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Faster Disc Covers on different wheels?
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PapaBear
Apr 22, 12 17:34
Post #1 of 19
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Faster Disc Covers on different wheels?
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Is there any time difference in generic time saved by upgrading a $100 wheel to a $1000 wheel if they are both covered with a disc cover? Would a deep section w/ disc be any faster than a generic box w/ disc cover?
I tried to find a question that was similar to this, but I'll bring up the question again.
styrrell
Apr 22, 12 18:39
Post #2 of 19
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Re: Faster Disc Covers on different wheels? [PapaBear]
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The Wheelcover mfg has done some aero testing, yes a slight difference but not a whole lot, deep rim carbon was faster than a low profile rim.
Styrrell
desert dude
Apr 22, 12 19:08
Post #3 of 19
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Re: Faster Disc Covers on different wheels? [PapaBear]
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A deep section w/ cover would be a little faster vs box rim with cover, 1-3w max.
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TriA6
Apr 22, 12 19:39
Post #4 of 19
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Re: Faster Disc Covers on different wheels? [desert dude]
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desert dude wrote:
A deep section w/ cover would be a little faster vs box rim with cover, 1-3w max.
I think that is what the data says. Sad, but true. For me the most compelling reason to have a rear race wheel with a cover on it is convenience. I appreciate the time saved not having to mess with taking it on and off.
0.1 lbs (50 g) of drag (at 30 mph) = 0.5 s/km = 5 W = 0.005 m^2 CdA = 0.0005 Crr -Coggan
matto
Apr 22, 12 19:41
Post #5 of 19
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Re: Faster Disc Covers on different wheels? [desert dude]
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Actually I have a theory here... That a wider rim, like an A23, with a cover might be almost or as good or better than the 808 w/cover results.
If you look wheelbulider's aero data (
http://www.wheelbuilder.com/...e/aerodisc-data.html
), the 30mm wheel they used was a DT Swiss RR 585, which is a narrow rim. At 0-yaw it was at a 20+ gram deficit to all the other main contenders, and I'm guessing this is because of the tire bulge from the narrow rim. I have a kinlin 300 with disc cover (similar to the RR 585 they tested) an it's an aero mess from the tire to the rim, then back to the cover.
The A23 is 23mm wide and wheelbuilder claims that their covers actually fit the A23 quite nicely and create a smooth transition from the brake track to the cover. My rampant aero speculation is that this wheel would do quite well against the other leaders in that graph. It would also be lighter than the covered deep wheels, and possibly lighter than a Hed disc.
(This post was
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by matto on Apr 22, 12 19:48)
chicanery
Apr 22, 12 22:19
Post #6 of 19
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Re: Faster Disc Covers on different wheels? [matto]
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This is patently false. (specifically for the A23 that you've mentions). Unequivocally, trust me.
I have an A23 and standard (uncut) Wheelbuilder cover. It "fits" very well, and can be setup with either tape, or just the 8 plastic screws. The problem is that the cover perfectly follows the path of the spokes, which is to say, it meets the rim right at the center. It has a more difficult path to follow on the leading AND trailing edge. This is not the way to go if you're looking for a wide rim plus wheelbuilder cover. The Velocity Chukker might might be a better start, being 30mm deep instead of 19mm.
I am currently sourcing a full CF cover from the UK that is semi-custom and should fit better. I will be posting about it when I get it in.
Chris
matto
Apr 23, 12 6:27
Post #7 of 19
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Re: Faster Disc Covers on different wheels? [chicanery]
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chicanery wrote:
The problem is that the cover perfectly follows the path of the spokes, which is to say, it meets the rim right at the center. It has a more difficult path to follow on the leading AND trailing edge
Wow really? Interesting. I explicitly asked them this and they told me that it fits really well and lines up directly with the brake track making a nice flat transition, and does not get sucked in by the spokes. He said something about there being a plastic lip on the un-cut covers that holds it in place. I wonder if their info was just flat out wrong, or if your cover is different.
I ended up buying a hed disc anyway because I never liked the idea of a cover. It's probably irrational but I always worried it was going to come lose during a race and destroy my wheel and/or frame.
(This post was
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by matto on Apr 23, 12 6:29)
jackmott
Apr 23, 12 6:32
Post #8 of 19
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Re: Faster Disc Covers on different wheels? [chicanery]
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i can't visualize what you are talking about.
