I’m 6-3 and race at about 162 lbs. I run a front HED3 and a HED3D rear in races. I’ve trained with both combinations, HED3 front and rear and my above race setup. The wind greatly effects the bike handling more with the HED3’s front and rear, then it does with the HED3 front and rear disc. I can get blown off the road when the Atlantic Ocean breezes on A1A kick up when I run both HED3’s. Its much more stable with the rear disc. My Zipp 3000’s, front and rear, are better in a wind then the HED3’s for handling. Not faster, just more stable.
If you are a poor bike handler, you need a shallower wheel than the Hed 3. Just my $.02
Helmets: My thoughts on this are that since consumers will likely never see the wind tunnel testing comparisons, we will have to rely on what the manufacturer shows us, and what the frontal area of the helmet looks like. If it looks aero, chances are that it probably is. That is the best we can do right now.
Disc: Josh at Zipp says they tested the CH cover, and that Cobb tested it, and both tests show that it tested slower than a disc wheel. Zipp’s competition is not a CH cover (as it weighs over 500g), so I see no reason to question his statement or honesty. Maybe it is only marginally more aero, however combine that with the 500-700g weight savings vs. a wheel with a cover, and the dimpling, and it is clear to me that the Zipp is faster. So I believe that a “disc is a disc, as long as it is a disc” with the 2004/5 Zipp 900 being the fastest of the discs.
Thanks for the replies regarding my HED 3/disc question. I’ve done quite a few rides with my current bike since getting 650 HED 3’s last summer. I’ve white-knuckled it a bit when it’s been very windy but I figure training on the wheels will help improve my bike handling skills. Also, the consensus seems to be to run the disc on the rear for more stability. I’ll probably do that for my next IM (IMA). I’ll be sure to get some rides in on the disc first, even though the weather here will suck that time of year.
I’m getting a disk to complement my HED3front and replace my Corima 4 spoke rear. The current set up can get exciting with gusty cross winds/passing trucks (I’m 5’11" and 143lbs)
I’m getting a disk to complement my HED3front and replace my Corima 4 spoke rear. The current set up can get exciting with gusty cross winds/passing trucks (I’m 5’11" and 143lbs)
Yes, my current HED 3’s can get quite “exciting” when fully-loaded logging trucks pass 6 inches by me at 60 mph and the only thing to my right is a ditch with a barbed wire fence at the bottom. The only thing I’m not sure about is how much of my training should be done on the disc vs. the HED 3, which is the only other wheel I’ll have.
John Cobb has placed a simple explanation on his site on side wind stability of 3 spoke wheels and how the rear disc acts to add stability to the system. The thing with composite spoked wheels is not so much that they have high lateral force issues in cross winds, but that they have very non-linear side loading in cross winds. My theory for a pair of these wheels is that you can have a very large shift in lateral loading with a relatively small wind velocity or direction change and since the rear wheel is somewhat fared in by the frame and rider, it will not see the identical wind velocity or direction shift. Both the disc and deep section wheels tend to exhibit very linear lateral loadings, making their behavior more predictable, and I think that it is predictability in handling and not magnitude of side load that makes people nervous.
http://www.bicyclesports.com/Side_Stability_of_Wheels_in_Crosswinds.html
As for the CHAero cover debate, I do not debate at all that these covers are a very good value, but I think Cerveloguy is missing my point on data collection. I understand that there is little unbiased information out there as far as tunnel testing goes, but it is so expensive to do that it is hard to get enough runs in to have statistically viable data. I find it interesting that the Zipp disc used in the mentioned test performed considerably worse than the 404 used in the same test? I think one change in protocol since then has been to take the wheels to the maximum yaw angle and then bring them slowly towards zero measuring at 5 degree increments. Prior to this we would measure from 0 to 30 in 5 degree increments, but if you run the test from 0-30 and back to 0 you have large hysteresis issues, where the 0-30 plots can look very (falsely) good as the wheel can be yawed slowly enough that the airflow separation is prolonged (this is only really works with lens type discs). The problem with the old method is that you could get wild swings in data, wheras with the newer method the data tends to run within a 5% or so band, vs. the +/-20% swings which were not uncommon with the old method, so in deriving data from a single run, there is a larger potential for error. Since real world airflow is generally turbulent, and not the perfectly straghtened flow we see in the tunnel, the change in protocols yielded not only more repeatable data, but more accurate real world data as well, plus it removes any temptation for manufacturers or whoever to selectively ‘choose’ what data to publish. We have tried to take this one step further by publishing only data averages of a minimum of 3 runs, and having the wind tunnel staff handle all the data to eliminate the claims that we are manipulating or selectively publishing some data over others, but doing both of these things is very expensive and would not be possible for everybody’s testing.