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Bike fit, from road to TT
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Just looking to pick the minds of some of the fitters here. I’ve had a professional bike fit on my TT bike but also love to tweak and tinker it.
I know there is some expectations for lower power on the TT bike vs the road, but I can’t seem to close the gap between the two.

So one of my questions: Are there any angles that’s translate well from road fit to TT bike? Should my knee extension angle match up? Hip angle?

For context, I rode a hard climbing on my road bike last week, 26 minutes long. Later that week, I rode a flat TT, 52 minutes long. The TT wattage was 19% lower. And I also understand it could have been a fitness/fatigue issue.

Alex Arman

Strava
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Re: Bike fit, from road to TT [doublea334] [ In reply to ]
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No.
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Re: Bike fit, from road to TT [doublea334] [ In reply to ]
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doublea334 wrote:
Just looking to pick the minds of some of the fitters here. I’ve had a professional bike fit on my TT bike but also love to tweak and tinker it.
I know there is some expectations for lower power on the TT bike vs the road, but I can’t seem to close the gap between the two.

So one of my questions: Are there any angles that’s translate well from road fit to TT bike? Should my knee extension angle match up? Hip angle?

For context, I rode a hard climbing on my road bike last week, 26 minutes long. Later that week, I rode a flat TT, 52 minutes long. The TT wattage was 19% lower. And I also understand it could have been a fitness/fatigue issue.

A good chunk of the lower power from last week will be because 52 minutes is twice as long as 26 minutes.
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Re: Bike fit, from road to TT [doublea334] [ In reply to ]
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My 20 minute tests on the road bike are about 345. (this year) Yesterday I could only manage 323 on the TT bike for 22 minutes. If I didn't have stupid UCI rules I think I could narrow it more but my saddle has to be pretty far back since I'm 6"5, so I think this is just to be expected. I'm still way faster on the TT bike at 320 watts than I am on the road bike at 350, so I don't worry about it.

The angles probably won't match up. You recruit muscles somewhat differently in the two positions.
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Re: Bike fit, from road to TT [vjohn] [ In reply to ]
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Yeah, certainly could be the case. But 19% drop in power seems high. Maybe I should just train more?

Alex Arman

Strava
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Re: Bike fit, from road to TT [doublea334] [ In reply to ]
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doublea334 wrote:
Yeah, certainly could be the case. But 19% drop in power seems high. Maybe I should just train more?

If you're going to compare, then at least do proper tests at the same duration. Right now you don't really have sufficient data to say that's the case if you're only comparing these two rides.

That said, I would say that anything over 10% is "too high", and can be lowered with training more on the TT bike. Ideally it's less than 5%. Are you using the same powermeter on both bikes, or are they at least both accurate, calibrated powermeters?

You mention that you've been professionally fit, but you keep tweaking your fit. This makes me (a professional fitter) think several things. First, perhaps you keep tweaking such that you never really get comfortable in any one position on the TT bike. Second, if there were problems with the original fit, then your fitter ought to be willing to do a re-check. I do that (for no charge) if the athlete is dissatisfied, and I think all good fitters do.
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