What bike? I believe something like an old p2/p3 is faster with a flat disc like a zipp 900, whereas a more modern bike can be faster with the new contoured discs. Personally I'd go with the premier or flo discs, leaning more towards flo since they're a slightly more proven wheelbuilder, nothing against premier but I just dont know enough about their wheels specifically while flo is a known

I do have a 2011 p2, interesting that the disc shape matters

Disc faster than wheel cover? The “whoop whoop” has to be worth at least 10 seconds

A disc cover is slightly slower I believe, while not a bad option, if the budget is there for a disc I'd still do that. A little looking says a flat disc is fastest on an old p2c, but there is also some disagreement. Best choice might be to just see what's available on the used market, unless someone has better information than I do

I had this dilemma and went with a used tubular Zipp discs. They are relatively cheaper and luckily I haven’t had a single flat for the past three years. I put sealant in there already so that might have helped. Anyway, it’s fast and I like it a lot. Great bang for the buck for me and it’s been serving me very well.

1. I'd go with Zipp 900 too. Old models are pretty cheap ( I bought two older models for my daughters and paid $350./ea. in mint condition, plus $30. for 11S machined cassette body). They're proven fast, bearings are easy maintenance. And they're half a pound lighter than most of the competition.
2. Maybe the only drawback I'd see is for a heavier rider, larger tires may not be as fast with such a narrow disc, and smaller ones not comfortable for long events.
3. Where do these left cloumn numbers come from anyways (don't understand !?!&!!&) ?

Louis :-)

Another option is a used Renn disc (flat, structural disc like the 900). Mine was ~$250 IIRC (it was years ago, and I still run it).

Personally, I'd go with the cover in your situation. The flat disc may be faster, but differences between discs (or wheel+cover) are in the low single digit seconds. The only thing you lose is the wuuump wuuump of the structural disc that basically is the Jaws theme as you come up on your minute man :).

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There is a guy on EBay with a whole raft of HED Jet+ discs. I am guessing that they might be the old Rally team wheels. Hard to go wrong running one tubeless with. Corsa Speed.

Haha this noise is unforgettable. Never heard it until my first 70.3 - lol

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+1 for the Renn 555. Really like mine. Full on whoomp.

Flat disc are absolutly not faster. If you take the exemple of the Hed jet disc, the wheel is not flat, and if you take the aerocoach data, you will see that this is the fastest disc wheel (after the aerocoach disc for sure.....). But the aerodynamic difference between Hed disc or Zipp disc will be 1 watt, or 2 max, depends of the bike.
But one thing is sure, i will not go with a tubular disc. I own tubular and tubeless wheelset. I use stinger 5 tubular for pleasure ride, because i love velofkex tubular. But for racing, i and you (if you have choice) must ride tube or tubeless. Why will you buy a disc wheel to save 5 or 6 watts vs your flo clincher, if you have to lose 5 watts in rolling resistance ?? (except if you ride on corsa speed tubular but so fragile, and still little bit slower than a gp5000 TL in tubular version.

To finish, i will speak about the wheelcover. I wanted to try, so i bought one to fit a rear Bontrager aeolus 7. It was so nice that i sold my Hed jet disc +, and bought another one for my Hed jet 9 + rear. The wind will never know if your rear wheel is a "fake" disc or not. What i can say is that's a really nice and cheap upgrade. And you can customize your wheelcover to have a special rear disc.

So Flo 45 + wheelcover + good latex tube or good tubeless, and you will be faster than a zipp 900 tubular.

I totally disagree about the tubular thing. Especially for 1hr and less TT's. You can flat and get lucky and maybe be close enough to ride it in and get a respectable time. If clincher you're boned and done. This answer is different for triathlon when it is a 112mi or 56mi ride with possible water/feed anyway.

There is nothing "that" fragile about a tubular TT tire. It's a TT, risks are taken. Do course recon and know where the gravel is in a corner, or that manhole cover.

As for the disc, this scenario SCREAMS for a disc cover. Once per year TT? Yeah, perfect application of this solution.

So Gp5000 TL ;-)

Perfect balance between rolling resistance and puncture protection. "Virtualy" no flat risk with a good sealant, and faster than all the tubular on the market, even corsa speed.

I did ride on tubular during a lot of TT and tri seasons, with corsa crono, corsa cx, veloflex record, sprinter, conti podium TT. And now, I do around 10 sub 1h TT in season. That's true that tubular don't flat very often on TT. That's why i'm still riding tubular all year with veloflex roubaix or vlaanderen, they are bombproof. But when you have to walk 5km with cleat because your tubular is dead, it's very very boring. I agree that with clincher it will be the same. That's why i think tubeless is so cool. If you choose the right tire, you can have very high performance for TT, and just have to focus on your Time trial because you know that you have less than 1% to be stopped by a flat.

Of course I do agree. But some day.

Sad face, not in the cards right now.