"I'm thinking about buying a disc wheel for my P3? I already ride 303's. Do you think it's worth the money?"
- - YES!!!!!!!!!!!!!!!!!

"I know they are bad in windy conditions."
- - Wrong. A disc rear makes your bike more steady in wind. Until the gusts get above 60mph, you'll be fine. Just don't put one on the front!

"Anything else I should know?"
- - Nope

"Also, do you think $600 is a good deal for one?"
- - Depends on new v. used and also brand. You can get a new HED for about that, and a Renn for less. Friend just bought a HED Disc on e-bay for under $200 (650). New Campy is about $2500...

---

Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...

Sounds like you dig it. It's a ZIPP, so I'm thinking $600 should be a decent deal.

So how do I ask this without sounding like an idiot. Okay, I give up.

how much faster is a disc wheel? Can anyone begin to quantify? Let me guess, it's just mental!

You may not go all that much faster, but the difference is you can go faster longer with the same effort!

---

TheBikeRacer.com

"how much faster is a disc wheel? "

http://home.hia.no/~stephens/aero.htm

Go to this page:

http://www.analyticcycling.com/...WindCourse_Page.html

you can play around with the predicted time differences between a number of wheel combos

For example, if you use the US Dis 20 TT Course (which apparently is 38K), running a rear disc (keeping the front wheel constant) saves you 18 seconds over a pair of 404s, 48 seconds over a pair of Rolf Vectors, almost a minute over a pair of Shamals, and 1:15 over 36-spoke box rims.

---

_______________________________________________

"Sounds like you dig it. It's a ZIPP, so I'm thinking $600 should be a decent deal."
- - Sho 'nuf... That's almost half off. Be careful, however, if it's an '03, they had some problems with the freewheel on many of the wheels sold in early '03.

"how much faster is a disc wheel?"
- - Significantly. Even over 404s, the disc is nearly 1mph faster. My first ride on the disc took me from 1:08 to 1:06 (40K).

---

Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...

Thought I read somewhere that an aero helmet (i.e. an LG) was equal to a disc over 40K (assuming you upgraded from a 404). The point being the helmet was the cheaper upgrade.

But what do I know - I own both.

I saw that too- I simpy can't believe an aero helmet saves you a minute over a 40K. I guess if I saw the actual tunnel data, then maybe.

---

_______________________________________________

An aero helmet advantage is at most 30s over 40k.

Gary is spot on, an aero helmet is worth something like 30s over 40k depending on what helmet it is and what helmet you are comparing it to in the first place, but it is give or take 5s at the most from what we have ever seen between various helmet types.

The numbers quoted by jhc is pretty accurate despite the drag data on analyticcyling.com being pretty old. The newer 404 is about 6-10 seconds faster than the older 404 (and about 18-20s faster than the previous 440), but the dimpled disc is also about 8-10 seconds faster than the smooth disc, so the difference between a 404 rear and a disc rear remains at roughly 18-22 seconds, however, this does not take into account any crosswind, which is where the disc truly shines. With an 8-10mph crosswind, the disc can be something like 32-36 seconds faster than a 404, and with stronger winds, the advantage only grows in the favor of the disc wheel.

Also, Cousin Elwood is right that there were some problems with late '02 and early '03 ratchet gears in the hubs stemming from a heat treat operation. The problem resulted in slightly out of round parts (about 0.005" diametral) which could break the internal sping in the freehub body (which has very tight clearances) and the solution was a design change in to the freehub (since the bad ratchet can not be removed from the hub body) to increase clearance, but the problem was quickly caught and only accounted for about 1% of the production for that year. We have since changed the entire manufacturing methodology of the parts in question to guarantee diameter control within 0.0002".

---

http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

"an aero helmet is worth something like 30s over 40k depending on what helmet it is and what helmet you are comparing it to in the first place, but it is give or take 5s at the most from what we have ever seen between various helmet types."

