If you don’t want to read the whole thing, here is the cogent statement:
Aero is THE primary factor of wheel speed. It’s not weight, it’s not inertia, it’s aero. Everything else is obviously huge in terms of nuance, but weight will save you a watt or two. Inertia will save you a fraction of a watt to a watt. Aero will save you 40 watts at certain speeds. It’s huge to go from a wheel like an R-Sys to a wheel like an 808 clincher which is a pound heavier, but it’s about 50 watts more efficient at 30 mph. But of course the problem is in the consumer’s mind, 1350 grams vs 1680 grams, that has real tangible meaning to people. Arguing about inertia seems tangible to people because they’ve always heard that weight is important in wheels because it hits you twice. There’s just nothing tangible about aero."
since the link seems to have issues - can you talk a bit more about how the aero advantage is so big? I mean, wow, 50W sounds huge to me (I think if I could generate/save an extra 50W I’d be flying!)…so very interested.
What conditions have to be in place to generate this? And what “else” do you have to do? Is this just relevant to TT/tris? Could I save that much if I put 808’s on my road bike? And how does this compare to other “aero” savings? For example, I’ve been told by people that having an “aero” helmet saves about as much W as aero wheels but at much lower cost.
or, how does the savings compare to the savings in putting yourself in a more aero position, i.e. well fitted on a tri bike, OR, buying a well conceived aero tri bike vs a road bike? and how do all these things work in concert?
Specialized advertises that 90% of a riders power is used to over come aero dynamic drag. Now 90% seems like a HUGE claim, but hey I haven’t spent any time in a wind tunnel studying the effects of drag. However their claim does seem to match what you saying.
I get the point of this article, but I think there are so many additional factors that play into this. You didn’t see 808s running up the mountains in the TDF, so weight does matter in some situations. Rolling hills or flats TTs yeah it probably doesn’t matter at all, but you throw some good climbs in there and you may wish you lost some weight in those wheels
why do you emphasize body weight? does it matter?
Common lore gives 2-3 seconds per mile per pound of body weight lost for running, so a 10 lb loss would be 20-30 seconds per mile faster. I don’t know if the same holds true for cycling, but enough weight loss would alter your profile on the bike, less wind resistance.
that does seem big,but potentially reasonable as the resistive forces one has to overcome are air resistance, rolling resistance, and gravity (when climbing). I could see how on a flat course, air resistance is much more significant than rolling resistance. Although it’s curious then that more manufacturers don’t have “aero” as a key aspect of their bike design.
but enough weight loss would alter your profile on the bike, less wind resistance.
bingo.
actually, nearly any weight loss alters your profile on the bike. and you are by far the biggest thing out there, so even a 1mm change in body or limb girth can mean an easily measurable drag reduction.
Specialized advertises that 90% of a riders power is used to over come aero dynamic drag. Now 90% seems like a HUGE claim, but hey I haven’t spent any time in a wind tunnel studying the effects of drag. However their claim does seem to match what you saying.
Using math to calculate the power necessary to overcome resistance on a flat segment of road, for CRR of .006 (typical), and CdA of 0.25 (pretty good) while going 24 mph, you need 244 watts:
59 watts to overcome rolling resistance (wheel weight affects this)
185 watts to overcome aerodynamic drag (shape affects this). 90% is a bit high; perhaps at 30 mph (some wind tunnel speeds).
The faster you’re going, or the worse you are aerodynamically, the bigger the difference between those two.
Not sure why the link is not working. It is fine for me and worked on the other thread as well.
I’ve read 80 percent of drag is the ride, so it is probably between 80 and 90 because newer aero bikes contribute less drag. I think Josh said 40 watts and I don’t know what conditions would generate this.
Personally, I’ve run my wheels on a loop course often enough to get pretty consistent results and found the front wheel (60mm Flashpoint with latex and PR 2s) was good for 15-20 seconds in 10K (over my front MA40 box section rim with 36 spokes, butyl tube, Conti Ultra tire). The rear disc gave similar results. Used together they produced about 35 seconds improvement. The aero helmet also improved things by 15-20 seconds, so yes it is a very good upgrade in the speed vs. cost category. Added in to the wheels it was good for another 10-15 seconds. This was at approx. 35kph. Higher speeds are going to produce smaller gains.
I’ve never tested my road vs tri position because the tri bike, for me, is so much faster there is not a question in my mind. My road position is quite upright, designed for climbing and easy training. The tri position is very flat with minimal frontal area. I would suspect the difference to be several mph, at least. Plus it does have narrower head and downtubes, much smaller shift/brake levers and aero bars than the road bike, so the actual bike is more aero as well, though that difference is much smaller than my body position change.
but enough weight loss would alter your profile on the bike, less wind resistance.
bingo.
actually, nearly any weight loss alters your profile on the bike. and you are by far the biggest thing out there,** so even a 1mm change in body or limb girth can mean an easily measurable drag reduction.**
Any published science out there to back this claim? I’m not saying you’re right or wrong; I’m just wondering…
ok, i didn’t think about it from that angle. excellent point. thanks. although what you’re really saying is reduction is body size - as someone could theoretically lose excess fat that was replaced by muscle, and weigh about the same, but be more aero by being thinner but more dense, correct?
Did you read the part about how Carlos Sastre keeps using the 202 … just because … he likes them? I suspect at the speeds tour riders are going the 808 is a faster wheel, even in the mountains, unless the race is an uphill time trial. I’ve read that it takes an 8 percent grade for a light wheel to catch up to an aero wheel in performance. That is to catch up, not surpass. I doubt there is any triathlon course anywhere where a set of 808 wheels would not be faster than a set of much lighter, non-aero wheels.
And don’t tell me about the Alpe D’Huez triathlon. I’ve ridden that valley a few times and from the reservoir to the bottom of the climb is dead flat for probably 25-30K. Any time you might lose on the climb would be more than recouped on the lead-up with the 808s.
Chad
but enough weight loss would alter your profile on the bike, less wind resistance.
bingo.
actually, nearly any weight loss alters your profile on the bike. and you are by far the biggest thing out there, so even a 1mm change in body or limb girth can mean an easily measurable drag reduction.
I would imagine that it depends quite a bit on where you lose the weight on your body.
ride the heavy aeros up an 8% hill for a mile - I’ll be waiting at the top with my shallow carbon’s at 1350g.
very, very few cyclists, even on flat courses, maintain anything close to 30mph
if you want to be truly precise, it is body size on the bike (for TT and tri events) that really makes a difference. but, you are correct, technically this is not always equivalent to body mass.
but that said, body mass and body size (for the same individual) are very closely correlated for 99.9% of the population.