Cycle Computer vs Strava

NITR8s
NITR8s Posts: 688
edited April 2013 in Road general
Ive just bought myself a cycle computer and have been using strava beforehand. However, these two devices are giving out much different readings for a cycle, which one do I trust.

Example. This morning comute to work.

Cycle Computer: Blackburn SL4.0 - Distance traveled 7.3miles Moving Time: 24.30Mins Average speed: 17.8Mph

Stava on LG E400 (Andriod) - Distance traveled 7.0 Miles Moving Time: 28.21Mins Average speed 14.9Mph (It also says I had a top speed of 36Mph, however looking at my cycle computer on the hills I never got over 30mph once.

Which one do I trust, I am so confused.

Comments

  • davem399
    davem399 Posts: 269
    I would tend to favour the computer. Several lads I know using GPS on their phones and Strava have had quite a lot of dodgy rides. One was regularly starting his rides in the North Sea and riding several thousand miles a day!
  • term1te
    term1te Posts: 1,462
    If the wheel/tyre size is correct in the cycle computer, then I'd go with that one being most accurate. Especially around high buildings or under trees, etc. the GPS signal can be less accurate. Even between devices running Strava there can be big differences. I've got a Garmin 800 and my son was running it on his phone. We both set off at the same time, I reached the end of the segment ahead of him, yet when the data was uploaded Strave claims he rode it faster.
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  • NITR8s
    NITR8s Posts: 688
    Ive used the wheel size quoted in the instruction manuel for a 700c x 23mm tyre and it is also the same size as listed on Sheldon Brown.

    I would like to go off the cycle computer as it would mean I can say I was faster, however I dont wanna lie to myself.
  • slowbike
    slowbike Posts: 8,498
    Surely you know what time you started & finished? 4 minutes is a long time to be out by - does the strava app autopause?
    Measure the distance using one of the online tools - 0.3miles isn't a huge distance to be out by - but will depend on the accuracy of the GPS and the accuracy of the computer.

    Tyres are not always the same outer diameter ... there may be a little error in that measurement which multiplied up will make a more significant difference.

    I've never found Strava "top speeds" to be accurate - so ignore that anyway! :)
  • philbar72
    philbar72 Posts: 2,229
    comparing garmin to strava is occasionally like night and day. i favour the Garmin, as it is far more accurate.
  • smoggysteve
    smoggysteve Posts: 2,909
    Too many competing standards mean you never get a cross the board accurate comparison. I have done many ries that on Strava have put me at least 10 metres off course on a particular road or bend. Over a 50-60km ride if you add all the discrepancies up it can make a big difference.
  • NITR8s
    NITR8s Posts: 688
    Slowbike wrote:
    Surely you know what time you started & finished? 4 minutes is a long time to be out by - does the strava app autopause?
    Measure the distance using one of the online tools - 0.3miles isn't a huge distance to be out by - but will depend on the accuracy of the GPS and the accuracy of the computer.

    Tyres are not always the same outer diameter ... there may be a little error in that measurement which multiplied up will make a more significant difference.

    I've never found Strava "top speeds" to be accurate - so ignore that anyway! :)

    I have cut down the start and end so the ride now and the moving time has reduced to 27:21 and average speed increased to 15.3 so now a difference of 3 mins. I know for a fact that the cyclecomputer stops recording when the speed is 0 such as at traffic lights, I know strava is suppose to cut out non moving periods but I guess its not as acuate of reading a 0 speed as the computer is.

    This with the possiblilty that the cycle computer is reading 0.3 miles more than it should over 7 miles (differnce of 4.2 miles over 100 miles, could be causing the difference. Would I need to increase or decrease tyre size in the settings to resolve an over measuring distance. I am guessing I should go to a 400 meter running track and keep adjusting the wheel settings so it acuatly records 400meters traveled after each circuit.
  • dabber
    dabber Posts: 1,978
    The stop time on Strava is calculated as follows (and I quote).....

    Strava considers a point "not moving" if your speed is less than 0.3 meters/sec (0.67 mph), but we don't start accumulating resting time unless you're "not moving" for at least 15 seconds.

    btw. Some gps will not be recording you totally stopped even if you are. They may show zero on the device display but may be recording something above zero.
    “You may think that; I couldn’t possibly comment!”

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  • NITR8s
    NITR8s Posts: 688
    Well both Strava (ended the route about 0.8 miles before the actual finish but with the time to complete the full route) and the cycle computer were playing up on the way home. Grrrrrrr

    Bit peed off as its a brand new cycle computer and it was dropping out the reading every so many second. Gonna have a good look at it tonight, otherwise its going back to the shop for my money back.

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