I’m struggling to find any good ballpark numbers on time/aero savings when lowering your aerobars. What I’m trying to sort out is it worth dropping my aerobars 1 cm. (Lowest setting on a DA4). Based on my prelim tests I am giving up around 5-10 watts NP by this tighter hip angle. Is the aero savings going to overcome the lost power? I am still comfortable enough to do a 20-40k in this position but my NP does seem to suffer slightly. The change seems small enough that any testing I do in the outside world is tough to read because conditions can change.
Does anyone have tips - links - evidence to help me make the decision here? Both positions are still pretty aggressive but I just feel like in the higher pad position I can scrunch down and get some noticeable Aero benefit so I’m wondering if I should slam the bars and just back off my power numbers 2-3%.
Just a little background on me if it helps -
Riding a 2013 DA4 - mostly stock - currently running 1 10mm spacer under the aero bars - testing the position of taking all spacers out.
NP over a 20k - 295-300
Typical avg speed over a farily flat 20k - 26 ish mph
Most other easy aero gains have been taken - 60mm front, disc cover rear, shoe covers, speed suit, aero helmet.
I stay in aero position on all TT routes unless speed drops under 13 ish mph on a climb.
I’m just doing some testing on my shiv and have found dropping the front end 2.5cm increases my speed from 36.4kph to 38kph at 230W, That’s about 26W difference or 10W/cm (I know it’s not that simple). Make of that what you will, but it at least gives you a ball park idea.
I’m just doing some testing on my shiv and have found dropping the front end 2.5cm increases my speed from 36.4kph to 38kph at 230W, That’s about 26W difference or 10W/cm (I know it’s not that simple). Make of that what you will, but it at least gives you a ball park idea.
Thanks - Your numbers basically make it a nearly even trade off. Although I’m looking at a little higher speed/power range so the 10w/cm could grow as speed and power increase. So I will chalk this one up to a slightly leaning toward dropping the 1 cm.
Go too low, however, and you could have trouble generating power, so lower is not always ‘better’
I agree - I have done some testing and my power loss for this change is about 5-10watts in NP. So that is the “known” factor in this equation for me. What I don’t know is if the power loss is worth the aero gain in this situation. It is close enough that is hard to measure in the real world. Wish I had a wind tunnel in my basement.
The question I would be interested in is, does the tighter hip angle affect my ability to run afterwards?? Lower power wouldn’t necessarily be a bad thing if it improved your efficiency on the bike, and then allowed you to be fresher and stronger for the run.
The question I would be interested in is, does the tighter hip angle affect my ability to run afterwards?? Lower power wouldn’t necessarily be a bad thing if it improved your efficiency on the bike, and then allowed you to be fresher and stronger for the run.
I would be curious of this as well but for my goals specifically right now is TT not multi-sport. I will do a hand full of sprints this year so I will see if the run is impacted too but short term it is all about the TT.
how did you determine that you are giving up that many watts?
As someone here (Steve Irwin I think?) pointed out, rather smartly, at 40km duration intensity you may not be giving up as much power as if you test it over say a 20 min (or less interval). i.e., it’s easier to ride the aggressive position at lower intensity
Also you may find that after some time you will adapt. (though personally I had to raise from what was a little better aero-wise, because it was making my hip hurt)
And note also that lower is not always more aero (also commented here numerous times)
how did you determine that you are giving up that many watts?
As someone here (Steve Irwin I think?) pointed out, rather smartly, at 40km duration intensity you may not be giving up as much power as if you test it over say a 20 min (or less interval). i.e., it’s easier to ride the aggressive position at lower intensity
Also you may find that after some time you will adapt. (though personally I had to raise from what was a little better aero-wise, because it was making my hip hurt)
And note also that lower is not always more aero (also commented here numerous times)
This was just my gut feel from looking changing over the bike and going out and doing a few 10 mile rides at 40k pace. How those felt and how my HR responded I planned to go out 10 watts under my normal target and pick it up at 25-50% race distance if I was undershooting. I have 20k’d and rode enough sprint tri’s to have a pretty good feel for if I can sustain a power after about 10 miles.
I did do 20 minutes on the trainer at a 90% 40k effort this morning in this position and was suprised by my low HR. SO the 10 watts would be the max I’m losing based on the little testing I have done.
As far as lower not being more aero. I have also seen some cases where lower is not faster but my position is pretty typical and my back is not flat so I would be surprised if in my case lower wasn’t some improvement. From what I have gathered the lower is not better is usually extremely low front ends and abnormal positions (arched backs, etc).
I’m probably over thinking it but I’m always trying to squeeze out those last few seconds.
As someone here (Steve Irwin I think?) pointed out, rather smartly, at 40km duration intensity you may not be giving up as much power as if you test it over say a 20 min (or less interval). i.e., it’s easier to ride the aggressive position at lower intensity
In 2012 I was riding in a position that was more powerful, but less aero, than the position I have now been riding in for nearly 3 years (apart from 3 months off in those 3 years due to an accident). Compared to my best power of 2012, my best power of 2015 has been 5W lower over 10 miles, but 25W higher over 100 miles. 25 and 50 miles are in between the two.
