Carbon seatpost flex (Seatpost sadlle mounting)

Discuss light weight issues concerning road bikes & parts.
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Burgunder
Posts: 60
Joined: Tue Aug 14, 2012 7:36 am

by Burgunder

Greetings from Denmark(this is my first post here)

I'm about to do a 375 km run in 4 weeks and I think I could need a little more comfort on my bike so I started looking at a carbon seatpost which will hopefully be more comfortable and if not at least a lot lighter than the standard EA30 seatpost that my bike has now. After some search I think I will try one of the Hylix seatposts but you can choose to different types of saddle mountings this http://www.ebay.de/itm/Hylix-Carbon-Seatpost-Road-MTB-31-6-400MM-180g-offset-/280938899417?pt=Cycling_Parts_Accessories&hash=item41694367d9 and this http://www.ebay.co.uk/itm/280861792766?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 is there ane reason to pick one or the other from a user point of view with regard to adjustability and durability or should I just go for the lightest one.

I hope this is not too trivial, but I'm rather new to cycling.
Last edited by Burgunder on Sat Sep 15, 2012 7:46 pm, edited 1 time in total.

by Weenie


Burgunder
Posts: 60
Joined: Tue Aug 14, 2012 7:36 am

by Burgunder

I'm open to other suggestions as well. After a windy solo ride of 105 kms today in 10$ shorts my buttom tells me that it will need some more cushion. (I have bought some new shorts, but they didn't dry before the trip, so I had to use the old ones)

eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
Contact:

by eric

A carbon post won't add any cushion. It won't even damp noticeably more vibration in my experience.

The best you can do is to use a smaller diameter post and a shim. The smaller diameter post will be more flexible unless you get a cheap thick-walled post.

The second type of clamp you linked to usually has serrations, which makes the seat angle adjustment have steps. Usually that means that you can't get the seat angle right. I prefer two bolt clamps because they're easy to adjust in very small increments.

Like this:
Image

Geoff
Posts: 5137
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

As you get more accustomed to riding, you will not be as affected. A big part of riding comfort is the choice of the 'right' saddle. Personally, if you cannot ride 4 or 5 hours in relative comfort, you probably should look at a different saddle.

Burgunder
Posts: 60
Joined: Tue Aug 14, 2012 7:36 am

by Burgunder

The saddle yeah, I think I need another one, but with only 16 days to go, there's not much time to experiment, and I live in a part of the countrywhere there's quite long to the nearest bikeshop.

On the other hand a new seatpost would not get here in time either.

Geoff
Posts: 5137
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

The seatpost will not help you. A conventional carbon post has to resist the compressive forces of the seatlug collar, as well as the other moments acting on it from above. As they are generally laid-up on a mandrel, they are light, but really stiff. One alternative is a 'tuned' carbon seatmast from an ISP design, but that is a whole other issue.

Omcannondale
Posts: 17
Joined: Tue Apr 03, 2012 8:51 pm

by Omcannondale

Maybe you can check air pressure on your wheels to add some comfort. If you are light can go with less pressure, if not another option could be 25mm on your rear wheel ...

Burgunder
Posts: 60
Joined: Tue Aug 14, 2012 7:36 am

by Burgunder

I did lower the pressure yesterday and took a quick 45 min spin and it seemed better than before. I have not had this bike for so long, but I'm sure the pressure was way to high when I got the bike, even to the point were it was over the factory limit.

I have also ordered another saddle to try but in 15 days I will have to ride 360 km, so I'm not to happy about chaning saddle when it arrives and then suddenly find out that it kills me after 150.

I have some new tires(Gp4000s) and latex tubes here too and hopefully they will sweeten the ride just a bit.

All in all I just need another month of training but since that's not going to happen, I've got to work with what I've got.

socratease
Posts: 169
Joined: Thu Oct 13, 2011 5:25 pm

by socratease

first off: you need bib shorts. Good shorts will make a huge difference to comfort.

Also, go with the largest tires you can fit into your frame.

In my experience, if using a setback seatpost, a carbon one will damp some vibrations a bit better. Not a huge change, so this is much lower on the list of priorities for comfort.

Burgunder
Posts: 60
Joined: Tue Aug 14, 2012 7:36 am

by Burgunder

I think an update is in place here.

I did in fact succeed with the 375 km challenge at 27,2 kph. And I felt pretty comfortable during the race.

I never bought a new seatpost.

But I did take the chance and bought a new saddle, with only 200 km to test before the race itself. I choose this as it seemed a good budget solution even though it's not a WW saddle at 225 g. I will never go back to saddles without a cutout, and now I can explore lighter alternatives
I also supplied the bike with Conti GP 4000s 23 mm and micheliin latex tubes, and the right pressures according to my weight.

During the race I had the oppurtunity to watch several large riders with thin carbon seatposts and I witnessed lot of flex at least 5 mm in each direction, so at least with thin seatposts and long clearance there seems to be some suspension to get from a carbon seatpost. And my guess is that you will even get some from a shorter one with a larger diameter.

Burgunder
Posts: 60
Joined: Tue Aug 14, 2012 7:36 am

by Burgunder

Here is a german test that seems to indicate that a carbon seatpost will flex a lot more than one made of aluminum. It also shows that a seatpost with setback will flex more than one with zero offset.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

Thanks for the link.
''However, as this distance is classified? It can also be too much of a good thing? The answer is definitely yes. Namely, when the prop flexes so much that she felt even at pedaling and jagged maneuvers gives way, creating an uncomfortable bloated feeling when sitting.(translated from German to English by Google translate)'' stated in the report of the test.
You may find it interesting to read my post. viewtopic.php?f=3&t=106727

tomgag
Posts: 44
Joined: Sun Jan 15, 2012 2:25 pm

by tomgag

Maybe it is just me but I never felt any difference with different seatpost.

Nearly same lenght.
Carbon off ebay 27.2
WCS 31.6
Boardman Carbon 31.6
WCS 27.2
IRONMAN 70,3 TARGET TIME 03:55

Slowman
Posts: 6
Joined: Sun Nov 13, 2005 12:51 am
Contact:

by Slowman

Check out the Specialized Pave seat post. It is designed to flex and dampen road buzz. At something like 220g it is light enough too.

The more seat post exposed the more flex you will have too.
witness the fitness, the profit in living, one hope one quest

by Weenie


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