Author Topic: Speedo inaccuracy  (Read 568 times)

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  • Offline wotbus@   fr

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    Offline wotbus@

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    Speedo inaccuracy
    on: June 24, 2021, 07:50:39 pm
    June 24, 2021, 07:50:39 pm
    I noticed during a recent trip my speedo is wildly optimistic  :016:. confirmed by my TomTom Rider and the speed panels in the towns. I mentioned this to my LBS and they confirmed the 950s speedo :003:  is inaccurate by 5 to 8kph (up to 5mph).
    If this is Big Brother's way of getting us to ride slower I would have thought an accurate speed readout would have been a better idea. I also asked if it was anything to do with the calibration facility provided - (50kph in 2nd gear for a few seconds) but was told no.
    Anyone else having this situation  :003:

    Edit corrects typo and handbook quote
    Last Edit: June 24, 2021, 08:26:38 pm by wotbus@

  • Offline MattR   gb

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    Offline MattR

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    Re: Speedo inaccuracy
    Reply #1 on: June 24, 2021, 08:35:44 pm
    June 24, 2021, 08:35:44 pm
    That's normal for all vehicles, certainly within the EU as it's based on an EU standard.

    Basically speedometers must never underreport a vehicle's speed but equally it must never overreport it by more than 110% of the actual speed + 6.25mph.

    So for example, if you are doing 50mph, then your speedo is allowed to read up to 61.25mph (50x110% = 55 + 6.25 = 61.25mph) - but it can never show less than 50mph.

    That's on the extreme of what's allowed, most are better than that.

    Wacky I know lol  :008:

     :821:

  • Offline wotbus@   fr

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    Offline wotbus@

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    Re: Speedo inaccuracy
    Reply #2 on: June 24, 2021, 08:42:53 pm
    June 24, 2021, 08:42:53 pm
    Jeez, and with the entire French Gendarmerie/Politicians totally paranoid about speed and the abundance of radars/private unmarked radar vehicles and a different Max Speed panel every 100yds I would have thought the least would have been an accurate speedo  :112:
    Ah well, thanks MattR 

    PS. What's wrong with being correct, really crazy  :087:

    Edit adds PS
    Last Edit: June 24, 2021, 08:47:39 pm by wotbus@

    Offline Paulel   gb

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    Offline Paulel

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    Re: Speedo inaccuracy
    Reply #3 on: June 25, 2021, 08:54:12 am
    June 25, 2021, 08:54:12 am
    As already stated, all speedos are optimistic, but my 950 is more so than any other vehicle Iíve owned since gps was invented.

  • Offline wotbus@   fr

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    Offline wotbus@

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    Re: Speedo inaccuracy
    Reply #4 on: June 25, 2021, 10:25:33 am
    June 25, 2021, 10:25:33 am
    Hi Paulel. I guess I was just taken by surprise and disappointed that with all the high-tech bells and whistles on the new 950s the speedo readout was so naff  :151:
    So, roadside/airborne speed control radars, fixed and mobile flash you at your true speed and as you never know your true speed  :172:
    Thereís talk, over here anyway, that soon new cars and probably bikes after, will be fitted with a black box which among other things will record speed. The question is what speed - actual or what the driver/rider sees on the speedo, what a bag of worms.
    I have already checked the net for an accurate GPS Speedo; if I can fit them why canít manufacturers.
    I suppose in a legal dispute the after-market more accurate speedo would not be recognised with preference being given to that fitted by the manufacturer.
    Ah well, if you are not travelling at the maximum permitted in all situations here, the driver behind you soon lets you know LOL.
    Safe riding, from what must be the only country in the world the have a national maximum speed limit which varies by 10kph depending on which department you happen to live or are passing through  :112:

    Offline Paulel   gb

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    Offline Paulel

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    Re: Speedo inaccuracy
    Reply #5 on: June 25, 2021, 01:39:21 pm
    June 25, 2021, 01:39:21 pm
    Hi wotbus, I lived in France for several years before returning to the UK 5 years ago so I have some idea of what you are talking about. They were just getting obsessed with giving every single driver speeding tickets when I left but I believe itís much worse now. I wouldnít worry about your optimistic speedo, at least you know you have a few kph in reserve before actually breaking the speed limit. I was just surprised to find my speedo was so far out compared to my Tomtom, but I canít say it bothers me. The only speed restriction I really take notice of is the 30 mph in built up areas. The rest of the time I just keep my eyes open for speed cameras and mobile radar speed traps. I find if you jam on your brakes as soon as you see a radar speed trap it doesnít clock your high speed.
    Ps do the French still restrict all bikes to 100 bhp?

