Interesting comments by Steve Hed (from a quick interview posted on CyclingNews)…
"CN: What is next on your list to make the fastest components possible?
SH: The next project I think is a new rear wheel. As bike design is changing, as aero seat-stays and aero seat-tubes are changing, a disc wheel is probably not the best wheel for the future anymore. I think a tri-spoke or some version of something else… that’s what we are working on next is trying to replace that wheel with a wheel that will be lighter and little bit more aero."
If there is one thing that I’ve always liked about Hed, its his ability to challenge even the most stoutly held dogma…even that which he had a heavy hand in creating in the first place.
Unless they find some way to geenrate extra thrust I fail to see how they can get round this. However challenging fundamental design principles is something the real innovators have always done. A formula 1 car nosecone is a great example of this.
Its probably important to note the words he used…i.e. “not the best wheel” instead of “not the most aero wheel”. There is quite a bit of room for Steve to clarify what “best” means…but remember…he’s talking about the rear wheel as part of an overall aero “system”…and not standalone.
OK. I really like the Hed products. I’ve used Jet, Cx and Deep 90 wheels and they’re all excellent. Also like that you can phone them up any time and the fact they publish their aero data on the website.
Steve’s obviously a very smart guy, but I’m curious to see what he is talking about here.
According to Zipp’s own data a set of 808’s is only 2-4 secs slower than the 999’s over a 40k. And they are 190g lighter. Not to mention the better handling and ride that spoked wheels offer. I’d say the “future” is close to being here.
In that same article it showed pictures of Lance’s TT helmet, that I assume must be legal here. Based on appearance alone it looks faster than the other enormous TT helmets on the market here.
I have been wondering if it would be posible to make a hub with and aero deep section/faring and then spoke it up to with a deep section rim what the ride and aero effects would be. I guess it might not be possible to make a stong wheel this way. I was thinking that the rim section need not be so deep making the wheel lighter at the rim. Say if you had a 40mm rim depth and 40mm hub depth you would have 80mm in total - the same as a 808. I guess there is probably a good reason people make the rim aero and not the hub - either more aero, easy/cheaper to do, stronger, handles better?
think about it. say you’re going 25mph. now i’m no physics major, but since the bottom of the wheel is going to be moving at 0mph (it stays on the ground), the top of the wheel moves at 50mph. since aerodynamic drag increases exponentially with speed(right?), the prime savings are at the point where the spokes/rim are moving the fastest, ie 50mph, or the top of the wheel. at the hub, you’re just moving the speed of the bike.
this ring a bell? someone tell me i missed something. this is really simplified, but i fell like it answers the question at least.
I barely remember science enough to follow your explanations, but I did read once that something in the area of 90 percent of the drag a wheel experiences is in the first 2-4 inches from where the spokes connect to the rim.
Thus the reason why most deep wheels are at least 50mm (25.4 x 2=51mm). As the rim becomes wider and wider the aerodynamic gap between a disc and a deep rim will close to close to zero. 50mm rims are really just a compromise between weight, aerodynamics and handling. A deeper rim would be less aero, but heavier and less versatile.
I think I know what he’s talking about.
I’d imagine he’s thinking of designing a wheel similar to the current design of his disc. (Lenticular.)
The idea would be to make the rear of the bike more tapered aero to try and clean up airflow coming off the bike and legs. It would probably be a pretty thick rim, with some reasonable depth. I’d doodled a couple bike frame designs that mimic the same idea, but I’m not really sure what kind of real world benefit they would actually have. Mostly the whole idea would be more trouble than it’s really worth. (It would look darn fast, though.)
He’s the wind tunnel expert, not me, but I can’t imagine it actually working well. It could cause quite a stir underneath a pro athlete or two, but I don’t think consumers would go for it.
A ZIPP disc, while expensive, is lighter than a rear Ksyrium SSC SL
And they added dimples … Hey, it does change the boundary layer, ala golfball, but I’m not sure exactly how much this helps. At last companies like HED and ZIPP are trying.
Interesting words from a guy whos disc wheels are the weakest thing in his line. Hed gets Aces for his Trispokes, deep dish and Alps. His discs are fragile, heavy and more expensive than some of the competitors. I ride his trispoke disc, which is the best wheel he has ever made (in my opinion) and the trispoke front.
I think the trispokes are getting out classed by the deeper dish aero weels in the front. Although for a what 12 year old design, not too bad. G
