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Carbon Seatpost for a 350lb Rider?

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Old 05-17-18, 09:25 PM
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DarKris
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Carbon Seatpost for a 350lb Rider?

So I found my perfect bike - Giant Toughroad SLR GX 1, put a down-payment on it, and then I found out it has a carbon seatpost....

Again I like everything about the bike from the components to the handling and the massive tire clearance. The only issue is with the carbon seatpost, which is Giant's proprietary D-Fuse post. The step down has the alloy post, however I would much rather prefer the GX 1 model for the drivetrain and frame color. My LBS said that Giant don't sell the post separate so I contacted Giant and they said to have the shop contact the warranty department to see if they have a replacement aluminum D-Fuse post.

The bike is on 90 day layaway, but it IS on layaway which might lead to some issues if I have to cancel it just because of the seatpost. I am a 350-360lb rider so I am pushing the limits of most bikes at this point.

Am I rightfully concerned or am I being paranoid?
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Old 05-18-18, 08:53 AM
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I'd be paranoid, too. I've had to make a "call of shame" when my aluminum seatpost folded backward and broke off; fortunately I was going slow enough to hop off. You might take the approach that Giant will replace the carbon seatpost if (when?) it breaks. A bigger question is whether the entire bike can support you, if they're shaving grams by putting in a carbon post.
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Old 05-18-18, 10:55 AM
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I beleive member @dagray has been using a carbon seatpost for a while.
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Old 05-18-18, 05:54 PM
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My Orbea Orca has a carbon post, I have been riding it from 396 pounds down to 350 pounds and back to 360 pounds.... over the last three and a half years. No issues what so ever.

I also upgraded the 105 groupset to 11 speed Ultegra, upgraded the bars to 35mm diameter carbon bars, and upgraded the wheels to Rolf Prima "Vigor RS" (OEM) wheels.

Now if I could find more time to ride.
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Old 05-18-18, 09:49 PM
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I'd get the bike plus have them order an alum post

https://bicyclewarehouse.com/product...nt=41676421514


if standard diameter, I'd trust a Thomson more then a OEM
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Old 05-18-18, 09:57 PM
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Originally Posted by jsigone View Post
I'd get the bike plus have them order an alum post

https://bicyclewarehouse.com/product...nt=41676421514


if standard diameter, I'd trust a Thomson more then a OEM
The seatpost that you linked is the carbon model, the same on my Toughroad. The Seat-clamp is aluminum.

I would have to either get lucky and find one or have my LBS contact their warranty department and see if they have any aluminum D-Fuse posts.
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Old 05-18-18, 09:59 PM
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The $60 COMP one? seems alum to me
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Old 05-18-18, 10:13 PM
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Originally Posted by jsigone View Post
The $60 COMP one? seems alum to me
Yup. Quoting the item description: “A replacement D-Fuse seatposts for equipped Giant bikes.

The proprietary “D” shaped composite seatpost dampens vibration—resulting in a smooth, compliant ride. Available in both SL and Comp grade carbon.”
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Old 05-19-18, 10:55 AM
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I think it could work. I am 280-290 so I'm a bit lighter but I have 1,200 miles on a Felt cross bike which has an OEM carbon seat post with one clamp. No problems at all - even after a minor crash where the seat did a 90-degree turn (ouch!). I rarely even have to adjust the seat back up.
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Old 05-22-18, 08:49 AM
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The carbon seat post is probably the toughest part of the bike; I've been riding a carbon bike with a carbon seat post from about 300 lbs.
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Old 06-06-18, 04:51 PM
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I've got about 250 miles on a carbon post with my Niner RLT (27.2) and zero issues with probably about 50% off-road riding. I try to be "light in the saddle" when approaching obvious ruts or crummy roads.

I put about 4000 miles on a BMC GF01 with a carbon 27.2 seat post (exclusively on-road) and cracked 3 of them before BMC stopped offering warranty replacements. They were quick to fault me for over torquing the saddle clamp but when the third one cracked on a demo day after the BMC rep installed it himself, they changed their tune. But that's also when they told me they're no longer going to warranty replacements. I started at 295lbs and by the time the 3rd post failed I was about 240lbs.
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Old 06-25-18, 12:58 PM
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Spend the money and get a Thompson Seatpost. They are the best posts made and will not let you down. They are Aluminum, and lets be honest, do we really care about the added grams of weight? Since they are known as top of the line posts they look like an upgrade on every bike.
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Old 06-25-18, 01:19 PM
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Giant says:
"The proprietary “D” shaped composite seatpost damps vibration, resulting in a smooth, compliant ride."

But it looks like a round post. I think the "D" is the internal shape. Most posts are thicker internally on two sides.

One bolt clamps can slip when the rider hits a jarring bump. Then the saddle tilts all the way back. I dislike having to crank down on the saddle clamp until it feels like the bolt will break.

Instead:
Thomson seatposts have two bolts that lock the seat tilt in place. It can't slip.
I'd get one of these, if it fits on the bike.

Last edited by rm -rf; 06-25-18 at 07:52 PM.
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Old 06-25-18, 02:30 PM
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Two bolt seat posts are typically much easier to adjust too if you're trying to get the angle on the saddle juuuuuust right.
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Old 07-07-18, 12:24 PM
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Carbon Tube can be Thicker tube wall, with more layers of carbon fabric ,
in its structure..

and you can also buy additional carbon tube ,
and epoxy it inside the manufactured seat post
made for someone half your weight..

to a similar effect...





...
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Old 07-07-18, 12:53 PM
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With body weight, the composition of the tube won't be an issue-- it's going come down to the clamp. Not all clamps are even remotely created equal. If it's the single-bolt cup/cone style like the old Bontrager XXX post (the D-Fuse SL,) you're probably in for a rough go. Those are remarkably difficult to get fixed in the place you want them.

That seatpost would be a dealbreaker for me. Frame fits the 2 flavors of D-Fuse post... and that's it.
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