Choosing the right size bike

Choosing the right size bike is an important step and some basic adjustments will help you get the best position.

Calculating your inseam is essential. With the help of a friend, you will need to stand against a wall, barefoot, heels, back and head against the wall and feet slightly apart, looking straight ahead.

Wedge a book or ruler between your legs, slightly spaced 20 cm apart, keeping the book pressed against your perineum and parallel to the ground. Measure the distance from the top of the book to the ground and note it.

To give the size of their bike, brands have long based themselves on the height of the

seat tube, calculated from the axis of the bottom bracket to the seat clamp.

It was then enough to multiply the value of the inseam by 0.65 to know the size of bike adapted to the cyclist. (0.59 for a mountain bike)

For example: 85cm x 0.65 = 55.25 cm. So a frame in size 55.

However, this calculation protocol is only valid with straight frames, that is to say equipped with a truly horizontal top tube that is found rather on older generations of bikes.

On a modern frame, the evolution of bike geometries with their sloping frames (the top tube is inclined) it is best to rely on the size recommendations given by the bike brands.

Below are tables giving you correspondences between bike size and inseam, indicative data that should be adapted to each morphology and practice:

If after your calculations, you fall between 2 frame sizes, you will have to take into account the measurements of the upper part of your body to determine the choice of one or the other size.

Indeed, it is the length of your bust and your arms that will be necessary to determine the correct distance from the handlebars or the handlebars. To do this, it is necessary to calculate your "APE Index", it is obtained by applying this subtraction:

APE index formula: Your height (in cm) - (Amplitude of your arms + bust) = APE Index If the value obtained is greater than zero, you must take the larger bike size, and conversely take the smaller size if the value is less than zero. Example: height 176cm - bust + legs 142cm = 34

It is possible to determine the saddle height by multiplying your inseam height by 0.885, a formula that allows you to obtain a value adapted to most physiognomies and types of effort. The saddle height of a bicycle is measured from the bottom bracket axle to the hollow of the saddle.

However, the value obtained will only be an indication since other criteria such as the type of pedals or shoes will have to be taken into account. It is once on the bike that it will be possible to precisely establish the correct saddle height.

By having a colleague hold the bike, sitting on the saddle, the cyclist must position his heel on the pedal and have the leg completely extended with the pedal at the lowest point of its stroke. You must ensure that your pelvis is horizontal and not tilt it to the right or left to reach the pedal. Adjusted this way your leg will be slightly bent once the front of the foot is placed on the pedal.

The saddle setback is also adjusted with the cyclist sitting on the bike. Once the cranks are placed horizontally, the feet on the pedals and the cleats engaged, it will be necessary to position a plumb line which will have to be positioned on the front face of the ball joint and then pass through the pedal axis.

The width of the road bike handlebar should approximately correspond to that of the shoulders.

To choose a suitable handlebar size, you will need to know the width of your shoulders. The width of the handlebars is expressed in axis-axis. A handlebar displays the correct size when, hands on the handles, the arms extended are parallel.

Depending on the type of practice, the handlebar height will be set very low for a courier, 8 to 12 cm, between 8 and 4 cm for a cyclosportive and between 0 and 6 cm for a use focused on comfort such as cycle touring.

By raising the cyclist's position, the center of gravity is higher and the bike will be a little less maneuverable on descents and your posture less aerodynamic. This position also generates more pressure on the buttocks; it will certainly be necessary to choose a comfortable saddle and a tire section in 25 or 28 to increase the cushioning with the ground.

Conversely, with very low handlebars and a more stretched position on the bike, the center of gravity is lower, the bike is more maneuverable and the support points on the saddle are reduced, but they will be increased on the arms, hands and handlebars.

Note that for people with neck pain, a slightly higher position will prevent cervical hyperlordosis and will be less restrictive for this area.

To determine the right stem size, you will need to place a crank parallel to the diagonal tube of the frame, feet clipped into the pedals and position your hands at the bottom of the handlebars. The slightly bent elbow should touch the kneecap. If it hits, you will need a longer stem, or a shorter stem if the elbow is too far away.

