Sounds like an issue I've had too. Check to see if there's any mechanical stuff going on with the TT bike. For me, turned out the brakes were rubbing (due to wheel flex), the tires were rubbing (frame was designed for 25mm, not 28), and the bolts connecting the rear dropouts to the frame were loose. Also, my frustration level caused me to start fighting my bike a lot while pedaling, which exacerbated all of those problems.

Got stiffer wheels, narrower tires, tightened the bolts, and got a cycling coach to help me work on my pedal stroke. Now TT bike is *finally* going faster than the road bike!

The fact that it's most noticeable for you on climbs definitely makes it sound like it could be some kind of rubbing... good luck getting it sorted out!

Cheers,
Ginger

the obvious thing you haven't mentioned is wind conditions - that could easily explain the difference.
since you say its a hilly course, also consider the descents - you may be faster descendig on the road bike, especially if they are technical descents.

strava gives you the ability to compare efforts on a segment to see where you gained/lost time - use that over the full course segment to identify areas of interest, then use specific segments to look at the power comparisons.

also check whether the power meters are consistent across the 2 bikes

 
No way you will ever have a fair comparison on that stretch. There's far too much/variable wind and there's fast moving traffic that can also skew comparisons, e.g. more truck traffic on one day vs. another could make a difference.

Beautiful ride, but there's no way I would ever do it. Not safe.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

 

p.s. I'll bet your FTP is set low.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Yes, I forgot to mention this. Oddly, conditions were almost identical with little wind and both years. Temperature was nearly identical, maybe 1-2°F warmer this year.

Descents were non-technical, the course is a straight road, out-and-back. My top speed was 3mph higher on the tri bike, so I was likely descending faster on the tri bike.

Power meters were identical (Favero Assiomo Duo).

I don't have Strave, unfortunately :(

These rides were done during races, so there was no traffic. Wind and temperature conditions were identical between the years (weird I know, but nevertheless that was the case).

FTP was probably too high; in Garmin I set it to my road bike FTP which is likely 10-15w higher than my TT FTP.

I'm also betting it was wind related (it doesn't take much), and the wind coming off the ocean on Hwy1 is quite variable.

You could always test the bikes on a controlled course where you normally ride. Literally doing two rides back-to-back on the same day with the two bikes at controlled power.

Aerobars make such a difference that it's highly unlikely the roadie is faster unless there was (as mentioned) mechanical issues or a wind delta.

Data point: My training rides through Woodside/Canada are repeatably faster on my tri bike than my roadie even if I spend most of the time on the bullhorns on the tri bike. The tri bike weighs more (~3lbs) but the frame is more aero and the bullhorns position is probably a bit lower than the hoods on my roadie (plus there is always some time in the aerobars).

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

Exactly. Canada road in Woodside on bicycle Sunday (no traffic) would be great for the OP to test. I used to test my bikes there. With the hills it's good for Chung testing too.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

You should be able to use DC rainmaker's power analyzer tool to compare the two files. Might cost you a couple dollars, but it's pretty cheap.

I'd be curious what you find out. 2400 feet of climbing over 56 miles isn't that much, even if one bike was heavier.

You can download the files as either .fit or .gpx and import them into excel. It's kind of a pain but only takes a few minutes to pull together the graphs. You have to go online and find a formula to parse the gps coordinates into distance between data points, but from there you can compare where on the course specifically was faster/slower.

My guesses are power meter calibration and wind.

Your avg cadence is lower on the tt if there’s anything in that? Could you have pushed too hard on the hills in too high a gear and blown for later?

Are your crank arms the same length between the two bikes? The calculated power could be off if the crank arms lengths are not correctly specified.

Your Torque Effectiveness and Torque Smoothness appear slightly different between he two bikes and I'm wondering if that isnt because of different cranks arm lengths... I suppose other elements of fit could also impact that.

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~Zac

I strongly suspect this is the problem - I made that error too - wondering why my road bike would read lower than my TT bike despite using the same Assioma powermeter. Turns out I had different length crankarms and was not setting in the Garmin head unit (which overrides the Favero Assioma app - don't set it there if you're using a Garmin).

It all became equalized once I got the crank lengths right.