Ali v Carbon

Hondated

I am currently riding a Bianchi ML3 Veloce Equiped Triple and i am thinking about getting a carbon bike.Can anyone tell me whether I would notice the difference. Obviously it will be lighter but then again I am hardly a lightweight anyhow.
What I am thinking of getting is a Specialised Roubaix or a Cannondale Synergy I think it is and both of these bikes have shock absorbing materials in their friends so my understanding is that this makes for a more comfortable ride. Can anyone confirm that it does.I ask because if I do buy one its going to cost £2.5k so I really don,t want to waste money particularly as I have yet to get it.

redddraggon

If you want a Comfortable robust bike, go Titanium.

A very nice one could be built up for your £2.5K

bompington

Was that before or after Ali v. Frazier?

dennisn

bompington wrote:

Was that before or after Ali v. Frazier?

ugo.santalucia

The only noticeable difference between aluminium alloy (both the 6 and the 7 series used in bike frames) and carbon fibre composite (CFC) is that, when it fractures, the former absorbs more energy than the latter... which means it bends and maybe saves your life (or maybe not).
Aluminium of course is more susceptible to fatigue even at low stress than other metals like steel alloys and titanium alloys... so as an average it will last less. Then of course somebody will comment that he had an aluminium frame since 1976 and it's still fine.
CRC fails a bit more unpredictably and in the cycling industry the material is not really tested for fatigue and creep, only tensile tests are run, but they don't tell much, other than carbon is great... stiff and strong (in tension, sadly there is no tension for a bike frame). What we know is that when it fails, it does so very fast.

There's an interesting website called busted carbon, or something similar... have a look at the pictures, they are quite instructive.

Comfort is not down to materials but frame geometry and more importantly tyre size and pressure. Those who say differently lie, cyclists for ignorance and manufacturers... well, do I need to tell you why?

These are facts... you make your choice

bompington

ugo.santalucia wrote:

sadly there is no tension for a bike frame

I am not qualified to comment on most of this post (not that most people round here regard that as a problem), but...
Engineering 101: When you bend something, there is tension in one side and compression in the other. The chief issue with bike frames is bending, not direct compression: so there definitely is tension in a bike frame.
Can anybody comment (evidence based preferably) on exactly what the mechanism is when carbon frames do break?

ugo.santalucia

bompington wrote:

ugo.santalucia wrote:

sadly there is no tension for a bike frame

I am not qualified to comment on most of this post (not that most people round here regard that as a problem), but...
Engineering 101: When you bend something, there is tension in one side and compression in the other. The chief issue with bike frames is bending, not direct compression: so there definitely is tension in a bike frame.
Can anybody comment (evidence based preferably) on exactly what the mechanism is when carbon frames do break?

Yes.
The tensile test is specifically designed to measure the Young's Modulus and tensile strength (or ultimate in the case of brittle materials like CFC). It does not involve bending, but ripping apart aspecmen by pulling from the two edges. Carbon fibre performs very well and in any application where this type of load is applied CFC should be used. This is not the case in bike frames.

More worrying is the behaviour upon fracture, or the "toughness", which is the amount of energy absorbed before rupture (essentially the integral of the area underlying a stress-strain curve up to the fracture point). In the case of CFC is very low... hence more chances of getting seriously injured when the part fails for any reason.

Bikerbaboon

bompington wrote:

ugo.santalucia wrote:

sadly there is no tension for a bike frame

I am not qualified to comment on most of this post (not that most people round here regard that as a problem), but...
Engineering 101: When you bend something, there is tension in one side and compression in the other. The chief issue with bike frames is bending, not direct compression: so there definitely is tension in a bike frame.
Can anybody comment (evidence based preferably) on exactly what the mechanism is when carbon frames do break?

you cant say what the mechanisam would be with out knowing how the frame is breaking.

if its haveing a off and the chain stay gerring ground away by the road is one thing. haveing the head snap off in a large pot hole would be another.

balthazar

EFBe conduct fatigue testing of bikes, though I don't know how many manufacturers take them up on it. There is an interesting account of an older test here:

http://www.sheldonbrown.com/rinard/EFBe ... e_test.htm

However, the OP was about comfort, and in that regard, I'll agree with Ugo, and say that ride quality is affected only by tyre volume and inflation pressure, your saddle, and what bar tape you use. Frame material and design has no bearing on the matter, within ordinary ranges, apart from novel frames with suspension elements (not those silly Specialized "inserts", or similar!).

redddraggon

ugo.santalucia wrote:

Yes.
The tensile test is specifically designed to measure the Young's Modulus and tensile strength (or ultimate in the case of brittle materials like CFC). It does not involve bending, but ripping apart aspecmen by pulling from the two edges.

