IM Bike Power Pacing


Doing IM Florida here in a few days and I am trying to lock down a bike power target. My FTP is allegedly 271-ish as per TR and Garmin but that was in August. Since then I have trained consistently and did a century ride and a Half Ironman. All of the calculators and suggestions I am finding online want to use % of FTP which I don’t want to test again 3 days out. Any way to find a good starting point by looking at my Century and/or HIM that was recent?
– Sept 10 - 105 mile on my tri bike…pushed fairly hard. Avg Power = 207 / Norm Power 215 (there were a few longer rest stops
–Sept 25 - 70.3 Avg Power = 212 / Norm Power 225

I was thinking in the 180 to 190 range maybe.

That 180-190 target seems reasonable, but there are a couple things to keep in mind.

  1. If you wan to update your FTP and don’t want to test, just use the FTP detection button. However, I’m not sure how much I would change based on that since your race is so soon. I would view it more as an FYI.

  2. How was your preparation for the other events? Did you taper, eat well, etc.?

  3. Be ready to have a flexible plan on race day, you may find you have great legs and can go for it (but be careful), or you may find its way hotter than you’ve been training and you need to dial it back a bit.

Overall I would rather stay under 200 watts (or less) and be able to smash the run vs overcook the bike and have to walk it in. But you know yourself and know if you tend to push to hard in races or leave too much in the tank, so keep that in mind as well.

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As @BenB noted, just use the FTP Detection feature from TR. It looks at all your rides, both indoor and outdoor, to determine FTP. I have found it to be pretty damn accurate.

Based on a 270w FTO, that puts you at .70IF. Could be a bit a low, but should leave you ready to run. Would probably not go above 200wNP (.75IF).

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Ask yourself how good of a runner you are off the bike, how long you expect to be out on the bike, and how long rides followed by runs have felt at various powers during training.

The operative IF range for most people is around .67-.77 – so, if your FTP is ~275 right now, think something like 185-210 NP. If you’re good off the bike, expect to be out low 5hrs/high 4hrs, and have trained higher wattage well, push toward the upper limit. If the opposite, then the lower limit. If a mix, somewhere in the middle should be safe.

190W +/- seems reasonable. That’s what i would go with.

You need to give more importance to your long bricks / rides.
I assume that the century @ 215 np was not a brick.

IMFL is flat so your Vi will be very close to 1 (not much hill) and 70% is a good IM target for flat continuous bike leg. 190/271 is 70% but more importantly you’ve proven that you can go 100+ miles at 215 so with 190 you’ll be well set for the marathon. aiFTP is for workouts and not for pacing so i wouldn’t detect again.

At mile 20 of the run, nobody wishes they went harder on the bike leg.

This seems reasonable. Even if your TR tested FTP is higher than your no-kidding functional threshold power, 180W is probably a good target. I just wouldn’t trust a ramp test or Garmin FTP. Based on some quick math, if your 70.3 was pretty well-paced, your no-kidding functional threshold is likely closer to 255-260W, and it’s pretty common for ramp test “FTPs” to be quite a bit wrong, 10-15W wouldn’t be uncommon. There’s just no way I would pace an IM based on a ramp-tested FTP personally… YMMV.

I would encourage you to start at around 175 and build into that 180-190 range. As @BenB said, better to lose a couple minutes on the bike and have good legs for the run than lose dozens of minutes to an hour or more because you’re forced to walk more than you want to.

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