Inline Seatpost. The work of the devil!

They’re very much in vogue.  But why is the fashionable inline seatpost such a menace?

There are two reasons why inline seatposts are popular – one good, one less so.

The good one is that they are, or can be, light and strong (and cheap!).  Which, with the appropriate frame geometry for the rider, makes them the ideal ‘saddle support solution’.  However most frame geometries, for most riders, are not appropriate.

The other reason, which might also seem like a good one, is that they typically allow a more horizontal torso with a more open hip angle on a standard geometry bike (which is what most bikes are).  This is good for being-aerodynamic-and-powerful-at-the-same-time.  Or in fewer words, for Simultaneous Aerodynamics and Power.

But whilst lightness and strength are almost always advantageous, and rarely disadvantageous, Simultaneous Aerodynamics and Power are, for the vast majority of cyclists, useful only occasionally and unfortunately come at significant cost.

I’ve mentioned physics and energy a few times before in my blogs, and I reference them a lot in my day to day coaching and bike fitting.  They’re fundamental to everything.  Including bio-mechanics and evolution.

Being aerodynamic typically means having a horizontal torso to reduce frontal area, but as humans we abandoned horizontal in favour of vertical many, many moons ago.  Vertical, it turns out, has many more advantages.  One result of us evolving to vertical is that our brains grew and become much heavier.  Another is that our front legs became pretty rubbish at bearing weight.  A third is that we became flat faced.

To support that heavy head, without using our weak front legs, we have to balance by staying vertical – and to do that we have to keep our centre of gravity over our feet.  We can bend forwards, but only by sticking our backside out to counterbalance.  Try standing with your heels against a wall and bending forward. You’ll fall (it’s obvious, there’s really no need to try it).  

So it should also be obvious that if you try to make your torso and head horizontal on your bike you’ll need to use your ‘front legs’ to support them unless you stick your backside out to counterbalance.  

And this counterbalancing is what that inline seatpost prevents.  Welcome back to the four-legged animal world, but with your big heavy head and now downward facing eyes. 

Aerodynamic? Yes.
Powerful? Yes. 
Simultaneous Aerodynamics and Power achieved?  Looks like a yes. 
Comfortable, safe, sustainable, practical?  Almost definitely not.

Is it that bad?  If you have the strength, power and energy to hold your head and body up, and the nerve and skill to handle the speed maybe not.  But it takes an awful lot of training and energy (eating) to achieve and sustain that state of Simultaneous Aerodynamics and Power for more than a few minutes at a time.  

The inline seatpost has a lot to answer for.  You can’t get your backside back far enough to counterbalance your head so your body weight falls forward and has to be supported by the the handlebars and the front of the saddle (which presses on your perineum, not your sit bones).  Reducing the pressure on one simply increases the pressure on the other – and involves switching on muscles in your back, your neck and your arms.  Ever wondered why it is so often not your legs that tell you you’ve had enough, but your hands, or your arms, or your neck, or your back, or your crotch – all things that should be doing no work at all?

Is the inline seatpost really the villain of the piece?  Arguably it’s the geometry of the frame.  But we are all different and the era of custom geometry frames has passed.  We are now all stuck with stock geometries, and they have very similar seat tube angles:  74 degrees plus or minus 1.

So why am I blaming the inline seatpost when you could simply swap it for a non-inline seatpost, one with more setback, that would allow you to get your backside and centre of gravity further back?  

Unfortunately swapping the seatpost isn’t typically the first solution that most people think of.  And unfortunately the main bike manufacturers, who should know better, seem to be equally naive. Instead of looking to physics to address the cause they’ve tried to cure the symptoms:

• changed the design of the saddle 
• added suspension to the seatpost
• added front suspension
• increased the stack
• shortened the reach
• made the handlebars more comfortable to rest on
• fattened the tyres

Because none of these actually address the cause they don’t really fix the symptoms, they just delay the onset (ideally for long enough to persuade you to buy the bike)

But surely, having come to the conclusion that those fixes haven’t worked, it’s easy enough to change the seatpost isn’t it?  

Yes – but only if it’s round.  

A round inline seatpost is not really a problem at all.  The real villain of the piece is a non-round inline seatpost.

Stuck in Hell with no way out.  Truly the work of the Devil.