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Finishing off a new gravel build, 853 frame, 40mm tyres, carbon bars etc.
BUT the budget is running out. I actually bought a very nice Roval Terra post but realised I need more setback so it's going back. However I noticed that Roval have been very honest about the compliance of the post - 18mm at full extension of a 380mm post, whereas I barely achieve 50% extension at best.
Am thinking a short extension carbon post on top of a skinny steel frame AND 40mm tubeless tyres is not going to make any difference. Anyone care to disagree? (this being STW 😉)
Not needed on steel. Alloy posts on my vintage 653 and Columbus SLX.
I did have a carbon post on an alloy framed fixed gear road bike, but can't say I really noticed as alloy bikes are more harsh than steel.
Personally I'd say yes, all my frames have carbon posts (other than the one with a dropper), not all steel is equal 😉
/\ carbon post, you need a dropper post :0)
I just got a cheap carbon seatpost off ebay for my gravel bike, weighs 135g and I've now done 2000 miles on it - plenty of 'flex' on it 🙂
But I thought you got a full-custom frame - why are you now needing a setback post?
I actually bought a very nice Roval Terra post but realised I need more setback so it’s going back.
But I thought you got a full-custom frame – why are you now needing a setback post
I don't personally believe a setback post suggests a poor fit? For the sake of argument let's say that my femur length dictates where my hips need to be relative to the pedals. I could achieve this with a mad seat angle (thus reducing tyre clearance or necessitating longer chainstays?) or I can just use the readily available and frankly fairly common solution of a setback post?
In truth though I went custom for reasons other than fit, so I didn't stray far from the geometry of my old bike, which I knew worked (with a setback post).
I just got a cheap carbon seatpost off ebay for my gravel bike, weighs 135g and I’ve now done 2000 miles on it – plenty of ‘flex’ on it
Yeah... I bought a cheap carbon post once, agree that it was noticeably flexy but it's also the only carbon post I've had that has ever failed! It's just one of those components where I prefer to buy known brands etc.
I have had carbon, alu, ti and steel seatposts over the years, I cannot tell the difference in vibration damping and I am generally very picky. I had a very flexy seatpost once, that bounced up and down, it was annoying as hell. I have a carbon post on my road bike simply because I already had it. I bought it years ago in an effort to make my old road bike more comfortable (it didn't) so I just put it on my newer one because it's quite light and won't corrode with the carbon frame.
is not going to make any difference.
Probably not, but if you want a carbon post, than get one. Not everything has to be for performance reasons. "I like it" is as valid reason as any other to get the thing you want.
any 27.2 post is going to be fairly flexy, the material won't make a huge amount of difference. buy a brand-x one and upgrade it later when you feel like getting yourself a present
Not everything has to be for performance reasons. “I like it” is as valid reason as any other to get the thing you want.
This has been my mantra for several years, but after a glance at my credit card bill and a stern talking to from my wife I'm finally trying to be a bit sensible! I'd seen an alloy Ritchey seatpost that I liked which would also leave change for a nice Fizik saddle I'd seen on sale, would finish the bike off nicely and I can still claim a saving on the CC bill after I get the original seatpost refunded. Win-win! 😎
If a carbon fiber post breaks its either time for a pointy carbon fiber enema or stop the femoral artery bleed.
But I thought you got a full-custom frame – why are you now needing a setback post?
Because the use of a set back post is built into the custom design?
Both the customs i've had use a set back of around 25mm to keep the seat tube in a sensible place for tyre clearance and front mech positioning/clearance (though probably less of an issue on a gravel bike!).
However I noticed that Roval have been very honest about the compliance of the post – 18mm at full extension of a 380mm post, whereas I barely achieve 50% extension at best.
Sounds like a tested figure expressed in a way that doesn't tell the full story. 1st, 18mm but under what load?
2nd, flex in a post is based on load X the length cubed. If the post flexes 18mm with about 300mm extension out of the frame, for the same load you'll be down to about 2-3mm if you half the extension. So you don't need a carbon post : )
(eg why compact frames make more difference than all the 'compliant rear triangle design' waffle. A smaller rear triangle flexes least but the longer post should make the most difference)
why are you now needing a setback post?
(edit, as others have said - ) It's quite normal to design a frame around a layback post, eg on bikes with tight wheel to seat tube clearance like road or CX.
alloy bikes are more harsh than steel.
Not always, not a safe rule these days.
I’m finally trying to be a bit sensible!
You sound like me, I want some expensive part, think: stop being silly buy a cheaper thing that will do the job just as well, and then finally circle back to the original thing, and buy it anyway, thus ultimately costing me more...
Get the part you want to build the bike in the way that you want.
I would be very tempted to seek out a steel seatpost, as the benefits of having the same material for both post and frame are significant.
If a carbon fiber post breaks its either time for a pointy carbon fiber enema or stop the femoral artery bleed.
I had one snap whilst seated pedalling. Not only was I easily able to arrest my descent onto the toptube/seatstay area with plenty of clearance, the post snapped clean off flush with the top tube without any splinters. Made it rather difficult to get the broken bit out.
Don’t buy a carbon post. I can see why people would buy a carbon post. But whatever the logic is for a carbon post wouldn’t that logic dictate a carbon frame as well?
Plenty of genuine second hand carbon seatposts on ebay, works for me
I bought a cheap carbon post off eBay. It works.
You don't need one, but I've got one of these ...
and it's the absolute mutts nuts.
Those Canyon posts are very good. One came on my grail and although you don’t feel any movement while riding, my friends said you could see it working on the rough stuff. Only issue is grit and small stones get in the gap and start to rub. I covered the area with a strip of helitape but it still started to eat in. Resorted to cutting a wedge of Moto foam to fill the gap and it’s been perfect since. Flip head came be rotated as well to vary amount of set back.
The screw holding the cradle on my Diverge seatpost snapped and Specialized don’t have any spares so they offered me a warranty replacement - the only one available in the right diameter and offset was the S-Works one. It is noticeably flexier that the regular carbon post it replaced. Always fancied the Ergon/Canyon one - Redshift or Thudbusters seem a bit of overkill.
The only seatpost that has ever failed on any of my bikes was the carbon post on my cx bike. The bike came to a sudden skidding halt after my plums were wedged between the rear tyre and seat-stays. 😫
Get the cheapest ‘trusted’ ali seat post and if it’s bad, save up. I’m guessing it will be fine as the tyres and frame will do the damping anyway.
I had a ti charge plug on fat tyres it felt like I was on a hovercraft, that had an ali post.
But whatever the logic is for a carbon post wouldn’t that logic dictate a carbon frame as well?
No.
The titanium frame resists cable rub and tyre/mud rub better than carbon.
Carbon seatpost adds a bit of different damping and differing materials cancel out the trail buzz better.