Looking for a new seatpost for a bike I am building up. I have always used Thomson posts but was thinking of trying a carbon post. Is this just a “cool factor” or will carbon really dampen some road vibration? I hav also worried a bit about the bond between seatpost head and post…do these ever fail? Appreciate any input from folks who have moved from aluminum to CF post.
Thanks,
Mike
I’ve got a BP Stealth carbon seatpost and a Thomson seatpost. I cannot feel any difference between the 2 although the BP Stealth looks a lot cooler. I have about 185 mm of seatpost showing. I am not much of a “princess” when it comes to bike feel.
In that vein - I suspect that there are a lot of bicycle parts (handlebars, frames, wheels, seatposts, etc.) that people could never differentiate between if they were blindfolded.
I agree with john. I know people will argue that they feel a difference, but I think people automatically think if something somehow feels or “sounds” different that it is therefore better.
I have one myself because it looks cool. I also have thompson post on two other bikes and really cannot tell a difference between any of them. So in short, I suspect they make a VERY small difference, but not on proportion to the cost and would be one of the last things I would change if I were seeking comfort . . . but they look cool and I could be spending money on worse things . . .
I have both - no difference in feel for me, but my frame is damn comfortable and I don’t think a seatpost can really improve it. Thomson is a zero setback, carbon post has a slight setback. Without question, the carbon looks cooler, so the Thomson is only installed when I neet to put the bike in the stand for tune-ups. I got mine from www.yaquiusa.com when I bought my bike - paid less than $70 for it.
It depends on the post. The Dedaccai Balckstick is extremely flexible and makes a substantial difference in ride quality. Others, perhaps less noticeable. Most do something to remove “buzz” or high frequency vibration from the road. Or you could just ride your tires at 105 psi instead of 120 psi.
This is one of these things that I don’t believe can be quantified easily. My road bike is an aluminium frame Giant TCR. I’ve tried both an Easton and the Giant carbon posts against an alloy one and can’t notice any immediate difference. However, maybe after a century ride my body might notice it. I’ve also added a titanium stem and Kestrel carbon handlebars for this reason. Next major purchase will be the composite TCR frame and then I’m sure that there will be a noticeable difference.
Yes they can make a difference, but not that much and it depends on which post, how much post is exposed and what the seat angle is. Selcof ti/carbon monocoque is the most comfortable post I have used - way better than the Easton EC-90. Bang for the buck American Classic Ti is the best one I have tried. A bit better on big bumps than carbon and almost as good with buzz.
Guaranteed your wallet will notice the difference if you get the Selcof monocoque.
By itself a carbon seatpost does not make a difference. It has to be part of an overall package. For example, if it could be quantified as a % how much more aero (due to design or weight) the seatpost could make your bike it might be a 1% improvement. Then add up all the little improvements (frame %, bars %, position %, etc. etc.) to determine how aero efficient your bike is. If you can determine that it is 40% more aero overall after adding all the small improvements together (39% without the seatpost) that’s when you can decide how much of a difference it makes. Easy to determine, heck no. Worthy of big $, probably not but most of us would do it - just to have a small % improvement in an overall package. I would probably not put a carbon seatpost on anything other than a carbon frame.
Zero dampening. Period. It’s been tested by ___, the big German bike magazine (forget the name). It’s also been tested by my butt. Zero difference. And, if you simply think through the engineering, you will conclude the same – zero dampening. A seat post carries a compressive load (even at a 72-78 degree angle). Plastic resin reinforced with carbon fibers has zero compressive “give.” It’s harder than concrete under compression.
Your tires and seat will dampen road shock, not your seat post.
I don’t even think there is a cool factor. A Tompson post is the coolest thing going, if you axe me.
Julian,
Now that is interesting, but we shouldn’t be surprised given today’s marketing hype environment. Did they also test any titanium posts?
Is your frame aluminum? Try this: mount the bike on a trainer with the aluminum seatpost and ride. While riding grab the frame where the top and seat tubes come together. Feel the vibration? Grab the seat post. Still feel the vibes? Now change to a carbon fibre seatpost, repeat test. When you grab the seatpost, do you feel any vibration, I don’t
“Is your frame aluminum? Try this:”
Good point. That’s why everything on my TCR is titanium or carbon. I feel the difference on this test. I’ll put up with this on a tri bike like the P2K but not on a road bike, since I ride the road bike a lot more I’m also building up a classic steel frame upgraded with all new carbon/titanium parts as my “comfort bike” for centuries and long rides. It’s fine if you’re a twenty-something but for us old guys, comfort becomes more of an issue.
