Thanks, yes, I have read the repost of the Neanderthal positioning and the new comments (I even copied it to my online google documents about aerodynamics). Till I saw my pictures I thought that I had to drop my aerobar at least 4 cm. But I think that my 'acromion process is no higher than the origin of the latissimus dorsi". I now have a drop of 13cm (saddle tip to armrest) on a bike with a 14cm headtube (incl headset).daveryanwyoming said:At first glance your TT position looks pretty good. Have you read Andy's neanderthal positioning post on the Google lists? That's a really good starting point. But from your pix it looks like you're close, are you reasonably comfortable and can you sustain your typical long interval power in that position? You might be a tad stretched in terms of the fore/aft positioning of your elbow pads, sorta looks like your upper arms are reaching a bit forward instead of resting nearly vertically on the elbow pads. How does your leg extension compare to your road bike position?
What do you mean with leg extension? My saddle height? My saddle point has the same distance to my bottom bracket, on both it's 74.5cm. Maybe the saddle is a little bit higher, but I am not sure.
Yes, the arm rest are too forward. This is the position I got when I build this bike with the Vision bar in the lowest position with an 9cm stem. I have the saddle 3cm behind the bottom bracket and I don't want to place it more forward. I want to try to get a very aero, still comfortable UCI legal position. But the problem I have is when I come out of the saddle my knees hit the armrests When I buy a 7cm stem my knees will probably hit the armrests more often and harder
That's a huge drop in CdA! It's worth to drop 10% of power for it... I am pretty comfortable in that position for less than 30 minutes. I don't know if I lose power at a 10-30min effort. Shorter and longer positions I will definitely lose power but I haven't ridden my TT bike that much to know. I could do a 2hr L3 ride with 270 watts on my roadbike (ok, felt hard last 30minutes) but after 70 minutes of 270 watts on my TT bike my m.glutus said stop and for at least 3 days it did hurt (and it did also hurt my CTL)daveryanwyoming said:I've been working on my TT position this season and I'm getting lower and faster with small changes over time but also trying to find a low CdA position that doesn't sap my sustainable power. Tough challenge. FWIW I rode my first TT of the season with 10cm of seat to pad drop, held roughly 300 watts for the duration but didn't go nearly as fast as I'd like. My seat to pad drop is now ~16cm, my sustainable power has dropped nearly 10% but my times are much faster. The current position has become really comfortable (even the 10cm drop felt really extreme back in April but seems ridiculously upright now) and I'm due for ratcheting down another notch in the adjustable stem but definitely don't want to lose any more power so I'm also doing comparisons to my normal road position to try to find a balance. Anyway it's an ongoing process.
Have you tried the Chung method for comparing position changes? I've been doing at least one day a week on the TT bike where I go around a 20 mile loop that fortunately has no forced stops or overly sharp turns. I try to ride it in the morning with very light stable winds and I've been using that to estimate CdA. I've also done more conventional regression testing to baseline CdA and Crr, but the Chung method is great since you can just go out and train as long as you maintain a constant position and get data as a side benefit. I've seen my CdA drop from ~.28 to ~.24 based on these tests and incrementally lowering my aero bars. I'm hoping to drop another couple of cm over time but I'll definitely stop when lower positions fail to lower my CdA, especially if they cost me even more power.
Good luck and keep us posted on your watts/CdA progress....
-Dave
You are lucky that you can do the Chung method during 20mile rides. I have the problem that where I live there is always wind. I have searched for a small course to do the regression method when there is no wind. When there is a weekend without wind I will do some testing. Do you have suggestions for 2 other positions?
I will report my progress, new positions and first tests results. 350w and 0.24m^2 here I come!!