Carbon Seatpost + Rider Weight

gb155

Just picked up a winter hack....My my my AMAZING, Pics to follow but I have a question, It has a carbon seat post, Do they normally have a max rider weight ? Being 22 stone should I change it ?

Stuey01

Is it carbon, or carbon wrapped aluminium?

If it were me, and if full carbon I'd swap it out for a cheapo alu one then switch back when you've got your weight down a bit more.
If carbon wrapped alu then prob would just use it.

Is it branded? if so google it?

gb155

Stuey01 wrote:

Is it carbon, or carbon wrapped aluminium?

If it were me, and if full carbon I'd swap it out for a cheapo alu one then switch back when you've got your weight down a bit more.
If carbon wrapped alu then prob would just use it.

Is it branded? if so google it?

Its a Custom Ribble, Invoice says carbon, how can you tell ?

Aidy

Imagine it'll be fine.

I wouldn't be forcing all your weight through it over bumps and stuff, but then, I wouldn't be doing this on any seatpost. No matter what the rider weight.

If you're nervous about it, swap it out for a aluminium one for peace of mind.

gb155

Aidy wrote:

Imagine it'll be fine.

I wouldn't be forcing all your weight through it over bumps and stuff, but then, I wouldn't be doing this on any seatpost. No matter what the rider weight.

If you're nervous about it, swap it out for a aluminium one for peace of mind.

Yeah I lift off on the majority of bumps but there is always that one you dont see

If it's fine then im fine

DonDaddyD

Some supercars are made entirely out of carbon fibre, though the fibre is subject to different stresses it still withstands far more than any human could subject it to under their own power/weight.

My wieght (16st without commuter bag) is well documented on the site, I have a carbon seatpost on both my commuter and really nice bike. Haven't had any problems, yet.

gb155

DonDaddyD wrote:

Some supercars are made entirely out of carbon fibre, though the fibre is subject to different stresses it still withstands far more than any human could subject it to under their own power/weight.

My wieght (16st without commuter bag) is well documented on the site, I have a carbon seatpost on both my commuter and really nice bike. Haven't had any problems, yet.

Cheers DDD, IT was a nice suprize TBH and I was just a little shocked, in a good way of course.

CiB

Trouble with CF is that it works as designed. The fact that an Iti supercar is made of CF means nothing when applied to a seat post made of the same material. Your seat post might be OK and be designed to cope with extreme compression along its length, but may or not be up to supporting 22 stone of downward force whilst silmutaneously resisiting the lateral forces generated by pedalling and riding over bumps. In short, Iti supercars made of CF have no bearing on your seatpost.

In your position, I'd check with the supplier or manufacturer. TBH an ally s/p will be only a tenner and won't have any bearing on your bike, except for a slight reduction in the bling factor, so I'd play safe and swap it out.

antfly

I`d swap it if I were you, they do have weight limits and they can and do break. I had one break a few weeks ago and I am only 12st. I would get an alloy with two bolts at the clamp.

jairaj

try contacting the manufacturer to see what weight restrictions the have for the post. If in doubt, maybe try a carbon post designed for mountain biking? A MTB one should be stronger than a road version.

Also swopping it for a random Alu version isn't necessarily a safer option. A poorly designed alu post can be weaker than the carbon fibre one.

jairaj

ChrisInBicester wrote:

TBH an ally s/p will be only a tenner and won't have any bearing on your bike, except for a slight reduction in the bling factor

I don't agree with this. A well designed post whether made from Alu, carbon or what ever will be strong, light weight and comfortable. A poorly designed may only have 2 or less out of the 3 desired properties

antfly

You can be sure the weight restrictions are less than 22st even for MTB carbon seatposts.Specialized {which mine was} suggest a 240lb limit for their carbon seatposts.There are plenty of good quality alloy ones. Having a seatpost break is not pleasant and it is just not worth the {not inconsiderable} risk at 22st.

supersonic

jairaj wrote:

try contacting the manufacturer to see what weight restrictions the have for the post. If in doubt, maybe try a carbon post designed for mountain biking? A MTB one should be stronger than a road version.

Also swopping it for a random Alu version isn't necessarily a safer option. A poorly designed alu post can be weaker than the carbon fibre one.

Very well said.

Roastie

supersonic wrote:

jairaj wrote:

try contacting the manufacturer to see what weight restrictions the have for the post. If in doubt, maybe try a carbon post designed for mountain biking? A MTB one should be stronger than a road version.

Also swopping it for a random Alu version isn't necessarily a safer option. A poorly designed alu post can be weaker than the carbon fibre one.

Very well said.

But not entirely correct.

I see this as much an issue of strength as an issue of failure mechanism. Although alu may crack, carbon shatters. I know someone who had splinters of carbon fibre rammed up where the sun don't shine when his post failed - didn't just hurt, but needed minor surgery.

I'll second what ChrisInBicester and antfly said. If in doubt, get a decent two bolt alu post. Don't skimp, but you also don't need to break the bank. A good LBS is (or at least should be) your friend.

UndercoverElephant

Given I'm less than 14 stone, and I've just had an aluminium one buckle and not hold the seat very well, I'm in no position to say one's better than the other. The bike radar review for the aluminium re-inforced CF one I bought to replace it said that "Heavier riders (those over 200 lbs) should go for the 350mm version".

Doesn't fill me with confidence TBH, but I'm sure it'll be fine. I went for the 350mm version anyway, as it was on offer.

Aidy

UndercoverElephant wrote:

Given I'm less than 14 stone, and I've just had an aluminium one buckle and not hold the seat very well, I'm in no position to say one's better than the other. The bike radar review for the aluminium re-inforced CF one I bought to replace it said that "Heavier riders (those over 200 lbs) should go for the 350mm version".

Doesn't fill me with confidence TBH, but I'm sure it'll be fine. I went for the 350mm version anyway, as it was on offer.

That's surely less to do with the strength of the post (as it'll have the same moment about the seat clamp regardless of length), and more to do with the strength of the seattube?

DonDaddyD

My example of carbon fibre sports car's was to demonstrate how strong carbon fibre can be made to be. Another example would be aircrafts.

Yes the stresses are different.

But I would be surprised if a manufacturer would make a seatpost or frame with only a 20stone limit in the torsion, tension, compression, strength department. Seems that would imply lack of quality. This would go against carbon fibre marketing, which is mostly about strength, stiffness and light weight.

Incidentally, having gone from an alu seatpost to carbon fibre on an alu frame (my CF seat post is a £100 bontrager xxx lite) I much prefer the carbon fibre one. It's not about the weight, it's the fact that it noticable (from my own personal experience) absorbs road vibration far better than my old alu post making the ride more comfortable.

antfly

http://cdn.specialized.com/OA_MEDIA/pdf ... ons_r1.pdf
In that case this may surprise you. Bottom right paragraph.

gtvlusso

13 stone me, never had a problem...interesting question though as wheelsets have weights associated.

DonDaddyD

antfly wrote:

http://cdn.specialized.com/OA_MEDIA/pdf/manuals/08 SW Carbon Mtn Seat Post Instructions_r1.pdf
In that case this may surprise you. Bottom right paragraph.

You learn something new each day.