Similarly, with your hands on the hoods, the torso should make a right angle with the arms. Be careful, this is a more demanding position typical of courier / cyclosportive bikes that promotes performance.

You must also take into consideration the height of the bike's head tube, a hill influencing the cyclist's inclination on the bike.

Manufacturers play on this value to offer ranges of bikes that are more typical of cyclosportives / couriers (shorter socket height) or more "comfortable" adapted to cycle touring or gravel.

The smaller the socket, the more the bike is manoeuvrable in curves and your aerodynamic position.
The higher the socket, the more upright you will be on the bike in a more comfortable but less aerodynamic position.
For example, at Lapierre, the Pulsium (comfort or endurance type) has a socket height of 195 mm in size L 55, compared to 160 mm for the Xelius and Aircode (courier-oriented) in the same size.

Bicycles are generally delivered with cranks of length 170 mm (inseam of 74 to 80 cm), 172.5 mm (inseam of 81 to 86 mm) and 175 mm (inseam of 87 to 93 cm). For an inseam of less than 74 mm, we will turn to cranks of 165 mm.

Why change the length of your cranks? By increasing their length, we reduce the effort required for a given effort, without changing the effort produced on the pedal. By reducing the length of the cranks, the distance traveled by the foot is reduced, which facilitates the speed of rotation of the pedal. The choice of crank length depends on many criteria: the type of practice, the physical condition of the cyclist… However, in the context of a time trial or a climb of a pass, requiring a significant effort, the use of longer cranks is an advantage.

The cleats of automatic pedals must also be carefully adjusted. We will start by locating the joint of the big toe and then marking its location on the shoe. We move the cleat located under the shoe back and forth until the axis of the joint of the big toe is located directly above the axis of the pedal when the foot is horizontal.

Also, you must align the foot from right to left so that your angular freedom is equivalent on both sides. You must take the time necessary to make this adjustment quietly at home in the parking lot. You will start by not tightening the screws of the cleats too much in order to be able to try several positions. Once the right compromise is found, tighten the cleats very tightly because they will be subjected to strong constraints.

Some pedals have an adjustment of the force required to release the pedal by means of a small screw.

Road pedals and shoes generally have prominent cleats fixed by three screws under the shoes. This system allows for very rigid and light soles, a wide support and therefore maximum transmission of force to the pedals. Depending on the color of the cleat, several choices of angular freedom are possible. If you are a courier, this is undoubtedly the best choice. Their main drawback is that they make walking very difficult and it is not uncommon to meet cyclists who have fallen on their feet while going to have a coffee because of them.

If you are a fan of walking, cycle touring or gravel, there are now road or MTB XC shoes (quite rigid on the bike) but with a MTB cleat (SPD type from Shimano) which is set back in the molding of the sole and which allows you to walk correctly. This choice can be more comfortable and judicious so as not to trip at the slightest step...

Adjusting a road bike is a matter of personal feeling, type of practice and physical age. Morphology but also experience in the sport vary according to each person. Nothing beats an exchange and a test at your bike shop in order to define the best choice for you.

When changing settings, you will need to check the validity of the changes made over a long enough period of time so that the body gets used to them.

A suitable position should provide a feeling of comfort on the bike: do not insist if pain occurs. Pain is a hindrance to performance and can take 25% of your energy. After a certain age, courier-type road bikes should be avoided and a more upright position will promote comfort, pleasure and therefore increase your endurance, performance and especially your longevity and pleasure.

Road bikes called "trekking" or "fitness" depending on the brand are lightweight road bikes with flat handlebars and often remain a very good choice for seniors. Don't hesitate to take the plunge if you feel the weight of the years...

In addition to geometry, other technical characteristics differentiate the families of "racing - cyclosportive" or "cyclotourism - comfort" road bikes. Indeed, the constructions of carbon frames have evolved and engineers give different characteristics to the various places of the frame depending on the thickness, the direction of the fiber and its weave.

For example, a time trial frame will be extremely rigid at the bottom bracket and chainstays and more uncomfortable in order to transform 100% of the cyclist's strength into speed, whereas a frame for cycle touring or gravel will be designed to filter vibrations and promote comfort, particularly at the head tube and fork.