I know this one will get people going (hopefully 
) but what is the truth about disc wheels at ironman, everyone tells me that you have to be a strong rider for the disc to have any real effect (like above 35 kph average) but I have a friend that keeps tell me this is a farce and a disc will make anybody faster becuase the wheel is stiffer and more aerodynamic, anyone got any comments or answers?? (I still like the HED3s )
A disk will save you time no matter how fast you go. It will help more at faster speeds but it will help anyone.
A rear disc is still the fastest wheel available and it doesn’t matter whether it’s a $1000. disc or a $60. CH Aero cover.
Anybody will benefit from a disc as the same % no matter what your speed. In terms of actual time gained it benefits the slowest riders most since their actual time on the course is longest. Here is a good url that explains this:
Whooops. Forgot the url:
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I fail to see how one would have to be going a certain speed for a disc to help. If a disc is more aerodynamic and produces less drag than your other wheel option, it will be faster. Its a simple law of physics.
I keep reading that also… but I’m still going to ride on a disc this year and I don’t ride 24, 25, 26 mph.
I do ride faster then 17mph, which is what Gordo/Friel states as being around the speed to gain affect from “race wheels”.
I’ll allow my bench mark races this year determine if the disc is faster… weather permiting.
In general, I’d agree with that statement. I ride a disc whenever possible except IM distance with gusting winds (sustained wind is fine).
However, your bike choice need to match the race. Aero tests are much different than starting/stopping/turning/absorbing. It’s unrealistic to assume that your watts are going to remain consistent…and thus I don’t believe any of the bellyhoo the aero test show. I’ll take the school of hard knocks and experience over lab rats…
I’m in agreement with Cerveloguy on this one. Disc or disc cover- you’ll go faster.
Also, when you hear concerns over crossiwnd turbulence/instability: Well, you only slow down if you slow down- in other words, if a gusty crosswind pushes you around a little no harm done. That doesn’t slow you down. What slows you down is when you freak out because the bike is being jostled around by the wind and you back off the power. You have to keep the power on. It is extremely, I mean- *extremely *rare for a person to actually be blown over becasue they are riding a disk wheel. It would take a very pwerful wind gust probably over 35 mph depending on rider weight- maybe much more.
"What are the rim requirements for a CH aero cover? "
Anything with a box rim works best. They can work with a small dish aero rim if you trim the cover which is a hassle.
What slows you down is when you freak out because the bike is being jostled around by the wind and you back off the power. You have to keep the power on. It is extremely, I mean- *extremely *rare for a person to actually be blown over becasue they are riding a disk wheel. It would take a very pwerful wind gust probably over 35 mph depending on rider weight- maybe much more.
I second this. I ride in the extremely gusty Floriduh spring winds (just this weekend it was sustained 20-30mph) and all you have to do is keep a little bit more shoulder space in case you get hit by a huge gust. Practice will let you handle the “shove” from the wind, but since the push is below your center of gravity, it will tend to push the bike out from under you (easy to recover) as opposed to force above the CG pushing you over (harder to recover). I’ve been hit by 35-40mph gusts frequently at 160lb with no problems.