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The life of Ti

James Spender
21 Apr 2016

Is a titanium bike worth the inflated pricetag? Cyclist examines what it is about this metal that lifts it up above other materials.

The last time a steel bike won the Tour de France was in 1994, when Miguel Indurain pedalled out of Disneyland Paris towards the Champs-Élysées on his Dario Pegoretti-built, rebadged Pinarello. The last time an aluminium bike took a star turn on the Parisian boulevard was in 1998, a Bianchi Mega Pro XL ridden by Marco Pantani. Ever since 1999 every overall Tour victory has come aboard a carbon fibre machine (although in light of historical misdemeanours, retrospective 2006 winner Oscar Pereiro rode a magnesium Pinarello Dogma FPX with carbon stays).

In the story of race-winning frame materials, one name is rarely mentioned – titanium. While Greg LeMond’s Z Team rode titanium Merlin Extra Lights in 1991 to much industry fanfare, and Armstrong pedalled a Trek-branded titanium Litespeed Blade to time-trial success in 1999, titanium has been a conspicuous absentee in the pro peloton. Yet it has somehow managed to obtain almost mythical status as the ‘bike for life’, more desirable than steel and more premium than carbon fibre – the thinking cyclist’s choice. 

But what gives titanium such prestige? Is it worthy of its niche pedestal, are we using it in the right way, why is it so expensive and, most importantly, is right for your next bike?

The first thing to understand about titanium is its nomenclature, and the fact that the titanium materials that dominate bikes are, like their aluminium and steel cousins, alloys. That is, they are mixed with other elements to enhance their properties.

‘My recollection is that the first titanium bike tubes came out of Speedwell Titanium in Birmingham in the 1970s,’ says Keith Noronha, managing director of Reynolds Technology. ‘It brought out CP2, which was a relatively low-strength but good material at the time. I think the initial attraction for framebuilders was that it wouldn’t corrode like steel if left untreated.’

‘CP’ stands for ‘commercially pure’, meaning an unalloyed metal; the ‘2’ denotes the grade, referencing aspects such as tensile strength (the capacity of a material to stretch before breaking) and ductility (how malleable a material is). But while Noronha says CP2 is the benchmark in industrial applications such as chemical containers and medical equipment, there are two other grades of titanium alloy that have become synonymous with bicycles: grade 9 and grade 5. Or, more commonly, 3/2.5 and 6/4, as Dr Martin Jackson, senior lecturer in materials science and engineering at the University of Sheffield, explains.

‘Pure titanium is relatively soft, so aluminium and vanadium are added to increase strength but retain workability. So when we say “6/4” we mean there is 6% aluminium [by weight] and 4% vanadium. “3/2.5” is less dilute – 3% aluminium and 2.5% vanadium. Add more aluminium and you’ll increase the strength and stiffness but reduce ductility, so you can get cracking. Adding more vanadium increases ductility – meaning it’s less brittle – but reduces stiffness, so it’s a balancing act.’

A frame needs to be at once stiff enough to not flex under load while being flexible enough to cope with big impacts without falling to pieces. And it also has to be light. Ask any titanium bike proponent and they’ll tell you titanium is the very embodiment of such characteristics, only with the added benefit that it doesn’t corrode, is robust and it somehow furnishes a bike with an enviably plush ride quality. But are they right?

Like for like

‘If you took the same tube diameter and wall thicknesses, aluminium has the lowest elastic modulus, or stiffness – half that of titanium, and titanium has half the stiffness of steel,’ says Jackson. ‘That’s back of the envelope stuff, as in reality it depends on the actual alloy, but it’s still interesting to me that people say titanium has a plush ride quality. In the simple mechanical sense, aluminium should have the most forgiving ride quality.

‘In reality you never have the scenario where those three materials exist in the same tube sizes and shapes,’ he adds, and if you compare three bikes in each material you’ll see he’s right. Bar a few exceptions such as Columbus’s latest 44mm wide Spirit HSS tubing, a general rule of thumb is that steel tubes tend to be the skinniest, then titanium, then aluminium. The reason is material density.

Aluminium is around a third the density of steel and half the density of titanium, meaning you can build bikes with bigger-diameter tubes from aluminium without a weight penalty, as compared to titanium and steel. To build a steel bike of acceptable weight, the tubes must be narrower. A wider-diameter tube is stiffer than a narrower tube, so an aluminium bike will often feel stiffer and much harsher than a steel bike, whose narrower tubes flex more easily. Titanium sits in a sweet spot between the two.

‘Because the density is lower in titanium than steel you can use a larger-diameter tube for the same weight,’ says Noronha. ‘So if a designer wanted titanium at its best, they’d use a combination of large-diameter tubes for the main triangle and small-diameter tubes for the rest. You’re building in compliance with narrow tubes, and you can do this to a greater extent with titanium compared to aluminium because titanium is very strong and has a very high fatigue life, so you can use it like a spring.’

This is another important factor in titanium: fatigue life. As Noronha explains, ‘Imagine a coil spring. If it is made out of titanium you can keep bouncing on it for an almost infinite number of cycles, provided you don’t exceed its maximum stress limit, whereas aluminium has a fatigue limit, albeit a very high one, after which the material will fail.’

Titanium has a far greater ability to bend without breaking, elongating by up to 25% compared to around 15% for steel and 8% for aluminium. Roll those factors up together and you can begin to see where titanium’s ‘bike for life’ moniker comes from. And we haven’t even come to the matter of corrosion.

