-over height is simply the distance between the top tube and the ground. The right road bike fit should have a few inches allowance between the top tube and your crotch when you are standing barefoot with legs straight and feet apart. A small bike will leave too much gap, while a big one will leave no room to maneuver.

Road bike size

Road bike frame size is related to the seat tube length. For instance, a 70 cm frame will have a 70 cm seat tube length.

Calculating the road bike size

Any bike size is calculated using the formula below:

Bike Type x Inside leg length = Your frame size (cm)

Therefore, Road bike (0.70) x Inside leg length = Your frame size (cm)

For example, if your inside leg length is 70 cm, then the correct frame size of your road bike will be 70 x 0.70 = 49 cm

At times, someone might be in-between sizes; that is, the measurements conclude that two road bike frame sizes are suitable. In such a case, the key measurement is the reach, how long and comfortable the road bike feels when they are in the riding position.

Everyone’s reach is affected by their upper body length (also called sitting height or trunk length). If your upper body is shorter than the average length, then the smaller of the two sizes will fit you. But if it’s longer than average, then go for the larger road bike of the two sizes.

Road bike size chart

Here is our detailed guide for road bike frame size to help you choose the right fit.

Height (inches)

 

Height (cm)

 

Inside leg length (cm)

 

Frame size (cm)

 

4’10” – 5’0″

 

147 – 152

 

66

 

47 – 48 (Extra Small)

 

5’0″ – 5’3″

 

152 – 160

 

69

 

49 – 50 (Small)

 

5’3″ – 5’7″

 

160 – 170

 

71

 

51 – 53 (Small – Medium)

 

5’7″ – 5’9″

 

170 – 175

 

76

 

54 – 55 (Medium)

 

5’9″ – 5’11”

 

175 – 180

 

79

 

56 – 58 (Medium – Large)

5’11” – 6’2″

180 – 188

 

81

 

59 – 60 (Large)

 

6’2″ – 6’5″

188 – 196

 

86

 

60 – 62 (Large – Extra Large)

 

6’5″+

 

196+

 

91

 

62 – 63 (Extra Large)

 

Nowadays, some manufacturers started to use small, medium, and large for road bikes, along with changing their geometry by incorporating more sloping top tubes. Sizing inventions like these can allow all kinds of riders; all they require is a longer seat tube.

Saddle position

You should be able to touch the floor with your tip-toes while sitting in the seat or saddle. Your bike seat is too low when the entire foot base touches the floor and too high when you can’t reach the floor at all.

You should adjust the saddle height to fit your legs even before testing a road bike frame. The right size frame can feel wrong when the saddle doesn’t fit your height. Just have it adjusted so that one foot is at the lowest point on the bottom of your pedal stroke with kneel slightly bent and not straight. A friend or someone at the bike store can hold it while you get on.

Pedal backward and stop when one foot is at the bottom of the pedal’s rotation, and then adjust the saddle height to a slightly bent position. Don’t shift or drop your hips with every pedal stroke to avoid dropping your foot lower than expected, resulting in an improper fit.

Reach

Although there are several measurements you can perform to ensure the right reach – distance from the seat to the handlebars – they all come down to the same thing; choose a reach you are comfortable with. Down the line, you will feel like the reach is proper when:

  • You can comfortably touch each shifter and brakes
  • Every elbow is slightly bent
  • You can easily bend from the waist and not the back to touch down with one foot
  • Generally, casual riders will choose closer but higher handlebars, while racers prefer longer reach.

Stack

Knowing the right stack for a road bike you want makes it easier to compare various bikes. For the right reach, an excellent stack puts you into a more upright riding position with your hands moved upwards, and your body positioned more towards the vertical.

Most experienced road bikers tend to prefer bikes with short stack height to easily get their handlebars in a lower and more aggressive position for aerodynamics and effective cornering.

Also, road riders with shorter arms and torsos or limited spinal mobility should go for taller stacks as it allows room for a more upright, comfortable position. Although to minimal adjustments, stack height can be adjusted by using angled stems and spacers.

Invest in a bike fit

The best way to make sure that your road bike will fit you perfectly is to invest in a professional bike fit. It doesn’t matter if you are ordering the road bike online or purchasing a new one from a nearby bike shop. A bike fit makes all the difference.

A bike fitter will spend some hours with you, preparing you for the bike test as they set up everything, including adjusting the seat, handlebars, and other parts, in order to learn how such changes affect your riding.

Knowing your fit measurements and having a fit expert help walk you through the process will ensure you are getting the right road bike size for your specific needs.

For beginner bikers and athletes, investing in a professional bike fit will be extremely helpful. You will save time and energy while avoiding injury, pain (lower back pain, neck pain, elbow pain, knee pain), and frustrations, which will make your biking more fun than it already is.

Conclusion

Remember that your comfort and safety come first. Everyone is different, thus if you don’t feel comfortable riding a road bike that should fit you, get it re-sized. Test as many road bikes as you can before purchasing, and feel free to play with the handlebars and seat until you find your sweetest spot.

With the above information at your fingertips, you should be able to get the right road bike size. Knowing the size you need will most probably help you narrow down your search. Even though there are different road bike shapes and sizes out there, the right one will depend on your body type and personal taste.