I’m a regular listener of the TrainerRoad Ask a Cycling Coach Podcast. In it, the hosts discuss using Best Bike Split quite a bit in preparation for their events, particularly races. Best Bike Split can take your riding profile, including your power and aero profile, event goals, and course map to create segment-based power recommendations.
I was really interested in trying out the service for Tierra Bella (more on that experience here), and the free version will let you do power-based goals. Paid versions let you to optimize for time and speed-based goals and really drive down into the customization.
In my plan, I set an Intensity Factor (IF) of .75 (actual result was .72) as my goal.
Based on this, BBS predicted:
- Ride time of 7:14 (actual: 8:13)
- Net Power of 175 (170)
- Variability Index of 1.05 (1.14)
- Training Stress Score of 405 (430).
I didn’t know how well I’d adhere to the plan, so my approach was to spend most of the time in aero down in the drops to get some (I had set up the BBS plan to simulate me primarily riding on the hoods) free speed. The plan called for me to be around 160-170 watts most of the time, which I felt I could maintain in the drops. I would have been unable to maintain 200 watts in the drops for longer periods, however, due to being much more compressed on the bike (legs get closer to the stomach, making breathing more difficult).
Even though I wouldn’t be putting in max power (and thus not maximizing air resistance benefits) on the ride, spending a lot of time in aero position would have cumulative effects.
Why was I so slow compared to Best Bike Split?
There are definitely a numbers of factors. I was able to maintain BBS’ power goals on flats and moderate climbs pretty easily, but I was not as good on sustained climbs and descents. BBS would ask for around 100 watts on descents, not much, but as I’m a shaky descender who didn’t know the roads and who also wanted to avoid the hoards of cyclists climbing the other way (I was on small lane roads with below-average road conditions), I focused on safety rather than speed. I am guessing BBS may have an option to tweak this. On sustained climbs, I found that getting up to 90% FTP after miles 50+ was getting tougher and tougher, especially as the weather moved from 43 degrees F (at 7AM) to a peak of 95 (during the Hicks climb) without airflow. I had to be careful about not overexerting myself – I didn’t want to bonk (run out of energy) with 40 miles to go.
Because I didn’t overextend myself on the climbs and didn’t work on the descents, I was pretty confident I had some energy left to use after reaching the last rest stop with about 12 miles left in the 124 mile (200KM) ride. I did these last segments with 15% higher power than BBS’ goals, making up for some of the lost intensity from the previous 100 miles.
If I look back at my other metrics, this is what I think happened. Overall, my per minute intensity was less (.72 vs .75 IF) than projected, but I worked for much longer, leading to a higher total stress (9 vs 8 hrs, 430 vs 405 TSS) score. Since I had descents of essentially zero effort but then tried to make up for these at the end of the ride, this led to more variability in the power, leading to perhaps less efficient use of the power in terms of speed. I lost out on a lot of potential gain by not putting power on the descents, but also taking them relatively slowly. For example, the Henry Coe descent is 10 miles.
There’s one stretch in the ride that I think can serve as a good example of what BBS thought would happen, and what actually did. BBS does consider weather conditions such as wind direction based on historical data, with premium membership including more data.
From the Henry Coe descent on to Bailey / Morgan Hill, Best Bike Split gave me a 10 mile flat segment of 156 watts on the hoods. I actually spent the entire time in aero.
Best Bike Split Prediction (#102)
In the first image, you can see that Best Bike Split was expecting a tailwind (see lower right corner of image), which explains why I’d be doing 20.78 MPH at only 156 watts. Keep in mind that this prediction was for me on the hoods, sitting more straight up with increased air resistance, not in the drops (aero) position.
In reality, looking at my Strava record above, I was consistently over the goal – my guess is I was around 15W above for the 10 miles and still 3MPH below BBS’s expected speed, again despite being in aero. This was a 5 minute loss on this segment alone.
I was able to integrate the BBS plan with my Wahoo Elemnt Bolt; one problem I noticed is that despite having the power levels pop up on screen, I would not get directional information on the display. Thus, cues would be for new power outputs, not road directions. I’m not sure if the original map for Tierra Bella is missing this information, but my guess is that BBS overrides it. As a result, you have to use the Elemnt’s map display – it took me a bunch of wrong turns on the course before I realized this. The disadvantage of having the map display on all the time is that you have access to fewer data fields. There could be ways to get both power and directional cues, but I will have to look into that more next time.
Overall, I liked working with the BBS plan. It gave me power levels to focus on while giving me the confidence that I wasn’t overexerting myself. I knew I could last the 125 miles.
Best Bike Split costs $20 per month or $120 per year to be a premium subscriber. Since I am not a racer and don’t do many events, it’s not worth subscribing, but I’d be open to paying per event (ex. $5-10 per event with more features than free but less than full premium).