Calories per Mile

This is a SWAG for calories burned cycling 12-15mph:

  • Divide your feet climbed by 10.
  • Divide again by your average MPH.
  • Add that to your total miles.
  • Multiply the new number by the weight in pounds of you, your bike, and everything you’re carrying.
  • Multiply the new number by 0.105 (or divide by 9.5).
  • (Use 0.115 or 8.7 if you only know your own naked wake-up weight.)
  • That is pretty close to your calories burned for the ride.
  • Baseline here is me, 6’5″, anywhere between 250 and 290 pounds plus bike weight (any bike).

BMR is not a part of this SWAG:

  • BMR is how much you burn in 24 hours of sleeping.
  • Most people are around 9kcal per pound per day.
  • BMR and is not based on your activity level (see TDEE).
  • BMR is based in your microcellular efficiency, and is influenced by hormones.
  • If you are on severe caloric restriction, it goes down.
  • Thyroid issues can affect this either way.
  • Baseline here is me, at 285 pounds, and averaging 2550 kcal per day.

Faster speeds pick up exponentially more wind resistance.

  • Twice the airspeed has four times the wind drag.
  • Higher density altitude has proportionally less drag.
  • Shorter and narrower shouldered people people have less wind drag.
  • Fatter people are slightly more aerodynamic, so the increased wind profile is not THAT much of an issue.
  • Cycling 10mph into a 5mph headwind has as much wind drag as cycling 20mph with a 5mph tailwind.
  • 12-16mph is the 50% transition for wind vs other factors on flat ground. (13mph for me at 6 sqft)
  • Baseline here is me, with about 6 square feet of frontal area, about 22 Watts at 10mph, and about 150 Watts at 20mph, just for wind.

Rolling resistance is a big part of drag.

  • Increases linearly with speed (2x speed is 2x the rolling drag).
  • Lower weight is better (because tiny bumps have to push you UP over them).
  • Race tires can be half the CRR of average tires.
  • Wider tires are better by around 1% per mm with 23mm as baseline.
  • Baseline is me, at 310 total, 31W at 10mph, or 61W at 20mph on 1% grade.

Routes with less uphill than downhill will cost fewer calories.

  • Increases linearly with speed (2x speed is 2x the gravity drag).
  • 1% uphill is 2x the drag of rolling resistance. 2% is 4x.
  • Lower weight people do way better on both gravity and CRR.
  • Baseline is me, at 310 total, 62W at 10mph vs 124W at 20mph on 1% grade.

Good links:


Cycle sensor batteries

Today, the black-bike started auto-pausing and ate lots of my track. I played with sensor alignment, but realized it was a failing battery.

At home, the multimeter showed 3.065v for that one’s original battery, and 3.05V for the white bike’s once-replaced battery.

I can’t remember when I changed the batteries last. My internet searching indicates that I failed to post about it. In theory, I should get 1.4 years or 500 hours. The best I can tell, I’m getting 400 miles or so.

I replaced them both with fresh, 3.30v CR2032 cells. Unfortunately, these were bulk batteries, and I actually threw several away as being faulty in storage.

I may also need to adjust the wheel magnet, so I can be spaced a little closer, but I’m using monster magnets which trip the sensor from 2″ away.

I thought I might be leaving the magnets such that they intermittently trip the sensor when not in use, but maybe not. The HRM (heart rate monitor) sensor has been replaced, and is down to 3.01v. For good measure, I replaced it with a new 3.31v cell. I think I got 65 hours out of the last one, but it was in the 2.7 volt range when I was losing signal from it. Obviously, it’s much closer to the cycle computer than the speed/cadence sensor.

Anyway, there’s not an easy reminder system for battery replacements, so I’m going to set up a reminder to swap all of the batteries every 5 months.

That’s a little too often, but it’s much better than getting into a ride and having half of the track missing because it keeps auto-pausing.