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Saddle Position – what a difference fore and aft makes.

I’ve spent a lot of time trying to understand cycling.  Over many years I’ve watched, listened, read, ridden and experimented.  I think about things from a power perspective, a speed perspective, a comfort perspective, an endurance perspective, a handling perspective, a physiological perspective, a psychological perspective, a mechanical perspective, a biomechanical perspective, an aesthetic perspective, an economic perspective, a design perspective, a practical perspective, a health perspective, a tactical perspective…  and if I think of anything else I think from that perspective too. 

When it comes to bike fitting I’ve developed pretty strong ideas about what constitutes a good set up:  being able to sit comfortably on the saddle without stress or discomfort, while pushing the pedals in the direction that they’re going to go anyway (they only follow their own circular path) using the strongest muscles (for maximum power with minimum waste), while being both aerodynamic and in full control.  The setup that we each need as individuals to achieve this is obviously dependent on our size, shape and flexibility, so it is as unique as we are. Of course we’ve very adaptable, but we adapt to survive, to cope. We might subsequently evolve to optimise and thrive, but evolution takes rather longer – certainly longer than the average cycling career!

Cyclists have known this for quite a long time.  Indeed when I started cycling it was normal for serious cyclists to have their frames made to their specific measurements.  In those days people went for their bike fitting not just before they bought their bike, but before it was even built.  Modern carbon fibre frames are moulded and don’t allow this type of customisation.  The first moulded carbon frames were fitted with highly adjustable stems and seat posts to allow riders who were used to custom-built frames to adjust them to their individual requirements.  

Adjustability isn’t great for weight or stiffness, however, so the adjustable components were quickly superseded by wider variety of more easily replaceable components.  This meant that it didn’t really matter if the frame wasn’t quite the right size or shape.  By swapping stems you could fix small discrepancies in stack and reach, and by swapping the seat post you could effectively modify the seat tube angle.

Of course there is more to frame design than the three ‘fit’ aspects of stack, reach and seat angle.  But, and this is an important ‘but’, if the saddle and handlebars aren’t in the right pace relative to the cranks the rider’s bodyweight won’t be in the right place – so manufacturers tweaking the head angle, the trail, the front centre, the bottom bracket drop or the seat stay length to fine-tune the handling of their off-the-peg frame is like shortening a new pair of trousers to fall perfectly around the ankles before you know who they are for.

I think that the latest top-end bike designs have lost sight of the basics.  The frames are still coming from moulds but whereas those before them allowed extensive customisation through extensive adjustment and replacement, the latest frames allow very little of either.  Seatposts are frame-specific, not round, and stems and handlebars are integrated to allow cables and hoses to run internally.  And what starts at the top of the price range trickles down.  You no longer have to spend the price of a car to buy an unadjustable professional rocket bike, you can buy an equally unadjustable starter bike for less than a grand.

How much difference can it make?  

Have a look at this little video. In it I move the saddle forwards cm by cm.  To make it I used an adjustable seatpost with a range of setback from 30mm to inline (zero) and used the full length of the saddle rails.  I started off feeling pretty comfortable and ended up with an aching back and an uncomfortable backside from sitting on the front of the saddle.  My bike started out feeling stable and ended up feeling twitchy.   I found it increasingly stressful to tuck down and make myself aerodynamic as the weight on my arms increased.  I also found that my quads burned and that my pedaling became choppy.  

The video unwinds, by the way, so from about half way the saddle is going back again.

My little experiment shows how much difference saddle fore and aft adjustment, and therefore adjustability, can make. It so happens that to get my preferred position with a 73 degree frame angle I need a seat post with 30mm of setback – so I’m very conscious that (as very few production bikes have a shallower frame angle) almost any bike with a non-round seat post would at best limit my choice of saddle to Selle SMP.  Perhaps I have a longish back and long arms but I’m not that unusual.

Note that I didn’t adjust the handlebars at all. The stem is actually 150mm so fitting a longer one was not an option.

To go back to my opening paragraph, I don’t understand why racing cyclists are now positioned with their saddles so far forward.  I kind-of know why:  bike fitting systems are trying to replicate the time trial setup and the wisdom is that this achieves an open hip angle and a flat back.  But the time trial set up has elbow pads to support the upper body, and without them there’s a huge amount of stress in the arms, shoulders, back and neck. It also doesn’t give good control for steering, cornering or braking, and isn’t good for going up hill because there’s a huge dead spot in the pedal cycle.   You might well ask why racers put up with it?  I think that it’s because nowadays they don’t know anything else!!  Whereas those early carbon frame users had previously ridden custom frames and expected to replicate their previous setup, today’s riders have only ever known off-the-peg setups. With the range of adjustment available they simply can’t get the saddle far enough back to experience sitting on the back of it so it’s completely unknown territory. And they’re good at putting up with a bit of discomfort and the odd crash

Read more of my pieces on bike fit and professional racing.

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