Generally speaking, I am curious to hear your thoughts on what the most aerodynamic position for descending on a tribike?
Does “generally speaking” mean that we should disregard anything that has to do with safety? The above looks pretty good though. I’ve personally hit 55 in the aerobars downhill, but that wasn’t exactly the smartest thing I’ve ever done.
That looks like Dev at epicman this year, in the rain. He is little and was able to stay with my fat assdown the hill into Keene. He was trying to teach me but I am too chickenshit to put my chest on the pads like that.
More concerned with aerodynamics over safety.
Most aero is as in your photo: hands next to the stem, chin on stem/hand, but in the air. OK on a road bike, but pretty damn unstable on a tri geometry bike!
On a road bike, next best is in the drops, chin on stem, slide rear way off bike - much more control and brakes close as well.
Ditto for IronTour. I had 35-40lbs on Dev, and yet on a descent from the tollgate on whiteface, i couldn’t get any distance on him at all. We both hit about 52mph on the way down, but i was in control and felt relatively safe flattened down on the aero bars; he was just insane 
When we did the Keene descent, in the rain, he actually pulled away from me (partly because my shades were causing visibility issues). he uses something pretty close to that position … and has to. he can kick my ass on the way up hills, and with this position, doesn’t lose an inch of that gain on the downhills.
*We have a weekly TT that’s 10K up a hill and 10K down I routinely run it up to 42mph on the tri bars, and I feel more stable on the tri bars then on the pursuits. So I think it’s very personal. *
*I have been doing that at 76 degrees seat angle, I have a new Felt B2 Comp running at 78 so we’ll see how I feel on that next week. *
Dan…
Most aero is as in your photo: hands next to the stem, chin on stem/hand, but in the air. OK on a road bike, but pretty damn unstable on a tri geometry bike!
Wouldn’t it be safer on tri geometry? I would think the longer trail and slower steering would be better.
Check this out about a minute in. Tried it before and its scary!
above 40mph, I’d use the position in the photo–below that, I’m pedaling…
It honestly doesn’t feel unstable at all, IME.
hah, the only difference is that this guy gets paid to descend foolishly fast…I just do it cause it is a cheap roller coaster ride.
My position as a slight modification on this one. I have one leg completely down with my weight on it and my butt is just in front of the nose of the saddle (actually I can steer the bike with the leg that is down and one sit bone steering the nose of the saddle). The head is in front of the pads and chest on the hands which is on the aeropads. The elbows are tucked into the hips Graeme Obree style. The hand on the other side from the leg that is down pushes the pad “back” to offer countersteering stability. It is actually super stable. If you big guys tried it, you’d hit 90-100 kph Keene!
Generally speaking, I am curious to hear your thoughts on what the most aerodynamic position for descending on a tribike?
Well, we dont know exactly “why” he is descending like that. It could be that in the wind tunnel he found this to be more aero than in his pedaling position. OR, the “effective” rake and trail created by a cockpit setup that is a touch too forward for the steering geometry of the bike could make it a rodeo ride on a fast descent. I have noticed in playing with my TT bike’s cockpit in different fore/aft positions that the bike can be completely stable with the setup at 50cm from seat tip to “cockpit”, and at 51cm its terrifying at speeds over 48mph. (coming down Del Dios heading back to the Coast on the second half of the Swami’s ride). I pulled the setup back to 50cm, and its steady as a rock again…go figure.
so, again: can anybody identify why he’s tucked like this? It appears nice and Aero, but looks are deceiving. I’d rather be putting a few watts into the drivetrain and get my speed higher, unless I wasnt geared for it, or was too gassed and just needed the break.
I decend well on a tri bike…I put my hands near the brakes and stay as low the rider pictured.
jaretj
i actually have zero doubt that this is more aero than any conventional position. the problem is that its also more or less useless for effective power generation. as for *“I’d rather be putting a few watts into the drivetrain and get my speed higher” … *if i am doing in excess of 32mph down a hill, i would never, ever waste energy trying to speed up. its simply not worth the cost to push my cadence up that high - much more beneficial to take the break and be ready to hammer again once the hill levels out.
i actually have zero doubt that this is more aero than any conventional position. the problem is that its also more or less useless for effective power generation. as for *“I’d rather be putting a few watts into the drivetrain and get my speed higher” … *if i am doing in excess of 32mph down a hill, i would never, ever waste energy trying to speed up. its simply not worth the cost to push my cadence up that high - much more beneficial to take the break and be ready to hammer again once the hill levels out.
If your choice of gearing puts you in that type of situation, then I would have to agree with you. I run a 41/56 up front, so I can push 50mph at 200 watts, and Im out there to train, so No coasting for me.
Now in a race, if I needed the break I’d certainly take it…but if I needed the break, then I probably did something wrong. During my outdoor rides I coast about 3 min for every 2 hours of riding, so I am used to working consistently, and I do that so that I can race just as consistently.
your mileage may vary, 
needing breaks and taking breaks are entirely different. if i was doing an ultra or a TT, breaks would be a problem. in a triathlon, if i can be moving downhill within 95% of the speed of the fastest rider without pedalling, then my run is going to benefit and i’ll take the break even though i don’t need it. i don’t know what your runs are like, but i’d be suprised to find more than a handful of triathletes riding with a 56 up front. thats a gearing range i associate with TT specialists, not triathletes who don’t want their quads blown out after T2. but your mileage may vary
needing breaks and taking breaks are entirely different. if i was doing an ultra or a TT, breaks would be a problem. in a triathlon, if i can be moving downhill within 95% of the speed of the fastest rider without pedalling, then my run is going to benefit and i’ll take the break even though i don’t need it. i don’t know what your runs are like, but i’d be suprised to find more than a handful of triathletes riding with a 56 up front. thats a gearing range i associate with TT specialists, not triathletes who don’t want their quads blown out after T2. but your mileage may vary
I’ve never had a problem yet, I guess this is a case of different training and racing philosophies. As you said above: you would take a break even if you didn’t need it.
I on the other hand, would not. Maybe that’s why I’ve never blown up, I"ve never trained myself to accept “breaks”.
cheers,
E_moto
I did that once on my old P2K on a steep downhill. Man I was flying. After the race I realized what an idiotic thing to do it was. Never done it since.
i actually have zero doubt that this is more aero than any conventional position. the problem is that its also more or less useless for effective power generation. as for *“I’d rather be putting a few watts into the drivetrain and get my speed higher” … *if i am doing in excess of 32mph down a hill, i would never, ever waste energy trying to speed up. its simply not worth the cost to push my cadence up that high - much more beneficial to take the break and be ready to hammer again once the hill levels out.
If your choice of gearing puts you in that type of situation, then I would have to agree with you. **I run a 41/56 up front, so I can push 50mph at 200 watts,** and Im out there to train, so No coasting for me.
Now in a race, if I needed the break I’d certainly take it…but if I needed the break, then I probably did something wrong. During my outdoor rides I coast about 3 min for every 2 hours of riding, so I am used to working consistently, and I do that so that I can race just as consistently.
your mileage may vary,
With what kind of grade and tailwind??? Seeing as how most of us wouldn’t have too much of a problem holding 200w for a bit over 2 hours, you should be producing IM bike course records left and right! You’ll be the first guy to ever go sub 2:30 on a full IM bike!
Generally speaking, I am curious to hear your thoughts on what the most aerodynamic position for descending on a tribike?
I’d say that his is pretty good. he still has control of the bike, it’s balanced well and it looks very safe.
Now since you asked what is the most aero, I’d say arms in the aero bars, butt behind the saddle, stomach pressed into the saddle and knees tucked in with a flat back.