Joining VeloClub not only supports the work we do, there are some fantastic benefits:
by Dave Rome
September 3, 2020
In the endless juggling act of balancing weight, rolling resistance, and aerodynamics, wheel and tyre choices can play a real role in the outcome of a race. And it’s exactly this technical advantage that keeps the fire burning in the debate about tubeless, clincher and tubular tyres.
Few brands have added more fuel to that fire in recent years than Specialized and its wheel division, Roval. Together, they’re the only single-company tyre and wheel combo truly being raced in the WorldTour.
Specialized says Bora-Hansgrohe and Deceuninck–Quick-Step are free to use any of the company’s tubular, clincher, or tubeless options. According to Roval, the fastest option is supple clinchers and there’s data to prove it – which we’ll get to shortly – but both teams still regularly swap between the three different formats depending on the day.
So that begs the question: if there’s data to suggest there is a fastest option, what’s with all the swapping and changing?
Specialized and Roval’s multiple attempted murders of tubulars are nothing new. It was 2014 when Tony Martin won the time trial world championships on Specialized’s cotton clinchers and latex inner tubes. Similar setups have been seen countless times in time trial events since because of the substantial rolling resistance advantage they offer over even the best tubulars.
A few years later, Specialized and Roval began to publicly trial tubeless products at the top level of the sport. The uptake was slow, until 2019 when Specialized went ballistic on the messaging, stating that tubeless was faster, more puncture resistant, and the future of road racing. The company invested a fortune into it, and tested it more than anyone else at some of the highest-profile events. And that was all hunky-dory until Roval released its latest racing wheels, which are clincher-only.
In marketing material from 2019, Specialized claimed its tubeless offering provided more grip and lower rolling resistance than tubulars, plus the ability to self-seal punctures. There was little mention of the pre-existing clinchers at this time.
This is a juicy topic in itself – one we’ve discussed before and probably will again. But at least for now, Roval states that with existing technology, a wheel dedicated to clinchers and inner tubes is the highest performing product the company can currently create. What Roval and Specialized haven’t mentioned at all are the safety questions circling existing tubeless offerings.
“We believe we’ve got a greater data set and real-world use case than anyone else,” said Roval brand manager Ben Capron. “We’ve done an extremely deep dive on the topic because we believe, at some point, road tubeless will reach the point where it’s the best option. That time is not now. To do the Alpinist and Rapide wheels in tubeless today would lead to a heavier weight.”
This is an awfully curious sticker considering the shape of the rim was clearly originally designed with tubeless tyres in mind.
Roval wasn’t willing to state a specific weight difference. Roval’s stated reasons for this weight difference have been covered previously, but the short of it is that a tubeless setup places more compression on a rim, and that requires more material to resist it.
Roval may be quick to cite weight as the primary reason as to why its latest wheels aren’t tubeless-compatible, but questions still remain given that the tyre bed of the production wheels still look very much like they were designed specifically with tubeless in mind. Roval and Specialized have said nothing of it, but industry and internet rumours all point toward safety concerns.
Perhaps more interesting, though, is that Roval has no tubular wheels in its development pipeline. Yes, you read right – there are no plans to release the new Alpinist, Rapide or any other wheel in a tubular version. If the sponsored teams want tubular, they’ve got the pre-existing CLX range to do so, but according to Specialized, it’s stopped tubular R&D and there’s nothing new coming.
So why kill off tubulars as a performance offering when tubeless isn’t yet ready to ascend to take its place? Well, that’s a debate about weight, rolling resistance and aerodynamics.
Specialized is far from the only voice in cycling suggesting that supple clinchers and tubeless tyres can offer reduced rolling resistance compared to a top-end tubular. The likes of BicycleRollingResistance.com, independent rolling resistance researcher Tom Anhalt, Silca owner Josh Poertner, and countless others have come to similar findings related to hysteresis losses when tyres are tested away from perfectly smooth and consistent surfaces.
For Specialized, its rolling resistance testing has a Turbo Cotton 26 clincher with a latex tube as its top dog (data not shown). Just behind that sits the same setup with the company’s lightweight Turbo butyl tubes. Then comes the Rapid Air tubeless, and finally, Specialized’s AllRound 3 tubulars roll through at the back of the bunch.
This testing, shared exclusively with CyclingTips, was conducted specifically for Specialized’s WorldTour teams. Roval requested that the absolute wattage figures were not shared.
Interestingly, even Specialized RapidAir tubeless tyres run with a lightweight tube show less rolling resistance than the company’s own AllRound tubular. And, as we’ll get into later, some riders have been running this very combo.
Despite testing as the fastest option, the team at Roval was reluctant to say latex tubes are categorically the best option for racing.
“Latex tubes have other aspects that are finicky and problematic,” said Capron. “The teams are racing on both butyl and latex tubes.”
Still, it seems likely that the Specialized-sponsored WorldTour teams would be rolling on the faster latex tube option, even if the company itself doesn’t produce such a thing.
Of course, these results are specific to just this one brand, and you don’t have to look very far to see that while extremely fast, Specialized’s tyres never rank as the absolute fastest in published tests. But at least within Specialized’s wheelhouse, its Turbo Cotton clinchers currently win the rolling debate.
Weight is certainly an area where tubulars have long ruled the roost. And weight remains a significant decision factor in pro racing, especially in the mountains. Give a rider a significantly lighter wheel and they’ll feel it immediately, and likely gain a psychological benefit as a result. Give them an aero wheel and you’re unlikely to earn such immediate praise.
However as rims and tyres are forever getting wider, the weight advantage of a tubular system has narrowed. Looking specifically at Specialized’s options, the new shallow Alpinist CLX setup with Turbo tubes and Turbo Cotton 26C clincher tyres (the likely wheel package that Julian Alaphilippe rode to victory a few days ago, but perhaps with a different tube) is claimed to weigh 1,880 g. By comparison, the nearest tubular option (CLX 32) the Specialized-sponsored teams have at their disposal is 1,941 g.
Missing from the list is the lightweight setup with latex tubes. Most latex tubes will add approximately five grams compared to a lightweight butyl tube.
That low package weight means we’re now seeing the teams use the Alpinist far more than we saw them use the similarly deep CLX 32. According to Chris Wehan of Roval’s product team, this is simply because the weight difference between the shallow wheel and the deeper options is now more noticeable.
Tubular wins one back in Specialized’s deeper wheel offerings, with the CLX50 tubular wheel package weighing some 64 grams less than the new Rapide CLX clincher offering. However, that weight difference isn’t much when you consider the Rapide CLX offers lower rolling resistance, along with improved aerodynamics and stability.
Regardless of wheel or tyre type, it’s clear that weight isn’t the absolute top priority. This is evident by the fact that Specialized supplies the teams with tyres in both 24 and 26 mm widths, with the heavier, yet faster-rolling, 26 mm version being what the teams choose to use most of the time.
Now, of course this isn’t an apples-to-apples comparison. In this case, the Alpinist and Rapide clincher wheels are a whole generation newer compared to the CLX wheels. In theory, an imaginary tubular Alpinist could well be a lighter option than the equivalent clincher offering. But that wheelset will remain a hypothetical, due to Specialized’s insistence that it would offer inferior performance in other areas.
Based solely on rim shape, the new Rapide CLX clinchers are certainly more aero than the older CLX 50 tubulars. There’s also some data out there that suggests clincher/tubeless tyres can be made more aero than tubulars, but I won’t get into that. Either way, Roval’s new clincher aero offerings are faster than the tubular wheels the team has access to. However, we’re talking about aerodynamic differences that typically require a controlled wind tunnel to measure, and even Roval is suggesting the real-world differences are fairly small.
Note that Roval designs its wheels around the wider 26 mm tyres. The higher drag figures in the shading are for the narrower 24 mm tyres.
