I race on enve 7.8s. I had a disc and sold it because traveling to races was slightly more inconvenient so I sold it.

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USAT Level II- Ironman U Certified Coach

I'd guess not. Just for tradition and historical consistency, so the next person to break the course record also does it without a disc.

But I'm just a roadie.

I do not think so, because now the legend is maintained that discs are dangerous in windy conditions, which they are not (only deep front wheels are dangerous in windy conditions).
In this way, bike industry can maintain selling deep rear wheels as well as discs to the same persons.
If discs were to be allowed in Kona, it would probably cause a lot of people to only have a rear disc, and the industry would miss a lot of deep rear wheel sells.

Of course this theory is only valid if WTC wants to be good to bike industry.

I assumed they were an unimaginably unaffordable luxury...for sponsored pros or the wealthy tier of amateurs. Springing for a TT bike was already a stretch on my current budget, so a $1,000++ add on was a scary thought. Nonetheless, I was always SO intrigued by these magnificent, futuristic carbon slabs which seem to slice through the air like butter...A specialist tool for a highly specific task.

Then, off a local listing, I found and bought one that must be a decade old (It's a 10 speed Zipp tubular) but I fitted an eBay Edco monoblock 11 and I am up and rolling quick. $250 for the wheel and $90 for the cassette.

Still tempted to totally baby it... because I know I won't be able to replace it at that price, but I'm thrilled I have one now.

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Clubs/Affiliations: The Rippers / Charles River Wheelers / Cambridge Sports Union

One of the best deals in tri was always the wheelbuilder $90 disc cover

That deal is long since gone.

They are now up to.

$98.95

(from their website this morning).

Mind you that is like, 140 Beaver bucks.

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http://www.fitspeek.com the Fraser Valley's fitness, wellness, and endurance sports podcast

Way back when I used a Jet 90 it was because I couldn't get a 650C disc with a PT built into it.

Now I'm using Power2Max and Garmin Vector 3

Tri bikes and TT bikes are often the same framesets, but they're different bikes. So, this line of questioning is totally irrelevant for 'TT bikes' as there is no Kona voodoo about not running a disc. British TT rules do stipulate a maximum "area" that can be taken up by front wheel though. Meaning you can't really run a front disc or an old HED 3D (the deep section trispoke).

Otherwise, I think the rumor mill is that discs don't handle well and are expensive. Despite neither of those being true.

I could see travelling with one being more problematic, but that's about it.

I don't train on one simply because I'd rather not tear it up. I have a 90 rear for the roadie I use.

The garage is:
FLO 60/90
HED 6+ full set
HED 9+ front
HED rear disc

They are? I used the same bike when I was doing both. Can't think of any changes I made.

All Cervelos at one time (don't know if it's still true) had seat posts that allowed them to be set up for both sets of rules. On my first one you reversed the seat post and on the second you changed holes. I have ridden the bike both ways and the difference is only important if you have to run after.

See the post right after yours. I didn't explain it well at all.

I was trying to say that some tri bikes and TT bikes share a frameset, but rules dictate different kit that can be attached to them. I hear USAC is pretty loose, but I wouldn't show up on a P5X to a P/1/2 or even cat 3 TT. I wouldn't blink in 4/5, need all the riders you can get.

Isn't the fork on the Shiv also different for TT versus tri? That wide and up to the headset deal on the tri version?

Just trying to point out that the rules are a touch different meaning the bikes do look a bit different sometimes. The first post said "TT bike". It didn't say "triathlon bike" despite mentioning the Kona disc rule.

Where was I going with this? Even I've forgotten. I'll shutup now. I just heard disc wheels and came running. I love disc wheels. Look, squirrel!

It wouldn’t be 2020 without a crazy-ass conspiracy theory so I am all in on the aero wheel cabal using the Kona disc wheel ban to sell more 90 mm deep wheels. Without the ban, there would be very few people who purchased a 90mm front so it would be super niche. Cutting those molds isn’t cheap, so knowing every serious triathlete is going to have a 6/9 & disc combo makes it cost effective to offer 90mm front wheels to the TT crowd.

