- Yes, they are
- Yes, it is
- Yes, it is (above 20mph, and below)

Thanks. So, what gives?

The problem at Kona sometimes is the climb to Hawi where you are doing like 10-15 mph. Lots of people go down there, even without discs....

Deep front wheels more of an issue imo....

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Randy Christofferson(http://www.rcmioga.blogspot.com

Insert Doubt. Erase Hope. Crush Dreams.

I suspect at this point it's also tradition. They have never been allowed in the past so even though the data says that thought process was wrong, they won't change just because it's always been that way.

It’s also my understanding at Kona it’s not sustained wind it’s the gusts of wind. Although it does help stabiliZe the bike with constant wind, getting hit with gusts can really throw you with a disc wheel.

It's also that while they stabilize the steering forces somewhat, they also contribute to more overall side force. So you can have a decent steering bike but still get blown 6 feet sideways.

But to the OP, disc are nearly always the fastest choice, and probably even faster than a the wind tunnel suggests due to both translational and rotational drag improvements, while the wind tunnel only measures translational.

Which is a gift for the bike industry: otherwise deep rear wheels would hardly been sold now. Most triathletes today think:
"I ride with a disk but with a lot of wind with a deep wheel because there must be some truth in the theory that discs are dangerous in side winds".

Look at discussions about Lanzarote where discs are allowed: a lot of people do not dare. and I must say I do not know what i will do. There were last year also (light) pro women riding discs in Lanzarote. But there are also Pro men who ride deep wheels. Whereby the pros probably ride what their sponsor wants.

I think it may be time for WTC to revisit that rule, mainly because we have a much greater understanding of overall aerodynamics, centers of pressure, wheel aerodynamics, etc. Modern wheel and bike designs have addressed a lot of the instability issues we used to see. That said, it's been a long, LONG time since I rode out there, so my memory may be less than reliable on how bad it can get...so maybe I'm over-stating the improvements. I just know there really isn't any place or condition that I wouldn't ride my current bike (QR PR6) with a disc. I definitely could not always say that in the past on other bikes and wheels.

The slow climb to Hawi description higher up in this thread is pretty general. I think of that section as from Mahukona to Hawi which is a climb, but it is generally east and if the wind is blowing it is mostly headwind. The sketchy sections are where the prevailing wind blows across the highway. This can happen along the Akoni Pule Highway between Kawaihae and Mahukona when headed northwest and north (or reversed on the way back). The worst sections are from about mile marker 9-10 to about 16 around Mahukona. This segment also has the winds varying between rock cuts and gullies which makes it highly variable. I’ve seen lighter riders blown half a lane width sideways in here and sometimes knocked down when limited to riding the shoulder on non-race days.

The worst race day I’ve seen up there was 2012 70.3 Honu where this section was ridden leaning over into the wind at various extremes. I had 404/808 combo and I’m not sure the disc would’ve been much worse as fighting the front wheel was most of the effort. The main issue was other riders - both heading down and coming back. Heavy wind narrows thing up thru here because no one wants to be near that ocean side (downwind) shoulder.

These conditions can also occur along the north section of the Queen K past the Mauna Lani Resort area. This probably doesn’t get as much mention because the QK is so much wider.

Yes, discs are more stable... but only up to a point. Once the crosswind speed starts getting ridiculous, you'll simply get knocked over no matter how stable the steering is. Sure your front wheel will be pointing straight down the road, but you're also laying on your side because you got blown over. A lot depends on your weight, but I'm guessing 35+ mph crosswinds are when you're starting to get shoved sideways into a ditch or the front end of a car.

If you were riding by yourself, on a closed course up and down to Hawi, I think there are some experienced cyclists who could ride a disc no problem on all but the craziest of windy days there. As mentioned already, the disc does stabilize your steering front end, but in turn means you are prone to more side to side movement while being stable.

The road isn't that wide, and the turn around is right after this nasty cross wind section which means there is a ton of two way traffic. If you get blown across the center line while trying to pass a sketchy rider that's swerving all over the place you could ride right into someone bombing down the hill at 45 mph.

Also, if you don't know how to lean into the wind properly, a disc is just going to make the bad bike handlers so much worse.