K2 / Proflex Riders Group
General => Tech Forum => Topic started by: wylyman on June 23, 2007, 11:33:57 am
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So has anyone witnessed or expeirenced carbon fiber catostrophic failure on the trail. Or is it just something that hapens in the R&D department when parts are pushed to the limit? Just wondering since I have been riding my 4000 carbon swing arm for a long time now and it would suck to have it "snap" on the trail someday.
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droputs coming loose, but haven't heard of any cat. failures, from normal use, whatever that is.
if you got smacked by a 747 at takeoff and the bike was sucked into one of the turbo fans after you clipped the nose gear, it would probably jam the fan, bend a few fins and crash the plane. The NTSB would keep you intact swingarm and frame. (don't get any ideas, please!)
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I was reading a forum on mtbr and their was a discussion on All Mountain carbon fiber bikes. Seems alot of people are convinced that carbon fiber will deteriorate from the inside out and that they will fail unnowingly. Wheras an aluminum frame would show signs of failure such as cracks which would be noticable.
I have noticed on mine some yellowing and some white in the outer weave. Probably normal on a 9 year old bike anywhay.
I really dont think mine will be a problem but their still are alot of people who wouldnt trust carbon fiber for mtn bikes. I am not riding 15' drops onto flat landings.
Has anyone looked at the new Ibis Mojo. Thats another carbon work of art.
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I have seen pictures of a broken 857 rear swing arm.
He landed very sideways on a big rolling jump and the RHS arm snapped about half way along the length..............Not really what the bikes are intended for.................
I think we've got a few carbon experts on the forum, including someone who works on Eurofighter? so I'll leave them to comment on the absurdity (IMHO) of Carbon Fibre/Thermoplastic deterioration.........???? (certainly not any worse than Aly fatiguing?)
Col.
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Seems alot of people are convinced that carbon fiber will deteriorate from the inside out and that they will fail unnowingly.
B*ll**ks! The inside's just as inert as the outside. Ally and steel frames aren't painted on the inside so will corrode from the inside for example.
This sounds remarkably like the microwave myth "from the inside outwards"
I have noticed on mine some yellowing and some white in the outer weave. Probably normal on a 9 year old bike anywhay.
Mine too, that's simple fatigue: the matrix (the plastic) separates from the fibre one by one and capilliary action allows water or cleaning agent into the matrix/fibre interface.
The fatigue characteristics of fibre reinforced plastics are vastly superior to metals, that's why I went plastic (I think I'll add my warranty replacements in my signature)
I really dont think mine will be a problem but their still are alot of people who wouldnt trust carbon fiber for mtn bikes.
Your bike (and mine) are on their way out, but don't worry, it'll just get less and less rigid (they started life pretty floppy) untill you don't want to ride it any more.
Not trusting carbon? Our Proflexes are easier to repair than ally bikes; a bit of fancy glue and it's fixed. The only disadvantage with modern carbon frames is if you drop it on a rock or drive the bar end bolt through the top tube in a crash (I did that on my Scott Strike :(( ) Thermoplastic doesn't seem to be as fragile; the abuse mine's put up with is quite unbelievable.
As we all know, the weak points are the interfaces with metal parts, for that I can particularly recommend Scotchweld DP480 if you can afford it! (I got mine from a surplus at work)
Ibis Mojo. Thats another carbon work of art.
MMM! One day I'm going to have to try out this VPP malarky, although I would have thought the lower rocker was too horizontal.
I'm a bit of a monopivot guy.
Happy trails
Luke
(For the record my masters thesis involved CFRP fatigue and rupture testing, I've worked on Carbon bits for a Shuttle payload prototype I had to build)
let's have a go at the signature history:
(Signature added)
I'm terrified of more than a foot of air (even then...)
My 5500 has lasted since 1999 with only some inserts coming loose.
Sorry, that was a bit long
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Funnilly enough rode mine at mountain mayham on the weekend just gone, took the OZ and the 656. Got some funny looks whilst riding the 656, but then it is anodised cherry red.
Test rode an IBIS , wicked bikes , very very light. Sub 25lb with an air shock, and circa 5 1/2 in travel. seemed very well made, ...however... a guy returned his to the dealer when i was there, he had been out racing on it and it broke, linkage plates i believe..
AND the marzocchi guy who had a look at my mararthons knew of another englishguy who was 'retiring' his oz as firstly the seatpost , then the BB had become unbonded. apparrently it has been ridden hard for about 6 years, and only superceeded in the last year or so.
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It seems the only problem anyone has had is loose dropouts. I myself had that problem last year, an easy fix. There's something to be said about monopivots with bushings and durability. I purchased a pivot rebuild kit last year. After removing the bushings and measuring with dial calipers, discovered the old bushings a better fit than the new ones! They measured .004 larger. Must have sloppy machining tolerance one these parts. So I put the new seals and old bushings back on the bike. Still good after 8 years.
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Hi there, only kevlar degrades in sunlight, carbon does not. it is stiffer than steel and lighter than aluminium but hates sheer loading, hence the different layers/ ply orientation. no reason not to trust it. steve
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Check out this carbon handlebar catostrophic failure. Inspect your handlebars and seatposts.
http://www.utahmountainbiking.com/UMBphpBB2/viewtopic.php?t=3477
Thunderchild
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WOW
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Hi,
I haven't posted on here is quite a while, but feel te need to now. I own 3 carbon fiber bikes, two mtbs (an Oz, a Giant hardtail) and 1 road bike (Calfee).
I have put many, many miles on all these bikes, and the only problem I've had was a broken carbon handlebar on the Calfee. It was a Kestrel bar and it broke because I was using a non-carbon approved alu. stem.
Just like the handlebar failure linked to above, if something is clamped to the bar and it is not filed on the inside to remove any sharp edges or burrs, the clamp can cut into the cf. Also, do not overtighten clamps on cf, it can be crushed.
anyway, cf really is a wonder material. All my bikes liste above have cf frames, bars, and cranks. Also, cf seatposts. My roadbike seat even has cf rails. Other than the handlebar I spoke about above, no problems what so ever. (oh yeah, I've got campy carbon drivetrain on the Calfee, no problems.)
my $.02.
DG