Al, C, Ti. What's the deal?

[ItalianStallion]

Hi guys,

I would like to know what are the main reasons for using aluminium, carbon or titanium for a bike.

The reason I am asking this is because I was reading about the bikes present in the tour, and one comment regarding a bike (can't remember which one) was that it had a aluminium frame and carbon fork. It also said that it was now common amongst top bikes.

This doesn't quite add up to me.

I will be back with the article and the bike name, but in the mean time, can anyone confirm/disagree with this?

[hwttdz]

Aluminum with carbon fork/seatpost is pretty common. Both aluminum and carbon have impressive stiffness to weight ratios. Carbon can take a little more of the high frequency buzz out of the ride, and I think aluminum is maybe a tad stiffer. Ti is supposedly like steel, removes some high frequency buzz, some people complain about stiffness. But really frame qualities are determined more by the design than the material, i.e. aluminum is not an inherently stiff material therefore it is designed with larger tube diameters which increase stiffness. There is no ideal material for all applications, and almost never is there an ideal material even for a specific application.

[mjw_byrne]

Originally posted by ItalianStallion
Hi guys,

I would like to know what are the main reasons for using aluminium, carbon or titanium for a bike.

There are dozens of sites on the net and even other threads in these fora which deal with your question, and because it's a question of a slightly technical nature, it often gives rise to rampant speculation, pseudo-science from unqualified individuals (these people invariably find themselves being jumped all over by people who actually know what they're talking about) and a fair bit of flaming. Basically, these materials' properties are as follows:

Aluminium: (i.e. various aluminium alloys)

Pros:
-Nice and light
-Can make stiff frames
-Easy to work, reasonably easy to weld
-Fairly corrosion-resistant

Cons:
-Prone to cracking and fatigue
-If damaged, often becomes unusable
-Said to give a "harsh" ride quality (fiercely debated, though - depends on construction as well as material)


Titanium: (titanium alloys)

Pros:
-Very durable: more likely to survive a crash than Al or CF, and said to last longer
-Virtually corrosion-proof
-Said to give soft ride without sacrificing responsiveness, efficiency, safety etc. (again, hotly debated)

Cons:
-Exorbitantly expensive
-Damn hard to machine/weld (hence the cost)

Carbon fibre composites:

Pros:
-Great strength-to-weight ratio - can make strong, stiff, light frames
-Said to dampen road vibrations without being whippy (usual caveats about subjective qualities apply)
-Corrosion-proof

Cons:
-If it fails, often fails catastrophically (e.g. just riding along, then it goes bang and you're lying on the road)
-Very expensive
-Reliability concerns, because it's a relatively new technology
-Can't be repaired

The reason I am asking this is because I was reading about the bikes present in the tour, and one comment regarding a bike (can't remember which one) was that it had a aluminium frame and carbon fork. It also said that it was now common amongst top bikes.

This doesn't quite add up to me.

I will be back with the article and the bike name, but in the mean time, can anyone confirm/disagree with this?

Aluminium frame with a carbon-fibre fork is very, very common among road/racing bikes, from middle-of-the-road machines costing USD1,000 all the way up to the uber-expensive top-end kit used by the pros. Aluminium has been around for a long time, so even though Ti and CF have some great properties, the wealth of experience in working with Al that has been accumulated over the years means that frame designers can make some great stuff out of it. You can make a fork out of Al, steel, CF, Ti or even mixes of these materials (steel steerer and carbon legs, or Alu steerer with carbon legs are both popular combinations), but carbon forks are strong, stiff and light, and so have become very popular.

[boudreaux]

Originally posted by mjw_byrne
Ah yes, the obligatory insult from boudreaux. Care to back it up? I'll hit just a few. All Ti is not exorbantly expensive,as there is inexpensive stuff. Soft riding Ti is just hooey, as it depends on the tube diameter,and lesser degree butting shaping and alloy. There are Ti frames out there that ride like jackhammers. Just like Al fframes that use to be built with standard diameter tubes were noodles. There is inexpensive CF,It's not corrosion proof,as there can and have been issues with galvanic corrosion when bonded to lugs of other materials, and CF, particularly any frame that is bonded can be repaired.And, CF is not exactly new technology.

[boudreaux]

Originally posted by ItalianStallion
Hi guys,

I would like to know what are the main reasons for using aluminium, carbon or titanium for a bike.

