Looking to buy a road bike - Carbon or not?!

bexford69
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Looking to buy a road bike - Carbon or not?!

Postby bexford69 » Tue Sep 27, 2016 7:10 pm

Hi guys - first post here and could do with some advice!

3 years since purchasing my Orbea Carpe H40 flat bar for 25km daily commute to the office - am now looking to add a road bike for longer weekend rides / possible racing. Ideally would like to stick with Orbea as have been more than pleased with the brand.....happy to consider a 2nd hand / near new buy - aswell as new. checked gumtree and found this one that seems a great price and exactly what I want:

http://www.gumtree.com.au/s-ad/virginia ... 1124964851

a trusted friend and bike fanatic however has advised me today to steer clear of secondhand carbon bikes as well as full carbon...his rationale being that carbon breaks down overtime due to the vibration - that UVB rays detiorate the epoxy that holds the carbon together - and if the bike has had a prang - there's no way of telling, until it shatters beneath you!

over cautious or sage advice?!!

any advice greatly appreciated....
Cheers
Bex

zero
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Re: Looking to buy a road bike - Carbon or not?!

Postby zero » Tue Sep 27, 2016 7:21 pm

I have ~15 year old carbon on one of my bikes. its fine.

Most people don't store road bikes in either the weather or the sun, and if the bike you are thinking about has been sitting in the sun forever, I think you'd notice when inspecting it to purchase (paint, corrosion etc).

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trailgumby
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Re: Looking to buy a road bike - Carbon or not?!

Postby trailgumby » Tue Sep 27, 2016 7:46 pm

Your friend needs to catch up with the times. :)

Carbon has a virtually unlimited fatigue life so long as its design limits are not exceeded. The UV thing was true once, but there have been great advances in UV-resistant resins and finishes so that this is no longer a concern. Additionally, a coat of paint protects from UV - that's it's job.

Aluminium bikes work harden and fatigue crack. Failure is a matter of when, not if. That's why otherwise serviceable military and civilian aircraft are retired after a certain number of flight hours. Unlike aluminium, carbon can be repaired back to original strength bu a skilled repairer. If a bike has been crashed, you'll see it on the paintwork unless it's been professionally repaired. If it's been professionally repaired, then you should be fine.

I ride a carbon Cannondale Scalpel 29er mountain bike. It took me awhile to get comfortable with the idea of using a carbon bike on our rocky sandstone trails and I was nervous, anxious and hesitant for a few months, but after awhile you just go "meh" and forgat about it. It's taken some massive hits off large chunks of rock bouncing up off the front tyre and I was certain that I'd busted the frame ... but not a mark. Covering in Frameskin probably helped that, but the bike has been incredibly tough.

I doubt you'll have any trouble with buying carbon secondhand. And if you do, it can easily be repaired.

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Duck!
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Re: Looking to buy a road bike - Carbon or not?!

Postby Duck! » Tue Sep 27, 2016 8:48 pm

bexford69 wrote: a trusted friend and bike fanatic however has advised me today to steer clear of secondhand carbon bikes as well as full carbon...his rationale being that carbon breaks down overtime due to the vibration - that UVB rays detiorate the epoxy that holds the carbon together - and if the bike has had a prang - there's no way of telling, until it shatters beneath you!
Your "trusted friend" is peddling 30-year-old misinformation, and frankly, needs to get a clue!

Carbon is exceptionally good at absorbing road vibration thanks to the compressibility of the resin component of the composite material. It will not break down from this vibration. All carbon frames and components are coated with paint, which includes clearcoat, which is UV stabilised, so the risk of the frame degrading from UV is pretty well non-existent. Finally, carbon frames need significant impact before the laminate is sufficiently weakened. Carbon does not just spontaneously shatter; it will do so at the time of impact if it is of sufficent severity, but otherwise the complex arrangement of the fibres within the layup provides some degree of self-reinforcement, so any failure will be progressive, with plenty of visibly obvious warning.
I had a thought, but it got run over as it crossed my mind.

mikaelkn
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Re: Looking to buy a road bike - Carbon or not?!

Postby mikaelkn » Thu Sep 29, 2016 3:08 pm

Watch this video and make up your mind:
https://www.youtube.com/watch?v=-qsLYlVWkbQ

* I had my Bianchi's rear stay repaired there. Not cheap! But that's proper repair.

Jawa
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Re: Looking to buy a road bike - Carbon or not?!

Postby Jawa » Thu Sep 29, 2016 3:39 pm

Can’t really comment too much considering ive never owned a carbon road. But wouldn’t you steer clear of second hand not so much for fatigue, more so it may have a hairline fracture though wouldn’t be detected unless assessed but a trained person.