You're not a materials scientist are you?

There are many tests to determine Young's Modulus including the 3-point bending test:

http://en.wikipedia.org/wiki/Three_point_flexural_test

redddraggon

ugo.santalucia wrote:

sadly there is no tension for a bike frame

You aren't even an engineer are you?

ugo.santalucia

redddraggon wrote:

ugo.santalucia wrote:

Yes.
The tensile test is specifically designed to measure the Young's Modulus and tensile strength (or ultimate in the case of brittle materials like CFC). It does not involve bending, but ripping apart aspecmen by pulling from the two edges.

You're not a materials scientist are you?

There are many tests to determine Young's Modulus including the 3-point bending test:

http://en.wikipedia.org/wiki/Three_point_flexural_test

Yes, but the numbers quoted are tension. carbon wouldn't outperform metal alloys in bending. That unless you find a way to have 3D distribution of the fibres, rather than a lay-up of bidimentional sheets.. but anyway, who gives a damn about stiffness, the point is toughness... there is no toughness in carbon... it snaps, it doesn't absorb energy... that's a problem

Splottboy

I like Youngs Modulus, but I also like Youngs Seafood pie.
Which is best?
There's only one way to find out...
FIGHT!!!

ugo.santalucia

redddraggon wrote:

ugo.santalucia wrote:

sadly there is no tension for a bike frame

You aren't even an engineer are you?

A bike frame is not subject to particular tensile stress, it's the diamond geometry.

Anyway.. the really worrying thing is that one can sell a 900 grams frame without any particular specification... unlike cars, there are no crash tests or dummies... nothing like that... even if failures and crashes are quite common and the sale price is in the same range of a cheap car.

It seems to me that the industry needs some sort of regulation that goes beyond the ludicrous ISO standards or the UCI rules for racing products. Components need to be properly tested, ideally by an independent entity which certify the quality and integrity of a product.

I suspect we wouldn't see many 900 grams frames around.

... yes, very off topic, but interesting discussion, nonetheless... more interesting than the usual plethora of "get a planet-x they're great!"

redddraggon

ugo.santalucia wrote:

redddraggon wrote:

ugo.santalucia wrote:

sadly there is no tension for a bike frame

You aren't even an engineer are you?

A bike frame is not subject to particular tensile stress, it's the diamond geometry.

In such a 3-dimensional structure there will be both tensile and compressive stresses.

What about when you are sprinting of the saddle? You are flexing the frame......

ugo.santalucia

redddraggon wrote:

ugo.santalucia wrote:

redddraggon wrote:

ugo.santalucia wrote:

sadly there is no tension for a bike frame

You aren't even an engineer are you?

A bike frame is not subject to particular tensile stress, it's the diamond geometry.

In such a 3-dimensional structure there will be both tensile and compressive stresses.

What about when you are sprinting of the saddle? You are flexing the frame......

I think the majority of catastrophic failures are due to compressive stresses (potholes, roughness on the fork and downtube)... flexing-bending (heavy on carbon bars).
Carbon per se wouldn't be a drama... if you're not doing the Paris-Roubaix (remember Hincapie in 2008?) the lack of carbon is a serious problem.... 900 grams... there is very little material there.

redddraggon

ugo.santalucia wrote:

I think the majority of catastrophic failures are due to compressive stresses (potholes, roughness on the fork and downtube)

For a crack or fracture to continue growing there much be a tensile stress at the crack tip - if there were only compressive stresses cracks would not grow.

TheStone

I'm not sure on the science side of this. I've read sheldon's page on it, but it didn't seem
to agree with my personal experience, but then that could be down to other factors in
the frame build.

Comparing my old Giant Alu and my newer Litespeed Ti, the comfort difference over
longer rides is huge. I mean HUGE. Everything else similar. Both weigh the same and
are quick, but the Ti is so much more comfortable.

ugo.santalucia

redddraggon wrote:

ugo.santalucia wrote:

I think the majority of catastrophic failures are due to compressive stresses (potholes, roughness on the fork and downtube)

For a crack or fracture to continue growing there much be a tensile stress at the crack tip - if there were only compressive stresses cracks would not grow.

Thing with carbon is not much about creep, but real fast failure... no warnings. Lots of failures on brand new components... unheard of in metal alloys... well, that unless you crash badly.