The anti-hero

Most titanium frames are instantly recognisable by their bare metal tubes, finished in a variety of ways from mirror polish to matt shot-blasted. Unlike steel or aluminium, titanium readily lends itself to being exposed to the elements without detriment. Yet the reason is somewhat counterintuitive.

‘You never actually touch titanium,’ says Jackson. ‘When you pick up a lump of 3/2.5 you’re touching an incredibly tenacious, nano-scale oxide, because titanium loves oxygen and nitrogen and oxidises immediately at room temperature. But once in place this nano-scale oxide provides a corrosion barrier [as the titanium itself is no longer in contact with the air], hence titanium’s anti-corrosion properties. It’s also why you have to weld titanium with an inert gas shield, like argon, as when titanium is heated [during welding] its structure opens up and it acts like a sponge, sucking in as much oxygen and nitrogen as it possibly can until it turns back into an oxide and the welder just has a horrible mess and a weld prone to cracking.’

Treated properly, titanium is great for longevity, but this also helps to explain why it’s so costly. 

‘There’s actually lots of titanium around the Earth’s crust, in the black sands of beaches in Australia, India and Sri Lanka, for example, but its high affinity for oxygen makes it difficult to remove,’ says Jackson. ‘You have to use expensive chemicals to plug it away from the oxygen, then you have to melt it in a vacuum, which is expensive too. Extracting and working titanium is a very intensive, small-batch process.’

Jackson reckons 50% of the overall cost of titanium is attributable to getting it out of the ground and into a form where it can be cast into the solid ingots that are extruded into tubes. That’s even before a company like Reynolds has got its hands on it, or a framebuilder has turned on the argon tap and lifted a welding gun.

Compared to carbon, titanium is a pricy option while being nowhere near as versatile, but according to Enigma Bikes’ Jim Walker, that shouldn’t necessarily put you off.

‘No doubt if you’re a racing cyclist, it has to be carbon,’ says Walker. ‘Stiff, very light and it can be aerodynamically shaped to go very fast. But then again, most people don’t race. They want a bike that gives them good performance, but with smoothness, comfort and longevity, and that’s where titanium comes into its own.’

This thought is echoed by Jon Cariveau at Moots when he says, ‘For many, titanium is still a relevant material due to its ride quality and durability. It will be really hard to compete with carbon in the weight category, but we can come close, and it will outlast carbon many times over, say in crashing or daily abuse. The material also lends itself to the builder being able to adjust ride quality with tube diameters and wall thicknesses for a given size of a rider.’

However one question still begs: has titanium gone as far as it can go, and are we really using the best materials for the job? For instance, all but a handful of titanium frames are made of 3/2.5 tubing, yet 6/4 is stronger and stiffer so can lend itself to lighter bikes. Are framebuilders missing a trick, and could there be more in store?

‘Titanium alloys such as 6/4 weren’t designed for the bicycle industry, but rather military aircraft in the 1950s, so it’s not at all optimised for the bicycle market,’ says Jackson. ‘The only reason the bike market uses it is because it’s there for aerospace, and it’s the same with 3/2.5. 

‘To put things in perspective, the steel industry makes more steel in an hour than the titanium industry does in a year. There are supply agreements lasting 10-20 years between the likes of Boeing and the titanium producers, so that doesn’t leave much left over, and what is left goes to places like the automotive industry before the bike guys can get hold of it. So really the bicycle industry is only getting the scraps, and they aren’t optimised for bicycles.’

The future is light

This lies in stark contrast to the wider titanium industry. Jackson says he and his team are developing new alloys for the automotive sector to use in suspension springs and valve springs. Here they are ‘fine-tuning’ the alloy mix according to very specific needs, as opposed to building out of what already exists. ‘There’s no reason why you couldn’t do the same for bicycles, to develop optimised titanium alloys tuned to have certain ride characteristics, but the problem is the bike market is comparatively small, so the money isn’t there to develop bike-specific titanium alloys.’ It’s a story all too familiar for Reynold’s Noronha.

‘6/4 is about 20-30% stronger than 3/2.5. We used to make 6/4 tubes at Reynolds, but we simply can’t get hold of the raw materials anymore,’ he says. Yet 6/4 does exist, but only in a few bikes. Engima’s Excel is made from 6/4 tubes sourced in the Far East – although Walker concedes they cost twice the price of 3/2.5 – and Lynskey uses rolled and seam-welded 6/4 sheets to form the tubes on its R460 frame. These frames have the ability to not only be stiffer, but lighter, leaving one wondering if maybe there could be new titanium alloy in the offing for the bike market. One man at least entertains this vision, albeit with a healthy dose of reality.

‘Yes, bike manufacturers are hanging on the coat tails of other industries,’ says Ben Kitcher, a technology fellow at the University of Sheffield’s Advanced Manufacturing Research Centre. ‘When you’re up against contracts to kit out the Airbus A350 landing gear for the next 25 years, you have to be a pretty big deal to break into the supply chain, and sporting goods manufacturers aren’t – hence the lack of 6/4 tubes. But there’s no reason why drives for developing new titanium alloys in other industries shouldn’t eventually give the cycling industry access to those materials, too. Right now at AMRC we’re working with a new proprietary titanium alloy, T5553. It’s even stronger than 6/4.’

While you won’t be able to order a T5553 bike any time soon, the future – conceptually at least – seems bright for titanium. And the present? Well, it’s just as shiny as ever.

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