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Duck!
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Re: Looking to buy a road bike - Carbon or not?!

Postby Duck! » Thu Sep 29, 2016 5:27 pm

No different to aluminium which might have a cracked weld, except carbon is MUCH more readily and reliably repairable.
I had a thought, but it got run over as it crossed my mind.

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Re: Looking to buy a road bike - Carbon or not?!

Postby warthog1 » Thu Sep 29, 2016 6:15 pm

Duck! wrote:No different to aluminium which might have a cracked weld, except carbon is MUCH more readily and reliably repairable.


:o :mrgreen:
You'll have some excellent steam generation if you can mention the strength/weight comparison with respect to steel also :P
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open roader
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Re: Looking to buy a road bike - Carbon or not?!

Postby open roader » Thu Sep 29, 2016 8:13 pm

Carbon fibre is not just plastic and will not melt or distress in the sun nor will it shatter underneath you from years of vibration.

Your trusted friend is still your trusted friend, however he is incorrect in his opinion of carbon fibre not being a suitable bicycle frame material.

He probably should have advised you take himself or someone else you trust with necessary bicycle mechanical knowlege and 2nd hand bicycle experience to inspect anything you feel is a real contender.

There are many genuine well priced 2nd hand bikes out there that make good buying when compared to a new purchase incl. full carbon framed bikes. If I was looking for a road bike of a brand I prefer then that Orbea with Shimano 105 running gear looks good to me provided 1) you take someone experienced with carbon frames to inspect with you 2) the bike actually fits you and runs perfectly 3) remember the price is always negotiable, more so on a 2nd hand purchase :D .
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cyclotaur
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Re: Looking to buy a road bike - Carbon or not?!

Postby cyclotaur » Thu Sep 29, 2016 10:56 pm

I've preferred aluminium over carbon until now, but mainly because of $$$ and the crappy carbon colour schemes they've often had in recent years. :P

But I'm coming around to carbon ....slowly....colour schemes are getting better !! :)

Material-wise I'm convinced though - recently rode a 5-6 yo Giant in Italy. The bike was a 'bitzer' and not much good overall (not enough gears, tyres too skinny etc) but the frame was sound. And this was a hire bike with plenty of kms on it.
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SheikYerbouti
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Re: Looking to buy a road bike - Carbon or not?!

Postby SheikYerbouti » Fri Sep 30, 2016 8:20 pm

trailgumby wrote: Aluminium bikes work harden and fatigue crack. Failure is a matter of when, not if.

What does "work harden" mean? Where are the fatigue points on an al frame? Not like a plane where lots of flex is normal. I'd like to keep an eye on my 2011 alloy bike if you're telling me that it IS going to fatigue crack.

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Duck!
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Re: Looking to buy a road bike - Carbon or not?!

Postby Duck! » Fri Sep 30, 2016 10:06 pm

Aluminium suffers cumulative fatigue; every flex of the material, however miniscule, weakens the metal. It will handle these stresses for a while, but eventually the accumulated stress will reach a point at which the material can no longer flex and breakage will occur. The heat stress from welding also affects the crystalline structure of the material. Heat treating the frame corrects it to an extent, but some alloys remain stressed around the welds even after heat treating.

The two areas most prone to fatigue cracking on an aluminium frame are around the bottom bracket, particularly the chainstay/BB shell welds, and the seat tube/top tube junction. The former is more likely if the bike gets a lot of trainer use, the latter if the rider is heavier and at the tall end of the range for the frame size, with a lot of seatpost out.
I had a thought, but it got run over as it crossed my mind.

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trailgumby
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Re: Looking to buy a road bike - Carbon or not?!

Postby trailgumby » Fri Sep 30, 2016 10:29 pm

SheikYerbouti wrote:Not like a plane where lots of flex is normal. I'd like to keep an eye on my 2011 alloy bike if you're telling me that it IS going to fatigue crack.
I hear you, but I disagree. My roadie flexes heaps. The shape is not a true triangle, it is a trapezoid. That flex is an integral part of the comfort a road bike provides, and it's handling. Mine's a CAAD9. You probably don;t notice it because it is the bike you ride all the time.

I particularly notice the contrast to my mountain bikes, which are build like brick outhouses. Especially my hardtail, which has massive seat stays by comparison, and is not real comfortable with 700c roadie rubber on it unless I have a long carbon seatpost.

If you can take a look down while riding over rough pavement (if it's safe to take your eyes off the road in front momentarily) you'll see what I mean.

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