One of the reasons for this is that a major effect of the less powerful position is to reduce the ability to apply force, and it simply doesn’t matter that much over longer durations, indeed I have even wondered whether the reduced ability to apply force might actually be better for longer duration efforts, by preventing you from putting out too much power for short periods.
The other aspect is that the less powerful position also appears to be less efficient. My 10 mile power is not only down 5W, but my HR was 7bpm higher when I put out that lower power. So, that leads me to believe that if I had stuck with the more powerful position, maybe I would by now have gained ~14W with the same 7bpm increase, i.e. might I actually be down 19W vs where I would have been. It would still be well worth it for me, because my current position is around 60W more aero at 10 mile TT speed.
Another factor is that a more aero position saves you more Watts of drag at higher speeds. So the aero benefit declines over longer distances, BUT so does the loss of power.
I’ve also found that adaptation to a more aero position can take a really long time, even longer than you’d expect from setting your CTL to zero on the day you make the change, though again it’s complicated by the fact that you never know how you would have progressed if you hadn’t made the change.
All this is why you see people getting faster and faster over many years, it takes a long time to fully evaluate the results of this type of experiment, indeed I would say most people never get close to realising their full potential unless they get lucky with picking optimal options early on.
This is seriously a marvelous post to read especially for me personally who has gone a lot lower the last year or so and seen the delta between road and TT bike power increase. Thanks so much for this info!!!
A lot lower for me has also meant a LOT faster. A crazy amount faster.
I’m chronically inflexible, have been all my life. Admittedly I have disproportionately long legs that make it difficult to touch one’s toes and so on, but through the hips and back I’m pretty stiff.
I know from other posts that you like to guard your aero and training secrets pretty closely, but would you be able to recommend some stretches or exercises one can do to improve flexibility.
I’d love to be able to ride lower, but just can’t do it comfortably enough.
would you be able to recommend some stretches or exercises one can do to improve flexibility.
First of all, simply riding in a “tougher” position will gradually make you more flexible over time. A position that feels unbelievably uncomfortable at first can become comfortable after months of putting up with the suffering.
However, even then I have had some residual issues with tendons catching and “clicking” while riding, which is very unpleasant, and stretching before sessions seems to resolve the problem. The stretches are common sense, really, I’m just looking to establish a free range of motion beyond that needed for pedalling. I spend 5-10 minutes doing it before every session now. A few weeks ago I got complacent and didn’t do it for a few days and my tendons started clicking again, so I resumed doing it and have been doing it even more thoroughly than I was before, and have had pretty much zero problems since.
This is a good point and after finding best spot for position for most efficient power:speed ratio (might not be the lowest); the ability to maintain the position (esp if for long course) and run off the position needs to be checked. Perhaps with some adaptation the later 2 would improve. If I didn’t need to run I could drop significantly more.
What I don’t know is if the power loss is worth the aero gain in this situation. It is close enough that is hard to measure in the real world. Wish I had a wind tunnel in my basement.
There is no hard rule for this. But I think most people can go faster if they go lower and adapt.
Is your lower torso already level? Are you shrugging and turtling, and can you hold that? Are you feeling any specific discomfort?
One thing I’ve noticed is that low pads make it easier to shrug and turtle. There is also a pretty huge range of torso heights you can adopt loosening and tightening your shoulders.
I’m struggling to find any good ballpark numbers on time/aero savings when lowering your aerobars. What I’m trying to sort out is it worth dropping my aerobars 1 cm.
my evidence across 100+ folks in a wind tunnel suggests that 1 cm lower bars results in a CxA decrease of ~1%. Average power is the metric you should be looking at in terms of measuring the response to 1 cm lower bars. If you are giving up more than 1% in supply side power after adaptation, well, then, odds are you will be slower. Personally, over the short term at least, I wouldn’t give up a supply side watt for a demand side watt (depending on your power meter of choice, of course!).
I was having a harder time burying my head with the 1cm spacer. It wasn’t due to the bar height but they were a little too close. If I shifted back on the seat and stretched out I could get pretty comfortable in the shrugged & turtle position. I did adjust the reach and put the aero bars and pads about 1cm farther out so I can stretch out without scooting back. Maybe I need to try the longer reach without changing the pad height first.
Based on your experience maybe I just need to focus on getting in the best position possible without giving up power. I can stretch out a little more without giving up power. I think this would effectively lower my shoulders/head. I may try that for now.
All,
Based on my prelim tests I am giving up around 5-10 watts NP by this tighter hip angle.
First, NP is the incorrect metric to use to measure in for this. Use average power, because that is the thing you want to maximize for this. NP is a physiological measurement, but physics does not care about it. Second, NP is much less valuable for efforts below 30 minutes (which is what your 20k time is).