The decision to go clincher is one of practicality. When you have to affect your own repairs and the right clincher tire/tube combo can outroll many tubulars, going wired is wise. This is the reason many will pull for the ENVE SES 8.9 Clincher Wheelset.
The ENVE clincher and tubular rims have exactly the same shape. The tubular 8.9 are so fast they rival disc wheel setup, so the same goes with the clincher version. The difference is what happens inside the brake track. The clincher adds a little weight to accommodate the unsupported walls. The trade-off is quick tire changes.
The great thing about the 8.9 is that the rear wheel rivals discs for aerodynamics—coming within 5% in tests—while being a better climber, easier to accelerate, easier to handle, and more comfortable to ride. And the front wheel is easier to handle than most deep wheels at approximately zero aero cost. In fact, if you want to optimize aerodynamics, use 23mm tires; they test the fastest.
The secret is Simon Smart. He took knowledge gained as a F1 aerodynamicist and applied it to bikes. In the real world, winds are gusty, so he designed for gusts. In the real world, wheels are locked into bikes, so he designed by working with the wheels in bikes. He found that a shallower, wider front wheel, 85mm deep by 26mm wide, when paired with a deeper, narrower rear wheel, 95mm deep by 24mm wide, offers better handling, better aerodynamics on the road, and has the benefit of fitting just about all bikes—particularly important when you have a narrow TT bike.
ENVE took their knowledge as a composites company and applied it to construction. Molded spoke and valve holes are stronger, so they did it. Removing bladders is lighter, so they did it. Laying up a unique blend of carbon and resin at the brake track keeps the track cooler and a cooler track is better for tire safety and braking, so they did it.
They also didn't like the performance of conventional carbon brake pads, so they designed their own. And they come with the wheel. Use 'em; they're essential to the warranty.
Not that they think you'll need it. ENVE takes pride in building their rims and wheels in Utah. They're so confident in them that they not only have a five-year warranty on their products, but they also have a lifetime crash replacement policy where they'll replace any destroyed ENVE product for 50% of MSRP, provided the customer has the paperwork to prove original ownership.
ENVE also packs in four valve extenders, two rim strips, and two titanium-shafted ENVE skewers into a bag along with the wheels.
These clincher wheels offer two hub options. One is Chris King's R45 Ceramic bearing hubs. The other is DT Swiss 240 hubs. Both sets come with DT Aerolite spokes; sixteen radially-laced in front and 20 two-cross rear. Both hubsets have the option of cassette bodies for either Campagnolo 9/10/11 or SRAM/Shimano 10/11 cassettes (and you can buy extra bodies to swap easily). The DT Swiss weigh in at 1800g for the set, with the Chris King at 1785g.
The ENVE SES 8.9 Clincher Wheelset is where you want time trial wheels and you do your own repairs on the road