I am always impressed how psuedo-scientific explanations of complicated phenomena become part of the standard lexicon.
Example: An airplane wing lifts the plane since its shape causes air to pass faster over the top than the bottom. The faster-moving air has lower pressure, causing net lift upwards. Is this really true? Anybody wanna give it a shot?
Example: Two cars hit head on going 50 mph. The effect on one of those cars is the same as hitting a brick wall going 100 mph. True or False?
Example: A seatpost with zero compressive elasticity that carries a compressive load will dampen shock in a material way. “Material” meaning in a measurable way once you’re actually on a real road with pneumatic tires and a semi-flexible seat mounted on horizontal rails. Anyone…?
I don’t sit on the seatpost, I sit on the saddle. The vibrations you are talking about with the aluminum seatpost will be attenuated by a Flite or most any other saddle.
Regarding the question about bonding of the head, there are many, many seatposts (and frames and forks for that matter) that use glue to bind the parts together. I would worry a lot more more about the steerer bond to the fork crown that I would about a seatclamp. However, if you are still really worried, the Thomson is one of the few seatposts on the market that is machined from a solid piece of aluminum. People tend to overlook the Thomson because it’s relatively cheap and commonplace, but all things considered it is arguably the best seatpost on the market.
Example 1 - False
Example 2 - False, though if both cars were equal mass and had brick walls for bumpers…
Example 3 - False by definition, but unless you have a 90 degree seat angle the load is not all compressive.
Example 2 - False, though if both cars were equal mass and had brick walls for bumpers…
If the cars are of equal mass and had perfectly rigid bumpers, the effect on either car is the same as hitting a brick wall at 50 mph, not 100 as is commonly taught in driver’s ed class and college dormrooms.
The answer is intuitive if we simply realize that each car deccelerates from 50 to 0 in 0 feet. Same as hitting a wall.
Example 1 is true. This is just the Bernoli (sp?) effect. This is why I spend lots of money to strap a roof to the walls during construction. Otherwise, when a hurricane visits, the lift as the wind goes over the roof will lift it right off and drop it next door.
Example is 2 is obviously true. It isn’t the speed that kills you, it is the sudden stop.
Example 3 seems false. If something is rigid, it won’t absorb energy as it is stressed along the rigid axis.
is compression the only factor? is vibration dampening another factor or only a form of compression. i have heard that some of the benefit of carbon/ti/steel over alu is that the vibration pitch of alu is an important factor, especailly on longer rides on asphalt. and that this was audible by tapping the tubes and listening to the sound of the noise (vibration?)
thanks
Oh, Art, you should know better.
Yes, a shaped wing will provide lift – but not enough to lift anything heavier than a balsa and paper glider. Lift is mainly created by air deflection. The air is deflected down, Isaac Newton provides an equal and opposite force up, and the plane stays in the air. It is a myth that the Bernoulli effect provides enough lift to fly a plane. Early aviation pioneers thought it did, and it made its way into textbooks and magazine. But it’s not true. Airplane wings are shaped the way they are to reduce drag, not to enhance the Bernoulli lift. BTW – what lifts a roof off a house is wind deflecting off the walls and pushing up under the eaves. An order of magnitude more force than the very, very modest Bernoulli effect.
In my second example the effect on either *one *of the cars is the same as hitting a stationary object. There is no “combining” of the impact forces onto one or the other car. If you were unfortunate enough to experience a crash into a wall at 50 mph, and a crash into an equally-sized car going 50 mph, you wouldn’t be able to tell the difference (assuming you lived, of course). Either way, you deccelerate from 50 to zero in zero distance (or the distance of the crush zone in your car).
As for carbon seat posts “absorbing shock” – here’s a little test for those who doubt you are correct. Take an aluminum post, place one end against your forehead and hit the other end with a hammer. Repeat with a carbon post. Compare the depths of the little circle in your skin. I’ll bet you two Bandaids they end up the same depth. Send pictures for confirmation, and I’ll mail out the Bandaids.
How about a carbon post on a compact frame? Because more of the post is showing, would the flex of a carbon post provide a dampening effect?