I have a Renn 575 and love it! Save yourself some money and get a Renn. For most people you will see minimal time savings from other disks.

I had started a thread about this a couple weeks ago, search for Renn vs. Hed and see all the results you get. I have been looking into a rear race wheel for about a month, comparing discs, tri-spokes, etc. I am getting a Renn, light, fast and cheap.

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Portside Athletics Blog

The Hed disks are unique because they have a lenticular design, while others, such as Renn and Zipp are flat. From what I have read, I don't see any consensus on one design being absolutely better than the other.

I bought a Renn 575 this summer and have been very happy with it, and and many others have said, their custumer service is first rate. I was nervous about getting the wheel in time for a big race for me, and Frank Rehnelt took it upon himself to personally call me as soon as UPS delivered to me.

Did a lot of research and Renn seems like the best all around deal. Hopefully mine will be arriving soon.

Lenticular discs have something like 0.0001g less drag. But they also inherently require more material (takes more to cover A-B in a arc than in a straight line), so they will be heavier than if they were flat. Basically, it doesn't really matter.

The new 2006 Zipp has a substantially improved hub. Both Zipp and Renn use sealed cartridge bearing, making them vastly superior to cup/cone arrangements.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Renn is the best deal. Zipp is the lightest. Campagnolo Ghibli is the most expensive (as far as I know). Blackwell and Hed also make them for more money than Renn, but less than Zipp or Campy. Also, Mavic makes one the is half lens shaped and half flat, weighs a ton, and is very pricey.

Well, it looks like Renn seems to get good reviews. I will check into ordering one. I would think the Hed would be pretty good as well, although it looks a little heavier and a little pricier. Thanks again.

Both Zipp and Renn use sealed cartridge bearing, making them vastly superior to cup/cone arrangements.

Really? Aren't some really high end hubs cup and cone? (ie Dura Ace and maybe Chris King).

thoughts on custom covers like what wheelbuilder.com offers?

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

King uses an adjusting cone to set preload on the whole assembly. But it is not a cup & cone bearing. The exploded diagram of the classic hub is here:

http://chrisking.com/pdfs/CLASSIC-rear.pdf

You can see they are all sealed bearings. They do have removable seals, and one of them is a needle bearing. But they are not cup & cone.

Dura-Ace does appear to be cup & cone. But I wouldn't list D/A at the top of the list for hubs. Certainly not over something like a Mavic/King/White Industries/Etc.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

I've not used one of the Wheelbuilder.com covers, but I've never heard anything bad. They are a tad heavy, but certainly are very aerodynamic. I would say that aerodynamically, you would not notice much difference between the cover and a disc. Kraig Willet has a paper where he tests the cover vs. a disc on BikeTechReview. I think it is like $15...

I would say the only reason for any differences in aerodynamics would be from the junction between the cover and the wheel. I would guess this would be similar to the findings Zipp posts for the lip on a clincher rim vs a tubular, which is like <5 watts or so at 30mph, but that is just a guess. A wheelcover is going to be faster than any other wheel (except a disc) in terms of aerodynamics.

It would be nice to have one since then you could train on a disc and get used to the handling, without worrying about cracking up an expensive race wheel.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

"thoughts on custom covers"

Renn is a better value than it's competitors, although a Zipp disc is a thing of beauty, but for sixty bucks for the same performance, how can you go wrong with a CH Aero cover.

thanks. it seems like an inexpensive alternative but i have not seens anything from anyone with experience with one.

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

where do i find more on the CH?

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

How about the Zipp clincher disc?

"where do i find more on the CH? "




Kraig Willet tested one against a Zipp disc in a wind tunnel. They work. The results of his test is available on his pay site.

http://www.excelsports.com/...major=1&minor=24

I've got a CH cover from wheelbuilder. It weighs just under 400 grams. It's pretty easy to put on and take off, though you do have to remove the cassette to do so. I plan on using it as my race wheel on my PT hub.

this is sounding better all the time.

thanks.

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

Not really true. Over 7.5deg yaw, the difference between flat and lenticular is significant:

http://www.bsn.com/...eelAerodynamics.html



-jens

Get it, its like $60 bucks and if you think it sucks, its not a huge loss. I and many others have used them, they work and make your bike look cooler... which admit it, is the whole purpose of a disk.

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- Nick
Now that I know some of you guys look through the special needs bags for kicks, I'm gonna put some really weird stuff in mine. I can see it now. "What the heck was he going to do with a family pack of KFC chicken, a football helmet full of peanut butter, a 12 inch rubber dildo, and naked pictures of Bea Arthur?"

so you think a disc will make my old Slingshot look hot?

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

Call Richard at Wheelbuilder.com He will cut a CH cover to fit any rear wheel you want (it's worth the extra $10).

http://forum.slowtwitch.com/gforum.cgi?post=474106;search_string=ch%20aero%20hed;#474106

summary: Did a time trial with velomax circuit wheels one week, then switched to ch aero cover in the rear and HED3 in the front. Time was about 1:30 faster with the aero wheelset (everyone who did both races had a faster time the second night, so I would guess I gained about 1 minute over 9.75 miles due to the wheel change.)

very unscientific, sorry.

http://hea-www.harvard.edu/~kwelch/soloist.jpg
http://hea-www.harvard.edu/~kwelch/PICT0006.JPG

What does that work out to for actual difference in drag at say 25mph? The only thing I couldn't figure was reference area. Is that just the surface area of the disc, or is it something like "effective" surface area (as in what the wind sees)? The difference in the Cx coefficients is certainly not negligible, but that doesn't mean the difference in drag is not (although it may not be). I will certainly argue that the 300+ grams of weight savings of a Zipp over a HED disc worth running a Zipp. The HED "superlight" is 1270g. Zipps 2006 disc is under 900g. That is ridiculous...

I don't think the improved aerodynamics is worth all the much in comparsion to the gross weight difference. Weight may be overrated, but lugging around an extra pound on a rear wheel for some minor aero gains seems foolish. If it wasn't, you would have seen HED discs under the USPS/Disco team...

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp