Numpty wheel size question

alpineaddict
alpineaddict Posts: 247
edited June 2012 in Road beginners
Hi Folks... Sorry for this potentially Numpty question re wheel size... but...

I have a Garmin 800 and am trying to input all the correct data... I am relatively new to taking cycling to my 'next level' so can anyone confirm for me that the info on my tyre of (700x23c) is the diameter and circumference of my wheel please???

Thx folks

Comments

  • schweiz
    schweiz Posts: 1,644
    It's neither

    23 is the width of the tyre in mm, but is not usually so accurate.

    700C comes from the French system of sizing wheels http://sheldonbrown.com/tire-sizing.html and corresponds with a rim (without tyre!) diameter of 622 mm.

    To measure the circumference of your wheels
    1. Line the wheel up so the valve is at the bottom.
    2. Put a line on the floor with chalk (best to do this outside unless the you want to mess up your carpet!) in line with the valve
    3. Push the bike forward one complete wheel revolution.
    4. Put another line on the floor in line with the valve.
    5. Measure the distance between the two marks with a tape rule.
    VN BMC Cube SS
    http://app.strava.com/athletes/30000
  • alpineaddict
    alpineaddict Posts: 247
    Ahh ok... Will it was a numpty question then... So if I was entering the wheel size into my Garmin, it would be the circumference and not the diameter that I needed?
  • snoopsmydogg
    snoopsmydogg Posts: 1,110
    would think so
  • schweiz
    schweiz Posts: 1,644
    RTFM!

    It will be circumference....

    Garmin have published this as a rough guide, https://support.garmin.com/support/sear ... 0000000%7D, but if you want an accurate value for your wheel and tyre then measure it.
    VN BMC Cube SS
    http://app.strava.com/athletes/30000
  • slowbike
    slowbike Posts: 8,498
    alpineaddict wrote:
    I have a Garmin 800
    I take it you don't have the Speed/Cadence sensor? If you do - just set it to Auto Detect and it'll do all the hard work for you - well nearly - you still need to ride it around whilst it works it out!
  • alpineaddict
    alpineaddict Posts: 247
    I do have a cadence/speed sensor but on my last ride it kept saying I was doing between 0 and 10 mph and I can assure you that was not the speed... :0( I was not sure if Auto would give a true reflection so I was trying to establish exactly what I need to put in if I used the 'custom' mode as opposed to Auto...

    @schwelz thx for your input... I'd love to read gamin's manuals... If they actually came with anything of substance... Bordering on useless. I did not realise there was a whole world of online manuals for them, so thank you...
  • captain_kelly
    captain_kelly Posts: 35
    Alternatively,

    Measure the diameter of the wheel (all the way across) then multiply this by 3.14 (pi) this will give you the circumfrence of your wheel.

    Christ i actually remembered something from my school maths lessons!
  • schweiz
    schweiz Posts: 1,644
    but measuring the diameter of a bike wheel is hard to do accurately with a tape rule as the hub and spokes get in the way!
    VN BMC Cube SS
    http://app.strava.com/athletes/30000
  • Pross
    Pross Posts: 43,181
    captain_kelly wrote:
    Alternatively,

    Measure the diameter of the wheel (all the way across) then multiply this by 3.14 (pi) this will give you the circumfrence of your wheel.

    Christ i actually remembered something from my school maths lessons!

    Or just take the wheel off and run a tape around the circumference!
  • edenchristopher
    edenchristopher Posts: 58
    schweiz wrote:
    but measuring the diameter of a bike wheel is hard to do accurately with a tape rule as the hub and spokes get in the way!

    OK, measure the radius and multiply it by 2 x Pi!

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