I don't understand the appeal of carbon... I do fall once a year or so... once it's the ice, once is some idiot clubmate who overlaps his wheel, once I misjudge a hairpin... do I want a 900 grams frame which will not survive the crash (not to speak about the total lack of toughness)... I really don't understand... to save a pound or so... I keep my pound thank you

STEFANOS4784

Hondated wrote:

Can anyone confirm that it does.I ask because if I do buy one its going to cost £2.5k so I really don,t want to waste money particularly as I have yet to get it.

I noticed a big difference when i got my carbon bike, people get niggly on this issue.
A cheap carbon is not as good as expensive alu, carbon melts in rain, alu will brake your bones due to the harsh ride. etc etc.

In reality if your spending that cash on a bike then you can surely expect a test ride?

A new bike is always a good idea but obviously depends on your circumstances, where are you located? Surely there's someone with a carbon bike who'll let you give it a try :roll:

ravey1981

Carbon melts in the rain? What?

What about carbon mtbs then? They get ridden in the rain and mud and I've never seen one melt...

ugo.santalucia

STEFANOS4784 wrote:

Hondated wrote:

Can anyone confirm that it does.I ask because if I do buy one its going to cost £2.5k so I really don,t want to waste money particularly as I have yet to get it.

I noticed a big difference when i got my carbon bike, people get niggly on this issue.
A cheap carbon is not as good as expensive alu, carbon melts in rain, alu will brake your bones due to the harsh ride. etc etc.

In reality if your spending that cash on a bike then you can surely expect a test ride?

A new bike is always a good idea but obviously depends on your circumstances, where are you located? Surely there's someone with a carbon bike who'll let you give it a try :roll:

... don't forget the carbon eating parassites in your garage.

On a more serious note, I don't know how much of an issue is UV light on the epoxy resin... probably not much if the lacquer is intact

STEFANOS4784

In other words, it's all rollox which is overblown due to too much ready not enough ridy

bompington wrote:

exactly what the mechanism is when carbon frames do break?

They get rained on


Bottom line is that if one was noticably superior in every way then it would be the only material used...........







Buy carbon 8)

dennisn

ugo.santalucia wrote:

Comfort is not down to materials but frame geometry and more importantly tyre size and pressure. Those who say differently lie, .........

+1

Hondated

Thanks everyone for your replies. I think that by asking the question I may have saved my self some money as well because it seems to me that before I buy I should improve my Bianchi ie better tyres, inflated correctly. better bar tape.And to be honest the main weight saving I need to do is to me rather than the bike.I also enjoyed reading the engineering replies and the Ali v Bianchi was after the Ali v Frazier .

ugo.santalucia

STEFANOS4784 wrote:

In other words, it's all rollox which is overblown due to too much ready not enough ridy

Bottom line is that if one was noticably superior in every way then it would be the only material used...........







Buy carbon 8)

No... if you race at a certain level (basically if somebody pays for your cyclingware) you want carbon, because it's the lightest among the stiff material. But if you race you are prepared to crash and dump bike and bones (like HIncapie at the Paris Roubaix).

If you ride a bike for fun and pleasure, doing sportives or the occasonal racing at cat. 4 (maybe 3), like the vast majority of people round here... you should probably look at a bike where quality of built and durability are more important than ultimate performance. Materialwise, steel and titanium would outperform aluminium and carbon fibre in this catgory. Steel is cheaper than Ti, hence the most sensible choice. If you combine it with the ease of repair and PROVED durability over decades, it's a no brainer really...

The problem is that most people think they're Cavnedish... or Contador

redddraggon

ugo.santalucia wrote:

The problem is that most people think they're Cavnedish... or Contador

I think I'm Boonen, maybe Cancellara

STEFANOS4784

Chad Gerlach here 8)

ugo.santalucia

redddraggon wrote:

ugo.santalucia wrote:

The problem is that most people think they're Cavnedish... or Contador

I think I'm Boonen, maybe Cancellara

Well... then I'll see you on the 6th of June at the Paris-Roubaix for amateurs... if we end up sprinting in the velodrome, I'm sure you'll win!

You doing that Tom?

redddraggon

ugo.santalucia wrote:

redddraggon wrote:

ugo.santalucia wrote:

The problem is that most people think they're Cavnedish... or Contador

I think I'm Boonen, maybe Cancellara

Well... then I'll see you on the 6th of June at the Paris-Roubaix for amateurs... if we end up sprinting in the velodrome, I'm sure you'll win!

You doing that Tom?

I wanted to do it, but I spent too much this year already.

Maybe in 2012

STEFANOS4784

My posts were really tongue in cheek, the guys been a member for ages, maybe he should know by now