Carbon stems : Bad idea?

RSV_Ecosse

Senior Member
Thinking of grabbing a full carbon stem. Not a carbon wrapped alloy one but full carbon. Got my eye on one on that well known auction site. ;)

Mentioned this the other day whilst talking to some roadie mates and a couple of them said "No!!!. They are not strong enough. Don't use a carbon stem, they can snap and cause a massive "get off"......!!!". They went on to tell me to stick with alloy or carbon wrapped alloy for a stem.

Surely that is a load of the proverbial bo11ox?. :tongue:
 

Mark_Robson

Senior Member
I find it hard to believe that they aren't designed to be fit for purpose. I would imagine that it would take some pressure to snap a length of carbon 10cm or so long. The only thing that may weaken the carbon is overtightening of the stem bolts.
I'm a keen sea angler and it never ceases to amaze me how strong carbon is. I've seen people drag in some amazingly heavy things using a 1" diameter length of hollow carbon.
 
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RSV_Ecosse

RSV_Ecosse

Senior Member
That's exactly what I was thinking. If they are good enough for the pro racers and good enough to be fitted as OEM to top spec bikes such as the Pinarello Prince or new Dogma surely they must as you say be "fit for purpose"?.

Otherwise anyone selling them as aftermarket parts would be basically selling a "lawsuit waiting to happen in a box". ;)
 

redddraggon

Blondie
Location
North Wales
I like carbon stems, they are pretty much bombproof and tend to be stronger than the alloy stems, but are also normally higher weight.

Carbons bars on the otherhand I think are overpriced, and aren't the best material for the job IMO, and would much rather have alloy bars. I have two sets of carbon bars, but my best bike uses alloy 3T rotundo Pros, which I like loads. I only have one carbon stem though, but wouldn't be adverse to buying more.
 

lukesdad

Guest
Like most things it depends on the quality of the raw material being used as there are many grades of CF it also has a limited life expectancy.

Ive got a couple of scandium stems and a custom one in ti now that is the dogs b----x! lighter and better looking than CF and they aint going to break.
 

MajorMantra

Well-Known Member
Location
Edinburgh
Carbon stems seem disproportionately expensive given that many of them aren't even all that light. If it's weight savings you're after, what about a Thomson?

Matthew
 

PK99

Legendary Member
Location
SW19
Mark_Robson said:
I find it hard to believe that they aren't designed to be fit for purpose. .

the issue with many carbon components is not design/fitness for purpose but the after care - according to a friend in the trade.

Use or torque wrenches set to the correct value is crucial - over-tighten and you risk the item failing catastrophically. Not an issue for pro teams with dedicated mechanics but will the saturday lad down the bike shop use the torque wrench or just crank it tight like he does with all the other kit?
 

Mark_Robson

Senior Member
PK99 said:
the issue with many carbon components is not design/fitness for purpose but the after care - according to a friend in the trade.

Use or torque wrenches set to the correct value is crucial - over-tighten and you risk the item failing catastrophically. Not an issue for pro teams with dedicated mechanics but will the saturday lad down the bike shop use the torque wrench or just crank it tight like he does with all the other kit?
Agreed.:whistle:
 

zacklaws

Veteran
Location
Beverley
Good Lord, I have enough to worry about when I'm speeding down a hill and look down at my carbon forks, which I try not to do, to see them shaking backwards and forwards violently at times, wondering if they are going to snap, to have to think now my carbon stem will snap when I am pulling hard up a hill and do a double back flip backwards when it does.

Stop scaremongering, their as tough as old boots, I hope!
 

HJ

Cycling in Scotland
Location
Auld Reekie
RSV_Ecosse said:
Thinking of grabbing a full carbon stem. Not a carbon wrapped alloy one but full carbon. Got my eye on one on that well known auction site. :biggrin:

Mentioned this the other day whilst talking to some roadie mates and a couple of them said "No!!!. They are not strong enough. Don't use a carbon stem, they can snap and cause a massive "get off"......!!!". They went on to tell me to stick with alloy or carbon wrapped alloy for a stem.

Surely that is a load of the proverbial bo11ox?. :smile:
Try asking your friend if the ever travel by air or even stand under a fight path, then ask them what the structural parts aeroplane wings are made of? The main problem with carbon is that it can do serious damage to your wallet... :whistle:
 

GrasB

Veteran
Location
Nr Cambridge
The uprights for the Exige's rear spoiler is carbon... at 160mph the damn thing is generating something like 150kg of downforce. If you can see a video of these you can see the whole spoiler including uprights flexing & shuddering over bumps etc. so it comes down to the engineering of the product rather than the material.
 

redddraggon

Blondie
Location
North Wales
GrasB said:
The uprights for the Exige's rear spoiler is carbon... at 160mph the damn thing is generating something like 150kg of downforce. If you can see a video of these you can see the whole spoiler including uprights flexing & shuddering over bumps etc. so it comes down to the engineering of the product rather than the material.
Aye CFRP can make plenty good bars, but they are expensive, and I like to treat bars as sort of a disposable item, if I crash them they get replaced - not too bad with £40 bars, but carbon bars are at least 3 times that.

Carbon stems on the otherhand I don't feel that they would need replacing in a crash, because I don't feel a crash would damage them, the crash would damage the bars or steerer. The stems tend to be hugely overbuilt and stiff anyway.
 
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