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Good grief I thought you were all kidding re the sweat thing my ears are full of the stuff and I've dripped through the house - I'm supposed to be a lady and glow

So daft quaetion coming up only just sneaked this past the HAT officer and so don't have a computer for the bike rear wheel that will do cadence etc so does anyone know how to work out distance covered by rpm and time spent - yes I know I'm deeply sad wanting to know but I like my little charts to be complete


  • TesseractTesseract Posts: 280
    Measure the outer circumference of your rear wheel, that will give you the distance per revolution (call that A).

    Formula should be A x ave RPM x time in minutes remember to divide back down to get it in metres/ km.
  • shadowone1shadowone1 Posts: 1,408
    ah the old physic distance = speed x time.

    I was going to delve into the theory of vector speed but I can't be arsed.
  • moonshinemoonshine Posts: 335
    ok egg heads

    tyre is a 700x23 so does that make the wheel size 70cm?
  • TesseractTesseract Posts: 280
    egghead huh?

    Nah - I tink the 700 is the diameter, although it can vary between manufacturers and depends on the tire. You'll need to measure around the outside to get an accurate measure.
  • moonshinemoonshine Posts: 335
    ok wheel=195cm
    rpm= 100
    time= 15

    and divide by?

  • You'll need to know what gear you're in to translate it to a wheel revs from pedal revs


    pedal revs x front cog teeth/back cog teeth = wheel revs per minute

    wheel revs per minute x wheel circumference in metres = metres per minute
  • moonshinemoonshine Posts: 335
    good grief - I'm still at the I'm on the big wheel at the front and middle wheel at the back description when it comes to gears
  • OKay.

    So let's assume (!!) that you're on 52 at the front and 19 (??) at the back.

    so that will be:

    100 x 52 / 19 = 273 revs of the rear wheel per min
    273 x 1.95m = 534m per minute so you're travelling 32kmh and covering 8km in your 15 mins.

    hope this helps.
  • DanteDante Posts: 22
    It's probably easier to buy a cadence sensor!
  • TRIumphantTRIumphant Posts: 850
    Have I logged onto the wrong Forum. Thought the maths on BCTTT was challenging, but WTF
  • gingertrigingertri Posts: 277
    so, what size are the rear cogs then? why do you need to know? does it matter?
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