Are carbon frames strong enough?

[billium]

if you're looking for value for money then go aluminium, if you want your bike as light as possible then go carbon fibre (but you will pay more for it) . Strength doesnt come into it at all with mtb frames.

Great discussion - I am learning a lot but it appears that there is no clear link between Carbon and expensive - e.g. Cube Stereo and Haibike Allmtn start at under 5K with Carbon front ends. For me an extra Kg is less of a concern than having a bike that won't have frame issues but it sounds like, in general, Carbon is strong enough and should not figure much in my decision making process.

 

[Mteam]

Great discussion - I am learning a lot but it appears that there is no clear link between Carbon and expensive - e.g. Cube Stereo and Haibike Allmtn start at under 5K with Carbon front ends.

I meant that there is a link between carbon and expensive within the same manufacturer/bike model , eg spesh aluminium models are always cheaper than their carbon versions when comparing spec for spec, same for orbea , trek etc.

Obviously different manufacturers have different price points to suit their brand positioning , economies of scale, size of their markets , perceived value etc etc. So one manfacturers carbon bike could be cheaper than anothers aluminium for a variety of reasons.

 

[B1rdie]

My full sus 26’ carbon stumpjumper with a carbon revelation fork is still my favourite bike, after 8 years and 6.000+ kilometers on three continents.
And I have four aluminum 29ers on the quiver, one of them with a rigid carbon fork 🫣 its my second favourite.
Yes, carbon is strong enough and its rapairable.

 

[2WheelsNot4]

Hold your horses, Hoss.
I thought this "debate" was settled twenty years ago. Nowadays all the top-tier bikes are carbon, and aluminum is used only to meet a lower price point. Aluminum certainly doesn't have the longevity against fatigue, as carbon does. So if you want to keep your frame for a long time, carbon is the only way to go. I'll admit I've broken carbon parts, but I've broken FAR more aluminum parts. And the only broken frames I've had to deal with have been aluminum.

A topic of conversation right now on this very forum is regarding "2022 Giant Reign Frame Cracking." It'a a brand new aluminum frame, an many of them are exhibiting cracks. The Fanboys tell us it's not a crack. Other folks don't care what they call it, we just won't ride frames that even "look" like they're cracked. This is only one example, so it's hardly relevant to our discussion, but I mention it because it cracks me up. Get it? "Cracks" me up!

Here's a short video from Pinkbike, that does some failure testing on both aluminum and carbon.

'Testing'
As in the vid above. The frame is held in a jig and the frame flexed to go through the travel of its suspension components.

Right. Try adding 90kg+ to that frame to simulate a rider sitting on it, or throw the weight back and forth to simulate the riders body movements.
So what exactly is it testing ?, whether the suspension units and their linkages work for a long time. Sure, but hardly a fair test of its actual riding conditions.
Example - when the suspension moves up, to indicate a hit, the weight on the top should increase to mimic the weight of he rider bearing down. These tests just dont do that. They just mimic the movement of the frame alone.

 

[Planemo]

Great discussion - I am learning a lot but it appears that there is no clear link between Carbon and expensive - e.g. Cube Stereo and Haibike Allmtn start at under 5K with Carbon front ends.

Tbf Haibike is a bit unusual with their pricing. My alloy AllMtn 3 was £4500, the AllMtn 6 was £5300. For the extra £800 you got not only a full carbon frame/triangle you also got Fox 38's instead of Yari's, and a Fox Float Evol instead of a Deluxe Select+.

That seems like a bargain to me in terms of price difference. But then the Haibike carbon frames have had pivot issues so...

 

[RustyIron]

So what exactly is it testing ?

I don't know, man.
It's just a video.
Go ride your aluminum frame.

 

[2WheelsNot4]

I don't know, man.
It's just a video.
Go ride your aluminum frame.

Just pointing out what appeared to be limitations of such testing.

 

[Growmac]

I'd challenge the idea that aluminium is easy to repair. You need a skilled welder, and then if you don't heat treat the frame again it's going to be seriously weakened. Heat treat it and you'll need to jig it or it's going to go out of alignment, a big job.

TL;DR: if you see an Aluminium frame that's been welded - run!

 

[cozzy]

Yes they probably are, but I dont want one.
I had one carbon bike for 6 months. I spent the whole of that time worried about crashing it on rocks and smashing it plus inspecting the downtube after each rock pinged off it.
It wasn't an enjoyable ownership experience, plus it felt really harsh to ride.
Back on alloy & couldn't be happier.

