Basic Bike Fitting
When we decide to start cycling either for recreation or to improve our health we often end up in a bike shop looking at bikes and wondering what is the right frame size? Usually despite the advice of bike shop personnel, we end up getting a larger bike frame due to cosmetic reasons. This though will have a big impact in our ability to ride and could cause injuries.
Thus it is vital to get the correct Frame size so the bike can easily be adapted (fitted) to the body. A general bike size guide is shown in Table. 1.
|General MTB Frame Size|
|Rider Height||Frame Size (inches)||Frame Size (cm)||Frame Size|
|148cm - 158cm||13" - 14"||33 - 37||X-small|
|158cm - 168cm||15" - 16"||38 - 42||Small|
|168cm - 178cm||17" - 18"||43 - 47||Medium|
|178cm - 185cm||19" - 20"||48 - 52||Large|
|185cm - 193cm||21" - 22"||53 - 57||X-Large|
Each bike brand designs its bikes with its own philosophy so their size guide should be advised first before any purchase. Moreover the advice of bikeshop personnel should be sought too. When a bike is purchased, it is recommended to have a professional bike fit. This comes at an extra cost that very often makes people unwilling to proceed with it. In such a case, we should fit the bike ourselves.
Following is a very basic guide on how an amateur rider should fit the bike. Pro bike fitters will take into account many parameters and use specialized equipment for high accuracy and improved results. For the average amateur rider the following guide should be a good starting point. For the purpose of this article a MTB Fitting will be used as an example due to the fact that most new cyclist start with a MTB. Road bike fitting is very similar.
The rider on a bike should have the following position when seated (Fig.1) so all adjustments should be made to achieve this position.
The human body has 3 points of conduct with the bike. These are the pedals, the saddle and the handlebars. All of these should be adjusted.
The first thing to adjust is the pedals (if clipless cycling shoes are used). The clits of the shoes should be screwed along a virtual line between the beginnings of the toes as seen in Fig. 2.
The second and most important adjustment is the saddle. For short rides in the city larger saddles are more comfortable but for long rides(more than 2 hours) smaller saddles are better. Female riders use larger saddles than male ones due to bigger pelvis.
The height is calculated by measuring the inseam as seen in Fig. 3. and multiplied by 0.886. This will give the correct saddle height.
The saddle height is measured from the middle of the Bottom Bracket to the top of the saddle along a virtual line, parallel to the seat post. The saddle should be level with the ground. The saddle position (forward/backwards) is adjusted by making sure when the foot is parallel to the ground, the knee falls to the center of the pedal spindle when the pedals are at 3 and 9 o’clock position respectively. This is demonstrated in Fig.4.
The final part is to adjust the handlebars. The handlebars should be 2.5 to 5cm lower in height than the saddle. When sited and leaning over, the angle between the arms and torso should be approximately 90 degrees. This would influence the size of the stem or how forward the saddle is. The brakes should be fixed so that 2 fingers at most touch them easily and at an angle inline to our hand as demonstrated in Fig. 5. The hands should be at the end of the handlebar.
All these adjustments will make riding a bike a lot more comfortable and will reuse the risk of injury. A pro bike fit will take into account factors like Sport, race and trekking fit thus improving this even further with big gains in performance and or comfort.
UCI Level 2 Coach
CCF certified instructor