Okay, before anyone jumps on me I did search the forum over the last couple of days for an answer to my question. I could not find an answer. If anyone has a thread they would like to share I would be very grateful.
My Question: On the bike, do you have to average a minimum speed to achieve the full benefits of something like a wheel cover on your rear wheel (from wheel builder)? This is my first half ironman. I did the course last weekend and I averaged 21MPH. I have a 55mm wheel from Mercury Cycling. Any idea on time savings? It’s a very very flat course.
Times saved depends a lot on the angle the airflow is hitting the wheel.
Generalizing hopelessley, if there is no wind, or if it ends up as being a straight head/tailwind then the savings are fairly minimal. At other angles there’s a lot bigger difference.
Okay, before anyone jumps on me I did search the forum over the last couple of days for an answer to my question. I could not find an answer. If anyone has a thread they would like to share I would be very grateful.
My Question: On the bike, do you have to average a minimum speed to achieve the full benefits of something like a wheel cover on your rear wheel (from wheel builder)? This is my first half ironman. I did the course last weekend and I averaged 21MPH. I have a 55mm wheel from Mercury Cycling. Any idea on time savings? It’s a very very flat course.
No, you don’t need to have a minimum speed. Aerodynamics doesn’t just suddenly turn itself on. Even for low speeds, aero drag is the largest component of resisting force on the flats.
I recommend you play around with this and see the impact of a 5% reduction of drag. Look at the difference in finish times between, say, “hands on drops” and “triathlon bicycle”: http://www.kreuzotter.de/english/espeed.htm
Using a wheel cover or disc wheel over your 55mm wheel would reduce drag by at least 100g in most conditions. 100 grams would very roughly translate to 10 watts. So given the exact same conditions, you’d likely go at least 21.5MPH had you had that wheel covered, or ran a disc. This is a 4 to 5 minute advantage over 56 miles.
in perusing the Hed link above I found C2 and FR technology… as well as Stinger and Jet differences in disc speeds.
know the deal with all that?
you have been here a while and you don’t know what c2 it?
c2 is a technology where HED makes the rims too wide to fit in your brakes so you have to adjust them every time you switch from training wheels to your race wheels
FR is a technology where HED shaves a couple grams of weight exchange for a couple hundred bucks.
the drag difference between stinger and JET discs is probably due to the shape of the Jet brake track being flat, vs part of the overala profile on the tubular wheel. also maybe marketing.
to totally derail… Zipp has 3 discs and Hed has 2 or 3 variants… does any of that matter in a properly faired frame like a P4? I’m thinking the difference would be minimal, even in high yaw.
“does any of that matter in a properly faired frame like a P4?”
Well, if you worked for HED/Zipp and were drawing up the chart, you would obviously make the more expensive wheel come up as more aerodynamic or it wouldn’t make any sense…and you definitely wouldn’t include a cheap ass plastic cover on a training wheel in your chart.
c2 is a technology where HED makes the rims too wide to fit in your brakes so you have to adjust them every time you switch from training wheels to your race wheels
FR is a technology where HED shaves a couple grams of weight exchange for a couple hundred bucks.
I’ve heard from people who have tested it in the tunnel that the differences are small
but that the flattish discs tend to do better in the well faired frames like a p4.
but yeah, small.
I’m a Zipp guy. Firecrest or death!
to totally derail… Zipp has 3 discs and Hed has 2 or 3 variants… does any of that matter in a properly faired frame like a P4? I’m thinking the difference would be minimal, even in high yaw.
