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Dish wheels and aero rims in brutal, intermittent crosswinds

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Dish wheels and aero rims in brutal, intermittent crosswinds

Old 05-10-10, 07:15 AM
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Flash
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Dish wheels and aero rims in brutal, intermittent crosswinds

At windy Deep Blue TT yesterday various riders were using disc wheels and aero rims. I saw a HED H3 as well (my personal favorite).

Several archival posts on BF suggest aero wheels offer benefits even when crosswinds are present. There were some turns on the course yesterday, so brutal crosswinds were only present at certain times.

Is it as simple as asgelle stated in his 2007 post below (emphasis added):

"If you don't want to trust Zipp's data you can look at results from Bike magazine or biketechreview.com. They all give the same results so you shouldn't jump to the conclusion that just because Zipp provides the data they aren't reliable. And I'm afraid you mis-state the relationship between the flow vector and drag. Drag does depend on frontal area, but that is not all it depends on. There is also the drag coefficient to consider. So your statement that "in a strong crosswind, you're simply adding surface area ..." is not correcdt. The drag coefficient is also changing. In the case of deep rim wheels in a cross wind, the drag coefficient decreases faster than area increases for a net decrease in drag force. "

Original thread re: Tour of California crosswinds (2007)
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Old 05-10-10, 07:21 AM
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for the first time ever, I chose not to use deep rims yesterday. I can generally handle crosswind gusts, but 40-50 mph gusts are just too much.

It didn't help though, since I was on the wrong end of a split coming in to the headwind. 250 watts to go 12 mph on a flat.
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Old 05-10-10, 07:26 AM
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Deep sectioned rims, or a disc are definitely going to be faster in a crosswind than conventional wheels. The issue is controlling the bike. In a TT, riding in the aerobars, a really strong crosswind can be a problem.

One advantage to being big, the wind has to be at least above 25-30mph before I would note use a disc/hed 3 setup in a TT.
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Old 05-10-10, 07:39 AM
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Originally Posted by merlinextraligh View Post
Deep sectioned rims, or a disc are definitely going to be faster in a crosswind than conventional wheels. The issue is controlling the bike. In a TT, riding in the aerobars, a really strong crosswind can be a problem.

One advantage to being big, the wind has to be at least above 25-30mph before I would note use a disc/hed 3 setup in a TT.
Thanks, duly noted. I'm all of 145 lbs and I rode standard clinchers yesterday. The crosswinds really knocked me off my line at times.
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Old 05-10-10, 07:47 AM
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Yesterday I rode my Williams 58 (similar to 404) front and rear but with a cover on the the rear at Deep Blue. I am 153 and didnt have any serious issues in the wind, sure it did affect me at times but wasnt anything I would consider scary. But I also did a lot of triathlons last year and rode my TT rig quite a bit to get used to the different type of handling.

I had other issues with my frame / wheel affecting my time instead of the wind. . .
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Old 05-10-10, 07:48 AM
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Not all rims handle crosswinds the same, I found Zipps to be the worst for the same depth. At Gila this year I used the same front rim I had used in all the road stages, a 46mm. Last year I hit 57MPH in that stage, get your front turned from a gust at that speed and the relative wind just keeps turning you; the deeper the wheel the worse this becomes. One rider who started just behind me opted to go deep and hit the deck on the descent. The GC leader in the pro field also opted to go deep and regretted it.

When I set the course record at one course last year (on a pretty windy day) I used an 85 that I knew handled crosswinds well; max speed was nowhere near Gila and the wind was steadier.

In both cases I used a rear disc.

More technical crits I'll move down a size or two on the front, again the aerodynamics on a deeper wheel make them harder to turn and keep on course.

I evaluate wind direction, variability, speed, and course when picking a wheel.

Originally Posted by merlinextraligh View Post
Deep sectioned rims, or a disc are definitely going to be faster in a crosswind than conventional wheels.
Nope. It's all condition and rider contingent.

Last edited by Racer Ex; 05-10-10 at 07:55 AM.
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Old 05-10-10, 07:52 AM
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Originally Posted by Racer Ex View Post
I evaluate wind direction, variability, speed, and course when picking a wheel.
Valid point. I was really thinking of a flat out and back TT with my comment about the HED3/disc combination.
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Old 05-10-10, 08:01 AM
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Originally Posted by Racer Ex View Post
Not all rims handle crosswinds the same, I found Zipps to be the worst for the same depth. At Gila this year I used the same front rim I had used in all the road stages, a 46mm. Last year I hit 57MPH in that stage, get your front turned from a gust at that speed and the relative wind just keeps turning you; the deeper the wheel the worse this becomes. One rider who started just behind me opted to go deep and hit the deck on the descent. The GC leader in the pro field also opted to go deep and regretted it.

When I set the course record at one course last year (on a pretty windy day) I used an 85 that I knew handled crosswinds well; max speed was nowhere near Gila and the wind was steadier.

In both cases I used a rear disc.

More technical crits I'll move down a size or two on the front, again the aerodynamics on a deeper wheel make them harder to turn and keep on course.

I evaluate wind direction, variability, speed, and course when picking a wheel.



Nope. It's all condition and rider contingent.
Factors that go into my wheel selection:
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Old 05-10-10, 08:13 AM
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Originally Posted by Racer Ex View Post
Nope. It's all condition and rider contingent.
yep
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Old 05-10-10, 08:36 AM
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We had killer winds on saturday for a 40K 2 man TTT. I still went with a wheel cover int he rear and one of my 50mm in the front. It was fine, but dicey at times. Alone would have been fine but the wind was pushing myself and my teammate all over - made for hairy close quarters riding. I figured I would be in his derail a couple of times.

