Carbon vs Alu Seatpost

[Nic0000]

Guys can anyone fill me on whether a carbon seat post will make any difference to ride comfort compared to an alu post? For my alu framed hardtail...

[bikemonster]

The difference will be exactly zero. On any bike, made of any frame material.

 

For more comfort, let a little air out of the tyres.

[Christie]

No difference. The seatpost is much stiffer than the seat, and seat rails. Best way to get better ride comfort is to reduce tyre pressure. Go tubeless, get a good pressure guage and lower the tyre pressure.

[Daniel XTR]

Go Ti.

Thomson

Tune

 

Ti has some inherent flex, and so on, can irritate though.

[The_Break]

Carbon is a better vibration damper than alu so I believe that a seatpost of the exact same geometry will produce less vibration from road surfaces, etc.

[Christie]

Has anybody felt a significant increase in vibration from the older Audi A4 with a steel chassis (or a Merc of Beemer, for that matter) compared to the new A4 with an aluminium chasis? (If aluminium gives a harsher ride like claimed)

 

If you make the chassis of a car from carbon or titanium, but you fit the same tyres, suspension, shocks, seats etc, will you feel less vibration if you drive it? So in other words, a Ferrari F40 of McLaren F1 will give a softer, more comfortable ride than most cars because they are made from carbon.

 

The reality is that the tyres, suspension and seat moves a lot under vibration, in the case of bikes and cars, and the properties of these dictate the vibration felt.

Edited January 7, 2011 by Christie

[Daniel XTR]

Has anybody felt a significant increase in vibration from the older Audi A4 with a steel chassis (or a Merc of Beemer, for that matter) compared to the new A4 with an aluminium chasis? (If aluminium gives a harsher ride like claimed)

 

If you make the chassis of a car from carbon or titanium, but you fit the same tyres, suspension, shocks, seats etc, will you feel less vibration if you drive it? So in other words, a Ferrari F40 of McLaren F1 will give a softer, more comfortable ride than most cars because they are made from carbon.

 

The reality is that the tyres, suspension and seat moves a lot under vibration, in the case of bikes and cars, and the properties of these dictate the vibration felt.

 

Afraid that your comparison doesnt work with cars. Suspension advances and so on rule that out.

 

Simply ride an alu road bike then a carbon, and you have the answer. simple really!!!!!

[The_Break]

Has anybody felt a significant increase in vibration from the older Audi A4 with a steel chassis (or a Merc of Beemer, for that matter) compared to the new A4 with an aluminium chasis? (If aluminium gives a harsher ride like claimed)

 

If you make the chassis of a car from carbon or titanium, but you fit the same tyres, suspension, shocks, seats etc, will you feel less vibration if you drive it? So in other words, a Ferrari F40 of McLaren F1 will give a softer, more comfortable ride than most cars because they are made from carbon.

 

The reality is that the tyres, suspension and seat moves a lot under vibration, in the case of bikes and cars, and the properties of these dictate the vibration felt.

 

You cannot use that argument in this case. Whilst true that vibration characteristics are system dependent the question here is whether a carbon or alu seat post will deliver a harder ride (obviously in this case on the same bike). So purely changing the seat post to carbon (assuming the same geometry as the alu) will allow less vibration transfer through to the seat and thus rider.

[bikemonster]

Simply ride an alu road bike then a carbon, and you have the answer. simple really!!!!!

 

This utter chestnut of an argument gets rolled out every time frame materials are discussed. And it's total and utter BS.

 

This answer only works if the alu and carbon bike have exactly the same frame geometry, you're using the same wheels, the same tyres inflated to the same pressure, same bars, same bar tape and so on.

 

Simple, really!

 

Frame material is just one of the factors that influences the way a bike rides, and the way that a frame is designed has a far bigger impact than what the frame happens to made of.

[Christie]

Afraid that your comparison doesnt work with cars. Suspension advances and so on rule that out.

 

Simply ride an alu road bike then a carbon, and you have the answer. simple really!!!!!

