I don’t get this.
A disc wheel in the rear makes you more stable in crosswinds.
It is illegal to use a disc in the rear at Kona because it is too windy.
I’m guessing this has to do with either the variety of disc wheels and therefore some will not stabilize the bike, i.e. flat disc, or lower winds a disc helps and crazy winds (40 mph) a disc is not stable?
And of course either of two premises may be wrong.
I welcome criticism.
It depends on the wind speed, wind angle and more importantly if the wind gusts. With a steady crosswind it can make a bike more steady, but when the wind gusts more area to catch the gust hurts.
Keep in mind that a disc can help steady a bike with a deep wheel, 2 low profile wheels will be even steadier.
Styrrell
Have you ever ridden up the hill to Havi? I know its different everyday but in 2008 I was 180lbs and on 808s and every time I went through one of the cut outs and then came out I was blown around, most of the guys ou there were considerably lighter than me. It could have been partly because of the 808 front, but I thought I had ridden in wind before and after that I realized that I had not ridden in WIND.
Of course YMMV.
This rule is precisely why I sell my 4Spoke wheel.
I was on 808’s last year and was knocked around. 404’s would have been a better choice. I don’t think a disc would have stabilized me.
It was considered a safety thing after some riders said they and their bikes were lifted off the ground by crosswind gusts (remember some of the women in Kona are <100lbs.), and crashed (one claimed to be lifted over the guardrail).
Is it actually an issue/concern? I don’t know, but the tradition has remained.
Personally I’d think an 808 on the front is a bigger handling issue than a rear disc (by a longshot), but the issue here might be lift, not handling.
The thing about this debate, is that the two parties are coming at it from different perspectives. The “disc is more stable” school only think about the moment of force around the steering column (ie the risk of wind causing you to steer off the road) The “disc is dangerous” school are concerned with the moment of force around the ground tire contact point (ie the risk of being blown over)
Have you ever ridden up the hill to Havi? I know its different everyday but in 2008 I was 180lbs and on 808s and every time I went through one of the cut outs and then came out I was blown around, most of the guys ou there were considerably lighter than me. It could have been partly because of the 808 front, but I thought I had ridden in wind before and after that I realized that I had not ridden in WIND.
Of course YMMV.
This. The winds on the road to Hawi that time of the year can easily be 30 mph 90 degrees to the road. They gust through the gullies and hit you broad side. Getting gusts up to 60 mph isn’t unheard of or even uncommon. The 2009 race had nasty headwinds both directions combined with nasty crosswinds at every gully. During the run up to Honu, my Zipp 404’s were a bit much for the winds at times (Honu was fine, but the October race is almost guaranteed to have nasty winds).
have you ridden Kona?
Nope–and no desire.
Blasphemy like that and your Slowtwitch account may be disabled.
OK, that explains it. I understand your philosopy, but would tell you that you probably don’t understand the type of winds we are talking about here. This is not a twitchy front wheel sort of thing, this is a lift you up off the ground and off the road kind of thing, extremely specific to that particular climb to Hawi, the trade winds that buffet the big island, and the cuts in the rock and the inland terrain on the route.
Hide-bound tradition, and nothing more. If one can’t ride a bike with a rear disc because it’s too windy, then it’s too windy to drive. No criticism implied or intended!
Yes and no.
I think there is a bit of tradition with this, but it’s more to do with safty.
Have you ever ridden or been over the full length of the IMH bike course - not just on one day but over more than a few days. If you have you’ll note a few things:
The winds on the course are extremely variable - howling gale force winds on some parts and dead-calm on others.
The winds never seem to come steadily from one direction. In fact there is the famous wind shift that takes place mid-morning on some days, which leaves you riding into a head wind around the whole course!!
On the way up and back from Hawi is often where the winds are at their worst. Here they typically blow from the land towards the ocean, so on the road this is a side wind. There are these long rock cuts on the road, that protect you from those winds and in here it’s relatively calm. However, there are breaks in the rock cuts and you are out in the open and in these spaces you are subject to the full blast of that side wind - it’s these rather unpredictable winds, that are the problem. I have seen Pros nearly blown off the road. I have seen top age-groupers blown off the road.
Finally, while I would say that 2/3 of the field at IMH is very good - some of the best in the world ( Pro & AG) you have about a 1/3 of the field perhaps a bit less, who are there via the lottery and other ways. These folks may not be so adept at bike handling as the other people.
The thing about this debate, is that the two parties are coming at it from different perspectives. The “disc is more stable” school only think about the moment of force around the steering column (ie the risk of wind causing you to steer off the road) The “disc is dangerous” school are concerned with the moment of force around the ground tire contact point (ie the risk of being blown over)
I am not a physics person, but if you have ridden a disc wheel at speed( 25mph +) you know what this means. You also get the sailing effect, which is quite strange, and very cool, if it’s a side rear quartering wind - you actually feel the bike being pushed forward by the side force of the wind. However, I can see at much slower speeds, being ridden by, with all due respect, people with much less bike handling skills, riding a disc wheel in certain conditions could be seen as being more dangerous and risky.
OK, that explains it. I understand your philosopy, but would tell you that you probably don’t understand the type of winds we are talking about here. This is not a twitchy front wheel sort of thing, this is a lift you up off the ground and off the road kind of thing, extremely specific to that particular climb to Hawi, the trade winds that buffet the big island, and the cuts in the rock and the inland terrain on the route.
Yup. I weigh 175 and have had the winds start lifting me off the bike. Never succeeded yet, but it’s not fun. Generally you watch what’s coming up ahead and what the bushes are doing and hold on, oh and don’t forget the backdraft. I really don’t like even thinking about the Hawi climb with a disc.
Just did the Honu with a 1080 rear and a 303 front. Was asking the same question you were before the race as I have a Sub-9 and felt like that would have been the choice due to the elevation chart. But now I am glad I had the 1080 and almost wish I went with a 808 rear. The 303 front was spot on and was able to stay aero up the climb.
If safety was really their concern then they would ban front wheels deeper than 60mm. As long as there is no restrictions on the front wheel depth, the rear disc wheel ban is STUPID! Yes, I’ve done the race several times. If I could, I would race a disc in the back and a 58mm in the front and would be a hell of a lot better off control wise than those running an 808 in the front.