The reason I am asking this is because I was reading about the bikes present in the tour, and one comment regarding a bike (can't remember which one) was that it had a aluminium frame and carbon fork. It also said that it was now common amongst top bikes.

This doesn't quite add up to me.

I will be back with the article and the bike name, but in the mean time, can anyone confirm/disagree with this? Given current technlogy, CF forks are relatively cheap to make,ride well and are light. They are standard fare on almost all but the lowest end road bikes today. Same goes for CF rear stays, wich may or may not add any real value, but are also common on frames of all other materials. CF has great bling value and it's use is a great marketing tool.

[mjw_byrne]

Any comment about how expensive something is is obviously a relative comment. In general, Ti frames and bikes cost more than Al ones do. There exist counterexamples, but unlike you, this does not prevent me from observing the trend. If my wording wasn't utterly watertight about this, who cares - I'm not a lawyer and this is not a courtroom. I said in my post that observations about ride quality were the subject of debate and that ride quality is influenced by construction as well as material, so I don't know why you're regurgitating that stuff. As for CF frames and lugs of other materials and galvanic corrosion, you may well be correct, but I was talking about all-CF frames. And your statement that "any frame that is bonded can be repaired" is simply not true. I don't know where you got that one.

[boudreaux]

Originally posted by mjw_byrne
Any comment about how expensive something is is obviously a relative comment. In general, Ti frames and bikes cost more than Al ones do. There exist counterexamples, but unlike you, this does not prevent me from observing the trend. If my wording wasn't utterly watertight about this, who cares - I'm not a lawyer and this is not a courtroom. I said in my post that observations about ride quality were the subject of debate and that ride quality is influenced by construction as well as material, so I don't know why you're regurgitating that stuff. As for CF frames and lugs of other materials and galvanic corrosion, you may well be correct, but I was talking about all-CF frames. And your statement that "any frame that is bonded can be repaired" is simply not true. I don't know where you got that one. Bonded frames can be repaired,and there is an outfit called Havnoonian Racing in the US that has made bonded frames of all materials for years and was or even may still be the repair facility for other manufacturers. Trek is an ALL CF frame with CF lugs, and can be repaired. Same for colnago C-40/50. Your'right, yer no Perry Mason.

[mjw_byrne]

Your original claim was that any bonded frame can be repaired, not that some of them can. And what do you mean by "can be repaired"? Are we talking scratches and dents, or snapped tubes? Ti and Al frames are tricky to repair major damage in, but it can often be done if you have the tools/money/know-how - often it may be cheaper to replace the frame but bikes can have sentimental value. I notice you have conveniently ignored my other points, too.

[boudreaux]

Originally posted by mjw_byrne
Your original claim was that any bonded frame can be repaired, not that some of them can. And what do you mean by "can be repaired"? Are we talking scratches and dents, or snapped tubes? Ti and Al frames are tricky to repair major damage in, but it can often be done if you have the tools/money/know-how - often it may be cheaper to replace the frame but bikes can have sentimental value. I notice you have conveniently ignored my other points, too. Maybe you are confusing bonded with monocouqe? Bonds/lugs can be undone.Tubes and dropouts can be replaced when bonded. There are even differences in the repairability of aluminum. 6xxx isn't due to the need for solution quenching to re heattreat it.

[mjw_byrne]

I'm familiar with the difference between bonded and monocoque, but are you sure bonds can just be undone? Surely many bonded frames are bonded permanently. In any case, not all bonded frames are bonded tube by tube - check out Lemond's spine/cockpit constructions. It's true that alu frames might need heat treatment after welding, which I suppose could be arranged for the right price....although this would admittedly probably be a very high price, and therefore not worth it.

[boudreaux]

Originally posted by mjw_byrne
..... and because it's a question of a slightly technical nature, it often gives rise to rampant speculation, pseudo-science from unqualified individus You got this part right. AFWIW, Aluminum isn't necessarily nice and light. Again it depends on the tubing. It comes in all flavors like ice cream and BS.

[ItalianStallion]

Thanks for the replies guys.

Not knowing much about frame technologies (or bikes, for that matter..... :(), it sounded a bit strange to hear pro's ride the same materials as I do. Also considering that the reason why I am not riding a full carbon frame is because I don't have any money......

But, hey, your posts more than explained the reasons!!

Thanks!