Tubular tyres are the recherché all-in-one tyre and tube combinations that racers glue onto their wheels. Not to be confused with clincher tyres which are more conventional in their construction and contain separate and easily replaceable inner tubes, or indeed tubeless tyres which are open tyres that form an airtight seal in conjunction with the rim, tubular tyres' expense and complex fitting mean they’re the preserve of dedicated competitors only. But do they still deserve your consideration?
John Dunlop’s development of the first practical pneumatic tyre in 1887 was to be for the greater good of all bicycles as it meant rubber tyres – at first only as glued-on tubulars – were quickly adopted by racers who appreciated the huge gains afforded by the new technology. Four years later, in 1891, Michelin introduced the first clincher type tyres for bicycles, but because these attached by means of external clamps – rather than a bead as we know it today – the tubular remained top dog.
Tubular tyres (or sew-ups, as they were often called, due to their entirely encased design with the inner tube sewn inside the cylindrical tyre) were the only option for serious racing. They were lighter, faster and more comfortable than the alternatives. During road races riders had to carry a spare wrapped around their shoulders (in that familiar crossed manner) in case of a puncture, as fixing a flat was certainly not something to be undertaken at the roadside. It required a needle and thread plus a whole lot of patience and time to first pick away the stitching under the base tape, then pull out the tube and find and repair the hole, before finally sewing everything back up.
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It was an awkward procedure then, and still is today – it’s the reason why most pro teams simply dispose of punctured tubulars rather than repair them. Then there’s the fact that tubulars must also be taped or glued to the rim in the first instance, itself also a dark and fiddly art.
So why then do tubulars (aka tubs) remain the de facto choice among the racing fraternity, especially in light of vast improvements in clincher tyre technology, rim shapes and road bike braking systems that might otherwise combine to exile tubs from the peloton?
Morgan Nicol of Challenge, a company best known for its tubular tyres, says, ‘The laws of physics are laws, not discussion points to debate. Clinchers cannot be superior just because big companies with lots of marketing dollars want them to be. For the past three years tubular tyres have won the World Championships in five segments – road, TT, track, cross and even MTB.
‘Tubulars cradle the inner tube inside a cocoon, protecting it from the sharp edges and extreme heat you find inside clincher rims,’ he adds. ‘That allows for the safe use of latex tubes which are much more supple than butyl rubber tubes, creating a much more comfortable, controlled ride. They’re lighter too. Then there’s the fact that tubular tyres will almost never pinch-flat like a clincher, but if you do flat you can still ride a tubular flat, making it much safer.’
Pros for pros
Weight – or a lack of it – has always been a big selling point of the tubular tyre, but that’s largely thanks to the simpler construction of the wheel rims, rather than the tyres themselves, offering a substantial weight saving.
‘It’s easier to design and manufacture a tubular rim of a given weight and strength than a clincher rim with similar mechanical properties,’ says Keith Bontrager, the engineer who has lent his name to the Trek corporation’s wheel line for the last decade or more. ‘The vertical walls and tyre retaining hooks that are necessities on a clincher rim add inefficient weight to the rim’s cross section and they also add complexity in manufacturing, especially when using carbon fibre. By comparison, a tubular rim is a simple box section with a concave outer edge acting as a well for the perfectly circular tyre to sit in.’
Weight aside, a huge benefit of the tubular system is that it’s virtually impervious to pinch flats, thanks to the cross section of the rim. That’s why pros choose wide tubs pumped to around only 60psi for rough races like Paris-Roubaix. Also, the Latex tubes often used in tubs tend to deform around sharp objects so not flatting as readily as the butyl tubes used in clinchers. It would be foolhardy to risk running a clincher at such low pressure, as it would almost certainly pinch the tube. A further consideration, at least for pro racers, is that when a tub does puncture, the fact it’s secured to the rim with glue means it’s safe to continue riding until a new wheel can be fitted.
Wolf vorm Walde is a former a tyre engineer for Continental (and the man in fact who controversially persuaded Tony Martin to race, and win, the 2011 TT Worlds on clinchers – but more of that later) and now heads Specialized’s hard goods department, including tyres. He sums it up, saying, ‘Because tubs fail “safely” they will always be a part of pro racing. Health is the rider’s capital, so to avoid crashes is paramount.’
The final advantage cited by many racers is that tubulars feel like they corner better than clinchers. Bontrager is unsure if it’s the perfectly round tyre profile or the security of a bonded tyre that produces the effect, but agrees: ‘The effect is definitely there. I’ve never seen any measurements to prove it, but that isn’t what’s important. If the racers feel like it works, that’s enough.’
With all those advantages, you may be wondering why we’re not all riding around on tubulars all the time. Well, for starters, gluing tyres on isn’t entirely practical. ‘Mounting tubulars is an elaborate process – chemical bonding takes time and needs care to ensure that once tubs are on the rim they stay on,’ says vorm Walde.
Done properly, you’ll need plenty of time to prepare both the tyre and rim surface for gluing, plus have to leave the tyre at least overnight (ideally longer) to bond securely before you can ride it. And then there’s the cost, which for most of us is prohibitive in the first instance, because every puncture means a whole lot of time and money, or worst case, a new tub. Clincher tyres by comparison are a breeze to change and, thanks to their construction, fairly cheap, which makes them vastly more appealing.
Here’s the curve ball, though: clinchers are also – whisper it – faster.
That’s right, clincher tyres, used correctly, can roll faster than tubulars. ‘Power losses in the bonded area between the tubular tyre and rim are fairly high,’ says Bontrager. ‘So a carbon wheel with a very light clincher tyre and efficient inflation has the potential to roll faster than a tubular.’
Vorm Walde goes on to explain Tony Martin’s choice of clinchers for his TT gold medal ride at the World Championships, saying, ‘Tony rides them now in most TTs. His Omega Pharma-Quick Step team has stocked up on clincher disc wheels to let the whole team ride them, because it’s proving to be the fastest set-up.’
It begs the question: why only in time-trials, as surely the benefits are useful for road races too? But to get the best results from clincher tyres means using both very high quality, supple carcasses and latex inner tubes, a combination that, as Challenge’s Nicol alluded to earlier, may be prone to safety issues when subjected to the extreme heat caused by rim braking on carbon clinchers, something that is much less likely to occur in time-trial events than, say, a mountain road stage.
Braking bad
Ah yes… rim brakes, carbon fibre and clincher tyres – three ingredients in a stewing pot that gives wheel engineers sleepless nights. The problem is that rim brakes generate heat in the wheel. Sometimes a great deal of heat. Alloy wheels are much more capable of shedding the build-up of heat than carbon, which tends to hold onto it. Heating carbon rims to extreme temperatures is not ideal for their construction – early clinchers failed, causing tyres to blow off as a result of resins going soft. That’s unlikely to be a problem on the flat where braking is less severe, but on descents it’s long been a cause for concern. It’s a problem that wheel manufacturers have invested huge sums of money trying to solve, and only now are they beginning to fully resolve this carbon clincher conundrum, almost two decades after carbon fibre wheels first gained acceptance.
Back to the argument for clinchers being faster, vorm Walde explains, ‘It’s because there is less deflection and energy loss in the combination of rim-tyre-tube.’ Simply put, more of the energy you put in at the pedals ends up on the road driving you forward. There’s also more potential for aero improvements with clinchers: ‘We’ve found clincher tyres can be adjusted to the rim shape so we manipulate the casing and the tread geometry so that airflow along the tyre to the rim is improved.’
It’s another feather in the clincher’s cap, but is it enough to secure its supremacy? On the horizon there’s some seriously disruptive technology about to make a huge wave in the bicycle industry, such that over the next five years, road bike wheels and tyres may be an entirely different prospect. The future could be about disc brakes and tubeless tyres.
First up, disc brakes. Regardless of the arguments for and against, there’s every chance that within five years disc brakes will become the default braking system for all serious road bikes. The same objections and subsequent capitulation happened in mountain biking a decade ago – ‘they’re too heavy’, ‘they’re too powerful’, ‘we don’t need them’ – and within five years rim brakes had been forgotten. What do disc brakes have to do with tyres? Up crops that word ‘heat’ again. As soon as you move the brakes away from the rim, you no longer have to cope with heat build-up interfering with clincher performance. That frees rim designers to use different grades of carbon fibre with different resins to create rim profiles dedicated to aerodynamics and compliance rather than a balance of wet weather braking performance and heat dissipation. This should lead to some groundbreaking developments.
Continental’s Rob Scullion says, ‘Once discs become accepted, rim designers will have a free reign for the first time, so I think we’ll see more collaborations between tyre and wheel manufacturers.’ As an example he cites triathlete Faris Al Sultan, whose wheel supplier created some special wheels for the Hawaii Ironman to allow him to use fast rolling 28mm GP4000S tyres in an aerodynamically efficient package.
Keith Bontrager is also enthusiastic about the potential of disc brakes: ‘Moulding carbon clincher rims is time-consuming and the material systems required to survive braking temperatures are expensive. I think there are likely to be incremental improvements in overall wheel performance once there are disc brakes on road racing bikes. Getting the operating temperature of wheels down by using disc brakes is a huge developmental step.’
So, if disc brakes gain acceptance from the UCI for pro racing, will this be the final nail in the tubular’s coffin? Bontrager is unequivocal: ‘At least until we can figure out how to keep clincher wheels rideable after a puncture, tubulars will stay. But, that may well be possible in the next few years of development, so that’s going to be interesting.’
Middle ground
This leads to another new technology that has the potential to move the goal posts within the tyre market: tubeless tyres. Another import from mountain biking, the road market has been sluggish in its take-up of tubeless, but with more manufacturers now coming round to the idea, it looks set to accelerate.
Felix Schäfermeier is a product manager at Schwalbe, and takes care of the road team liaison with pro teams such as FDJ, Ag2r, Trek Factory Racing and IAM Cycling. Together with some of those teams, he’s been testing road tubeless with plenty of success. ‘Tubeless tyres show great promise for high performance. They’re characterised by low rolling resistance, high snake bite [pinch flat] resistance and due to a wider contact surface to the asphalt an outstanding performance on tough roads,’ he says.
The low rolling resistance comes thanks to there being no tyre and tube rubbing against each other creating energy loss, and with no inner tube to pinch it’s surely win-win, right? Schäfermeier is confident the system is the future: ‘We did comparison studies between tubeless and tubular in preparation for the infamous cobbled stage five of the Tour de France this year. We compared a 28mm tubular against our 28mm ONE Tubeless. All participants evaluated the tubeless tyre as the fastest and smoothest set-up on the pavé and we were able to ride with only 55psi [75kg rider weight] without having any punctures.
‘Especially for a cyclist who doesn’t have the support of a mechanic, tubeless tyres are much easier to handle and are closer to their needs. The acceptance of tubeless in road cycling will go on step by step and it’s comparable to the trend of wider tyres. Pro racing is very conservative and traditional in many ways – tubulars have been used for decades and they won’t disappear overnight.’
Schäfermeier is probably right that tubulars won’t disappear overnight, and we’d bet they’ll outlive rim brakes in the pro peloton. But with the possible move to disc brakes and an increased interest in tubeless, the once-maligned clincher tyre looks set to start building its palmares in the top level of road racing – and is likely to claim top spot in a Classic or two in coming seasons. Tubeless or not, the future is unlikely to be glued on.
