I have the same thing problem. I do all my riding and bike racing on my road bike and TT's and du's on the TT bike. When I happen to allow the TT bike out the door for the occasional interval session my avg MPH is 1-1.5 higher than on my road bike. Same work/rest intervals and same course. My TT bike is set up 76.5 and the road bike is 73.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

you needed to:

shorten the stem & aero bars

lower the saddle

roll your hips

this is called the Slam position, it is very powerful for some riders, see www.bicyclesports.com for details.

This is total, sample size of one anecdotal, but for me personally I feel I get more power from a steeper geometry setup, but for longer distances I think I can sustain power better with a more slack seattube angle.

Everyone talks about simply establishing position and being able to rotate that position around the bottom bracket to reduce frontal area, etc., but I think the thing that's not talked about often is the relationship of the position triangle to gravity. With the steep seattube setups, I think there's more quad emphasis during the power part of the pedal stroke. With slacker setups, body weight is transferred to the pedals during the power part of the pedal stroke more through the glutes. Generally, I don't think your butt tires as fast as your quads. Another personal observation... Steeper setups favor faster cadences, slacker geometry favors a lower cadence, greater sustainable force pedalling style.

My simple take....

My experience (again, this is totally anecdotal) is that I seem to be going better with a shallow seat angle.

a week ago I did the Brick Du in Waterloo ON, and had a good race, 2nd fastest bike split in my AG and placed 5th in AG, 23rd overall. Not bad.

After that race, my back was a little sore, so I figured I would try a steeper angle, so I shoved the seat forward about 2 cm, and raised the seat a little.

Yesterday I raced a local sprint, and I have to say it was the worst result I have had in a couple of years, around 5 minutes slower than a sprint tri 3 weeks ago. I started cramping after only 10K on the bike, had no power, and ran a couple of minutes slower off the bike, including a horrible transition. The good side was that my back didn't hurt.

This poor result could simply be because I have raced virtually every weekend for the last 2 months, and I am just tired. Another explanation is that I do *all* of my bike training on my road bike, and such a drastic position change is no good for me. I am also not willing to change my training to do more on the TT bike, since in my other life I am a roadie.

I think I'll be putting the seat back to a nice shallow angle(~74*), more in line with what I train on every day.

I have started to experiment with different set ups as well. I was surprised to see how good the Slam position feels. I put the Jammer GTs on my road bike, shortened the stem by 1cm and did not change the seat at all. I like the fact that my crutch gets less pressure and I seem to have a stronger power out put and my chest opens up more. However this year I have spent very little time on my TT bike so far, so it may take a while to get used to it again.

I wonder if one could develop a basic test to see which position works better for a particular person and/or which position works for a particular distance?

Also is there a crude method to determine the actual seat angle one is riding at? My TT bike is 76degree, but my saddle is very forward, how do I know I am at 78degrees?

Two points,

First, is there a difference between the position that allows maximum short term or momentary power output and the postion that allows the highest long term or sustained power output. For me, closing the hip angle (more saddle setback) gives me the highest sustainable power. Steeper geometries, I tire faster.

Second, you may have a point regarding using gravity as any type of a reference. Even though with a steeper setup I keep the same pedal to saddle distance and lower my hand position, my hip angle is still probably more open in a steep seat tube position as neck flexibility (being able to see down the road) limits how much I can lower my hands with a steeper seattube.