“Aerodynamics in wheels is getting maxed out,” said Wehan of the current aero wheel market. That’s a pretty surprising statement from the company that coined the phrase, “aero is everything”, but Wehan’s point isn’t that all potential gains have been reached – just that there is more speed to be gained elsewhere.
According to Roval, that new frontier is stability, and its research to date suggests that the energy and time losses resulting from fighting wind gusts is measurably greater than the time losses experienced from swapping from one modern aero wheel to another. This is in line with what Zipp and DT Swiss have been saying in recent years, and it certainly shouldn’t be a surprising finding to anyone who’s ridden a deeper wheel on a gusty day. The ultra-wide shape of the Rapide CLX is said to be some 25% more stable in brief gusts than the CLX 50, however putting real-world quantitative data to the speed benefit of this is easier said than done. Either way, where smoother is faster for tyre rolling resistance, the same can be said for aerodynamics.
A look at the weight averages of the aero data that’s displayed above.
Interestingly, at high yaw angles, the Alpinist actually loses ground to the outgoing CLX 32 in the wind tunnel. This is the result of a new, narrower rim shape that aims to maximise weight savings. The differences are small, but they are there. Roval believes that ultimately, weight matters more than absolute aerodynamics for a wheelset intended to grind up steep mountains, stating that the yaw angles just aren’t as extreme when you’re descending at pro speeds.
Ok, so Roval has suggested that its shallow clincher wheel package is its fastest-rolling and lightest-weight option for the mountains, while the aero clincher package is its fastest rolling, most aero, and most stable option for flat and rolling terrain. So then why are we still seeing Bora-Hansgrohe and Deceuninck–Quick-Step ride the older tubular CLX wheels?
Defending champion Julian Alaphilippe (Deceuninck-Quick-Step) had a day he’d rather forget at this year’s Strade Bianche. All told, he had six punctures and three bike changes. Rumours suggested he was trialling a new tubeless or clincher system, however Scott Jackson of Specialized Racing told CyclingTips that Alaphilippe raced Strade Bianche on the CLX 50 with 26 mm tubular tyres.
This comes down to system reliability, and tubulars remain the preference of the pros in races/stages where flat tyres or lack of access to mechanical support is more likely. The simple fact is that if a flat were to occur, then a tubular can be ridden until a support vehicle can swap out the wheel or bike. By comparison, both tubeless and clinchers are more likely to unseat and then become entangled in the frame.
Compounding this issue is that Specialized’s claimed fastest setup, the Turbo Cotton clincher with either a Turbo butyl or latex tube within, offers minimal sidewall protection. The setup is built for speed, not durability.
To counter this, some team riders are using the more puncture resistant Rapid Air tubeless tyres with tubes inside. Not only is this heavier setup less likely to flat, but the bead lock of the tubeless tyres is said to hold better in the event of a flat compared to a full clincher setup. This tubed-tubeless setup is something that Roval suggests is still faster rolling than the tubular equivalent – but of course, the performance gap is far narrower.
You’ve probably read this far and felt the argument for the use of clinchers in pro racing isn’t completely clear-cut, and you’re not wrong. The ability to ride a flat tyre remains a major deal for professional racing and will continue to be a sticking point for the acceptance of clincher and tubeless setups.
I’m sure the likes of Bora-Hansgrohe and Deceuninck–Quick-Step would love some new tubular rims that are lighter and more aero, and I don’t doubt they’ve requested them. However, it’s clear the investment in technology is moving in a different direction to gluing tyres. For Specialized and Roval to cease its development of tubulars signals that they strongly believe the performance progression lies in clincher and tubeless technology.
“We make the decisions based on what we truly believe is the best for riders,” said Capron. As of this minute, Specialized and Roval maintain tubed clinchers are the best performing option for its professional riders – and seeing as they’ve just released new Rapide and Alpinist wheels that follow that format, you’d kind of expect them to say that. However, it sure sounds like we’re only at the beginning of the story for road tubeless in professional racing.