Best bike split and a potential sub 5hr century attempt

So I’m going to ride a century on Saturday, it’s going to be a nice day and my first ride outside in 6 weeks. I’m doing a course I often do when I’m visiting my parents and doing a conservative endurance pace get somewhere between 5:15 and just under 5.5hrs. I was curious to see what it would take to get 5hrs and decided to try best bike split for the first time. According to that and my data input (non-aero stuff, so hopefully conservative), it says that if I avg 213w and have a NP of 216 (0.75 IF) I can do it in 4:50 (I set the parameters to not really have me going over threshold, just to be conservative). I’m a little dubious, but I’m gonna give it a try. Normally, I end up with an NP around 200, so it’s going to take a bit of focus for me to stay on the higher end of endurance. I’m not going all in as far as following the proposed power plan from BBS, just doing my best to stay in the 210-220 range and trying to stay as aero as possible.

Anyhow, any comments on BBS accuracy welcome here, otherwise wish me luck and hope to report back a positive outcome (although just going for a nice ride on Saturday after my short power build HV progression is enough of a positive outcome!)


Unless you are very heavy, the route is hillier than average or the wind is quite strong I would say that power figure for that speed is not too far off. Good luck and have fun.

Yeah, the route isn’t very hilly (the course is actually an organized century typically put on this coming weekend called the Flattest Century in the East, 3800ft or so on the southern MA/RI coastal region where I’m from) and I weigh about 160 at the moment. If only I had a friend with aero wheels lol I may shave the legs just to get a marginal gain!

The IF looks reasonable.

But stop lights and self-supported “feed zones” can add half an hour to your total moving time, as can even the slightest headwind.

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Don’t worry, I won’t be stopping lol (except for lights) I last did this route on July 4th, my total time was 5:28 and moving time 5:27!

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For some it seems to be very accurate, for others its totally useless.

For you, I would suggest a tt bike would save you those fifteen minutes and no analysis needed.

If you feed the numbers from previous rides into BBS does it predict times which are close to what you actually did? If so that’s a pretty good indicator that your parameters are in the right ballpark. From what you’ve posted it seems a little optimistic, i.e. a raise of ~15W in NP knocking 25-40 minutes off your time. Unless maybe you haven’t ridden that steadily in the past and have had say NP of 200 and AP of 180? AP is generally a better predictor of average speed than NP.

That’s in line with my previous ride(s) on the course, last time I did 174 AP and 199NP for 5:27 ride time, and in a previous ride I did 184 AP and 206NP for 5:16 ride time. But I was watching NP to keep it around 200 and not watching AP, so I’ll keep an eye on my AP this time around and see where I can keep it. It’ll be a fun experiment, at least a fun reward for paying my dues with sticking to the whole base/build cycle indoors

I tried using BBS for a 35.5km ride near home. I used their plan on my wahoo head unit but in the end I had a hard time holding the target power. I ended up being about 10w lower. That being said, I actually achieved a time only 1 second longer than the anticipated time.
Not sure if my experience tells you much but it will be an interesting experiment.

Good luck!

:rofl: :rofl: :rofl: :rofl:

I’ll see your 3800 ft and lower you 3489 ft.

The “Flattest Century in the South” is only ~311 ft (and is tentatively on my calendar this year).

If you could get a set of clip on Tri bars, that will get you more aero. I have a 50mile route that i sometime practice TT position on and have managed to do a time 15-20 min quicker.

@hubcyclist, how did you do?

Just finished! 5:14, still my best time ever but I knew 5 would be tough. I had AP of 197 and NP of 212 so short of what best bike split planned but I think even if I had nailed the power it would have been a tough target. No stops except for traffic and once because I lost a contact, so I spent most of the ride with one good eye lol.

As for nutrition I had 8 Sis gels, one bottle with beta fuel and one bottle with nuun. So about 1100kj on a 3700kj ride. All in all a good day and perfect weather here


I used BBB at the very end of my training for a sub hour Mt. Diablo attempt and it was quite accurate I would say. Really gave me confidence at the end that I was close. I undershot the avg power just a bit, but, still completed within my goal time. Just a bit higher than its prediction at the higher power so, all in all, I’m happy with it. Not quite enough to pay for its services yet though. Perhaps if I was regularly doing TTs it would be worth it.

Well done!

I would guess that BBB is probably a lot better at both shorter efforts than 5 hours as well as more hilly efforts. It’s a lot easier to calculate the uphill force working against gravity given all of the data you give it versus the CDA of any given rider/bike setup and I’d bet that inaccuracy slowly accumulates over time to give these kind of differences.

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BBS is usually spot on and very good on predictions on TT.

Nice work.

You could potentially be leaving minutes on the table with that fueling strategy.

In a 5 hour ride, you could easily fuel 2000 kJs . It may or may not decrease your RPE enough to bump your AP up by 10+ watts. Worth experimenting, IMO.

Eh, I kind of doubt it, I was more diligent the first few hours with gels every 20mins or so, and it didn’t make any difference performance wise, I was pretty steady the whole time, it’s just tougher for me to mentally focus on the higher end of z2 and it always has been, partially because I ride 8 speed so I sometimes end up going lower power at a more comfortable cadence. But I definitely wouldn’t say I felt limited by fueling or lack thereof, I’m also someone who at most takes on 100 calories during high volume indoor workouts, it’s rarely if ever has been something that has limited me.

Nice effort! I think wind direction might play a big role, I think you said this was a point-to-point ride? Even if you hardly had any wind, over 5h it will make a difference.