ColinJ
Puzzle game procrastinator!
- Location
- Todmorden - Yorks/Lancs border
If you know what speed you are doing, just calculate it from your gear ratio!On a slightly more serious note is there a reasonably reliable technique for working out cadence without a computer. I find it impossible to count pedal rotations and seconds at the same time.
Cadence (rpm) x 60 (mins per hour) x gear ratio x circumference of wheel in metres / 1,000 (metres per km) = speed in kms/hour
Gear ratio = teeth on big ring / teeth on sprocket
Circumference of 23C tyre is about 2.1 m according to the table on this page (other common tyre sizes included)
So, your cadence if you are in a 53/13 gear, with 23C tyres and riding at 40 km/hr would be (40 x 13 x 1,000)/(60 x 53 x 2.1) or about 78 rpm
If you fancy some other numbers ... 25 mph = 1.609 x 25 km/hr = 40.22 km/hr. Let's assume a 52/14 gear (top gear on my Basso)...
Cadence = (40.22 x 14 x 1,000)/(60 x 52 x 2.1) or about 86 rpm.
I tend to spin out on descents in my 52/14 gear at about 38 mph or 61.1 km/hr. That means my maximum cadence is about 130 rpm. I could probably manage a little bit more but really anything over 120 rpm feels too high for me.