Question about aluminium frame challenge to carbon fibre frames?

[Ajax Bay]

Aluminium frames appear to be resurgent in challenge to carbon fibre frames, in both light weight, and compliance. Is this sensible with regard to durability, and longevity? Aluminium has problems in situations where it is subject to continual flexing, which leads to fatigue failure. (Sudden snapping.) . . . . Carbon fibre, provided it does not exceed its design limits of flexing, is almost impervious to fatigue.
It will be interesting to see if these lightweight alloy bikes with higher compliance (comfort) now challenging the role of carbon fibre

Where have you learnt there has been a resurgence in alu ?
Magazine article ? Bloke who owns a bike shop ?

Cycling Plus magazine appear to be favouring the 'latest breed' of aluminium bikes in their tests as worthy rivals to carbon fibre bikes.
Aluminium alloys have a definite fatigue half life when subject to flexing. The more the flex, the shorter the half life, after which the alloy is claimed to case harden and become more brittle, which eventually leads to failure. . . . . but the latest aluminium bikes are lighter and boast more compliance (flexing) which is the opposite to rigidity.

The other obvious shortcoming of aluminium alloy is corrosion from heavily salted winter roads, especially where the alloy is mixes with stainless steel fittings which causes galvanic corrosion. We all choose what risks to take, and extensive use of alloy and its failings in salt water has turned me against its use, long term, on salty winter roads, as my older alloy Boardman Comp bike was heavily used. I was almost waiting for that sudden bang, as something snapped!

I'll ask again @Rain drops , where do you get this "Aluminium frames appear to be resurgent in challenge to carbon fibre frames" - is this just marketing hype from some magazine? Both materials are perfectly good to make bicycle frames from. Who's trying to create a 'challenge' story?
From your posts I'm not sure you grasp the failure from fatigue mechanisms ("definite fatigue half life"!!) or the disconnect between that and "galvanic corrosion".
Do you seriously think that "obvious shortcoming of aluminium alloy is corrosion from heavily salted winter roads"?
I'm guessing you're just cut and pasting here, from some marketing codswallop (but "you don't have to swallow and regurgitate it, uncritically!"), but then this has "turned you against" an aluminium framed bike.
And how much galvanic corrosion did you experience on your Boardman? Did your seatpost get stuck?
Well done getting 5 pages worth.

 

[SkipdiverJohn]

'Cannondale, for example, make some alloy frames that are at least equal to their carbon ones, and almost as light.'

Well they would say that wouldn't they. (Along with some of the bike mags.) It's called advertising, or the big sell. But you don't have to swallow and regurgitate it, uncritically!

Cannondale have made some very good aluminium alloy frames which have lasted many years of intensive use. That's a big compliment from me as I'm not generally a fan of alloy frames, but there are some good ones out there.

Old Cannondales tended to have very good, tidy welding, without faults like undercuts that cause stress raisers and can propagate cracking.
Weld defects are probably the biggest single cause of crack failures in metallic cycle frames, and alloy and titanium frames are more prone to this than steel, especially cooking grade hi-tensile.

 

[ColinJ]

That escalated quickly !

I did a few rides with a former forum rider. He woke up in hospital with his family at his bedside after a serious accident caused by the front end of his CF MTB suddenly snapping off!

 

[keithmac]

How many fatalities from failing carbon forks vs aluminium I wonder 🤔

 

[DCBassman]

Oh dear! Quote-

'Cannondale, for example, make some alloy frames that are at least equal to their carbon ones, and almost as light.'

Well they would say that wouldn't they. (Along with some of the bike mags.) It's called advertising, or the big sell. But you don't have to swallow and regurgitate it, uncritically!

Also, nobody here is suggesting that carbon fibre is ideal for mountain bikes. (though some manufacturers do sell such). As stated, mountain bike frames can be made strong and rigid from aluminium alloy, with minimal flexing and reduced chance of metal fatigue, though quite a few hot shots DO break them, and let the suspension take the flexing and shock loading.