 

[irie]

Yes they probably are, but I dont want one.
I had one carbon bike for 6 months. I spent the whole of that time worried about crashing it on rocks and smashing it plus inspecting the downtube after each rock pinged off it.
It wasn't an enjoyable ownership experience, plus it felt really harsh to ride.
Back on alloy & couldn't be happier.

A difference between carbon frames and alloy frames that is widely ignored. I'm pretty crap on a mountain bike, but coming from a motorcycle racing background bikes with some flex built/designed into them are much nicer to ride and are less tiring than ultra stiff bikes where the frame provides little or no vibration damping.

 

[Streddaz]

Just pointing out what appeared to be limitations of such testing.

That's also not the only type of testing that they do

Yes they probably are, but I dont want one.
I had one carbon bike for 6 months. I spent the whole of that time worried about crashing it on rocks and smashing it plus inspecting the downtube after each rock pinged off it.
It wasn't an enjoyable ownership experience, plus it felt really harsh to ride.
Back on alloy & couldn't be happier.

That doesn't mean that a carbon fiber frame is no good, you could also worry about an alloy frame just the same if you were not convinced of it's structural integrity.
The suspension would be far more likely contribute to the harshness than the frame. I would bet on a blind test that you couldn't pick the frame type if the suspension components were identical.
I've had a carbon frame Norco Sight for 7 years and done over 10 thousand km on it, raced three EWS enduros and dozens of state rounds and the thing is still going strong.
If an aluminium frame is what makes you feel good, then ride one, but it doesn't mean the carbon frame is rubbish.

 

[Streddaz]

A difference between carbon frames and alloy frames that is widely ignored. I'm pretty crap on a mountain bike, but coming from a motorcycle racing background bikes with some flex built/designed into them are much nicer to ride and are less tiring than ultra stiff bikes where the frame provides little or no vibration damping.

The thing is that carbon frames aren't necessarily ultra stiff, depending on the layup of the carbon fiber the frame can flex in the way they want it.
Some of the new bikes with flex stays for example. This can be done with carbon as they can have it flex in a certain direction but not another. I can be done with aluminium as flexing it will cause it to fail.
Yes, a carbon frame could be too stiff but an aluminium frame could also be too stiff. It's got nothing to do with the material, it's to do with the design.
As I said before, your suspension would make a vastly bigger contribution to how stiff a bike is compared to a frame. If we are talking hardtails the frame would be a bigger factor but if you want a compliant hardtail frame, steel is better than aluminium any day as the grades of steel used in bike frames won't work harden like T6 aluminium will

 

[2WheelsNot4]

Carbon fiber is primarily used in places like moto/formula 1 etc, because it is very light and can be made as stiff and as strong as metal components.
But that doesnt make it the ideal material for everything. Perhaps transferred into MTB, but it is only really at its best in professional racing teams, much like moto/F1, these components are pretty much disposable, and in the latter uses wont see more than a single race before being discarded.

Of the professional teams currently racing on carbon fiber bikes in the tour de France. Do you think any of the bikes they are currently riding on they're going to be using the same bikes next season. No, they will be discarded, sold off because for the disciplines to which carbon fiber was pretty much invented, it is not a product with longevity in mind.

If you are a professional or team rider, looking to shave seconds of a race or personal best, then fine. But the vast majority of users arent pro, arent in a team and are more about personal fitness and fun than shaving time by using lightweight frames or componentry. The bikes in use for these riders are really going to be abused. Falls, general rough handling, hung on the back of a car and bounced 100mile round trip once or twice a week etc etc
In these instances, the bike isnt going to last. its inherent flaws will come to the fore and unless you are happy or well off enough to buy and replace a £2 1/2k+ carbon frame, then you would be far far better sticking to alloy and telling the cycling industrial complex to go f itself.

 

[Streddaz]

Carbon fiber is primarily used in places like moto/formula 1 etc, because it is very light and can be made as stiff and as strong as metal components.
But that doesnt make it the ideal material for everything. Perhaps transferred into MTB, but it is only really at its best in professional racing teams, much like moto/F1, these components are pretty much disposable, and in the latter uses wont see more than a single race before being discarded.

