After reading Daniel Connely’s blog post on the effect of road grade on VAM, I thought I’d try using my Strava data from last weekend to predict my climb times this weekend.
Taking liberties to simplify Daniel’s work, I will use my data from the Cavedale climb last weekend to predict my time on the Orr Springs climb this weekend. These climbs are both Cat 2′s and similar in length and average grade. This exercise is really only interesting because I don’t ride with a power meter. Instead, I’ll attempt to ride both climbs at the same perceived effort.
Here’s my Strava data from Cavedale:
Step 1 – Relative Power
Calculate relative power in Watts/kg on Cavedale.
Gradient factor = 2 + (% grade / 10)
2 + (7.3% / 10) = 2.73
Relative power (Watts/kg) = VAM (meters/hour) / (Gradient factor * 100)
1066 / (2.73 * 100) = 3.9 W/kg
Step 2 – Relative Power to VAM
Calculate expected VAM on Orr Springs.
Convert from relative power to VAM:
VAM = Relative power (Watts/kg) * (Gradient factor * 100)
3.9 * (2.79 * 100) = 1088
Step 3 – VAM to Ascension Time
Calculate expected time on Orr Springs.
Convert from VAM to ascension time:
Minutes to ascend = (meters ascended * 60) / VAM
(490 * 60) / 1088 = 27 mins
27 minutes. It’s practically done!
I’ll give Orr Springs a go this weekend and report back.