The differences in terms of time saved on a race course are, to close approximation, the same at 20mph as they are at 30mph.

The most important feature in a wheel for speed advantage is less aerodynamic drag. A distant second would be weight, a very distant third would be hubs.

Flo may be just as good, or nearly so, as Zipp aerodynmically. Boyd's I don't know.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Thanks. I would have thought hubs would have been more important. Specific to aerodynamics, what's more important, rim depth, width, shape, dimpled/non-dimpled, etc...

A hub that has gone bad can be a big problem, but bearings are not complicated things and the differences between various hubs are usually pretty small.

dimples or not is a very small detail that can probably be entirely ignored.

shape and depth are the key things. A good shaped 60mm deep wheel can be faster than a not so good shaped 90mm deep wheel.

for the rear, if a disc is allowed, it is pretty much always the fastest choice, and it doesn't matter much which disc you use, or you can use a disc cover.

for the front, go as deep as you are comfortable with in crosswinds. More important to pick a good shaped wheel here, since aero matters more up front.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I have a pair of 1080's circa 2009/10. I could probably handle the 1080 front in moderate winds, but would want to get a second front wheel (50-60mm) for those occasions when it's too windy. I also thought about getting a pair of 50-60mm that could also be used for crits and use a wheelcover during tris. I'm just trying to find the best balance between function and price. Thanks for your help.

Please excuse the thread highjack but this area has been a question for me as well:compare a 60mm to a 50mm-say Dura Ace c50 vs.HED jet 6.

You're deep into the area of fine tuning when you compare a 50mm deep aero rim to say a 46mm or 60mm rim. In the wind tunnel or in theory for similar cross sectional shapes the 60mm rim will perform a bit better to slightly deeper yaw angles (so better in cross wind situations) but will do so at some price in terms of handling in gusty cross wind situations. So the irony being the situations in which the deeper rim can give you some advantage is also the condition where in gusty conditions a deeper front wheel can make things more difficult.

Different rim cross section designs will handle a bit differently and the vendors show data that some of the newer blunt designs (like the Zipp FC series) can be a bit lower drag at shallower depths and may handle better for roughly the same depth.

All of that is great for choosing say a 46mm deep rim for general purpose road racing in windy conditions vs. say a 90mm deep rim for timed events in less gusty conditions or for a bigger rider or one who has a better tolerance for bike handling in challenging winds but for splitting hairs between say a 46mm and a 50mm rim of similar design or a 50mm vs a 60mm deep rim of similar design it's gonna be tough. The differences aren't so dramatic for a few mm here or there that it's a slam dunk and a lot of it depends on your own tolerance for gusty winds.

Sure look at the aero data for the wheels in question and if the designs are substantially different the answer may jump out at you or think about what conditions and what kind of races you'll use these in but it's not a black and white question for small changes in rim depth. So make the call on things like: price, weight, looks, published data and how you think you'll use the wheels.

-Dave

I hear this statement ("if a disc is allowed") every now and then. What races are they not allowed in generally? Does it have to do with who sanctions the race or weather conditions?

Thanks for the response Dave.I've felt like it was kindof splitting hairs so to speak but wanted to pose the question for those much more knowledgeable than myself.I can only read the different charts for so long and even then I wonder how much they are skewed toward different manufacturers.Lately "real world" scenarios have been posted a bit and that seems to give quite a bit of useful info.

I ride my Enve 6.7's (tubular) almost all the time. If I compare them to the Neuvation 50mm tubulars I had before, I can tell you that:
1. The braking is 100% better. They are 95% of the braking you get with a good alloy wheel.
2. They are so stable in cross winds that you can't tell you are riding deep rims.
3. They are spectacularly fast and durable.
I have to admit that I use Jantex tape, and not glue on them. I also use swisstop yellow pads. I also run Vitorria corsa Cx tires for every day (they are so cheap from the UK) and continental Podium TT's for triathlons.
I haven't ridden the 404 firecrest, or Hed Stingers, but the 6.7's are as close to being the perfect wheel set I have come across.

discs are generally not alowed in any sort of road race, except a TT.

I'm not so sure about dsics for ITU goverend races. never seen it before, so I'm assuming it isnt allowed.
for triathlon, discs are not allowed in ironman races if very strong winds are predicted- e.g. case in point being kona.

In the U.S., disks are legal for mass start events (1I1c)

Kona does not allow disc wheels. For many of us (including me) it's likely never an issue.

http://forum.slowtwitch.com/...um.cgi?post=3390626;

from personal use. HED vs Easton vs Boyd. Boyd hangs just as well and is a lot more affordable

So far I really like my Williams 85 Clinchers. $1200 for the set