From day one with aluminium, it was understood that the frames of the time, which had tubes to the same dimensions as steel bikes, glued together, would last top pros one season. That same frameset would last the more mundane cyclist, essentially, as long as any steel frame. As the technology improved, this became even more so, and the pros would get longer out of a bike. Mountain bikers can break anything; it's the nature of their sport.
Unless you do tens of thousands of kilometres a year of really hard riding, you are, barring accidents, unlikely to even put severe stress on ANY bike frame.

 

[Ajax Bay]

How many fatalities from failing carbon forks vs aluminium I wonder 🤔

I think the number of aluminium framed bikes with aluminium forks is rather small. I have a late seventies glued and screwed ALAN with a fork made of Al tubing (which has done many thousands of miles, though not recently), but I think that manufacturers determined/realised that aluminium was not a sensible material choice, in the same way as the number of forks made of Ti is very small.
So I'll be guessing that far more carbon forks have failed than ones with blades made with aluminium (this based on no evidence).
Perhaps a similar question could be addressed: "How many fatalities from failing carbon bars vs aluminium (as a proportion of the 'bar' population)?"

 

[Daninplymouth]

Don’t have much to add other than I’m riding an ali endurance bike and have been smashing some popular strava segments around me so it’s definitely not slow. Although I do question if I’d be much faster on a semi aero carbon frame 🤔

 

[I like Skol]

Don’t have much to add other than I’m riding an ali endurance bike and have been smashing some popular strava segments around me so it’s definitely not slow. Although I do question if I’d be much faster on a semi aero carbon frame 🤔

Lol! I ride an old 1996 hardtail MTB, a steel framed commuter road bike with panniers and mudguards and a carbon gravel bike on 35mm tyres rated as awful for drag on that tyre comparison website. Don't have a clue what any of them weigh? I have managed to achieve 40+ Strava segment KOMs using all three bikes.


I reckon it's not about the bike......

 

[cougie uk]

Lol! I ride an old 1996 hardtail MTB, a steel framed commuter road bike with panniers and mudguards and a carbon gravel bike on 35mm tyres rated as awful for drag on that tyre comparison website. Don't have a clue what any of them weigh? I have managed to achieve 40+ Strava segment KOMs using all three bikes.


I reckon it's not about the bike......

That sounds highly impressive. Road koms?

 

[FishFright]

Cannondale have made some very good aluminium alloy frames which have lasted many years of intensive use. That's a big compliment from me as I'm not generally a fan of alloy frames, but there are some good ones out there.

Old Cannondales tended to have very good, tidy welding, without faults like undercuts that cause stress raisers and can propagate cracking.
Weld defects are probably the biggest single cause of crack failures in metallic cycle frames, and alloy and titanium frames are more prone to this than steel, especially cooking grade hi-tensile.

Also were well known as Crack n Fails back in the day but they had a great replacement policy.

 

[I like Skol]

That sounds highly impressive. Road koms?

Does it sound any better if I say I'm nearly 50, work 12hr shifts and religiously don't 'train'?

 

[Rain drops]

As a final attempt to put my side of it, much information about stress failure in aluminium alloys can be gleaned from the aero industry. Fatigue testing at fixed intervals, and replacement sections, just adding doublers over cracks in older lower performance aircraft is routine. Salt corrosion also adds to the problems on low flying smaller aircraft used in marine environments.

My experience of alloy fatigue failure is from using alloy booms for windsurfing (and in earlier times alloy masts) in surf, and for salt water corrosion failures due to Galvanic action in mast tracks of old long racing boards. The earlier alloy booms used to last about a year when constantly flexed in surf conditions, (snap after the alloy lost its spring and became brittle with use) ,and the alloy mast tracks held in the board by stainless steel screws would last around 3 years before the holes in the alloy beneath the screws would corrode away., the whole mast track, complete with rig would yank clean out of the board. (Those folk who only used alloy booms sparingly, mainly in summer and then just laid them up would have corrosion failure within about a couple of years, rather than fatigue failure.)

My Boardman alloy bike was used every winter on snowy and salted Dales passes, because I found it fun to ride (or try to) a narrow tyre road bike in such conditions. I had no idea how the stressed area around the bottom bracket welds (the tubing just beyond the welds) had corroded inside, and possibly been weakened, so I laid it up and bought a carbon fibre bike. (Spesh Roubaix)

That was my assessment at that time. It may have been wrong according to those who claim to be still riding alloy frames in such winter conditions for many many years, but it was my neck at stake, and I make my own decisions.

