Carbon seatpost verses alum
09-30-15, 04:21 PM
#26
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The first thing that I would do is get a blow dryer and peel off those Dura Ace C50 stickers on the wheels. They are totally distracting.. but hey that is just me... apart from the bill board stickers on the wheels the bike looks hot.
09-30-15, 08:13 PM
#28
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Everyone says that, but I don't think it's right. By design a CF seat post has to be designed to withstand clamping forces along its entire length.
It's common for manufactures to spec CF seat posts for tandems, where the stokers stem is clamped to the Captains seat post. The forces imposed from that with the stoker hammering out of the saddle, yanking on the bars have to exceed those imposed by a 20lb static load on a clamp on rack.
It's common for manufactures to spec CF seat posts for tandems, where the stokers stem is clamped to the Captains seat post. The forces imposed from that with the stoker hammering out of the saddle, yanking on the bars have to exceed those imposed by a 20lb static load on a clamp on rack.
09-30-15, 08:28 PM
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Yes, I used the Finish Line brand and FSA, both had the same result. I won't say I'll never try another carbon post but my first attempt was a failure. Maybe the diameter of the post was manufactured under specification? I could have returned it if I had not removed the Bontrager graphics, lesson learned!
10-01-15, 05:24 AM
#30
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I did use a combination of acetone and 2000 grit paper to remove the graphics but was careful not to sand below the minimum insertion line which is still visible when installed.
10-01-15, 07:45 AM
#31
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I'm pretty confident with 40,000 miles using CF seat posts with stoker bars, attached, and having used a clamp on rack on a CF seat post several times, that a rack with a 20lb weight limit isn't a problem.
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10-01-15, 09:26 AM
#32
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I picked up an FSA SLK carbon post at Performance for $80. Its great compared the alu. Looks nice, and i can feel the difference when riding over some bumps. Just use carbon paste when you install to keep it from slipping
10-01-15, 09:50 AM
#33
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I just went from a Pro PLT alloy post to a Deda Superzero carbon post on a carbon frame, and after 200mi I swear my bike feels just very slightly more smoother on the road and more comfortable. The comfort part is far more likely because of minor differences in trying to replicate saddle height and roughly compensating from 15mm to 21mm setback. Whatever it worked!
Fact: I can say without reservation that my bike is 63gm lighter, though.
Fact: I can say without reservation that my bike is 63gm lighter, though.
10-01-15, 10:42 AM
#34
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There are a number of seat posts that have come out in relatively recently that are specifically designed to be shock absorbing. Ritchey, as I previously mentioned, specifically designed in a flex capability into several if their seat posts. Its a significant enough flex that you can actually see it flexing or even flex it yourself by hand. That gives it a distinct capability to take off the sharp edges of a road hit that other more rigid seat posts will transmit right up to the rider. Specialized also offers one and then damps that flexing with an elastomer on top of it.
J.
J.
10-01-15, 02:27 PM
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FYI i've snapped two of similar styled ebay 'carbon' posts during routine use.
cheap yes... durable no.
cheap yes... durable no.
10-01-15, 05:26 PM
#36
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Buy a post that will give you the ability to adjust saddle position to where you need it. Carbon is nice, but not necessary.
I have ridden and raced thousands of miles on aluminum and carbon posts - in aluminum and carbon frames - and I honestly cannot tell a difference.
I have ridden and raced thousands of miles on aluminum and carbon posts - in aluminum and carbon frames - and I honestly cannot tell a difference.
10-01-15, 11:03 PM
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Looking at the OP's bike, I'd bet he'd notice a difference using carbon because he's running a good amount of extension.
Offset carbon post head is going to enhance the likelihood of perceptible difference.
Personally, I love the feel of my FSA SLK SB20 post, though I'd describe the feel as invisible. I cannot say the same of some of my other bikes' posts. I have a Syncros Ti post which flexes so much that I'm aware of it. It's comfy, but not invisible. USE Alien Ti and Karbona carbon are both less comfortable, but on bikes with less visible seatpost extension.
Offset carbon post head is going to enhance the likelihood of perceptible difference.
Personally, I love the feel of my FSA SLK SB20 post, though I'd describe the feel as invisible. I cannot say the same of some of my other bikes' posts. I have a Syncros Ti post which flexes so much that I'm aware of it. It's comfy, but not invisible. USE Alien Ti and Karbona carbon are both less comfortable, but on bikes with less visible seatpost extension.
10-02-15, 12:02 AM
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Stems generally spec a 5Nm torque in order to limit crushing forces on the steerer tube (or seat post). I suppose if we postulate that 5Nm torque on the cantilever rack bracket results in the same hoop stress as 5Nm on the stem, then one can carry the load without fear.
My Ritchie torque wrench for installing stems at 5NM torque has a 4mm allen key. My rack uses 5mm bolts. I guess I can get a feel for 5Nm and transfer the feel to the rack bolts.
10-02-15, 05:01 AM
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) and have a carbon post. Use CF paste and torque wrench and do not have slippage. I had a different problem - the clearcoat finish on the back of the post eventually gave way and an interminable creaking set it. I can re-assemble and torque and it clears up for 50 to 100 miles. I am looking to return to an aluminum post because of this.
10-02-15, 07:30 AM
#41
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What I found out is that the clamping forces are the potential issue. If you over torque, you can crush the post. It may make a low cracking sound.
Stems generally spec a 5Nm torque in order to limit crushing forces on the steerer tube (or seat post). I suppose if we postulate that 5Nm torque on the cantilever rack bracket results in the same hoop stress as 5Nm on the stem, then one can carry the load without fear.
My Ritchie torque wrench for installing stems at 5NM torque has a 4mm allen key. My rack uses 5mm bolts. I guess I can get a feel for 5Nm and transfer the feel to the rack bolts.
Stems generally spec a 5Nm torque in order to limit crushing forces on the steerer tube (or seat post). I suppose if we postulate that 5Nm torque on the cantilever rack bracket results in the same hoop stress as 5Nm on the stem, then one can carry the load without fear.
My Ritchie torque wrench for installing stems at 5NM torque has a 4mm allen key. My rack uses 5mm bolts. I guess I can get a feel for 5Nm and transfer the feel to the rack bolts.
__________________
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
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