Your feet are fantastic at supporting your body weight and maintaining balance. While your hands excel at complex tasks that require a delicate touch. This is what they both do day-in, day-out and, respectively, they have evolved to become quite specialised. They certainly aren’t interchangeable. If you need further proof then try walking around on your hands while peeling a banana with your feet. You get the idea. But mountain bike manufacturers often seem to forget this.
If you’ve ever tried riding with as much of your weight supported through your arms as possible (perhaps whilst bored waiting for friends to put their bikes together at a trail centre car park or, more commonly for me, while trying to coax a bike home when it has a slow puncture in the rear tyre) then you will know how little finesse you have over steering inputs when in this position. The way that weight is distributed between your hands and your feet is critical to the level of control you have over a bicycle.
It helps me to use the following car-analogy when thinking about weight distribution on a bicycle… A front wheel drive car is asking these wheels to do a lot. The rear wheels are only really present to keep the back of the car off the ground. The steering and acceleration (and the majority of the braking) are all being done by the front wheels. Often this can mean that they become overloaded and start to spin or slide if driven hard with torque-steer being the bane of many high-powered front-wheel drive cars. Conversely, a rear wheel drive car is spreading the jobs around. The rear wheels are asked to cope with the tough but relatively simple job of driving the car forwards, while the front wheels are left to provide the more subtle but complex job of adjusting the cars direction. Each pair of wheels can be designed to do a specific job very well, much like the way our hands and feet have evolved.
So, a rear wheel drive car is similar to a rider in a neutral, balanced and stable position, with their weight supported through their feet. Their hands can focus on the steering, uncorrupted by the donkey work of supporting their body weight, other than for a little fine tuning. While a rider lent forwards with a significant amount of their weight being supported through their hands is like a front wheel drive car, trying to cope with both the manual labour of supporting their body weight whilst at the same time trying to execute the delicate job of picking the desired line.
Because of the above, it is my opinion that the position of your contact points, and therefore the shape of your bike frame, should be defined by the need to maintain a neutral, balanced and stable body position whilst allowing for your limbs to properly suspend your core. Just like any good suspension system, you want to start with your arms and legs part-way through their range of movement as having them slightly bent whilst riding provides far greater stability. This is something that most public transport commuters are all too aware of. Try to stand on a bus or train with your legs locked out straight and you will spend the journey shuffling around and bumping into people in order to stop yourself from falling over. However, bend your legs slightly and it becomes far easier to absorb these external forces, isolating your bodies core and keeping it stable.
Translating this to the bike, the most obvious scenario is when riding over something such as a rock or root, in which case you will want your limbs to compress to isolate your body from the impact. But equally, if your front wheel drops into a dip or off a ledge then you need your limbs to extend to maintain stability. A common problem is to see a rider knowingly approach a drop-off with their arms fully extended to allow them to get their weight as far back as they can based on the assumption that this will reduce their likelihood of being thrown over the handlebars. But at this point your arms will have lost any ability to react to the bike dropping away from you and therefore the ability to maintain a stable core. If anything, you will be more likely to topple over the front of the bike in this position as the handlebars will pull you forwards as the front end of the bike drops away. Partly, this situation is the result of poor technique, but often it is also because the geometry of so many bikes places too much of a riders weight on their hands and many of these riders, quite understandably, attempt to counteract this.
In many instances riders are having to reach forwards and down too much. This is particularly true for taller riders as most bike manufactures fail to increase their frames’ stack heights in proportion to either their reach or likely saddle height. Trek, for example, maintain exactly the same stack height across four different frame sizes on their 2017 Fuel EX, supposedly covering everyone from 5’1’’ (155cm) to 6’4’’ (193cm). The lines in the graph below should be horizontal if bike manufacturers increased a frames stack height in proportion to its reach. Instead, for all of these bikes the taller you are, the more you are expected to reach down to meet your handlebars.
Stack:Reach ratios across a range of frame sizes for some popular mountain bikes
My view is that current mountain bike geometry tends to place the handlebars too low and too far forwards relative to the bottom bracket, requiring riders to support a significant proportion of their body weight through their hands, reducing the ability to steer accurately or maintain a stable body position. Something that seems to only get worse as riders get taller. It’s time for a change! So, next month I’ll be suggesting what I believe to be the correct relationship between your bottom bracket and your handlebars to ensure that all of you weight is supported through your feet, leaving your hands to focus on steering and braking.