Discs will never be allowed and should never be allowed at Kona. On it's day the descent from Hawi is the scariest section of road I have ridden. For those who haven't ridden there it's not a cliff but steep down to the water where the wind hits you in gusts. In 2014 was probably the worst I have raced it and I just committed thinking if I get blown off the bike here then so be it I'm racing. I know definitely three lighter women were blown off their bikes that day.

In 2017 I did it in the week before the race it was probably the worst I have ridden it and my friend a lighter woman got blown off her bike twice with no deeper than 60mm wheels descending with caution.

A disc is potential suicide for some there. Notice how Ryf often only runs about a 40mm front there. Yes a disc is on the rear but it is still a big surface area I wouldn't be prepared to trial...

Ditto this. I've been blown nearly off the road on that descent riding a road bike with "standard" rims, just out riding by myself. I've also changed more than one pro's wheels out for shallower depths the day before the race based on the race day forecast. It would be super fun to be manning a booth in the expo the day before the race when some real weather was forecast, though; all the age groupers scrambling to find a way to get their disc off the bike would be pretty intense to observe.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

I don't remember the calculation but one can determine the cross wind speed velocity that would actually move the rear wheel. For me, if I recall, it was a velocity well over 67mph to actually lift/move me. At winds far slower, the front would be impossible to control, so I really don't think a disc on Hawi would ever be a real issue, for all but the smallest riders.

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"Only those who risk going too far can possibly find out how far one can go." T.S. Elliot | Cycle2Tri.com
Sponsors: SciCon | | Every Man Jack

No they won't be allowed in Kona. The trade winds are too fierce and the reason they aren't allowed is not to sell more other types of wheels. It is a safety issue. Having raced Kona 13x, I can say with certainty it is truly a safety factor & in no way should be considered an option (unless it was a pro only race--they would be able to probably handle the winds safely). There are too many unskilled "wind" handling riders (yes, in the WC...) to use a disc in those crosswinds, as well as elderly who will maybe end up with permanent injury or worse.

Have you ever ridden the Hawi descent?

About 15 times

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"Only those who risk going too far can possibly find out how far one can go." T.S. Elliot | Cycle2Tri.com
Sponsors: SciCon | | Every Man Jack

Well your about the only person I know that would consider riding a disc down there... All well and good to calculate what wind speed will affect you if it was constant but it is the gusts and the fact they are coming from below and lifting you that you can't calculate. It would be suicide plain and simple.

It really is a so much more a front wheel issue. I have ridden a 40 mm front with a disc on days where they are pulling people out of the barb wire fence on the side of the road. In contrast, I had a couple of really really scary incidents riding a 90 mm front at our state TT this year. Zero comparison between the wind on both occasions. That being said, I have ridden Hawi using 60 mm front and back wheels when wind was howling. I am just glad I stayed out of the ditch.

I just pointed out that maths suggest the fear is overblown. Try not to take offense at that. If you don't want to use a disc in Kona, you are in luck since its not allowed, making your fear unfounded.

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"Only those who risk going too far can possibly find out how far one can go." T.S. Elliot | Cycle2Tri.com
Sponsors: SciCon | | Every Man Jack

How can you know if you've never ridden a disk there?

What's your point? It would be a serious danger to ride a disc there and I have shit myself with shallow wheels so would never attempt it. Hence the logical and common sense disc ban. Feel free to have a crack and report how it goes...

I bought an ex-demo disc wheel in 2005. Loved it, but stopped using it about 3 years ago after the bike shop suggested it was on its last legs.

My current TT bike is 10 years old, still running 10 speed with rim brakes. I expect to purchase a new TT in a few years time (maybe longer now due to COVID19) and don't want to outlay the cost on disk wheel that will not be compatible with a new bike. Currently using a set of Zipp 808 Firecrests (purchased with the TT bike nearly 10 years ago).

While I loved the disc wheel, it did have some issues:
- main issue was discs being banned if it became windy
- big races often involved travel and only room to take 1 set of wheels.
- Zipp 808 rear is lighter if course if very hilly (ie. Nice 70.3 Worlds)
- Zipp 808 rear corners marginally better (saw so many disc wheels crash at the London Sprint Worlds in 2013)

So if I only had enough money to buy 1 rear race wheel, I would go deep dish. But am hoping/planning to get another disc wheel. Always felt faster when using the disc