Memorial day sale at ATC and Meet Pro Triathlete Matty Reed - Sat May 25 - Captex!
The newest tri shop in Austin - ATC 360
Freelance sports & outdoors writer Kathryn Hunter
matto
Apr 23, 12 6:39
Post #9 of 19
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Re: Faster Disc Covers on different wheels? [jackmott]
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jackmott wrote:
i can't visualize what you are talking about.
The A23 rim really has no flat surface other than the brake track. It's a very shallow rim so there's not a lot to hold the outer edge of the cover at 23mm wide. If it slips in it will come together at the spokes so the edge of the cover would be much narrower than the rim.
jackmott
Apr 23, 12 6:45
Post #10 of 19
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Re: Faster Disc Covers on different wheels? [matto]
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i see, though im not so certain it would be all that bad aerodynamically. how different is that than some of the bulgy discs that zipp and hed make ?
Memorial day sale at ATC and Meet Pro Triathlete Matty Reed - Sat May 25 - Captex!
The newest tri shop in Austin - ATC 360
Freelance sports & outdoors writer Kathryn Hunter
matto
Apr 23, 12 6:48
Post #11 of 19
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Re: Faster Disc Covers on different wheels? [jackmott]
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jackmott wrote:
i see, though im not so certain it would be all that bad aerodynamically. how different is that than some of the bulgy discs that zipp and hed make ?
Well if it's a sharp edge it's bad right? Maybe chicanery has a picture.
cmscat50
Apr 23, 12 6:53
Post #12 of 19
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Re: Faster Disc Covers on different wheels? [matto]
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If it slips in....but I don't think they are designed to do that.
I recall my conversation with WB and they did state the covers are never intended to lay on the spokes. Maybe there are acceptions, but the rim "should??" hold the cover up off the spokes.
chicanery
Apr 23, 12 8:13
Post #13 of 19
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Re: Faster Disc Covers on different wheels? [jackmott]
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It's pretty bad. I'll take a picture of it this afternoon.
Chris
PapaBear
Apr 23, 12 8:57
Post #14 of 19
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Re: Faster Disc Covers on different wheels? [jackmott]
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jackmott wrote:
i see, though im not so certain it would be all that bad aerodynamically. how different is that than some of the bulgy discs that zipp and hed make ?
What if it was wrapped in duct tape. Serious question
matto
Apr 23, 12 9:03
Post #15 of 19
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Re: Faster Disc Covers on different wheels? [PapaBear]
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PapaBear wrote:
What if it was wrapped in duct tape. Serious question
I'd contact wheelbuilder before resorting to duct tape. If they believe it should fit properly, they'll probably help you resolve the issue. They're one of those companies that actually care about their customers being happy.
(This post was
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by matto on Apr 23, 12 9:04)
PapaBear
Apr 23, 12 9:12
Post #16 of 19
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Re: Faster Disc Covers on different wheels? [matto]
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What about the Aero properties of an all duct tape wheel
bradl016
Apr 23, 12 9:25
Post #17 of 19
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Re: Faster Disc Covers on different wheels? [PapaBear]
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Quote:
What about the Aero properties of an all duct tape wheel
Well, I imagine that it depends on the color of the duct tape. Black is obviously faster
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chicanery
Apr 23, 12 17:40
Post #18 of 19
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Re: Faster Disc Covers on different wheels? [jackmott]
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This link should bring up a 4 photo set:
https://plus.google.com/.../5734758314603623586
I've done the flow simulation on this, and it's quite bad from all yaw angles. Much worse than with a 30mm rim and a better contact point. I didn't run it with a seat tube in front of it, which should improve the leading edge for the top half, but the bottom half would still be bad, and the trailing edge would be approximately the same.
Chris
matto
Apr 28, 12 6:02
Post #19 of 19
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Re: Faster Disc Covers on different wheels? [chicanery]
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chicanery wrote:
This link should bring up a 4 photo set:
https://plus.google.com/.../5734758314603623586
That is, without a doubt, terrible! It's actually still pretty hard to see what's going on in the pictures, but for those not familiar with the A23, the silver brake track is at 23mm, but the black part above it goes inward very quickly. Lots of abrupt angles there.
So much for my theory.
(This post was
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by matto on Apr 28, 12 6:03)
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