How to adjust your bike?
Whether you are a competitor daIn the soul or contemplative practitioner, a good position on the bike is essential to optimize your performance, your comfort and limit the risk of injury. Before you consider making an appointment with a specialist position, some basic concepts already allow you to avoid gross errors.
Even if things evolve slowly, the specialists of the position are still too rare for the prices of this type of service to be really democratized. In general, you need to count between 150 and 300 € so that you are measured from all angles, and you leave with a bike set to the millimeter. This can be essential in case of a particular physical problem (chronic tendonitis, significant difference in length between the two legs, recurrent pain in the back, for example) or search for optimal performance. But most of the time, the investment is not mandatory, as long as you respect the basic rules of an efficient and comfortable position. Obviously, it starts with choosing the right size of the bike. A selection not necessarily obvious for the novice, because according to the brands, there are models classified as clothing (XS, S, M, L, etc.) or according to the length of the seat tube (48, 49, 50, 51 , etc.). You must already look for some correspondence if you hesitate between two models for example. Then you have to consider the particular geometries, because not all brands offer frames with the same angles, or the same lengths of horizontal tube relative to the seat tube. Finally, it is complicated when you know that some models are only available in three sizes, while others are available in fourteen sizes, with very fine differences between each of them. Fortunately, you can adapt to all these models of series by adjusting the saddle in height and receding, by modifying the size of the stem or the cranks, even by changing hanger for a model more or less high and deep.
The size of the frame
An empirical way of selecting the right frame size is to measure your crotch and multiply this value by 0,66. This is primarily an order of magnitude, as modern frames are rarely straight, and often have a sloping upper tube. Fortunately, manufacturers often deliver the virtual height of the frame, which you can see on the model's geometry chart. This is a tube height as if the frame was straight. Then, an ideal size is defined mainly by the length of the frame. Firstly because it is easier to change the seat height adjustment than to adjust the length of the stem, but also because a good length makes it possible to obtain an adequate weight distribution between the two wheels. , which is essential for handling. Finally, you must also consider the height of the steering socket, which could limit you either to climb, or to lower the cockpit. Overall however, virtually all manufacturers offer balanced frames, and by adopting this calculation, you are unlikely to go wrong.
Everything starts from the shoe
Whatever the type of pedals used, the principle remains the same: it is from a good adjustment of the cleats under the shoes that we then adjust the other elements of the position. The first rule to follow is to materialize the big toe joint on the inside of the shoe. Then, by drawing a vertical which passes through the axis of this joint, it is sufficient to adjust the middle of the hold (which represents the axis of the pedal longitudinally) so that it is in alignment. Some adjustments are possible, depending on individual preferences and the camber of the shoe, knowing that a setting on the front favors high mobility of the ankle and therefore good velocity, while a setting of a few millimeters back gives a little more strength, at the risk of chopping the pedal stroke and mobility of the ankle and hip. For adjustment of the shims laterally and for their orientation, it will proceed by trial and error if you do not have pedals with high angular freedom (Time or Speedplay). The trick can be sit on a table, knees square and legs dangling. Note the natural orientation of your feet, and try to reproduce this orientation with the setting of your holds. This is a good starting point, subject to checks, to avoid possible joint injuries.
Saddle height
The saddle height is measured between the crank axle and the top of the saddle, at its hollower point. It's about mechanical efficiency, as well as comfort on any type of distance. A good method is to multiply the height of the crotch by 0,885. This value can of course undergo some adjustments of the order of 10 to 15 mm, depending on the arch of the shoe and the thickness of the sole, the size, your flexibility or your muscle strength, as well as the level of engagement of the shoe. foot on the pedal. With moderately arched shoes, it is possible to carry out a simple check: by putting the heel on the pedal, the leg must be fully stretched, with a very slight sway when pedaling (Daniel Clement, 1984). We must not believe that the higher the saddle, the more power is developed. The height of the saddle should just allow the ankle to rotate around the axis of the pedal to better erase the upper and lower dead spots of the pedaling cycle, which is feasible on condition not to pedal with the legs too much strained.
Saddleback
Adjusting the correct seat height is only considered when considering its recoil in relation to the crank axle. Indeed, taking into account the inclination of the seat tube, it is easy to realize that the higher the saddle is mounted, the more it moves back from a vertical passing through the axis of the pedal. And conversely of course. A very good approach is to adjust with a plumb bob. With the cranks horizontal, well seated on the saddle, the plumb bob passing on the top of the kneecap must fall in line with the axis of the pedal, or slightly behind. This academic adjustment must be possible with a large majority of commercial bikes, whose saddle angle varies from 74 ° 5 to 72 ° 5 in general. The more the angle is marked (closer to 73 or 72 °) the more it allows to adjust the saddle backwards, taking into account the possibilities of adjustment of saddles and seat posts on the market, and especially a certain consistency and of a certain balance of the position of the cyclist in relation to the geometry of the bicycle. Contrary to popular belief and to what would seem logical at first glance, the best comfort and the best setting of the cyclist on his machine is not necessarily obtained by bringing the saddle closer to the handlebar while reducing the recoil. You may feel too far away from the handlebars, gasping for air, simply because you are not properly seated in the saddle. Better to change the length of the stem or the height of the cockpit. Namely: pedaling with a forward position in relation to the axis of the crankset optimizes instantaneous power, by promoting the use of the front muscles of the legs, which are richer in fast fibers. However, a more rearward position favors the use of the posterior muscles of the legs, which are richer in slow fibers and therefore more economical over long journeys. As for the inclination of the saddle, it must be adjusted perfectly horizontally, even very slightly inclined forward, to avoid discomfort in the genitals.
The cockpit
Finally, the proper length and position of the cockpit must be determined, so that you can ideally spread your weight over the three points of support that are the saddle, the pedals and the handlebars. Aerodynamics is secondary if you're starting out or if your goal is to accumulate miles for fun or for great cycling events. The important thing is that you can sit on your bike without any tension. A good length of stem, the one that will be adapted to your level of practice must be able to allow you to catch your hanger in several positions, as well hands up, hands to the pots, that hands down at the bottom of the hanger. There are stems 80 140 mm long, but also with different angles, which ultimately changes the distance between the saddle and the hanger. The choice of the shape of the hanger, when you have the possibility, is also essential to be able to control your bike in the best conditions. Do not hesitate to raise the stem a little at first, if you do not have all the necessary flexibility. For that, it is not necessary that the pivot of fork is cut too short, to be able to allow you to put the rings of raising necessary under the gallows. If you want to adopt a position of reference, the ideal can be tohave your elbows very slightly in front of the knees, in a speed-seeking position, your hands at the bottom of the handlebars. To avoid falling on the front of your bike and feeling unnecessary tension over the miles, we can advise you to orient the bottom of the handlebars upwards a few degrees. This will prevent you from tingling in the palm of your hands on the one hand, helping you to wedge yourself to the bottom of the saddle by pushing the handlebars, not by pulling it. But above all, it can be essential to think about pulling the brake levers upwards, especially since these are now intended to “drive” the bike, with the gear changes integrated. Many back pains can be avoided by simply thinking of relaxing and relaxing the upper body, simply by putting your hands on these reefs. These small adjustments do not represent much, if not some trial and error, but in the end it is a lot of unnecessary fatigue and less over the miles. Think about it!