The relationship between bike and biker is rarely without teasing. When things don't run smoothly, pain and frustration quickly set in. A bike fitting can bring the couple back into harmony.
Bikes are a bit like shoes: they have to fit so that you can get around comfortably and effectively. It's not always possible to find this out during a quick test ride - if one takes place at all. This is because more and more bikes are being bought online, and a more or less sophisticated calculation tool is usually used to help you find the right bike for your body measurements.
However, the data that is fed into the tools on the shop websites is often sparse: when it comes down to it, in addition to height, the leg length and rarely the arm length may decide which frame size the system ultimately spits out.
Simon Karosser's bike purchase shows that this can go very wrong. He was advised to buy a 44-centimetre frame on the shop's website. When he went to pick up his newly ordered dream bike, it also happened to be available in frame size 41 - and after checking his riding position, the sales assistant advised him to go for the smaller bike.
How good this decision was turned out to be during the subsequent bike fitting: "With the 44 mm bike, almost nothing could have been saved," he explains. After all, it is easier to fit a longer stem, for example, than to take a lot off here.
Simon's path to bike fitting
How did you come to do a fitting in the first place, and what is it? "After the first long ride, 50 kilometres along the Isar, I noticed that my back was hurting. And I had the feeling of falling forwards over the handlebars, especially when riding downhill - the centre of gravity was probably too top-heavy," recalls the hobby cyclist. "The handlebars were also too straight for me and my wrists and forearms were forced into an uncomfortable position." He then came across the topic of bike fitting on the YouTube channel of a bike shop. This involves the entire seating position being adjusted by a professional after a thorough analysis.
In this case, the provider was Radlabor München (www.radlabor.de), which also operates locations in Freiburg and Frankfurt and supplies its fitting software to bike dealers (www.smartfit.bike/haendler). There are a handful of other providers on the fitting market, some of which use different methods but ultimately pursue the same goal: To weld bike and body together into an efficient and harmonious pair. Every bike fitting basically follows a similar pattern. We show an exemplary overview based on the fitting we did in the bike lab.
Bikefitting step 1: The anamnesis
Where is there pain, problems, weak points? What is the purpose of the fitting, more performance, more comfort, or both? A questionnaire is usually used here.
The process is similar for the various fitting providers: First you answer questions about your problems, goals and type of biking: Where does it hurt, are there older or acute injuries? What is your previous riding impression, comfortable or problematic? Do you want to compete, tour or travel? Simon Karosser has set himself the goal of crossing the Alps on his new bike this summer. He doesn't want to be slowed down by orthopaedic problems.
Bikefitting step 2: Measurement of bike and rider
The software uses a laser scanner to record the geometry data of the bike brought along (including saddle height, stack, reach, handlebar height and angle). Also using laser point detection (body height, sternum height, inside leg length, lower leg length if applicable, arm length, ischial tuberosity distance on measuring stool).
To make sure this works, we continue with a complete measurement of the bike and rider. To do this, fitter Uli Plaumann uses a laser to scan predefined areas in order to record the geometry. The expert then repeats the same process on Simon's body: size, sternum height, inner leg and arm length are measured by laser, and the distance between the seat legs is determined by measuring the pressure on a stool. For other fittings, there may be even more measurements, depending on the issue. After entering all the data into the software, the result is a kind of point cloud that depicts the entire bike-relevant physique.
Bikefitting step 3: Video analysis
Three-dimensional evaluation of the seat position and pedalling movement while riding on the clamped bike.
The aim is now to place the virtually depicted body on the digitalised bike in the best possible way. In addition, the evaluation of the data is given a dynamic component via video analysis. Riding on the bike clamped in the roller trainer shows how ergonomic the sitting position and pedalling movement are. This is filmed before and after the fitting, and possibly also during it.
Bikefitting step 4: Wheel adjustment
Following a fixed sequence, the hips, knee angle, shoulders/upper arms, brake handles, knee axis and feet are brought into the best possible position.
Do the saddle, handlebars, seat, arm and knee angles fit? "These and other questions are answered by the Smartfit system on the one hand and personal experience on the other," explains Plaumann. She then adjusts all adjustable parts on the bike millimetre by millimetre and optimises the movement and angular position of the relevant joints. If the adjustment options on the bike are not sufficient, she suggests replacing certain parts. "Our database contains components from many manufacturers with their dimensions, so we can find more suitable alternatives."
In Simon's case, it was mainly the handlebars. The top-heavy riding sensation and back pain came from an unfavourable backsweep, the backward bend of the handlebars. The solution was to fit a model that was angled more backwards and upwards. The saddle, grips and pedals also showed potential for optimisation: a stepped saddle with an adapted width now offers the sit bones more support. Ergonomic grips are easier to hold. Plaumann also recommended a different, slightly larger model for Simon's platform pedals. She also gave tips on the best foot angle for standing on them.
Bikefitting Step 5: Checkup
At the end there is a check on the newly adjusted bike, with repeated video analysis and a final discussion with documents to take away.
And - was it worth the effort? During a test drive, again on the home track, the impression soon emerged: yes, much better this way! "Even after a long ride, I no longer had back pain and the feeling of tipping over forwards was gone," says Karosser. "So when I cross the Alps in the summer, at least I won't be slowed down by pain due to the wrong sitting position."
Further bike fitting offers
Retül Bikefitting
Retül was developed in the USA and has been cooperating with Specialized for around ten years. After a physical check-up, the biker is marked with LEDs at relevant points and filmed while riding on the roller. Their movements are analysed by image recognition software using 3D animation technology. Viewing in slow motion or still images enables an even more precise analysis. By varying the camera position, problems such as pelvic tilting or knee swaying can be detected. With the help of the software, the adjustment is carried out on a fitting bike or your own bike. Prices from approx. 200 euros. More information at Retül.
Waytowin
MQ Fit Bike
In the future, purely digital fitting systems that work with the help of AI (artificial intelligence) are likely to become increasingly important. One example is the MQ Fit Bike tool from digital start-up Motesque, which has just been integrated into the Fahrrad.de online shop. Strictly speaking, this is not yet fitting software in this form, but rather a purchasing aid that helps you choose the right bike online. Prospective buyers can upload two full-body photos during the purchasing process. From this, an AI calculates a three-dimensional avatar with the most important variables and recommends the appropriate frame size. The technology is used for fahrrad.de
