Time trial and triathlon bike 2014 round-up
Eurobike gave us the chance to have a look at most of the latest time trial bikes on the market at the moment, and it’s an area where developments continue at pace.
The UCI have many equipment rules that govern bike design, including the stipulation that a frame tube’s depth to width ratio can’t be greater than 3:1, and that the deepest any tube can be is 80mm. One effect of these rules is that they force frame manufacturers to go down similar paths, so you see a lot of very similar designs emerging…
A decade or so ago, for example, Cervélo came out with a cutaway seat tube, the trailing edge following the leading edge of the rear wheel (this, above, is their up-to-date P5). These days, every single time trial bike on the market has something similar. Yes, there’s a degree of variation, but the principle is proven to work so everyone follows it to a greater or lesser extent. The same is happening in other areas of the bike…
Take the head tube area, for example. CFD (computational fluid dynamics) and wind tunnel testing have convinced most people that an integrated design is the most efficient way of managing airflow. In other words, rather than having a fork steerer that extends up beyond the height of the top tube with a stem added on top, manufacturers are now almost universally reducing the length of the head tube so that the stem sits flush with the top tube.
Manufacturers are doing a similar thing at the bottom of the head tube to bring the fork crown within the silhouette of the frame so as not to increase the size of the frontal area.
Here’s an example provided by the Merida Warp TT, for example. So, rather than having a head tube, a stem and a fork crown all presenting themselves to the wind, everything is integrated within the frame’s existing silhouette.
And here’s the Lapierre Aerostorm. It’s certainly a different design, but it has similar head tube elements with the integrated stem and the hidden fork crown.
The other basic head tube design that has been around for a few years now is with an external fork steerer. Running a fork steerer inside the frame means you need a head tube with a wide diameter. Run the steerer externally, with a bearing at the top and bottom of the head tube, and you can slim it down.
Here’s Look’s solution on their 596.
And here’s the Stevens Super Trofeo. They’re showboating it with an integrated stem too.
Interestingly, Focus are bucking the trends with the front end of their new Chrono Max. Check this out (above). So, they have a traditional-style fork steerer running through the head tube, then a stem, and then a bit more head tube. Is that how we're describing it? An interrupted head tube, maybe? Anyway, it's the first time we've seen this particular way of doing it. They certainly like it at Eurobike: the Chrono Max won a design award.
You’ll notice that the Merida (scroll up) and the Look (above just a little bit) have their front brake stuck out there in the traditional place at the front of the fork crown. When we went to see Merida earlier in the year, they told us that positioning the brake there meant a penalty in drag, but a tiny one. They were prepared to stick with that design for the convenience – simple wheel changes and so on.
Other brands, though, have been busy working on brake placement. Here’s the Ridley Dean with the V-type brake hidden behind the fork legs so that it’s just the brake shoes and brake blocks that increase the size of the frontal area.
And Cannondale do something similar with their Slice.
Storck position the brake within the fork on their Aero 2 and run the cable in via the fork crown. Check out the Lapierre (above) for a similar solution.
Trek weren't at Eurobike because they do their own Trek World shows in the summer where we saw the latest version of their Speed Concept TT bike.
The level of integration they've developed for their front brake is amazing.
Positioning the rear brake behind the bottom bracket is a common approach. Not only is the brake sheltered there, it allows manufacturers to do without a brake bridge between the seatstays, as on this Wilier Twin Blade. That’s an aero benefit and also allows for a greater amount of compliance.
Felt have gone for a similar rear brake position on their new IA although this bike, unlike the others here, doesn’t comply with UCI regs. It’s designed as a triathlon/non-UCI time trial bike – hence those low slung seatstays and the super-deep frame elements.
Trek have a Speed Fin that they fit to smooth the airflow over the rear brake on their Speed Concept TT bike. It's not UCI-legal, though, because it's a fairing; it's for use in triathlon.
Speaking of incompatibility with the UCI rules, this is the front end of the Cervélo P5 with a fairing running from the stem to the fork. This breaks the rules although it’s allowed in triathlon. Cervélo do make a UCI-compliant version, of course, without this arrangement.
That brings us neatly on to another frame element that’s doing the rounds now… the super deep seat tube and top tube junction. This is the P5’s (you can tell by the massive P5 written on the side!).
And here’s the same area from the Scott Plasma. It’s a broadly similar design.
Lapierre’s Aerostorm is less extreme, but you can see that it’s coming from roughly the same place.
And the same goes for the Fondriest TVF.
One final feature that’s made ground over the past few years is the use of widely spaced seatstays, the idea being to get them as far as possible away from the rear wheel to help manage airflow over the back end of the bike.
You can easily see what we mean here with a rear view of the Ridley Dean. The chainstays kink out from the seat tube and give the rear wheel plenty of space before heading down towards the dropouts.
Here’s a side view of the Cannondale Slice doing a very similar thing.
And the Scott Plasma. Cervélo, Merida, Wilier, Storck… They’re all at it!
http://road.cc/content/news/93470-2014-time-trial-and-triathlon-bike-round
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