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Aero testing 808 w/wheelcover vs 808 w/out
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Just thought I would pass along some results that my wife tested this week. I know everyone here realizes that a disc wheel is faster in almost all circumstances but for a very specific reason we needed to test this to verify to her team that she would in fact be faster with a disc wheel. The protocol was very simple. We live close to a 5 mile loop in which you almost never have to hit the brakes and allows for all yaw angles especially on windy days and in TX you can pretty much count on that. We used everything she would normally use in a race. Aero helmet, skinsuit, etc. Tires, pressure, enviromental factors were all controlled for due to the fact that all runs were within the same hour and nothing changed in that hour. If anything, the later runs with the 808 alone would have slightly elevated tire temps leading to decreased rolling resistance. The results were as follows:
808 with wheel cover for two 5 mile loops
average power for each loop 202
average time for each loop 12:11.5
808 only for three five mile loops
average power for each loop 205.3
average time for each loop 12:27.6

Range on the tests were +/- 3 watts and she held aero position the entire time on all 5 runs. To be honest that was a bigger difference than I expected. I expected it to be less than 10 seconds and when asked, she said she "felt" the 808 by itself was faster I think due to the fact that it has less rotational inertia but I could be wrong. The one amazing thing that stands out to me is that she can go 24.9 mph on 202 watts. Road condition is good but not great. Winds and temp on that day were 52-58F and 12-15 mph can't remember wind direction but it was consistent. Hope yall get something out of this and if you have any questions let me know.
Last edited by: fwrunco: Apr 7, 18 15:44
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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who is this "team" that needed verification

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Re: Aero testing 808 w/wheelcover vs 808 w/out [ericMPro] [ In reply to ]
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Rather not say and probably shouldn't have included that. Not important anyway.
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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Re: Aero testing 808 w/wheelcover vs 808 w/out [Thomas Gerlach] [ In reply to ]
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Uhhh yeah.
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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Can you say what bike and front wheel?
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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No surprise there. I thought the difference might be bigger.

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Re: Aero testing 808 w/wheelcover vs 808 w/out [Fishbum] [ In reply to ]
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Fuji Norcom Straight w/808 front and Schwalbe Ironman tubular latex tube front tire. Back tire was Zipp Tangente tubular 27.
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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Ty
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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If you are going through all this trouble, you should find a course that requires no braking, do it on a super low wind day, and put the data through a virtual elevation style analysis. "Chung it".

As it stands, this test is sort of pointless, but we already know discs are faster.
Last edited by: FindinFreestyle: Apr 8, 18 10:43
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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Always good to see people testing.

Some tips: use multiple smaller loops. Traffic free and sheltered help. Early morning testing can help with traffic and supply calm weather. As mentioned above the Chung method is good because you can typically see when issues occur (like needing to brake).

Have a look for the ‘platypus’ thread on here for lots more tips on aero testing.

Developing aero, fit and other fun stuff at Red is Faster
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Re: Aero testing 808 w/wheelcover vs 808 w/out [SkippyKitten] [ In reply to ]
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SkippyKitten wrote:
As mentioned above the Chung method is good because you can typically see when issues occur (like needing to brake).

Right, VE is really a way to evaluate goodness-of-fit, with the side effect of being able to be used for parametric estimation.
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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fwrunco wrote:
Fuji Norcom Straight w/808 front and Schwalbe Ironman tubular latex tube front tire. Back tire was Zipp Tangente tubular 27.

27C is quite large for that wheel...my guess is you would also see some aero improvements running a narrower tire (I'd go no greater than 23-24C) on the back. Although the leading edge of the rear wheel is mostly shielded by the frame, it's still important to consider trailing edge discontinuities as well.

Just a thought...

http://bikeblather.blogspot.com/
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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I'm curious what power meters you used, or did you use only one?

I use Vector 3 pedals along with multiple Powertaps, always calibrated before riding. I see +/- 10+ watt drifts throughout a workout. The pedals normally start off reading higher, but then I often see the power numbers converge during a workout.

Sometimes the Vector 3's end up being 10 watts higher again in the third hour, sometimes the Powertap is reading 10 watts higher in the third hour.

The 16 second difference in loop time is probably somewhere around 5-12 watts. I'm not saying the disc is not faster, but that the time differences can also have other explanations.

