Carbon seatpost - any real difference from alloy?

[tv_vt]

Question for those who may have swapped out an alloy seatpost for a carbon one: what difference did you notice? Anything? Smoother? Harsher? Etc?

And would differences be more or less noticeable on a 27.2 post vs. a 30.9 post? (Edit: actually, a 31.6mm seatpost)

Thanks. Just thinking about ride quality on a bike...

[Llewellyn]

I replaced a carbon Fizik Cyrano with an aluminium Thompson and can't tell any difference between them.

[Gummee]

Depends on how long they are.

IME regular road length? one post pretty much feels the same as another.

Mtn length posts? Different story. Some posts you can feel, some you can't depending on how they're made

How's that for a mostly non-answer?

M

[Peter P.]

My buddy had a 27.2 carbon post on his Cannondale. He didn't like feeling the flex of the post (he weighed 160lbs.). So he replaced it with an aluminum post.

[rustychisel]

Some you can, some you can't.

But really, 5psi difference in tyre pressures is more noticeable.

[tv_vt]

I replaced a carbon Fizik Cyrano with an aluminium Thompson and can't tell any difference between them.

Hmmm. That carbon Cyrano was what I was thinking of putting on - to replace an alloy Cyrano.

[wombatspeed]

Carbon is not carbon. Some are stiff, some are comfy and springy, e.g. the Niner RDO or the syntactic hiflex.

Need to have lots of seat post showing (like a MTB), but then the,differences are huge.

And 27.2 is noticeably more springy than 30.9. So much so that I like to use a shim to run smaller diameters, even 25.4.

YMMV, mine doesn’t!

[ultraman6970]

I have used carbon seatposts and for some reason the harmonics on them mess me up. I used (not anymore :() to spin a lot and carbon seatposts for some reason made me bounce weird like off tempo or i shouildnt bounce over the saddle but i did... moved to aluminum and no problems. Maybe is because im too fat? :D

The other detail, and is not because im a darn elitist campy guy but so far to me the seatposts that always give me no problems of harmonics are the campagnolo ones, not super light but they work. Eastons and 3t or any other modern brand i feel them weird even zipps... u go figure :/

[rustychisel]

I felt the difference when my Easton EC-70 broke.

Ya know what I'm saying?

[onomic]

I’ve ridden Carbon, Ti, and Aluminum. Couldn’t feel any difference, although after hearing several stories of broken Carbon posts I just ride Aluminum and Ti now. Agree about lowering your tire PSI by 5-10, much nicer ride and better cornering. If you can move up a tire size that helps too.

[happycampyer]

Carbon is not carbon. Some are stiff, some are comfy and springy, e.g. the Niner RDO or the syntactic hiflex.

Need to have lots of seat post showing (like a MTB), but then the,differences are huge.

And 27.2 is noticeably more springy than 30.9. So much so that I like to use a shim to run smaller diameters, even 25.4.

YMMV, mine doesn’t!This is very true. Velo News did a test many years ago and it was interesting to see the variability in damping and flex among different seatposts. In general, straight posts were stiffer than setback posts, 30.9 etc. stiffer than 27.2, etc. I would agree that the amount of exposed post will affect the extent to which any of that can be felt.

I have a 25.4 ti post on my most recent bike, but there are too many variables at work for me to say conclusively if it makes a difference.

[robt57]

I have CG_R, P6 hyflx, and 25.4 Canondale shimmed in a 2.72 bike. These are better feeling, as in I can feel a difference from other posts previously used in same bike.

If you are not showing 5-6" of post minimum, a flexy post may not flex enough to make a difference.

Read this: I have an ALLOY WCS Ritchey post that feels as good as any of these others, and with 4-5" showing. It has 'Thinner' side walls internally than front/back, as do the Thomsons. In other words, round OD and Oval ID to allow fore/aft flex and stifle side/side flex.

[shinomaster]

Yeah they shear off at the seat collar, that's one difference.