Of the professional teams currently racing on carbon fiber bikes in the tour de France. Do you think any of the bikes they are currently riding on they're going to be using the same bikes next season. No, they will be discarded, sold off because for the disciplines to which carbon fiber was pretty much invented, it is not a product with longevity in mind.

If you are a professional or team rider, looking to shave seconds of a race or personal best, then fine. But the vast majority of users arent pro, arent in a team and are more about personal fitness and fun than shaving time by using lightweight frames or componentry. The bikes in use for these riders are really going to be abused. Falls, general rough handling, hung on the back of a car and bounced 100mile round trip once or twice a week etc etc
In these instances, the bike isnt going to last. its inherent flaws will come to the fore and unless you are happy or well off enough to buy and replace a £2 1/2k+ carbon frame, then you would be far far better sticking to alloy and telling the cycling industrial complex to go f itself.

I don't think that carbon fiber frames are any more disposable than and aluminium frame.
As I've said above, I've had a carbon frame Norco Sight for 7 years and done over 10 thousand km on it, raced three EWS enduros and dozens of state rounds and the thing is still going strong. I've had two aluminium frames before that an one of them cracked and had to be replaced.
If you want to save so cash there's no real issue with buying an aluminium frame as long as you don't believe that you can repair it if it cracks. If you are more concerned with weight and can afford the price difference, going carbon is pretty safe.

 

[cozzy]

That's also not the only type of testing that they do

That doesn't mean that a carbon fiber frame is no good, you could also worry about an alloy frame just the same if you were not convinced of it's structural integrity.
The suspension would be far more likely contribute to the harshness than the frame. I would bet on a blind test that you couldn't pick the frame type if the suspension components were identical.
I've had a carbon frame Norco Sight for 7 years and done over 10 thousand km on it, raced three EWS enduros and dozens of state rounds and the thing is still going strong.
If an aluminium frame is what makes you feel good, then ride one, but it doesn't mean the carbon frame is rubbish.

Disagree. I've put scrapes, gouges and dings in an alloy frame that would have likely splintered carbon and not given it a second thought.

 

[BeBiker]

Disagree. I've put scrapes, gouges and dings in an alloy frame that would have likely splintered carbon and not given it a second thought.

So worse than the impacts in the end of the video ??

 

[billium]

Disagree. I've put scrapes, gouges and dings in an alloy frame that would have likely splintered carbon and not given it a second thought.

That's my concern. Sure, Carbon may be stronger in 'testing' which simulates high loads from jumping etc but could be way more susceptible to damage from a rocky low speed crash. I have no desire to try high jumps in a bike park but know that I will eventually crash on a rocky trail that may even have loose flint. Broken levers - fixable. Dinged Alloy frame - who cares. Splintered Carbon frame - Yikes!

 

[Mikerb]

This discussion on the relative virtues of carbon v ally is largely focusing on the materials and in my opinion....and experience that is not really the defining factor. The defining factor is the expertise of design and construction.

Both are far easier and lower cost to achieve well with ally given that both hydro tubes and frame construction can be largely automated and replicated. Assuming the design and construction method has no flaws, every frame is almost guaranteed to perform the same. Failures on ally frames are mostly due to design failures and will occur in every frame with that design flaw. Design flaws include using inappropriate welding techniques!

Any carbon composite construction is fairly labour intensive and far more expertise is required in the design. Decisions need to be made about the modulus of carbon to be used in whatever mat format, and in what combination and orientation, and whether to incude other materials such as glass or kevlar, and how to integrate component fixing points.

Both materials can be designed to be either stiff or allow some flex, however the degree of stiffness that can be achieved with ally ( with different hydro formed tube shapes) is limited by the grade of ally used. The majority of bike frames use 6xxx series ally which better enables shaping and welding ( TIG)........meanwhile 7075 series ally is both lighter and stronger/stiffer but is much more difficult to both shape and requires a special technique and filler to weld.

My experience with carbon composite is largely with windsurfing equipment where boards, booms and masts can all be made with carbon. A 100% carbon mast 460cm long is fabricated on a mandrel in spiral format using pre preg. It is designed to bend to extremes under the load of full race sails ...with fast reflex. A 100% carbon boom meanwhile is made to be super stiff such that it does not distort under load from the sail....which would alter the outhaul setting. A full carbon board is very light and very stiff......and very fast, but very harsh to use for extended periods! My lesson from decades of buying and using this type of kit is you get what you pay for and there is no such thing as a cheap carbon board, boom, or mast. If the product is indeed 100% carbon it is brittle, meaning any blunt impact can damage the structure, and not necessarilly with any visual damage, and not necessarily leading to immediate failure....that could come at any time thereafter. My buying decisions were based on full knowledge of the composite design.....100% carbon or a mix with other materials, what modulus of carbon, what weave ( UD/matrix etc), what layup process ( wet/pre preg), what epoxy, ........who made it! There is no way I would buy a carbon component without that information.

