出处 : bikeradar 作者 : Simon of Bromley
While today's bikes are all about aerodynamics, the aerodynamics of time-timing bikes still stand out. The use of ultra-flat tubes, closed wheels, resting handlebars, etc., almost sacrifices handling for aerodynamic performance. This dedication to aerodynamics makes the time trial look very aggressive and very fast, approaching and reaching speeds of up to 50 km/h on the World Tour for both men and women.
Below, we'll explain what makes a timed bike so fast, from geometry to design, and list other things you need to know about UCI rules and restrictions.
什么是计时赛（Time Trial）自行车？
Unlike road bikes, which are designed to be versatile and perform on a variety of terrains, the primary goal of a time trial bike design is to be as fast as possible on a straight, mostly flat road.
To achieve this, the time-paced bike uses professional geometry and handlebars to force your body into a more aerodynamic position, plus aerodynamically optimized tubes to work together to break the air. Using a time trial position can affect handling and can be strenuous to maintain, but the advantages often outweigh the disadvantages. After all, in the overall system of rider and bike, the rider alone bears the vast majority of air resistance.
What is the difference between a time trial and a triathlon?
Time trial cars and triathlon cars have many similarities, and are usually time trials that are performed by a single person. The main difference is that triathlon is not subject to the UCI and is not allowed to be accompanied by a logistics vehicle, and triathlon designed for this purpose is not subject to the UCI rules.
This makes the triathlon more adventurous in its design choices, with flatter tubes and even more bizarre frame shapes, thanks to the use of carbon fiber materials that allow designers to design non-classic double-triangle frames.
Considering long-distance events such as triathlons, many triathlon cars also consider storage space for food, drinks, tools, and spare parts. Road cyclists tend to keep their stuff in their jerseys or handlebar bags, while triathletes can put their belongings in the integrated pneumatic storage compartment, which can reduce air resistance when properly designed.
The UCI rules currently prohibit the use of these tubes and fairings, but they can be used in time trials administered by CTT, a UK-based time trial governing body that is not regulated by the UCI.
It's all about aerodynamics......
handlebar
The timer handlebar consists of an airplane handlebar and a set of resting handlebars located in the center. The handlebars are extended forward to allow riders to adopt a more aerodynamic riding position than they would otherwise be, and the width and length of the handlebars and lounges can be adjusted for greater comfort, although UCI has specific rules to limit extension and range, and if you're going to be competing in a UCI-approved event, the referee may use complex clamps to make sure your bike fits the rules. Events outside of the UCI's management are unlikely to be a problem.
The disadvantage of this type of handlebar is that the brakes are usually located at the end of the handlebar pair, and the shift button is at the top of the handlebar, so it is not so easy to handle, so time cycles and triathlon bikes are usually not suitable for group riding. (Except, of course, for team time trials).
Tube shape and geometry
When it comes to timing cars, aerodynamics are paramount, and weight is secondary. Therefore, within the scope of the UCI rules, the tube shape is optimized as much as possible to match the aerodynamic effect.
Whereas older time bikes were accustomed to narrow airfoil designs, modern time bikes have begun to favor a wider Kamm tail. This wider shape allows airflow over the surface for longer, giving it advantages in terms of rigidity, weight, and protecting accessories such as the kettle from airflow.
The geometry of a time-paced car is also different from that of a road car. The most notable difference is that time bikes typically have a steeper effective seatpost angle (about 75 to 78 degrees) compared to road bikes. This allows the rider to tilt forward and prevent the rider's hip angle from being too tight and affecting performance. However, it affects the distribution of the center of gravity, bringing the center of gravity closer to the front wheels, which can have a negative impact on handling, especially when going downhill.
Wheels
As with the frame, the aerodynamics of the timing wheel set are paramount.
In time trials, it is common to use fully enclosed or over-frame high rear wheels and low spoke counts (e.g. three-spoked wheels) (front enclosed wheels are usually only allowed on track races).
Striking a balance between the tallest, most aerodynamic wheels and the negative impact of crosswinds on handling is something to consider. However, according to AeroCoach's Xavier Disley, using a rear closed wheel can "help improve handling in strong winds because it shifts the handling pressure backwards away from the front wheel." So, if you choose the front wheel too aggressively, it will be difficult to control it, and it is not the optimal solution.
brake
Until recently, bike manufacturers were working aerodynamic efforts to hide rim brake calipers inside the fork or under the bottom bracket. Although this will affect the braking effect and be complicated to repair, it is acceptable for the sake of aerodynamics.
Recently, with the use of disc brakes in the road car field, most time racing cars have been equipped with disc brakes. Many believe that this is a step backwards in aerodynamic performance. However, it eliminates the challenge of integrating wheel brake faces and rim calipers, opening up new design possibilities for wheel and frame manufacturers.
Therefore, it would be an oversimplification to say that rim brakes are always more aerodynamic than disc brakes, as the judging effect depends on the components coming together into a single system.
There is no doubt that better braking performance can help you ride faster, it can allow you to brake later and be more confident, all else being equal, helping to increase your average speed.
Transmission system
Time trials are usually played on flat or undulating tracks, so drivers looking for a variety of advantages need to optimize their drivetrain to suit the race.
Larger platters (53T or larger) and tightly spaced flywheels are usually used. The former helps optimize the chain line and cadence, while the latter helps the rider to adjust the riding rhythm more precisely, which is important when approaching the limits of the body.
Because power is lost due to friction within the drivetrain, elite athletes also seek to optimize the efficiency of their drivetrain. For example, larger discs, more precise flywheels, larger guide wheels and faster chain oils, high-quality ceramic bearings, and even a 1X drivetrain or short crank.
These small marginal benefits may take a lot of effort, but on race day, some small gains can add up to more significant gains.
tyre
The performance indicators of tires may be rolling resistance is the key, and aerodynamics are not so obvious. As a result, optimizing the tire settings to suit the track can bring significant benefits.
Tubeless tubes generally have less rolling resistance than equivalent tube tires, and even the type of inner tube and the quantity and quality of tubeless sealant can affect the rolling resistance generated by the system. Time trial-specific tires go for absolute speed at the expense of everything else. This generally means that puncture protection is significantly reduced and abrasion resistance is reduced.
You need to choose your tires carefully depending on the nature of the race. Short races on good roads can require the fastest, most refined tires: like Vittoria's Corsa Speed, Veloflex's Record, Schwalbe's Pro One TT or Specialized's Turbo Cotton are good examples.
Longer races or riding on rough roads may require more durable tires. The time wasted by stopping to change tires or fixing punctures can outweigh the time saved by using faster, more refined tires. Continental's GP5000, Goodyear's Eagle F1 or Schwalbe's Pro One are all all-rounders, with decent speed and good puncture resistance.
The balance of risk and reward will vary from race to race and to rider. If you're looking for speed, tire aerodynamics are also an important consideration. For time trials, the choice of tyre width maximizes aerodynamics. Many wheel manufacturers will provide guidelines for the best tire width for a given wheelset, for example, if your wheels have an outer width of 28mm, then 25mm tires may be the best choice from an aerodynamic point of view.
Recent tests have shown that the tread pattern has little but measurable effect on aerodynamics.
It is also important to optimize tire pressure, as either too high or too low pressure can significantly increase rolling resistance. Always pay attention to the manufacturer's suggestions and explore in practice to comprehensively determine the required tire pressure.
Fit and adjustability
Cushion
Given the aggressive riding position of the time trial, the choice of saddle is essential to maintain comfort and prevent injury.
Use saddles that are specifically designed to reduce soft tissue stress when riding in an aerodynamic position, as they will allow you to move your hips forward and exert more power in an aerodynamic position.
The relatively long rails will also allow for a wider range of adjustments, and the seat tube of some older time cyclists is limited to a fixed position, and the saddle's function is even more obvious.
The choice of saddle is somewhat personal, and you shouldn't experience noticeable numbness or pain while riding a time trial. If you have this condition and need to seek professional help, fitting can help optimize your saddle selection and position.
Handlebar Part II
When buying a time bike, the adjustability of the handlebar is absolutely crucial. If the handlebar can't be adjusted enough to allow your body to adopt a sustainable aerodynamic position, it doesn't matter how well it performs in the wind tunnel.
Generally speaking, a good handlebar can be raised and lowered to extend the rest handlebar, and it can be adjusted front, back, left and right. Adjustable angles to extend the handlebars are also important, and many riders find that relatively high and steep handlebars are more aerodynamic and comfortable than low, flat handlebars. A low frontend isn't always faster.
How to find the right posture for you requires a lot of experimentation, and everyone's posture is unique. You can conduct these experiments yourself using equipment such as power meters and/or speed sensors, or get professional help in a wind tunnel or on the track.
As of 2023, drivers competing in UCI-approved events have more freedom in terms of timed handlebar extensions.
Time trial jerseys, helmets, and accessories
Time trial equipment isn't just about bikes, your body is the most resistant part of the system, and anything that improves the flow of air through your body can make a huge difference.
Tight-fitting cycling suits, time trial helmets, pneumatic socks, and shoe covers can all be used to make yourself more slippery. Helmets, in particular, can be difficult to know which one is the fastest for you without testing, and its interaction with where you are on your self-ride is crucial.
However, there is a current trend towards timed helmets getting bigger, with the Giro Aero head II being the most striking and controversial example. Other pro riders use lighter, more ventilated time trial helmets, such as the POC Procen Air, on the track.
Time Trial History
The earliest example of the use of a time-trial-specific handlebar was at the Tour de France in 1989, when Greg Lemond used the Scott handlebar to overcome a 50-second deficit behind Laurent Fignon to win the overall by 8 seconds.
Previously, drivers had just used standard road bikes and regular down-turn or horn handlebars for time trials, only changing wheels, drivetrains or tires depending on the track.
As Francesco Moser prepares to break the one-hour record in 1984, he upgrades his bike, wheels and clothing, but his riding position remains largely the same.
Lemmon's victory ushered in a new era that followed with an arms race that eventually led to riders like Graeme Obree and brands like Lotus and Pinarello pushing things to extremes.
UCI Time Trial Rules
At this point, the UCI (International Cycling Union) stepped in to control the development of events, introducing a strict set of rules (known as the Lugano Charter) that dictated how road, time trial and track bikes were designed and the riding positions that riders could adopt on these bikes.
The UCI's ban on the use of innovative equipment and technology is a great (and much-criticized) tradition in cycling that continues to this day.
Some ingenious drag reduction concepts, such as the "praying mantis" time trial position, overly long socks, etc., have been used in cutting-edge areas, but have since been banned. The goal of these rules is to ensure that cycling should remain competitive rather than engineering, and this is a credit to UCI, not without value.
It gives you an idea of what would have happened without such a set of rules: the one-hour record for a human-powered drive is currently 92.432 kilometers (set by a recumbent bicycle with a MetaStretto fairing). This is 35.64 km away from the men's UCI one-hour record (56.792 km) set by Filippo Ganna in 2022. This difference is almost entirely due to aerodynamics, so UCI has to draw a line somewhere.
But as with any rule, savvy athletes will continue to look for loopholes and overlooked exploitable opportunities. And, given that the aerodynamic performance of traditional upright riding bikes is very unsatisfactory, there are undoubtedly opportunities for improvement.