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speedo accuracy

Discussion in 'Technical and Troubleshooting Torque' started by geeth, Jul 12, 2009.

  1. I got my bike yesterday and all is great but there is one thing that I am questioning, the speedo.

    When I went through the toll booth it had my speed at 51 -52 km/h which was spot on to what I was doing.

    But when I am on the motorway at the speed limit I notice more then the 'normal' amount of cars passing me. To keep up with them I was going up to 120 - 125 acording to my speedo.
    Also on the way back from the dealer I was needing to do up to about 125 ish to keep up with my sister who pretty much never speeds.

    I am not to sure if the speedo is out because at 50 it's bang on or if it's just that I am being paranoid and thinking that I am noticing more people then normal passing me.

    Any thoughts or suggestions?

  2. what i did was get my wife to drive the car with the gps hooked up. the cars speedo is a few k's out.
    i rode next to her and got her to tell me when she hit 60,80,100 either by screaming out the window or by a thumbs up(this is probably a better option and checked my speedo and compared the speeds.
    mine was pretty spot on actually.
    its best to try to find a road thats not to busy at the time to do this as you might get abused for holding up the traffic.
  3. I am thinking of doing that with my dad.
    Or maybe just take to a bike shop and get them to have a quick look at it if i have to.
  4. Love the highly unscientific approach ;) Tankbag with gps in sounds easier.

    Speedos are often (usually) out by a few %, I'd guess the average would be 3-7%, obviously some are more some less. My 09 commodore is pretty much bang on, whilst my zzr250 was significantly off; top indicated speed the zzr did (closed road) was 170, but actual gps speed 152.5.

    Most manufactures will keep this fudge % to allow for changes in tyre profile, wear, etc. Its normal.

    edit; If you want to correct it you can buy a speedohealer, enter the appropriate number (eg. do 100 with gps and if bike says 95, then -5, etc.) and then its fixed. Cost is about ~$120ish last time I checked.
  5. Mate it's an ER6, get used top people passing you :rofl:

    Seriously though, the GPS in a tankbag is the best option .

    Most speedos are manufactured with an error built in to satisfy the ADR requirements of being 10% +-

    My GPS is spot on with the speed check device on the Princess hwy.
    My bike is out around 4km/h.
  6. This is correct, as is Vic with manufac's allowing for err's to be had on the safer side of the speed limit. Remember that the reading is out by a percentage so the faster you go the greater the variant I.E 5% of 50kph = 2.5kph but 5% of 100kph is 5kph etc etc.

    Also consider that most dyno operators who calibrate well can give you speedo readings at any speed.
  7. Another option - get a Sigma Sport cycle computer, say the BC800 for under $40. Install it. Then calibrate it using a GPS. Find a deserted road that's flat and straight. Do a number of runs, each time adjusting the wheel size until the speed and odometer readings line up with what the GPS is doing.

    You'll then have a number of things including a speedo that's spot on, a clock and a trip computer of sorts.

    The only problem is that they don't have backlights that stay on or come on with the bike's ignition.
  8. So run an LED to the bike computer.
  9. Thanks for the input guys, I will try to borrow a gps and go from there. At least if I know how far it's out I can easily work it out from there.
  10. didnt think about the tankbag thing but then i dont have one so i spose thats why i didnt think of it.
  11. Anti slip plate mat from BigW $7
    Roll of Gaffer Tape from bunnings $5
    GPS from Supercheap Auto $200

    The looks you will get from the Gino's as you park next to their Ducatis, priceless.
  12. :rofl:

    When I end up getting a gps for the bike, I will be planning on getting one and having it in a tank bag instead of spending $800+ on a bike specific one.
  13. Buy a Zumo, then you can send it back to them for repair/replacement :p
  14. Or you can get something like the Garmin Etrex Legend C. It's a handheld form factor. The bike mounting kit is under $50. All up you're looking under $300 from soemwhere like Johnny Appleseed.

    While it doesn't have the turn by turn nav instructions out of the box, (you need to spend a couple of hundred bux on the Garmin City Navigator software and maps) and the screen is fairly small, for a basic navigator and full functioned trip computer it doesn't do a bad job.
  15. NO! I refuse to!!!

    :cool: :twisted:
  16. Not that I would ever disagree with our fearless leader BUT a GPS is slow to react so you have to be dead steady in your speed for several seconds and if you are going up or down hill they don't apply the trig calculations allowing for the elevation changes as you are moving along (at least my Tom Tom V3 doesn't). They also don't like corners when it comes to accurately calculating distance to work out your speed.
  17. That's why I chose a flat and straight bit of road when I calibrated my cycle computer with the GPS.

    And in recent times, since they've upgraded the speed check technology on our highways, I've found that they too are fairly spot on.

    The original equipment was based on the same gear that they used for the Western Ring Road speed cameras which, as we all know now, were as accurate as a Herald-Sun journalist's report.
  18. are you saying herald sun reporters only write shyte? :shock:
  19. Hmm I don't know about that, every time I go through the speed check it says 'XS'

  20. Returning from a work trip to Horsham tonight I compared the speedo on the car with my Tom Tom Sat Nav and the overhead speed checker near Ballan.

    Speedo 117km/h
    GPS 113km/h
    Sign 112km/h :roll: