Cervelo’s new P4 may have been turning heads at Interbike, but it’s not the only good looking new aero bike on the block. Scott’s all-new Plasma 2 frame is a looker too with aspirations to be top dog. Scott’s objective for the Plasma 2 was simple: to make the fastest time trial/triathlon bike in the world and they have obviously spent a lot of time and money trying to make it so. Two models in the ’09 range get the new P2 frame, the Plasma LTD and the Plasma C20 The bike boasts a claimed frame weight of 1390g for the medium with a 380g frame (a Cervelo P3C is roughly 1300g and the P4 is likely to be around the same) and there is a definite accent on aero shapes and narrow tube profiles: the chainstays are a mere 11mm deep and in all it’s main dimension bar one the Plasma 2 has a narrower profile than the Cervelo P3, interestingly from the pictures we’ve seen it looks like Cervelo too have gone for narrow tube profiles on the P4.
The frame features a number of details designed to boost its aero advantage, most striking are probably the front and rear wheel cut outs – the rear wheel can be adjusted to give the tightest possible clearances – down to the width of a credit card, say Scott. To allow for this Scott have also come up with a very nifty way of adjusting the brake position to accommodate different wheel and tyre choices.

The seat tube features a dramatic cutout shape to give shelter to the back wheel, as does the downtube for the front. Scott claims that this gives a combined 127 deg of “seamless wheel coverage” (47deg at the front and 80 deg at the rear). Ironically Cervelo, who claim to have pioneered the front wheel cutout have abandoned it on the P4 because they now say it doesn’t give any advantage outside of the wind tunnel – cynics might wonder why it’s taken them 13 years to find this out. The new Trek Equinox, on which. Trek insiders say, they spent “a shed-load” (that’s a technical term apparently) of R&D money also does without the front wheel cut out. As with all cutting edge aero bikes, the C2’s fork is fully integrated, and Scott have even given the bottle bosses the aero treatment. The bottom bracket is another area that Scott have obviously given a lot of thought – coming up with a system they dub the Speed Skeg. This aero optimised bottom bracket has a Down fin that channels wind around the rear wheel, allowing for narrower downtube construction, and helping with the internal cable routing. No surprise then that Scott say this is the most sophisticated carbon structure they have ever built. Using their own Integrated Molding (Scott’s spelling) Process 5 (IMP5) the five main tubes on the bike are one structure with only the seat stays and the ends of the Twin Turbo Aero Shock chainstays being added afterwards. Climbing on to one of our current hobby horses for a moment, the laws of physics being immutable and what’s required of all aero bikes being the same you would expect |TT bikes, like Formula 1 cars to all more or less look the same. It does seem that bikes designed purely in the wind tunnel have a particular look as do those designed using a comination of computational fluid dynamics (CFD) and wind tunnel fine tuning – the most cutting edge bikes. Stick the Plasma C2, Trek Equinox 9.9, and the Cervelo P3 and P4 together and you’ll see a lot of similarities. In fact we can’t help wondering if the differences are more to do with marketing than the demands of aerodynamics. Anyway, back to the Plasms C2. No doubt about it this is an impressive machine and Scott claim some impressive drag figures for it too 4.952N of drag (we’re presuming this is frontal drag, we have no figures for yaw), against 5.010 for Cervelo’s P3 – it will be interesting to see how it stacks up against the P4 and Cervelo are already hard at it on the P5…