 

[irie]

This discussion on the relative virtues of carbon v ally is largely focusing on the materials and in my opinion....and experience that is not really the defining factor. The defining factor is the expertise of design and construction.

Both are far easier and lower cost to achieve well with ally given that both hydro tubes and frame construction can be largely automated and replicated. Assuming the design and construction method has no flaws, every frame is almost guaranteed to perform the same. Failures on ally frames are mostly due to design failures and will occur in every frame with that design flaw. Design flaws include using inappropriate welding techniques!

Any carbon composite construction is fairly labour intensive and far more expertise is required in the design. Decisions need to be made about the modulus of carbon to be used in whatever mat format, and in what combination and orientation, and whether to incude other materials such as glass or kevlar, and how to integrate component fixing points.

Both materials can be designed to be either stiff or allow some flex, however the degree of stiffness that can be achieved with ally ( with different hydro formed tube shapes) is limited by the grade of ally used. The majority of bike frames use 6xxx series ally which better enables shaping and welding ( TIG)........meanwhile 7075 series ally is both lighter and stronger/stiffer but is much more difficult to both shape and requires a special technique and filler to weld.

My experience with carbon composite is largely with windsurfing equipment where boards, booms and masts can all be made with carbon. A 100% carbon mast 460cm long is fabricated on a mandrel in spiral format using pre preg. It is designed to bend to extremes under the load of full race sails ...with fast reflex. A 100% carbon boom meanwhile is made to be super stiff such that it does not distort under load from the sail....which would alter the outhaul setting. A full carbon board is very light and very stiff......and very fast, but very harsh to use for extended periods! My lesson from decades of buying and using this type of kit is you get what you pay for and there is no such thing as a cheap carbon board, boom, or mast. If the product is indeed 100% carbon it is brittle, meaning any blunt impact can damage the structure, and not necessarilly with any visual damage, and not necessarily leading to immediate failure....that could come at any time thereafter. My buying decisions were based on full knowledge of the composite design.....100% carbon or a mix with other materials, what modulus of carbon, what weave ( UD/matrix etc), what layup process ( wet/pre preg), what epoxy, ........who made it! There is no way I would buy a carbon component without that information.

The amount of carbon fibre cloth used in so-called "100% carbon" products is far smaller than the combined amount of resin and other fibres used, both by weight and volume.

 

[2WheelsNot4]

My buying decisions were based on full knowledge of the composite design.....100% carbon or a mix with other materials, what modulus of carbon, what weave ( UD/matrix etc), what layup process ( wet/pre preg), what epoxy, ........who made it! There is no way I would buy a carbon component without that information.

I've yet to see any of such information about a manufacturers Emtb frame printed anywhere.

Outwith that, unless you come from a materials design or testing background, or have carried out a specific study, I cant see how the average punter, yourself included would have the qualifications and industry knowledge to judge how the methods of construction, lay up process etc .
I mean no offence to you. But are you capable of looking at a bit of carbon fiber cloth and know exactly what you are looking at, its strengths, weaknesses, how it was produced, the methods and machines used ?.

 

[Mikerb]

The amount of carbon fibre cloth used in so-called "100% carbon" products is far smaller than the amount of resin and other fibres used, both by weight and volume.

Yes of course epoxy resin is a component of the build but my point is it is normal to specify the lay up in % terms so you know what you are paying for. 100% carbon means all the composites consist only carbon fibres in either UD or matrix mats. 80% carbon would signify that the materials in the composite are 80% carbon fibres and 20% some other material such as glass or kevlar. 100% carbon gives the lightest possible build whereas 60% or 80% would be heavier, lower cost, and more impact resistant. Most composite construction now is done using pre preg ( carbon fibre or a fibre mix pre treated with epoxy resin). Layup is by hand in a mould and then baked to a ver specific temperature in an oven. Pre preg ensures the minimum required amount of resin is used.