[mtechnica]

Carbon posts break? I have a 3T carbon post on my bianchi that sticks up like 2 feet, hopefully it’s OK...

[fogrider]

I have 4 bikes with carbon seatposts, 2 with ti, and a couple with aluminum. A couple of bikes have enough post showing that might make a diff, but I"m not sure I notice it...but I will say I don't notice an issue. Which is about all you an ask for in a seat and post isn't it? There are some builders and manufacturers that use the post to tune the ride:

http://www.englishcycles.com/design-philosophy/
https://www.trekbikes.com/us/en_US/inside_trek/isospeed/

When using a carbon post, be sure to use carbon grip paste and follow manufacturer's torque settings. As for dropping your psi, there's a lot to be said on this topic...I would say run the right psi for your tire size and your weight.

Question for those who may have swapped out an alloy seatpost for a carbon one: what difference did you notice? Anything? Smoother? Harsher? Etc?

And would differences be more or less noticeable on a 27.2 post vs. a 30.9 post?

Thanks. Just thinking about ride quality on a bike...

[martl]

Question for those who may have swapped out an alloy seatpost for a carbon one: what difference did you notice? Anything? Smoother? Harsher? Etc?

How a seatpost performs is not down exclusively to the material it is made of.
Any seatpost is technically a spring/damper which will flex a certain amount unter a given load, how much is determined by the part geometry (diameter and thickness of the tube, seat setback) and its material (E-Modulus).

It is entirely possible to have seatposts that are more flexible or less flaxible than your current one from either material, alloy of CFK. So the question isn't answerable :)

[mulp]

I could never tell a difference, but i dont ride with my seatpost that high. Although they definitely look the nicest which is reason enough to use them!

[cmg]

just notice weight reduction. have a larger diameter 31.6 and like it for the stiffness.

[jet sanchez]

Carbon looks cool.

Pretty sure my Campy Record carbon post is heavier than my Thomson aluminium post

[RoosterCogset]

Velo News did a test many years ago and it was interesting to see the variability in damping and flex among different seatposts. In general, straight posts were stiffer than setback posts, 30.9 etc. stiffer than 27.2, etc. .

This one? from 2012 so all bets are off now I assume.

https://forums.mtbr.com/attachments/endurance-xc-racing/717600d1345204464-carbon-bars-seat-post-dampening-velonews_seatpost_june2012.jpg

[tv_vt]

Thanks for all the feedback. I will shelve that idea of switching to carbon.

But..., I am thinking of going to a 27.2 post with a shim to downsize from the 31.6 post on there now. Same Fizik post, only smaller diameter.

OK, thoughts?

[robt57]

Just a thread note: The Syntace Hiflx P6 is life warranty including for MTB use. Light, expensive, VG looking, and IMO about the best clamp design out there.

[skouri1]

I have a hiflex 27.2 on my indy fab with a lot of exposed post (frame is only like 15" seat tube and I ride 71cm saddle height). Flexes visibly, even with me putting pressure on saddle. Great improvement.
On my road bikes with only ~13cm exposed, i dont feel much in 31.6. Maybe on sharp impacts, that's about it.

I have a focus CPX concept post (same as BBB flypost) in 27.2 also with 13cm and it feels nicer than my thomson. Also visibly flexes when you put weight on it...

As others have stated, except for a super compact MTB, very heavy rider and 27.2 post (or 25.4), the differences even in the engineered posts are not eye opening. perhaps the leaf-spring style canyon, but other traditional posts...not huge. Still nice though. For the same price on the used market, I'll take it.

[Ozz]

Yeah they shear off at the seat collar, that's one difference.
On the other hand, they are typically much more expensive.;)

[Rpoole8537]

I built a BMC Team Machine 5-6 years ago with a Thompson straight posts, 31.6. It was somewhat abusive. Switched to a Ritchey carbon with 20 mm setback, and liked it much better. I didn't think of using a shim. I use a shim on my Waterford with a Dura Ace post and it works and feels great. Carbon with a shim, not sure I could make that work consistently.

[johnniecakes]

I have had a few carbon posts over the years but mostly aluminum now. The only difference I could notice was in the wallet. Aluminum posts didn't shake it as much

[uber]

I have had carbon, aluminum and Ti. Can't tell the difference. I like to match to the stem and bar because of vanity. The ability to accessorize is what separates us from the animals.

[tv_vt]

Was thinking about the carbon-aluminum seatpost question today, on this rainy afternoon, and came across this old thread. With some changes over the last two years, have a few things to add to this discussion.

I've put Eriksen titanium 27.2 layback Sweetposts on two bikes that had aluminum posts and immediately noticed a difference. Hard to say exactly what is different, but the ride is smoother in a nice way. Definite improvement.

Also put a Deda 31.6 carbon post on an aluminum bike with an aluminum post and that, too, had a noticeable, positive effect on ride quality. The Deda carbon posts were a nice discovery. Very user-friendly adjustment mechanics and nice looking post.

[benb]

I'd tend to side on just make sure your bike fit & tire size are appropriate.

I've run a straight Thompson on my old mountain bike for like 17 years and the shock is totally not noticeable there. What I have would be one of the "most abusive" posts in that test.

I would say the Specialized CG_R definitely makes a difference. However it has a ton of setback. I can't even use it on the bike I bought it for unless I find a saddle that has the rails in the right place for it. Right now I have the CG_R in a box and have a straight aluminum Zipp post on because I'm running a saddle that I can't position correctly on that bike with the CG_R. And as long as the tires are good the straight aluminum post is fine.

The ISO Speed doo-hicky on my Trek Domane is vastly more effective than the CG_R. But that's an entirely different can of worms.

A lot of carbon seatposts and masts I've had also came along with worries about breakage, putting the bike in the workstand, or had really dumb saddle rail clamp designs. I would kind of say both the carbon topper on my Domane and the CG_R have annoying clamp designs. They are both very hard to precisely adjust the saddle on compared to more traditional 2-bolt designs.

99% of the annoyances of carbon posts IMO though can be avoided by not buying a carbon frame with an integrated seat mast. Being able to switch out to any seatpost you want is very nice.

[robt57]

Yes and No.

2 seat posts as compliant as most carbon posts I've used are alloy. More compliant than most, and are alloy.

What they have in common is being round OD, and oval ID. Masterpiece and a Ritchey WCS.

The WCS seems most compliant when less post is showing than Masterpiece. (Thomson) I should say as compared to MP showing proud of frame. Not that it's more compliant when it is deeper inserted.
I reread my post and thought I should edit.

[tbike4]

Weight weenie carbon post for me and I like the looks. Install is not so easy unless you have a cut out in your saddle but once you get it no problem IMO.
Not cheap. 136 grams. Roval Alpinist Seat post.

[Gianni Bianchi]

I have had a carbon post on my bianchi with a lot of it out, and the ride is sublime:

https://clickpix.org/images/ju7iIb.jpg (https://clickpix.org/image/ju7iIb)

On my cross bike, it came with a Deda carbon that I swapped to an alloy Fizik principally because the adjusting screws on the Deda were a PITA and always came loose even with some loctite. So i swapped to the Fizik, which as it turned out was lighter than the carbon. No real noticeable ride difference.

https://clickpix.org/images/jsIKWc.jpg (https://clickpix.org/image/jsIKWc)

[pasadena]

I did this on one of my road bikes. 31.6 alloy zipp to 27.2 carbon
I actually went to a 25.4 but with such a thick spacer, the bolt clamp tension required was too high and I stripped a bolt. So I moved up to 27.2

The difference is night and day for me. I'm not heavy and it's noticably more comfortable with the 27.2

Won't be going back to 31.6, which is overkill for a road bike imo. I don't know the logic of that choice but don't think anyone specs it anymore.

I guess the upside is if I ever want to put a dropper post in, it will be easy. LOL

Thanks for all the feedback. I will shelve that idea of switching to carbon.

