We were lucky enough to be given access to the extensive R&D process behind these wheels, the second in the Smart ENVE System range after the deeper 6.7s that we tested last year, so we know just how much work went into them.
Not only are these carbon hoops light and aero, but ENVE say the specific front and rear shapes – the front is 35mm deep and 26mm wide; the rear 45mm deep and 24mm wide – make the wheels more linear in their reaction to crosswinds for more stability.
We weighed this pair at 1,277g so you won’t be surprised that they climb like a Saturn V rocket. And yet they feel like specialists on the flat too, holding speed better than all but the very best 60mm wheels that we’ve ridden. Everywhere during our first few rides on our local roads we found we were pushing speeds that we’d never reached before. One 31km 'long route home' has only been ridden faster on a time trial bike.
We didn’t expect ENVE’s stability claims to translate into noticeable characteristics on the road but these wheels aren’t just a bit better behaved in blustery conditions – the difference is incredible. Gusts of wind are able to grab some deep-section carbon wheels, to the extent that your stomach lurches from the surprise and the expectation of getting dumped onto your face. In contrast, the 6.7s seem even more stable than regular aluminium rims.
The superlight Chris King R45 hubs are so called because they have 45 pawls on the freehub ratchet so there’s no slack when you get on the gas out of tight corners. This set bedded in and came a little loose after 100km but adjustment is quick and easy. There’s also the option to have DT Swiss 240s hubs for £2,200 ($2,900).
Each wheelset comes with valve extenders and specific pads for the machined brake tracks. Braking performance is excellent in the dry but only average in the wet. The extreme width means you'll have to set up your brakes from scratch when you fit them and, like all of the new wave of super-wide rims, the ENVEs stretch the limits of a dual-pivot calliper's efficient range. This can create a different feel at the lever but no significant loss of power.
There are cheaper and lighter carbon wheels available with similar rim depths and aero properties to the 6.7s. But ENVE's wheels have a reputation for bombproof strength – their moulded spoke holes have apparently never suffered a failure and they make the only carbon fibre rims ridden to victory in the UCI Mountain Bike World Cup downhill series – and the 3.4s offer exceptional stability. They're up with the very best wheels that we've ridden.