True, and an aero helmet gives about the same advantage as taping over the holes on your regular hemet. Also a $60. CH Aero disc cover is about the equivalent to any other disc. There is an actual wind tunnel comparison of this on this site. So for a fify cent roll of tape and a sixty buck cover you'll save a theoretical minute over 40 kms. Aerodynamic improvements aren't as expensive as some people want you to believe.

http://www.biketechreview.com/

I've read time and again that a disc is OK in the rear as it will stabilize the bike...is it still true if you're reasonable tall (close to 6') and very light (140-145lbs race weight)? I'm getting a new bike and am hesitating between a pair of Zipp 404s (or Hed Alps) and a disk rear (with maybe a 404 in the front)...

Also in your opinion would I be OK with Zipp 404s given my low weight on a windy course?

Thanks for some advice...those wheels are sexy and fast, but it's no good spending over $1000 if you can't get your wheels out when it's windy!

"is it still true if you're reasonable tall (close to 6') and very light (140-145lbs race weight)?"

Should be OK. I'm 5'10" and 145 lbs with no problems. I've found a deep dish front to be more problematic in wind than a disc.

Thanks Cervelo guy...that's encouraging (although my wife wouldn't like your reply as this means more $$ will go into tri gear!)

"is it still true if you're reasonable tall (close to 6') and very light"

More so. The disc stabilizes the bike in a cross wind. If you have a very aero wheelset, like HED Deeps or Zipp 404s, don't EVER go out with a standard rear and one of those on the front, it will scare the hell out of you on a windy day. It will, however, make you a believer in running a REAR wheel with lots of surface area.

One of my athletes just added a HED disc to her bike and test rode it last Saturday in miserably gusty conditions. I was hanging on for dear life (I weigh 178 and was riding on Rolf Vector Pros) and she was having a ball. She's 120 and she said she could feel the wind pushing her like a sailboat. I've never really felt that affect because I'm pretty large, but I did notice at CaliMan (very windy) that I managed to average 20mph for a half iron split.

---

Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...

I've been meaning to ask this question, I'm 150 lbs, fairly poor bike handler, I guess, but have done lots of IM's. I'm stepping up to 700 wheels and a new bike after riding 650's for the past several years. I'm getting HED 3's on my new bike but I also have a new HED disc. Would riding the disc actually make me more stable, generally speaking? Also, I'm particularly concerned on training rides where big box trucks pass me at 60 mph. They can throw off quite a bit of wind. Thanks.

You will be more stable in windy conditions with the HED3 rear and a box rim front or the disc rear with the HED3 front. Not sure about circular gusts from trucks, because I only ride my disc in races and haven't had that experience, but at CaliMan it was very windy, and at Santa Cruz it's usually gusty. Disc wheel + HED Cx front = totally stable.

Whatever combo you run, if the rear offers more surface area than the front, you'll be more stable if they're the same (32 spoke box rims), the wind hits you. If they're the same (HED 3) the wind hits you and the two wheels, but the front takes a beating. Depends on how bad it is. Last Saturday up on an exposed hill, major gusts were kicking me all over the place with aero rims (Rolf) F&B. Meanwhile, the 120 chick with the disc wheel was totally under control.

---

Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...

"True, and an aero helmet gives about the same advantage as taping over the holes on your regular hemet."

>> When compared to a LG Prologue, taping a helmet is probably the next best option according to John Cobb. However I would wager that the new models from Giro, Bell, Uvex and the Louis Garneau Rocket, etc. are much more aerodynamic than taping a helmet. We now have new legal aero helmets that can be placed in to an array of aerodynamic categories, based on performance in the wind tunnel (of which we may never see!).