 

[Ajax Bay]

As a final attempt to put my side of it, . . .
My Boardman alloy bike was used every winter on snowy and salted Dales passes, because I found it fun to ride (or try to) a narrow tyre road bike in such conditions. I had no idea how the stressed area around the bottom bracket welds (the tubing just beyond the welds) had corroded inside, and possibly been weakened, so I laid it up and bought a carbon fibre bike. (Spesh Roubaix)

That was my assessment at that time. It may have been wrong according to those who claim to be still riding alloy frames in such winter conditions for many many years, but it was my neck at stake, and I make my own decisions.

1) Not quite sure what you mean by 'my side': what is your hypothesis? Is it "Aluminium frames are more likely to fail catastrophically than carbon ones"? Sorry to be so thick.
2) How (by what process) do you think "the stressed area around the [Al framed) bottom bracket welds (the tubing just beyond the welds) [might have] corroded inside"? What is the chemical process here and how do you think salts get inside a frame to do the dastardly deed? Wouldn't steel frames all be falling apart by now, "corroded" from the "inside"? And has this got anything to do with fatigue life (see your posts above)?
3) Of course we all make our "own decisions" "my neck at stake" - give us a break - you decided to ride multiple "winter on snowy and salted Dales passes, because [you] found it fun [on] narrow tyre". Then you buy a carbon framed bike and use that instead. Ride on.
4) Your Spesh has an aluminium stem and bar, right? Are you not concerned they might fail?
5) But your post posits (I think) that carbon frames are less likely to fail than Al ones (or have I misunderstood?) I am just seeking your basis for this assertion. A good start would be to share where you get this "Aluminium frames appear to be resurgent in challenge to carbon fibre frames" - is this just marketing hype from some magazine?"

 

[Alex321]

Oh dear! Quote-

'Cannondale, for example, make some alloy frames that are at least equal to their carbon ones, and almost as light.'

Well they would say that wouldn't they. (Along with some of the bike mags.) It's called advertising, or the big sell. But you don't have to swallow and regurgitate it, uncritically!

I can't think of a reason why "they would say that wouldn't they". They mostly try to sell carbon framed bikes at a premium over their alloy framed bikes. So it isn't in their interest to say the alloy frames are as good. It certainly isn't going to be something they will just say without being very sure it is true.

 

[Alex321]

As a final attempt to put my side of it, much information about stress failure in aluminium alloys can be gleaned from the aero industry. Fatigue testing at fixed intervals, and replacement sections, just adding doublers over cracks in older lower performance aircraft is routine. Salt corrosion also adds to the problems on low flying smaller aircraft used in marine environments.

My experience of alloy fatigue failure is from using alloy booms for windsurfing (and in earlier times alloy masts) in surf, and for salt water corrosion failures due to Galvanic action in mast tracks of old long racing boards. The earlier alloy booms used to last about a year when constantly flexed in surf conditions, (snap after the alloy lost its spring and became brittle with use) ,and the alloy mast tracks held in the board by stainless steel screws would last around 3 years before the holes in the alloy beneath the screws would corrode away., the whole mast track, complete with rig would yank clean out of the board. (Those folk who only used alloy booms sparingly, mainly in summer and then just laid them up would have corrosion failure within about a couple of years, rather than fatigue failure.)

My Boardman alloy bike was used every winter on snowy and salted Dales passes, because I found it fun to ride (or try to) a narrow tyre road bike in such conditions. I had no idea how the stressed area around the bottom bracket welds (the tubing just beyond the welds) had corroded inside, and possibly been weakened, so I laid it up and bought a carbon fibre bike. (Spesh Roubaix)

That was my assessment at that time. It may have been wrong according to those who claim to be still riding alloy frames in such winter conditions for many many years, but it was my neck at stake, and I make my own decisions.

Even on wet salted/ gritted roads though, the amount of salt water getting on the bike frame is going to be FAR less than the amount getting onto the boom of a windsurfer. And things like the bottom bracket are also much better sealed, meaning even less getting into the iternals of the frame.