That's the first time I have had to shoulder bump in anything outside of a crit.
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Old 05-10-10, 08:44 AM
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Originally Posted by jslegacy View Post

I had other issues with my frame / wheel affecting my time instead of the wind. . .
Details?
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Old 05-10-10, 09:06 AM
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Originally Posted by Racer Ex View Post
Not all rims handle crosswinds the same, I found Zipps to be the worst for the same depth. At Gila this year I used the same front rim I had used in all the road stages, a 46mm. Last year I hit 57MPH in that stage, get your front turned from a gust at that speed and the relative wind just keeps turning you; the deeper the wheel the worse this becomes. One rider who started just behind me opted to go deep and hit the deck on the descent. The GC leader in the pro field also opted to go deep and regretted it.

When I set the course record at one course last year (on a pretty windy day) I used an 85 that I knew handled crosswinds well; max speed was nowhere near Gila and the wind was steadier.

In both cases I used a rear disc.

More technical crits I'll move down a size or two on the front, again the aerodynamics on a deeper wheel make them harder to turn and keep on course.

I evaluate wind direction, variability, speed, and course when picking a wheel.



Nope. It's all condition and rider contingent.
VeloNews' coverage of the Gila TT this year mentioned wheel depth a tiny bit

http://velonews.competitor.com/2010/...r-leads_113849

Basically, Steegman's crashed in Paris-Nice because of wind, so Lance and Levi opted for lower profile winds for the TT. Jesse Sergent won it with a disc wheel and what looks like not more than a 30mm front rim.
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Old 05-10-10, 10:08 AM
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Originally Posted by Flash View Post
Details?
Had my Ridley setup 20C tires Dismal Dash, decided not to run them and ran my GP4000S. Adjusted the screws in the drop outs to account for it while the bike was on the workstand, assumed that was fine but didnt account for weight on the bike and didnt do a shake down ride to make sure everything was kosher.

Well a few minutes into the race I hear a chriping and feel it in the frame. All of the details here
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Old 05-10-10, 10:28 AM
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Originally Posted by jslegacy View Post

Well a few minutes into the race I hear a chriping and feel it in the frame. All of the details here
Man that sucks. I got into town the day before and drove the course a couple of times on Saturday. That really helped (I thought about riding it but the winds on Saturday were practically hurricane force ;-)

I race infrequently due to my coaching responsibilities, so Deep Blue and a few other TTs are tops on my list and I've got a good amount of shakedown time built in for each race. Better luck in September!
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Old 05-10-10, 10:30 AM
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Originally Posted by jslegacy View Post
Had my Ridley setup 20C tires Dismal Dash, decided not to run them and ran my GP4000S. Adjusted the screws in the drop outs to account for it while the bike was on the workstand, assumed that was fine
Really tight fit back there on the Dean, especially for a clincher.
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Old 05-10-10, 10:59 AM
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Originally Posted by Flash View Post
Man that sucks. I got into town the day before and drove the course a couple of times on Saturday. That really helped (I thought about riding it but the winds on Saturday were practically hurricane force ;-)

I race infrequently due to my coaching responsibilities, so Deep Blue and a few other TTs are tops on my list and I've got a good amount of shakedown time built in for each race. Better luck in September!
I did Deep Blue last September on my Pedal Force TT2 bike and the winds were relatively calm, nothing like yesterday any means. But when i registered for it it was advertised or promoted to be a 12 mile TT. On my garmin I had the milage up and was flying down that hill not expecting a turn around at 5.45 miles, went right through that little traffic triangle, locked up my rear wheel almost slid the bike out from under me at the turn around. Lost a bunch of time in the turn around needless to say.

I finished, with a time of 25:18, got me 3rd in the Cat 5, first was 25:16, 2nd was 25:17.

And yes Racer Ex, it is tight back there, I am still debating if I should always run 20C or 23C. The 20C are Conti Supersonic tires with little to no flat protection. In a normal TT i dont really care but I am doing some stage races based on time and a flat there could be a huge set back. Versus the GP4000S which have been rock solid for me for 1000s of miles. Any words of advice?
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Old 05-10-10, 12:03 PM
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Originally Posted by jslegacy View Post
Versus the GP4000S which have been rock solid for me for 1000s of miles. Any words of advice?
If you're running clinchers I'd go with these:

http://www.biketiresdirect.com/pmip3...ce_tire/pp.htm

The 20c (scroll down) will give you the clearance to get the wheel in tight. They aren't paper thin like the Supers, decent flat protection and very good RR numbers, especially if you use latex tubes.
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Old 05-10-10, 12:31 PM
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Originally Posted by jslegacy View Post

I finished, with a time of 25:18, got me 3rd in the Cat 5, first was 25:16, 2nd was 25:17.
Fast stuff. I think the Cat 5 winner yesterday was around 27 minutes and change. To adjust yesterday's times for last year's race you'd probably have to subtract about 2 minutes.

I got 8th in the Cat 5s yesterday, my first race ever. Took all the turns conservatively, including a very slow turnaround. Looking forward to opening it up in September now that I know the course.

Oh, and my Garmin 305 went into ghost auto-pause mode during my warmup on the trainer! First glitch I've had with it. Therefore no timer for the race!

Last edited by Flash; 05-10-10 at 12:36 PM.
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Old 05-11-10, 08:12 AM
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I used my Williams 58 CF tubulars at the RATL circuit race Last Saturday. The race follows a 1.2 mile circuit and was held under a "high wind warning". We had sustained winds of 35+ mph with gust of 45+ mph. I weigh 185 lbs and don't usually have issues with the wheelset. On the final lap while going through a 90 degree corner with concrete curbing a wind gust hit my front wheel and knocked me off line just a little resulting in the rear wheel clipping the curb causing a big hop and wobble. I lost about 5 to 7 places and my lead out in a heartbeat.
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