 

It is not so simple. This article was published in Tour magazine in 2005, where the took 8 frames, from aluminium, steel, carbon and titanium, and masked them with extra fittings and paint so you could not see which is which. They then fitted exactly the same components, and asked a bunch of experienced cyclists to test them over a week or 2. Their finding was that the riders could not tell the difference between the bikesin terms of ride comfort - its all in the head.

 

http://farm6.static.flickr.com/5243/5333701994_4518d7fb0e.jpg

 

 

So purely changing the seat post to carbon (assuming the same geometry as the alu) will allow less vibration transfer through to the seat and thus rider.

 

I'm saying that the rider won't be able to tell the difference. The damping related to frames, handlebars etc. is called structural damping. This is defined as energy lost during elastic deformation. Larger deformation gives more damping, small deformation gives small amounts of damping. The difference in deformation between an alu and carbon post is so small that any effect, if there is a difference at all, would not be noticed.

[Daniel XTR]

This utter chestnut of an argument gets rolled out every time frame materials are discussed. And it's total and utter BS.

 

This answer only works if the alu and carbon bike have exactly the same frame geometry, you're using the same wheels, the same tyres inflated to the same pressure, same bars, same bar tape and so on.

 

Simple, really!

 

Frame material is just one of the factors that influences the way a bike rides, and the way that a frame is designed has a far bigger impact than what the frame happens to made of.

 

In Isolation yes, maybe.

I've owned and rode enough carbon, and alu bikes, to stand by this conviction. In fact, even done the steel bike bit too.

 

It's not surprising that Carbon is progressing and selling at the rate it is. Would not go alu on a road bike ever again.

 

 

Thats just me, some dudes dig the buzz from a steel or chormolly frame, or like alu. That said, I love my GT Zaskar Pro MTB which is alu. Different applications.

[javadude]

I think there is a difference when it comes to seatposts. On some club rides there is this big guy on an Alu Giant with a carbon post with quite alot of extension. I got quite nervous riding behind him one day because that post was flexing so much it was swaying backwards and forwards on every pedal stroke. I can't imagine an alu post flexing to that extent(but I could be wrong). It may be possible that you can build a really stiff carbon post and a really flexible one, ditto with alu and steel.

 

So, I dont think the difference is as subtle as vibration damping, but possibly the extent to which a seatpost flexes(regardless of material). On a frame its a different story, the tubes are joined to form two very stiff triangles, so I can understand the argument that you wont notice the difference between two frames of different materials but with exact same geometry and components.

[Bspoke]

couple of options:

1. Ride titanium , its far and away more compliant .

2 Use a qaulity suspension pin, USE is the simplist and works well if you really have too!

3. Ride more ,develop your callous

4.Use tyres like the Michelin range with the heavier side walls run 2 bar , feel the traction everywhere .

Good luck

[Christie]

Agreed, velo. For any damper to function you need displacement. The longer the displacement, the more energy can be taken up by the damper. It would not matter what shock absorbers you have on a car if you replace the springs with rigid cylinders - 0 movement means 0 damping. This is true for srtuctures too - frames, handlebars etc.

 

For a seatpost factors to consider would be seatpost extension, diameter and wall thickness. Aluminium typically has a structural damping value of 2%, carbom from 4% to 6%, but this depends very much on materials used and layup. An alu post with a 2mm wall thickness could give more damping than a carbon one with 3mm wall thicness. I have measured carbon components at work that have less damping than aluminium and steel ones of exactly the same geometry.

 

I still stand by my original opinion that a softer saddle and lower tyre pressure will have a much bigger effect on the same frame than changing a seatpost. But I suspect most bike shops will tell you different.

Edited January 8, 2011 by Christie

[Christie]

couple of options:

1. Ride titanium , its far and away more compliant .

2 Use a qaulity suspension pin, USE is the simplist and works well if you really have too!

3. Ride more ,develop your callous

4.Use tyres like the Michelin range with the heavier side walls run 2 bar , feel the traction everywhere .

Good luck

Agree with 2,3 and 4.

1 =

[eggsovereasywithteandtoast]

I once saw a monster guy, who must have been two and a half meters tall on a black MTB. The seat post stuck out by half a meter. Ever since seeing this, I think of this guy, when reading threads about cracked seat tubes.