-Physiojoe
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Cycling coach, Elite racer on Wooster Bikewerks p/b Wootown Bagels
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Re: Aero testing 808 w/wheelcover vs 808 w/out [fwrunco] [ In reply to ]
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fwrunco wrote:
Just thought I would pass along some results that my wife tested this week. I know everyone here realizes that a disc wheel is faster in almost all circumstances but for a very specific reason we needed to test this to verify to her team that she would in fact be faster with a disc wheel. The protocol was very simple. We live close to a 5 mile loop in which you almost never have to hit the brakes and allows for all yaw angles especially on windy days and in TX you can pretty much count on that. We used everything she would normally use in a race. Aero helmet, skinsuit, etc. Tires, pressure, enviromental factors were all controlled for due to the fact that all runs were within the same hour and nothing changed in that hour. If anything, the later runs with the 808 alone would have slightly elevated tire temps leading to decreased rolling resistance. The results were as follows:
808 with wheel cover for two 5 mile loops
average power for each loop 202
average time for each loop 12:11.5
808 only for three five mile loops
average power for each loop 205.3
average time for each loop 12:27.6

Range on the tests were +/- 3 watts and she held aero position the entire time on all 5 runs. To be honest that was a bigger difference than I expected. I expected it to be less than 10 seconds and when asked, she said she "felt" the 808 by itself was faster I think due to the fact that it has less rotational inertia but I could be wrong. The one amazing thing that stands out to me is that she can go 24.9 mph on 202 watts. Road condition is good but not great. Winds and temp on that day were 52-58F and 12-15 mph can't remember wind direction but it was consistent. Hope yall get something out of this and if you have any questions let me know.

WOW, I keep going back and forth on this. I run same 808 front and rear with a power tap hub. I always decided not to as it just seemed like a huge inconvenience.
Mainly race fairly flat to pancake flat tris. due to location, as well as size 220 lbs. So that would then in theory save me 6 min in an IM.
I've been looking at all the data, but couldn't find anything that made it this black and white.
I rode IM last year on a flat course (Maryland) 4:41 on 220 NP, but I was confused as when I used BBS the change from 808 to disc yielded no improvement.
I guess I need to just get a cover and test.
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Re: Aero testing 808 w/wheelcover vs 808 w/out [CJAC] [ In reply to ]
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CJAC wrote:

I guess I need to just get a cover and test.


Yeah, get your own cover and test. Because none of the other tests ever done on this topic are valid. You are sure you find some unique aerodynamic principles that apply just to you.

http://www.wheelbuilder.com/aerodisc-data.html


Data such as this have been confirmed a bunch of times, notably by our own JonnyO who found his 808 with cover faster than a flat disc. (Probably because it resembled a bulged disc).


For 808 vs disc, you could just check Zipps data, which has been very robust when compared to independent testing. IIRC, a disc is less than :10 faster over a 40k compared to an 808. So less than :50 over a 112 mile ride. Certainly not super precise numbers, but nobody is picking up 5:00+ in am IM by covering their 808 or running a standard disc (which are basically the same thing).
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Re: Aero testing 808 w/wheelcover vs 808 w/out [FindinFreestyle] [ In reply to ]
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FindinFreestyle wrote:
CJAC wrote:

I guess I need to just get a cover and test.


Yeah, get your own cover and test. Because none of the other tests ever done on this topic are valid. You are sure you find some unique aerodynamic principles that apply just to you.

http://www.wheelbuilder.com/aerodisc-data.html


Data such as this have been confirmed a bunch of times, notably by our own JonnyO who found his 808 with cover faster than a flat disc. (Probably because it resembled a bulged disc).


For 808 vs disc, you could just check Zipps data, which has been very robust when compared to independent testing. IIRC, a disc is less than :10 faster over a 40k compared to an 808. So less than :50 over a 112 mile ride. Certainly not super precise numbers, but nobody is picking up 5:00+ in am IM by covering their 808 or running a standard disc (which are basically the same thing).

Exactly, Big D. Jonny did this test in like 2006 and posted about it. Back when the 808s were tubular only.
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Re: Aero testing 808 w/wheelcover vs 808 w/out [CJAC] [ In reply to ]
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4:41 on 220W at 220lbs...is that possible?
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Re: Aero testing 808 w/wheelcover vs 808 w/out [IronStork] [ In reply to ]
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I think I have a pretty aero set up, and the course is pancake flat. That result doesn't match up with anything else I have done, due to how flat and fast it is. On a neutral to flat HIM at 255 I have been around 2:20 repeatedly.
That why I was intrigued.
I'm a little fitter this year and based on current FTP should be able to hold 240, but that only nets me 5 min according to BBS.
If the math above held true for me, I could basically add cover and save 20 watts of effort.
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