I picked up a used P5 and it had the High V mount for the aerobars which made the saddle to aerobar pads drop a lot less than what I usually run for sprint triathlons. Typically I run 10ish cm of drop from saddle to the aerobar pads and with the high V mount my drop was just a little over 4 cm. I found a low mount and while I was waiting on that to be delivered I did a local course (29 miles of mostly rolling hills) with the high V mount still in place at 184 avg watts, 19.5 mph. Low bars came, I installed those which gives me a little over 8.5cm of drop, rode again doing the same course at slightly lower watts (180w) but the speed was down to 18.6 mph. This was slower than I was expecting. Temperature was the same both days, although the humidity was 20% higher on the slower day, winds were minimal both days (3mph avg wind on the “fast” day and 1 mph on the “slow” day). And to confuse things further I did have a helmet mounted light on the slower day which could have accounted for some of the drag. Otherwise the setup was really similar.
I need to gather more data but changing from high to low mount is kind of a pain! Could going from 4 cm to 8.5 cm of drop create more drag? Trying to decide if I should switch it back. Thanks.
I have a very hard time finding a low position because my body type just doesn’t allow it. Most people who fit me who think about aero, aero, aero always try to get me lower. Anecdotally, John Cobb, as one of his athletes, fit me personally with a vested interest of making me the fastest possible version of myself. He told me he wanted me upright, that I couldn’t be slammed… That to this day was the fastest position I ever had. I have gone to the wind-tunnel a couple of times just to play around. Here is my only published wind-tunnel example where moving me up actually made me faster. Also it was makeshift and actually added more A to the CdA as well because we did it crudely with just additional pads to keep the change fast in the tunnel.
I think it was Kirk Willett who used to laugh at people talking about dropping the bars 1-2 cm and saving 20 watts. His back-of-the-envelope calculations and experiences at San Diego put the typical savings at a watt or 2.
It is personal, but I think a lot of people start going slower in low positions because you lift your head too much to see up the road. Your 10cm of drop is pretty aggressive unless you are taller than 6 ft. I would do a mental check and see if you are straining to look up the road and lifting your head more in the lower position
Being narrow and a low head position is probably almost always better than trying to drop those last few cm.
This is my experience too. The main reason for the super slammed position is that it looks cool with no rider on it.
I have short legs so my saddle is not very high but my cda is low.
Could going from 4 cm to 8.5 cm of drop create more drag?
Yes, depending on what you did to compensate for that change. Pad height doesn’t dictate your torso angle, or anything else really. Posture is the important thing… how you hold your back, shoulders, neck, head, etc.
My guess is that the minimum drop that allows you to acheive a level torso will end up being fastest most of the time.
But you also didn’t do a proper test to see which was best, so…
I just did my own little experiment with adding pads to get me back higher, snapped some photos, and my trunk angle in the higher position is really really close to the angle you have on your web site wind tunnel photo. Hmm… In my lower position my back is almost flat. It’s hard for me to get my head around how a flat back could be slower, but the numbers don’t lie. Thanks!!! I may switch it back.
Given everything you said about the helmet mount etc I’d not believe those #s. Now I may not not believe them either. In fact until I did more testing, much more testing in fact.
For the same reason you can be more aero on the pads on a road bike than a drop position if your drop position is a big scoop with your drops way too low.
This guy’s low pad position was creating a lot of drag (but hey, you can still win the Tour de France that way)
and this guy finishing second on the TdF
You can see how they would both benefit from a higher pad position to get more like this position:
Levi’s high pad position but more like the speed skier
Granted Levi’s arms are like a T Rex but you get the point.
Given everything you said about the helmet mount etc I’d not believe those #s. Now I may not not believe them either. In fact until I did more testing, much more testing in fact.
Yeah it wasn’t enough tests to make a real conclusion.
I am fortunate as I have 2 devices that allow me to get pretty accurate drag numbers on the road.
I do a 15km TT every 2nd or 3rd week. Last Thursday was my fourth of the season.
I control the variables quite closely. Same skit suit, same helmet, device measures temperature and air density, wind…
Last week I raised my pads by a whopping 4cm. My ability to generate power went up by 13watts and I know this is NOT because of training. It is entirely comfort in the new position.
My drag went up by .008 which is significant, but my overall time dropped 19 seconds.
I just did my own little experiment with adding pads to get me back higher, snapped some photos, and my trunk angle in the higher position is really really close to the angle you have on your web site wind tunnel photo. Hmm… In my lower position my back is almost flat.
Now get your back flat with the higher position. Levi’s photo is a clue.