But..., I am thinking of going to a 27.2 post with a shim to downsize from the 31.6 post on there now. Same Fizik post, only smaller diameter.

OK, thoughts?

[rice rocket]

This article is 6 years old but nothing has really changed since.

https://www.bikeradar.com/features/five-soft-riding-road-seatposts-tested-in-the-lab-and-on-the-road/

[robt57]

I did shim down from a 27.2 to a 25.4 Cado carbon post on a frame. Only because I did not wanna cut a 27.2 due to a butted SeatTube, the butt 4" from the top.

I had a short carbon post [older easton] and put in the 25.4, the bottom passing the ID of the butt. Did not notice a difference. I also tried the mentioned WCS alloy, and noticed it was more compliant. New frame old seatpost, I wanted fresh/new, but was NOT cutting the intended P6 for the build, yada

This article is 6 years old but nothing has really changed since.

https://www.bikeradar.com/features/five-soft-riding-road-seatposts-tested-in-the-lab-and-on-the-road/


Well, maybe? I'd say all those are round to be compared to each other. Thus round VS shaped not addressed. Each reader may decide if that data point not being included in [for what ever reason] makes a difference? Not sure my pointing it out adds value or not, reader to decide I guess. Just where my brain went.

A minds a terrible thing...

[rice rocket]

Well, maybe? I'd say all those are round to be compared to each other. Thus round VS shaped not addressed. Each reader may decide if that data point not being included in [for what ever reason] makes a difference? Not sure my pointing it out adds value or not, reader to decide I guess. Just where my brain went.

A minds a terrible thing...

There's data presented in there, showing you the load vs the amount of deflection, and the amount of vibration measured. Use one of the tested posts or don't, I'm not sure what you're arguing.

[benb]

The article looks like typical bike science though, it's pretty horrible. Plenty of the comments call out the issues I'd call out. Equating deflection under static load with being better at absorbing hits is interesting.

By far my biggest takeaway from that bike radar article is you should choose a compact frame over a horizontal frame if you have a choice and care about deflection. And if you have a choice of two sizes that will fit take the smaller one. More seatpost exposed has a big effect on all the seatposts they tested.

I think absorbing vibration has to be further quantified.. what frequency and magnitude of vibration is the seatpost tuned for?

One thing I can say for sure.. the CG_R does not nullify the horrible vibration from "scarified" pavement that is so great at making butts, hands, feet go numb on a road bike. The Trek ISO Speed stuff is tuned to remove that stuff really well. But so are bigger tires!

[callmeishmael]

IME, the difference is anywhere between 50-100g and twice that difference in £ (so a negative Hairsine ratio). I can’t say I’ve noticed a ride difference.

[litcrazy]

I too am fond of Ti posts, particularly the Eriksen Sweetpost. However, I will also concur that the amount of exposed seatpost makes an enormous difference.
On a steel, rigid mountain bike, the ti post does flex much more than aluminum. On my gravel bike, I feel it less than on mountain and more than on road--which aligns with how much post is showing.

[DeBike]

The bikes I have switched to cf posts are all road bikes. A couple of them have been back and forth with the cf and aluminum. I really feel no difference. I go with what I think looks best with a particular bike. I do prefer saddle clamps that have front and rear adjustment bolts. The biggest difference to me is the use of cf paste, instead of grease, to keep the post from slipping.

[robt57]

There's data presented in there, showing you the load vs the amount of deflection, and the amount of vibration measured. Use one of the tested posts or don't, I'm not sure what you're arguing.


Pointing out, not really arguing. If it is more in line post wise with the OP due to a round 27.2 only I may have missed it..

:p

[martl]

Question for those who may have swapped out an alloy seatpost for a carbon one: what difference did you notice? Anything? Smoother? Harsher? Etc?

unless we know which specific posts we are talking about, it isn't possible to tell what is harsher or smoother, because there are all four combinations available, from harsh alloy to smooth carbon and vice versa.

Saying "carbon is softer than alloy" is like saying a Ferrari is faster than a Porsche because its red.