 

[Mikerb]

I've yet to see any of such information about a manufacturers Emtb frame printed anywhere.

Outwith that, unless you come from a materials design or testing background, or have carried out a specific study, I cant see how the average punter, yourself included would have the qualifications and industry knowledge to judge how the methods of construction, lay up process etc .
I mean no offence to you. But are you capable of looking at a bit of carbon fiber cloth and know exactly what you are looking at, its strengths, weaknesses, how it was produced, the methods and machines used ?.

Mostly! Assuming the carbon composite is bare ( unpainted etc) you can certain see the position of each mat and whether that mat is UD ( uni directional) or matrix ( ie a woven structure of fibres) . Yes, I know the virtues of each. In reality what we should be getting from the manufacturers is a specification.........saying it is carbon means a bsolutely nothing.........you may as well just call it plastic!

 

[irie]

Yes of course epoxy resin is a component of the build but my point is it is normal to specify the lay up in % terms so you know what you are paying for. 100% carbon means all the composites consist only carbon fibres in either UD or matrix mats. 80% carbon would signify that the materials in the composite are 80% carbon fibres and 20% some other material such as glass or kevlar. 100% carbon gives the lightest possible build whereas 60% or 80% would be heavier, lower cost, and more impact resistant. Most composite construction now is done using pre preg ( carbon fibre or a fibre mix pre treated with epoxy resin). Layup is by hand in a mould and then baked to a ver specific temperature in an oven. Pre preg ensures the minimum required amount of resin is used.

I was taking issue with the misleading marketing use of the term "100% carbon" which is intended to mislead purchasers into believing that such described products consists of only carbon fibre which are perceived as superior and thus worthy of premium pricing.

(FYI - in a previous life I was involved with building windsurfing boards using both wet layup and prepreg).

 

[Mteam]

Yes they probably are, but I dont want one.
I had one carbon bike for 6 months. I spent the whole of that time worried about crashing it on rocks and smashing it plus inspecting the downtube after each rock pinged off it.
It wasn't an enjoyable ownership experience, plus it felt really harsh to ride.
Back on alloy & couldn't be happier.

Why were you worried about the carbon bike? genuinely interested....I mean what made you think you should be worried, because I dont give it a second thought?

I've had various carbon bikes and dont worry about them any more than the alloy bikes I've had. The carbon bikes have been crashed, dropped, had massive rocks bounce off the downtube , and generally treated the same as the alloy bikes, and they've been fine.

I've had 2 alloy bikes and 3 carbon bikes . The carbon bikes have not failed in any way. One aluminium bike cracked on a weld, the other got dented by a rock but I carried on riding it for a couple of years .

 

[2WheelsNot4]

In reality what we should be getting from the manufacturers is a specification.

And do you have the experience or qualifications to understand what any of that would mean ?. I would think the majority of riders, by which i mean 99.9% wouldnt have a clue.

 

[BeBiker]

---what if---
Do the big manufacturers sell an empty carbon frame ?
What would be the price for the front frame of my fully ?
1000€ ? 2000€ ?

 

[Growmac]

What’s your plan with that Spec. Are you going to run an FE model to analyse how you think it’s going to hold up? Get a sample and impact test it?

 

[Mikerb]

What’s your plan with that Spec. Are you going to run an FE model to analyse how you think it’s going to hold up? Get a sample and impact test it?

Come on.........you buy a car and dont understand any of the spec? You buy a sat nav and do not understand the spec? You buy endless components for a bike.........bars, suspension, brakes and you do not understand any of the spec? Yet you are happy to pay a premium of £2k because it says the frame is made of carbon...and thats it!!! Carbon fibre composites are hardly anything new!

 

[Silent Drone]

I had to check the date of the original post, this feels like a thread from the 2000’s. Lol.

There’s nothing inherently inferior about an aluminum frame, especially on an ebike where weight is basically a non-issue. But it’s not stronger or more durable than a carbon frame. I can’t believe in 2022 there are people who still believe that carbon frames are fragile or prone to failure. The material is very tough.

 

[Streddaz]

Disagree. I've put scrapes, gouges and dings in an alloy frame that would have likely splintered carbon and not given it a second thought.

How do you know it would have splintered carbon? You only had the bike 6 months.
In any case, there's thousands of carbon bikes out there, most of the people I ride and race with have carbon framed bikes. I hardly ever see a failure and no more than aluminium framed bikes.