So the argument goes on and on about aero and benefits, if you are faster or slower, does it help etc. etc.
My question is, is the benefit of a disc wheel equivalent when you are riding into a strong headwind, albeit slowly due to that strong headwind (and because I am a bit of a wimp) as to say riding along smoothly at say 22 mph with minimal headwind?
Say 20 mph hw for the sake of argument.
I’m no expert on discs or wheels, but to use aeronautical terms. It is the air speed. (In this case, the head wind plus the bike speed.) Down it is the ground speed minus the wind speed. If you are going 10 mph into a 20 mph headwind the aerodynamic effects are pretty close to 30. Rolling and bearing friction are not effected by the wind.
you get much more bang for your buck in a head wind. Just like the previous poster described. It’s all about airspeed.
What about a crosswind ? The wind can’t pass through the wheel like it can with a spoked wheel. Surely that must slow the bike down ?
Depending on the angle of the headwind/crosswind/tailwind, you may still find a small percentage of net gain. For example, when riding in quartering headwinds that can become direct crosswinds - well, this would be dependent on wind velocity (20 mph+) - I think we probably would realize a slightly reduced aerodynamic advantage over someone riding aero/deep section, spoked wheels due to the fact that some amount of effort will be used simply to maintain a straight line when riding the disc. As the wind changes so that it becomes more of a tailwind component (quartering tailwind), then to some extent my experience indicates that the disc will begin to act similar to a sail which increasies efficiency while reducing the effort required to maintain tempo. In most cases, it is probably a good idea to take two sets of wheels to a race - a disc/full aero setup and a more conventional set in the event that on race day, the wind on the course is such that it would blow you off the road with a disc in back (been there - done that)!
Michael
So the argument goes on and on about aero and benefits, if you are faster or slower, does it help etc. etc.
What argument are you referring to?
I’m not sure there is any argument at all the a disc is almost always faster and the best choice. The only possible exceptions are uphill time trials and a very light, weak rider on a very windy day.
the only argument that I know of is cost/benefit and that is an individual economic decision, not a speed question.
I ride in 20-30mph crosswinds with a disc frequently down here in Florida because of the direction of my standard 20 mile loop. Going 20mph with a 20mph 90 degree crosswind equals a 45 degree incoming wind vector at about 28mph. The disadvantage of the disc is that it “pushes” you a lot with that kind of wind. A “push” from the rear of the bike is very easy to control though… The nice part is the disc has pretty close to zero rearward drag (0.15lb approx) at that wind angle compared to a spoked wheel at 0.8lb approx. It’s still a significant advantage in a direct headwind, consider the same 20mph headwind is an effective 40mph forward airspeed…but it only takes a 5 degree wind shift from direct to allow the disc to have half the drag of a conventional 32 spoke wheel. In fairness to other wheel types, a good aero wheel such as an H3 or 404 will have drag numbers at low wind angles (0-10 deg) that are almost as good, but the disc is far superior above that.
The real issues I’ve had with being shoved off the road are with the front wheel. I bring two wheels, a Hed Jet60 and a Velocity Spartacus…60mm vs 30mm rim depth. If I see huge crosswinds I use the Velocity…even going between buildings where the wind is 0mph and then suddenly 30+mph I have no handling problems. With the added side area of the Jet60 it gets a little twitchy with massive crosswinds, but anything at or below 20-25mph seems pretty stable.