carbon v titanium seat posts

[fossyant]

As for the best looking seatposts, you can't beat either the Dura Ace 7400 aero or Record aero of the early 90 - works of art !

 

[MacB]

As for the best looking seatposts, you can't beat either the Dura Ace 7400 aero or Record aero of the early 90 - works of art !

Oh man, you think they are works of art? taste is as taste does I suppose

 

[Globalti]

I gave up on alloy seatposts after a Control Tech post bent on me - I'm only 72 kgs and it even had an internal reinforcing strut.

Carbon is more comfortable and looks better against my Ti frame.

 

[fossyant]

Oh man, you think they are works of art? taste is as taste does I suppose

At least I have Taste !

 

[jackthelad]

Hi guys seems a few posts since I was last on .Basically I was trying to find out

(1) if titanium seat posts soak up road buzz the same as carbon.
(2) are they more robust
(3) do you need to be as careful with titanium as like carbon using a torque key to avoid over tightening
(4) are they like aluminium seatpost, is it just a case of coating the bottom part in copper grease to avoid the post jamming
(5) how do they compare against the thomson elite
seatpost

I am fitting to a steel Reynolds 725 genesis equlibrium 20 frame

 

[smokeysmoo]

the following one made the ragged end of the broken shaft enter his body near his rectum.

Is it wrong that I'm crying laughing at this sentence, wait! I actually know the answer already

 

[HLaB]

I could be wrong but I thought most Ti framed bikes had a carbon post because it was comfier.
Touch wood I've not had any problems with my own carbon post, there's a pave on my sirrus with zert inserts, it done just over 7,500 road miles in extreme conditions at times, before the bike was retired to the turbo (its now 4&1/2 years old); the carbon post on my Bianchi has 4700miles in less extreme conditions (it just over 4years old now) and the carbon post on my Kinesis has done 9300 miles in just over 2 years (in less pleasant conditions).

 

[craigwend]

My Van Nich has a Ti seat post, though difficult to say if more comfy than carbon as i've not tried this

The overall ride is very comfy, though this depends on so many other factors

The price looks good - it will last forever & I like the setback position, no issues with 'sticking' either.

Got a good review in C+ a while ago

So:-

1) if titanium seat posts soak up road buzz the same as carbon. - DIFFERENTLY
(2) are they more robust - YES
(3) do you need to be as careful with titanium as like carbon using a torque key to avoid over tightening - SEE 2
(4) are they like aluminium seatpost, is it just a case of coating the bottom part in copper grease to avoid the post jamming - ERM - I LET THE SHOP DO THIS...
(5) how do they compare against the thomson elite seatpost -THAT DOES LOOK A GOOD PRICE & THE REVIEWS TEND TO BE EXCELLENT FOR THOMSON

 

[bonj]

If you want a light one the clamp makes more difference than the material its made of.

 

[jackthelad]

lightness is not an issue with me,but i do like my comfort,and with this being a new build from scratch with just the frame,thought I would get it right first time.The carbon and titanium dont have a massive cost over a decent alu,so this is why i brought the question to the forum for differnt opinions.And thanks again to the guys there has been a few

 

[Smokin Joe]

Anyone who is suffering from "road buzz" should check out the quality of their tyres, the pressure they run at and their saddle. That is where harshness can be reduced (along with a more relaxed frame of course). Changing the six inches of rigid tubing connecting the saddle to the frame will only make a difference in your head and your wallet.

 

[fossyant]

If you want a light one the clamp makes more difference than the material its made of.

Exactly.

 

[RecordAceFromNew]

Curiosity got the better of me, so I decided to work out how much the top of a seatpost would deflect vertically if a 200 lb sack of potato sits on the saddle.

For the base case, I assume:
Seat tube angle of 73 degrees
Young's Modulus of 22,000,000 psi (approx. for carbon, Ti is ~16,000,000, aluminium is ~10,000,000)
Seatpost outside diameter 27.2mm, wall thickness 2.5mm (based on my Campag Record carbon post)

I calculated vertical deflection due to bending as well as compression. Contribution from the latter is always small compared to the former, and is ignored for this discussion.

The answer I found, is 0.04mm for a 6" exposed post, but 0.32mm for a 12" exposed post - deflection is proportional to the exposed length's power of 3.

In relation to the motions and deflections of tyres/wheels/forks/frame/saddle we experience trundling down the road, I doubt this level of deflection can be detected in a blind test.

Finally, I found the nearest alloy post at hand to have the same wall thickness - being less stiff, it should be more compliant.



============================

For those who would like to check my calculation, for 12" exposed post:

Second moment of inertia: 0.036 in^4
Bending load: 58 lbs
Bending deflection: 0.043" or 1.08mm based on this formula

 

[lukesdad]

Have a look at the KCNC scandium post, Ive got one,best ali post ive ever had.

 

[MacB]

Curiosity got the better of me, so I decided to work out how much the top of a seatpost would deflect vertically if a 200 lb sack of potato sits on the saddle.

For the base case, I assume:
Seat tube angle of 73 degrees
Young's Modulus of 22,000,000 psi (approx. for carbon, Ti is ~16,000,000, aluminium is ~10,000,000)
Seatpost outside diameter 27.2mm, wall thickness 2.5mm (based on my Campag Record carbon post)

I calculated vertical deflection due to bending as well as compression. Contribution from the latter is always small compared to the former, and is ignored for this discussion.

The answer I found, is 0.04mm for a 6" exposed post, but 0.32mm for a 12" exposed post - deflection is proportional to the exposed length's power of 3.

In relation to the motions and deflections of tyres/wheels/forks/frame/saddle we experience trundling down the road, I doubt this level of deflection can be detected in a blind test.

Finally, I found the nearest alloy post at hand to have the same wall thickness - being less stiff, it should be more compliant.



============================

For those who would like to check my calculation, for 12" exposed post:

Second moment of inertia: 0.036 in^4
Bending load: 58 lbs
Bending deflection: 0.043" or 1.08mm based on this formula

Bravo that man, I doff my hat in envy