  • Offline Paul_Smith   ie

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    Offline Paul_Smith

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    Re: Speedo inaccuracy
    Reply #6 on: June 25, 2021, 02:10:34 pm
    June 25, 2021, 02:10:34 pm
    *Originally Posted by wotbus@ [+]

    PS. What's wrong with being correct, really crazy  :087:

    The problem with being correct is that it doesn't stay correct. A little tyre wear or a little overpressure and the diameter of your tyre changes. Put the wrong size wheel on (more problem for cars then bikes) and you can be even further out. The law in most countries demands that the speedo must not under read the actual speed so, among other reasons, that you can not use it as a defense when charged with speeding. Read your User Manual and I think you will find it says something like
    (From the MTS1200)
    The instrument panel receives information about the actual motorcycle speed (calculated in km/h) and displays the value increased by 5%.
    The max. displayed speed is 299 km/h (186 mph). When speed exceeds 299 km/h (186 mph) a string of dashes "- - -" (not flashing) will be displayed.

  • Offline wotbus@   fr

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    Offline wotbus@

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    Re: Speedo inaccuracy
    Reply #7 on: June 25, 2021, 04:02:28 pm
    June 25, 2021, 04:02:28 pm
    @Paulel. Nahh not too worried, just a bit mifffed to mentally add 5kph all the time  :015:
    The 100bhp went with the introduction of ABS but still applies to older bikes without. There is a two-tier licence which may have always been, not sure. A1 up to a certain bhp, 60bhp I think and A2 over.

    Problem is: When the national limit was reduced from 90 to 80kph there were nationwide protests such that protesters incinerated cameraís, so paranoia increased and war was declared to get more fines to pay for new ones, under the political banner of ďDoing all we can to save more livesĒ, yawn...
    One could be forgiven for thinking the minister who introduced the law had a relative who was the owner of the speed panel factory as the cost of changing them all was astro mega huge. Thereís now more max speed panels than trees LOL.

    @Paul. Appreciate that Paul, I was referring to a GPS unit. I have since discovered there is a Smartphone app which would give a larger read-out than the TomTom (need for specs in my case) but thatís something else to mount...and I believe for the price of my new multi I shouldn't have to when insurance companies recommend fitting GPS trackers whatís wrong with Ducati fitting a GPS speedo. Seems thereís no problem with Govt telling manufacturers to fit a black box so whatís the problem with an accurate speedo.
    Rant over. Love Dukes really.
    Dry roads everyone and ride safe.  :821:




  • Offline Paul_Smith   ie

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    Offline Paul_Smith

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    Re: Speedo inaccuracy
    Reply #8 on: June 25, 2021, 10:53:53 pm
    June 25, 2021, 10:53:53 pm
    *Originally Posted by wotbus@ [+]
    ... whatís wrong with Ducati fitting a GPS speedo...
    The problem is that GPS doesn't work too well in tunnels or cities. Even if it did work perfectly all the time, to be legal it would still have to overstate the speed as that is the way the law was written.

    Why do you need to know the exact speed anyway? You know you are going too fast when you don't have time to look at the scenery, and if you are worried about tickets then you know for certain that you are safe if your speedo is not above the current limit, and the 5% safety margin means you don't have to keep looking at the speedo all the time so you can look at the road instead. Almost all the cops I know work to the principle of 10%+3. In a 100kph zone, they usually ignore you unless you are doing over 113 (100+10+3), in which case your speedo would be reading 119kph so you know you are pushing the limits. In a 120 zone, they will pay attention if you register 135 (120 + 12+3) so your speedo is reading 141! In a 50 zone you become interesting at 58kph (50+5+3) giving you a speedo reading of 61, So again, you are not just a little bit over the limit, you are bordering on taking the piss. According to cops I have spoken to, the reason is pretty simple; In a court of law, for a cop, a computer or a camera to prove you were 1 or 2 kph over the limit requires a very high degree of provable accuracy which is expensive, but if they can prove you were  10 or 20 over the limit, it doesn't matter if they are out by 1 or 2.

  • Offline MattR   gb

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    Offline MattR

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    Re: Speedo inaccuracy
    Reply #9 on: June 26, 2021, 11:21:56 am
    June 26, 2021, 11:21:56 am
     :762:

     


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