Balancing Act (Part 1)

Two separate things have conspired to make me question the modern mountain bike: my slightly odd physical proportions and a nagging sense that bike geometry took a wrong turn sometime in the late 80s.
 
I have mentioned elsewhere that I have long legs relative to my height. At a little over 6 foot (184cm) I have the legs of someone closer to 6’ 4’’ (192cm). This means that I have a rather lofty saddle height of just over 32’’ (82cm). One of the practical ramifications of being at the extremity of the physical-proportions bell curve is that I have always struggled to achieve a comfortable handlebar height. This is compounded by my poor circulation (probably linked to my lanky limbs) that tends to leave me with numb hands if my handlebars are too low. Therefore, I’ve probably spent far more time thinking about my handlebars than most people.
 
Coupled with the above is a concern that mountain bike geometry, after a promising start, quickly looked to road bikes for inspiration. And despite subsequent refinements, I suspect that it has been constrained by this fundamental decision ever since. Essentially, it would appear that the mountain bike has charted the following evolutionary path:

1. Repurposed from a laid back beach cruiser in the 70s for a good giggle getting loose down a fire road
2. Forgot its roots in the late 80’s and instead looked to the world of road bikes in search of a more efficient pedalling position as some of us decided that racing each other around a rutted farmers field in fluorescent Lycra was the thing to do
3. Adopted crude suspension forks during the 90’s to ease the pain in our wrists and the loss of our fillings caused primarily by our head-down-bum-up position
4. Steepened the seat tube angle while maintaining the effective top tube length to get more weight over the front wheel during the 00’s so that we could all get the most out of our ever-improving front suspension
5. Adopted shorter stems and lengthened top tubes (while still maintaining effective reach) in the 10’s to increase wheelbase for extra stability as more effective suspension meant greater speeds

 
So, after a strong start using bikes that just-so-happened to have pretty good geometry for having a laugh in the woods, we seemed to quickly replace these with bikes designed to excel at something that only a relatively small number of people have ever been interested in doing. The intervening years seem to have been spent trying to make comparatively superficial changes to overcome the inherent limitations of a bike designed for XC racing. There’s been plenty of other developments, like rear suspension, 29er’s and disc brakes, but I don’t believe that they are fundamental to this particular discussion. Essentially, I believe that we started with something fun, decided to junk that and instead created something for turning ourselves inside out and have been trying to fix the problem ever since. I would suggest that it might be worth pausing for a moment so that we might look out of the hole that we’ve been busy digging?

As I’ve pointed out before, the likes of Honda, Yamaha, KTM, et al. have far more money to invest in the development of their Motocross bikes than any mountain bike company does in the development of their own products. So maybe we should look over the fence at what they are doing? After all, they like to ride around in the mud just as much as we do, they just can’t be bothered to pedal. Fundamentally then, where does a Motocross bike place the riders contact points relative to the wheel axles and how does this differ from a MTB? Does a Motocross bike tip the rider forwards on to their hands and let the front suspension disguise the inherent issues with the resulting weight distribution as we appear to be doing in the world of mountain bikes?
 
The first thing to note about a Motocross bike is that its geometry is nothing like that of a road racing motorbike (see my previous blog, Assume the Position). The reach to the handlebars is only around 420mm while the stack height registers a mountainous 800mm or more. This gets the riders weight back and off their hands, despite having a fork with around a foot (300mm) of travel. The resulting position is a long way from that dictated by many current mountain bikes, with a seat angle of about 75 degrees and a handlebar height somewhere around the 660mm mark, a MTB rider is essentially preparing to do a forwards-roll by comparison.
 
Ah, but what about pedalling efficiency I hear you cry! Well firstly let’s be honest about why we ride mountain bikes. If you’re primarily interested in trying to claim every Strava KOM within a 20 mile radius of your house on you sub-20lb bike then this discussion probably isn’t for you. Stick with the bikes that have geometry perfected in the late 80’s and feel the burn – the best tool for the job is likely to be the equivalent of a road bike with knobbly tyres anyway. For everyone else I believe that there is real merit in finding out where the limits lie in terms of handlebar stack and reach.
 
This is where my genetic oddity comes into its own (like the worst X-Men ever). I suspect that for the vast majority of people, a handlebar height of 800mm will be too much once you’ve factored in that your pedals will, at some point, be around 170mm lower than the bottom bracket (resulting in a maximum vertical distance from the handlebars to pedals of almost a metre). However, as I’ve already mentioned, my saddle height is 82cm. Admittedly, this isn’t a vertical measurement, but even so, an 800mm stack height to the handlebars suddenly starts to seem quite reasonable.
 
This means that I can build a frame that puts me in exactly the same position as a Motocross bike safe in the knowledge that, for me at least, it won’t be completely beyond the realms of what is sensible. To borrow a saying from snooker, it would be a shot to nothing (for those not gifted in the ways of the green baize, this just means that I can give it a go without really risking anything). Then all I need to do is line up all of my mates in height order, ask them to throw the bike down some singletrack and find out at which point the inescapable magic starts to wear off! Simple.
 
Over the next couple of months I want to explore the fundamentals of achieving a good position on a bike – one that provides stability and control for the rider. As it is only once you have these that I believe you can then start to have fun playing with the bike on the limit.