Some Flex Is "Good"

The Salsa Cycles "Regulator" Ti Post

If you just pay casual attention to the cycling industry, you'll hear the words "stiffness" and "stiff" used a lot. You might begin to think that cyclists are looking for the most rigid structures known to Man to ride upon. If you are in this camp, please know that this is really not the case. Some "flex" is good. Really good!

In fact, like most things in life, balance is key to cycling comfort, and not just for the painfully obvious reasons. A good balance of stiffness to flex is not only good for riding, but it is necessary. But it goes beyond this- Flex needs to be not only something in a balanced proportion to stiffness, it needs to be in the right places as well. 

Okay, here's a "Captain Obvious" example for you. Think about tires. A totally stiff, unforgiving tire is a bad thing. Uncomfortable, slow, and hard to control. However; a nicer, pliable casing with a reasonable amount of air pressure? Heavenly! (And faster to boot, I might add.) So it is with flex in some other places on the bike, and here is one place you may want to consider having a modicum of flex: that being your seat post.

Mountain bikers kind of figured this out a long time ago. Due to the necessity for more clearance when standing over the bike on uneven terrain, or for bailing off the bike in a hurry without entangling one's appendages on the frame, mountain bike design started to make the main triangle of the frame smaller and shorter. This also had the added side benefits of making frames stiffer and lighter, both good things in an off road frame. However; leg extension needs meant that seat posts needed to become longer. In making these posts, a side benefit was discovered in that while seated, the post tended to flex backward slightly under the rider's weight when the rider hit a trail obstacle. This lead to some wacky designs like the Allsop/Softride beam, various suspension posts with linkages, and to some degree was a factor in the Unified Rear Triangle (URT) designs for rear suspension.

The Ergon CF-3 Pro Carbon Post

Some materials technology advancements have also helped bring some of these mountain bike bred ideas further. Titanium was discovered to have exemplary attributes for a seat post, so Moots, then Kent Eriksen, (under his own name), started making titanium posts that have become standard fare for those looking for something to take the edge off on hard tail rigs. Cane Creek bought the Thudbuster design, refined it, and now it is also a highly regarded design for a bit of engineered flex.

Ergon has taken the beam idea and turned it into a spectacular post with the CF-3 Pro Carbon model, which unfortunately is only rated for road bikes now, although a mountain bike version is said to be in the works. Modern choices in "flexible' posts have also been proffered in carbon fiber, maybe none more specifically than Niner Bikes RDO post, which is marketed as being made from "Unstiff Carbon".

Okay, so that's all fantastic, but is it a good idea? Well, from my experiences, and from those of others I have spoken with, and watched riding, the unequivocal answer is "yes", flex in the seat post is great, but maybe not at the expense of toughness, durability, and weight. The trouble with many of the suspension posts is mainly weight. Durability has been an issue with some, and tough carbon posts exist, but the spectre of shards of broken carbon fiber jamming into a rider's thigh after a sudden breakage of a carbon post, (either real or imaginary), is enough to put some folks off that idea for good.

All that to say that the off road, or heavier rider, that wants a bit of edge muted during seated riding usually favors titanium posts. They seem to have the greatest following now, although the Niner RDO post and the Ergon post may change some minds there given time and the proper post for the job. I am helping to conduct a test of some of these ideas over at Gravel Grinder News. (You can see the initial Ergon post write ups here and here. The Niner RDO post and the Salsa Cycles Regulator post reviews will follow soon.) The biggest negative I can see so far is the price of entry, with all of these posts falling between the 200-300 range. But if they do the job as advertised, it may actually save you money in searching for a more comfortable saddle or it may allow you to run a slightly more efficient air pressure in your rear tire, saving a bit of energy. Or, maybe you'll just be more comfortable, and that may be all it takes to get you out more and for longer rides on your bicycle.

Of course, there are other places flex is good, but for now, I will be focusing on the seat post. Stay tuned, there will be more to come.....