VeloNews seatpost test

Discuss light weight issues concerning road bikes & parts.
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djconnel
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by djconnel

They didn't use maximum deflection as their comfort metric but rather as a supporting measurement. Comfort was ranked based on peak acceleration. This seems reasonable.

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andy2
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by andy2

You are correct there maxxevv, it would certainly be better to test with more realistic loads!
It looks like they just loaded it up enough to get a deflection number and not cause any damage.
Certainly a 3000N load rather than the 300N they used, the former would be like a 100kg rider/bike hitting a 3g bump, would be far more realistic.

That said all carbon tubes will to a certain extent display fairly linear spring characteristics, getting progressively stiffer as it loads up.
So ( as DJ just pointed out) the relative differences between the post most likely would stand.
In the hierarchy of things without relevant deflection ( i.e a good working spring and all of these post are pretty darn stiff springs),
you will have a very hard time to make up with damping to reach comfort.




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MileHighMark
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by MileHighMark

I'm curious why they didn't compare the SB32 'post to the SB25--especially since the SB25 performed so well in their tests.
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maxxevv
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by maxxevv

As I may refer to the analogy of a MTB suspension fork.

All else being equal, a good fork covers several areas of shock absorption. There is the spring rate, the damping co-efficient and the rebound rate.
The spring rate only covers the deflection of the fork for shocks. How much force does it take for it to deflect a certain amount.

The damping co-efficient affects how the energy is absorbed by the fork and dissipated. It helps widen the range of frequencies the fork is able to attenuate through, usually the very low displacement and very high frequency stuff.

And the rebound rate covers how fast the fork recovers to its original position post shock deflection. Its the difference between a waterbed and a trampoline.

The article seems to be covering only the spring rate there. But as we all know, a nice cushy spring is pretty useless as a suspension for an MTB as it would rattle the front end like the proverbial jackhammer!

Shock absorption has many factors, and spring rate likewise is just one of them. The most obvious, but that's about it actually.

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djconnel
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by djconnel

The primary test is described:

Damping was measured while riding a set of rollers with 1/4-inch tall ridges, welded longitudinally along the front roller and the forward of the two rear rollers. This produced a high-frequency vibration similar to riding fast on a bumpy road. An accelerometer mounted to the saddle rail took 1,000 readings per second (1,000 Hz) and measured the magnitude of the up-and-down acceleration of the saddle rail, which was then converted into a G-force measurement; 1 G is equal to the acceleration due to gravity. We measured for 30 seconds, garnering a total of 30,000 data points per vibration test for each seatpost. A lower number of Gs for any given seatpost would indicate more vibration damping by the seatpost and saddle, and therefore less transfer to the rider.

Here's the results:

Image

So I think the discussion of the loading is related only to the deflection measurement. The vibration isolation was measured riding the bike over rollers with a bump.

maxxevv
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by maxxevv

DJ, you missed me there. I was referring to the German test.

I'm generally alright with the Velonews one (the idea behind it, though much can be done on the methodology), just perhaps some additional tweaks to make it really useful and less subjective with regards to the human in the loop.

They had to shift the saddle to center the riding position of the cyclist but that doesn't give a direct comparison between posts. In an ideal situation, posts should be selected to give an optimum riding position, not the position of the rider being shifted just so that the post can be fitted. In other words, the load on each post should be smack in the center, not shifted in the test.

A single displacement, at a variable (human input) speed over 30,000 points doesn't mean much since it cannot reliably reproduce the frequencies accurately. Unless there was a fine print in there that says the rollers were powered by motors ?

A 1/4" wedge on roller at 15km/h will produce very different vibration frequencies from say a 1/8" wedge on roller at 25km/h.

Damping is inherently about frequencies and their interruption. Since there was no specific frequency range being generated by the rollers, there really isn't much of a scientific result to compare the posts. Reason being that some posts will do much better at one frequency range than the others and vice-versa.

Ypsylon
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by Ypsylon

andy2 wrote:It's obviously taken from the Schmolke site so you can guess who the winner is,


Just to avoid misunderstandings. It's on Schmolke's site because they won, not the other way around. It was a magazine that tested it. It must be a rather small one and two college students did the measuring and I believe the design of the testing, which I have no reason to believe they got wrong, you just gotta realize that not all comfort is created equal.
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MagnusH
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by MagnusH

MileHighMark wrote:I'm curious why they didn't compare the SB32 'post to the SB25--especially since the SB25 performed so well in their tests.


Maybe they wouldn't have been able to get the same saddle position with the SB0 as the SB32?
"We tested the seatposts with each saddle mounted in exactly the same position relative to the cranks and handlebar on the bike."

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kgt
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by kgt

@ maxxevv
Nice post. At the end I am not sure if the test adds anything on what we already know by experience.

maxxevv
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by maxxevv

@kgt:

yes indeed. Too many open ended variables to be objectively useful. Subjective, anecdotal experiences many on this board have had, seem to have glossed over much of the stuff observed in the article already. :noidea:

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