"Also a $60. CH Aero disc cover is about the equivalent to any other disc. "

>> As an update, the CH cover tested slower than a disc: http://forum.slowtwitch.com/gforum.cgi?post=221795

"Cerveloguy: As somebody who counts Kraig Willet as a friend (and one of the smartest people I know) I have to say that we have been trying for years to replicate the data you reference from him and have not been successful, also having looked at and compared historical data from A&M along with data from John Cobb and a couple of other companies in the industry, we have never seen similar results to the Willet testing with any disc wheel. I can say that when you only run one test per wheel, you can get outlying data due to a million factors, so no doubt that his data is real, but it is not representative of the 100+ runs we have done in the last 4 years on ours and most every other disc currently available. The testing we have run lately is all based on average drag profiles of a minimum of 3 runs, but generally more than 7 for statistical purposes, this is specifically to eliminate abnormal high and low drag data which can be captured in single run testing. What we have seen in the past 4 years is that most all discs show near identical aero profiles in the tunnel, flat, lens, cone shapes, you name it. About the only thing that seems to make a difference from an aerodynamic pressure point of view (and John Cobb has discussed this as well) is whether the wheel has a lip at the OD or not. Many discs have a lip where the outer rim was attached, and some do not. We feel that the lip (and there may or may not be when using a cover such as the CH, depending on how you assemble the thing, and what rim you are using) tends to show increased drag, particularly with the wheel in the bike, as the back half of the wheel is the primary aero surface in the bike/wheel system. Our testing shows the lip of a post bonded rim tends to cause 0.05-0.075 lbs of drag increase over a continuous surface (this test done with identical non-dimpled discs). "

"all discs show near identical aero profiles in the tunnel"

And as I posted back to you previously, what else would you expect a Zipp representative to say considering Kraig's original results with a cheapo cover against a Zipp disc. Of course they "can't" duplicate his results. Even if the Zipp was faster (which contradicts Kraig's study), it would only be marginally so and doesn't change the fact that the cover offers tremendous bang for the buck.

You can't make any legitimate speculation on the new helmets until the manufacturers (1 first do the wind tunnel tests and (2 have the balls to make such results public. You're only guessing otherwise. These helmets were probably products of a design studio rather than a wind tunnel. Any wind tunnel testing would probably come after the fact so is likely why it won't ever be done.

I'm 6-3 and race at about 162 lbs. I run a front HED3 and a HED3D rear in races. I've trained with both combinations, HED3 front and rear and my above race setup. The wind greatly effects the bike handling more with the HED3's front and rear, then it does with the HED3 front and rear disc. I can get blown off the road when the Atlantic Ocean breezes on A1A kick up when I run both HED3's. Its much more stable with the rear disc. My Zipp 3000's, front and rear, are better in a wind then the HED3's for handling. Not faster, just more stable.

---

.
.
Paul

If you are a poor bike handler, you need a shallower wheel than the Hed 3. Just my $.02

Helmets: My thoughts on this are that since consumers will likely never see the wind tunnel testing comparisons, we will have to rely on what the manufacturer shows us, and what the frontal area of the helmet looks like. If it looks aero, chances are that it probably is. That is the best we can do right now.

Disc: Josh at Zipp says they tested the CH cover, and that Cobb tested it, and both tests show that it tested slower than a disc wheel. Zipp's competition is not a CH cover (as it weighs over 500g), so I see no reason to question his statement or honesty. Maybe it is only marginally more aero, however combine that with the 500-700g weight savings vs. a wheel with a cover, and the dimpling, and it is clear to me that the Zipp is faster. So I believe that a "disc is a disc, as long as it is a disc" with the 2004/5 Zipp 900 being the fastest of the discs.

Thanks for the replies regarding my HED 3/disc question. I've done quite a few rides with my current bike since getting 650 HED 3's last summer. I've white-knuckled it a bit when it's been very windy but I figure training on the wheels will help improve my bike handling skills. Also, the consensus seems to be to run the disc on the rear for more stability. I'll probably do that for my next IM (IMA). I'll be sure to get some rides in on the disc first, even though the weather here will suck that time of year.

I'm getting a disk to complement my HED3front and replace my Corima 4 spoke rear. The current set up can get exciting with gusty cross winds/passing trucks (I'm 5'11" and 143lbs)[reply]