Carbon a bad idea for hard-tail 29er?

[chriscole]

Hi folks,

Looking for something that can be taken more easily onto stuff that my CX bike isn't quite suited to. Aiming for a hard-tail 29er MTB. Would like something with decent components, and preferably reasonably light, but durability is more important.

Seeing some nice options in carbon at the ~$2,000-$2,500 price point but have reservations about the robustness of a carbon MTB in the long term.

Any opinions / suggestions ?

[thecaptn]

You can get some very light alloy frames, mine is a large and weighed under 10 when I bought it. Carbon is great but I'm not sure if it's going to be much better in any way. If the riding you do doesn't cause you to drop the bike then a nice carbon frame could be good. If It were me I'd put more emphasis on the components and weight in comparison to price. Don't buy a Giant cause they suck.

[zero]

I wouldn't worry about it - half the bikes I see at any race are carbon.

My original dually frame fatigued and failed in 2.5 years - IMO light alloy mtb frames are finite lifespan objects anyway. Trek, giant and several others offer crash replacements - original owners can get relatively cheap replacements.

[ball bearing]

One stone flicked up from the front wheel and your downtube is cactus.

[Mulger bill]

One stone flicked up from the front wheel and your downtube is cactus.

There's various guards available for that, whether there's a suitable one for the OPs prospect is another thing

[trailgumby]

It depends. There are pros and cons to each.

Carbon has a shorter fatigue life, but is easier to repair than aluminium. My concern with carbon is the lack of warning you get and the catastrophic nature of its failure. Yes, it's stronger, but when it goes it fails explosively. No creaks, can look fine on the outside, and then BANG! You're bike is in two pieces, with you arranged somewhere on the ground between them.

I use carbon bars and seatpost on both bikes, but never stems. So far I've resisted but am looking at a carbon Cannondale Scalpel 29er purely on performance.

Luescher Technik in Melbourne and Bike Addiction in Sydney both do high quality repairs they warrant for 5 years.

In my opinion all the manufacturers need to do something about using Kevlar in the prepreg to add greater toughness to the brittle strength of carbon.

Chances are it will fail at some point in its service life. You want a company that has a reputation for being fair-minded and easy to deal with. On that front I'd recommend Giant and Yeti, and recommend against Scott and Cannondale.

[Fixie82]

Carbon composites actually have a much much higher fatigue life than other frame materials, as such carbon composites are not subject to fatigue failures as metals are. If your frame or component is only stressed within the design paramaters it was intended to it will do so essentially forever, an aluminium frame for example will eventually fail even if stressed within the design paramaters of the frame. So the fatigue life of a properly made carbon composite is essentially “infinite”. Durability is often cause for concern and I still think the fragility of carbon frames is overstated, especially with mountain bike frames. Manufactures realise the intended purpose of the frame and design accordingly, I can guarantee that if a flicked up stone ruined the down tube on a carbon frame it wouldn't matter if a different material was used, it would still be cactus. If you haven't seen this video check it out, it will help dispel some persistent rumours http://www.youtube.com/watch?v=xreZdUBqpJs" onclick="window.open(this.href);return false;

For more information on carbon composite use in bike frame design check out the calfee white paper on the subject, it covers the pro's and con's in detail and is a good read.

Just remember that all bike parts will break if stressed beyond what it was designed for, buy a carbon frame from a reputable company that knows how to work with the material and you will have something that will be more durable than options made from other materials. Wether that is noticeable for the duration of your use of it is another matter.

[trailgumby]

Thats industry sales propaganda and cheap words. What you want if you want the truth is to observe how they actually behave once they've got your money and they are responding to your warranty claim.

Then that supposed infinite fatigue life becomes a lot shorter. Lets say 5-7 years for lightweight alloy, less for carbon. This quoted from a manufacturer's rep responding in writing via email to a warranty claim for a failure on an alloy frame. Startling that he would volunteer such an admission for carbon when it wasn't in scope, but volunteer it he has.

Hence my focus on manufacturer track record in dealing with such claims.

[Fixie82]

You obviously arent doing your homework here. It's not industry propaganda about carbon, carbon having an essentially infinite fatigue life is a well known fact. It has not been made up by people who want to sell you a bike. Why do you keep insisting that carbon has less of a fatigue life? Your example of a warranty claim on an alloy frame further supports what I am saying, alloy has the shortest fatigue life so I am not surprised your claim was denied as that is a lifetime for the frame not your lifetime and an expected lifetime for alloy is a lot shorter than carbon.

Manufactures customer service has nothing to do with the durability and fatigue life of carbon.

[toolonglegs]

It depends. There are pros and cons to each.

Carbon has a shorter fatigue life, but is easier to repair than aluminium. My concern with carbon is the lack of warning you get and the catastrophic nature of its failure. Yes, it's stronger, but when it goes it fails explosively. No creaks, can look fine on the outside, and then BANG! You're bike is in two pieces, with you arranged somewhere on the ground between them.

I use carbon bars and seatpost on both bikes, but never stems. So far I've resisted but am looking at a carbon Cannondale Scalpel 29er purely on performance.

Luescher Technik in Melbourne and Bike Addiction in Sydney both do high quality repairs they warrant for 5 years.

In my opinion all the manufacturers need to do something about using Kevlar in the prepreg to add greater toughness to the brittle strength of carbon.

Chances are it will fail at some point in its service life. You want a company that has a reputation for being fair-minded and easy to deal with. On that front I'd recommend Giant and Yeti, and recommend against Scott and Cannondale.

The exact same can be said for lightweight alloy frames... I have never owned a carbon mtb but every mtb I have owned ( except for the one I have now, steel On-One... give it time ) steel or alloy has failed, sometimes without any warning.

[thecaptn]

The exact same can be said for lightweight alloy frames... I have never owned a carbon mtb but every mtb I have owned ( except for the one I have now, steel On-One... give it time ) steel or alloy has failed, sometimes without any warning.[/quote]




Remind me to never lend you a bike

[trailgumby]

Yes, it can, but the usual scenario is creaking that warns of fatigue cracking underway... you usually get *some* warning. Other faulures I've had exhibit as bending or creasing. But yes, not always.

I do agree though that sudden failures can also occur with alloy - youve had a few and I've seen a few at local bike shop too.

The CF frame cracks that other friends have found in frames before they let go were from visual inspection while cleaning, and in one case a loud "CRACK!"sound when he shoulder charged a tree (nil bike contact). So in contrast the warning signs are more usually absent than present compared to other materials.

Bottom line is you need to be more vigilant with carbon and aware that it is a little more failure prone. On the upside, when it cracks if you catch it before it fails completely you can - like a surfboard - get it repaired. Luescher will even ultrasound check it to ensure the rest of the frame is fine to ensure it is worth fixing.

But infinite fatigue life... nice theory!

[RonK]

Carbon fibre composites were developed by the aerospace industry and have been used for many years in high performance military aircraft.

Now the wings on the Airbus 380 are made from it, as is the entire airframe of the new Boeing Dreamliner.

But there are still people here who would have us believe that this is all based on industry propaganda.

Ludicrous!

[Nobody]

TG, you're starting to sound like me (which must be a little bit scarey for you).

TLL, you're going to have to start doing some drops on the On-One soon. It's starting to wreck your wrecker reputation. The Ribble isn't helping either.

It's been a while since we've done one of these threads. As I couldn't be bothered typing all the arguments out anymore, below is one we prepared earlier.
viewtopic.php?f=11&t=54347" onclick="window.open(this.href);return false;

[toolonglegs]

The on-One hasn't been ridden for 6 months... weather hasn't really been inviting for VTT rides... but I should probably get out on it a bit now!.
Yeah the Ribble is doing me proud.
Slightly OT... but yesterday I had a REALLY big hit on my carbon deep dish wheels ( front & rear ) ... I know for a fact it would have buckled alloy clincher rims, but carbon tubulars "seem" to have got away with it with out an issue.

[Mulger bill]

Remind me to never lend you a bike

You should see what he does to high end cranksets

[chriscole]

Thanks for the input, guys. Much appreciated.

I don't think I've really changed my mind that carbon is lighter and stronger, but more likely to SPLAT me without warning when Things Go Wrong (TM).

I'll test ride a few options in my price range in both their alloy and carbon incarnations and see if there is any appreciable (for me, anyway) difference in weight/performance/comfort and then ponder the merits of whether to spring the extra $$ for carbon, or buy the alloy version and spend the $$ on nicer bits & pieces.

Cheers,
Chris

[thecaptn]

Remind me to never lend you a bike

You should see what he does to high end cranksets

If there was a Royal Society for the Prevention of Cruelty to Bikes they'd have TLL under surveillance.

[__PG__]

Carbon fibre composites were developed by the aerospace industry and have been used for many years in high performance military aircraft.

Now the wings on the Airbus 380 are made from it, as is the entire airframe of the new Boeing Dreamliner.

But there are still people here who would have us believe that this is all based on industry propaganda.

Ludicrous!

And some people here would have us believe that cheap mass-produced bicycle frames use the same design tolerances, quality of fibre lay-up, resin, quality control and inspection methods used by aerospace giants.

Here is a recent article regarding the Airbus A380 wings.

What's the recommended crack detection inspection interval using high-frequency eddy current equipment specified by Trek and Giant for their bicycle frames

Would you suggest that the aluminium construction methods used in a Reid bike are the same as those used by Airbus in the A380 wings?

[Ken Ho]

The usual carbon vs alloy discussion. All I have to add is that I would go DS rather than hardtails.
You already have a CX, which will handle a lot of stuff. A hardtails is not a big step up. I use my Rumblefish as a roadie at present, with narrowere tyres fitted, and I'm loving the comfort.
It took a bit to talk myself into teh luxury of a DS bike, but I am so glad I did now.

[toolonglegs]

Hardtail Mtb vs CX bike... No comparison IMO. CX bikes and tyres are designed for grass paddocks. I get no fun in riding mine on single track.
Dualie... That's another debate.

[barefoot]

The usual carbon vs alloy discussion. All I have to add is that I would go DS rather than hardtails.

Ah, the usual DS vs hardtail discussion.

All I have to add is that when I had a DS, I rode my hardtail by preference. When the dually was stolen, I used the insurance money to upgrade my hardtail.

tim

[Ken Ho]

The usual carbon vs alloy discussion. All I have to add is that I would go DS rather than hardtails.

Ah, the usual DS vs hardtail discussion.

All I have to add is that when I had a DS, I rode my hardtail by preference. When the dually was stolen, I used the insurance money to upgrade my hardtail.

tim

Not a knock on HTs.
The new DS suspensions are a treat to ride, with no appreciable bob while riding seated, but with a big comfort bonus.

[chriscole]

The Avanti Competitor 29.2 is looking like a contender...

[durianrider]

Giant Australia have excellent warranty service from what I have seen from local riders.