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Discussion Starter #1
Is there any way to fix the accuracy of the speedometer? I finally took a look at the GPS when driving ad my Thruxton 1200 it's very optimistic.

Same thing on my old BMW.
 

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They have to read over the actual speed by law, so that no-one can claim that they weren't speeding because their speedo read under. Been like that since the 70s or 80s. My Scrambler 1200 and Guzzi Stelvio aren't too far out - at low speed (say 50 km/h) it's only 3 or 4 out. Bit more at higher speed. My old Scrambler 900 was way out - 7 -10 mph (10-15 km/h) right across the range. Not much help with your actual question, I know, but I'm bored :D
 

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not sure if TuneECU work on yours but I think that has an option to tweek the speedo adjustment..
 

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Speedo recalibration software is available, but ONLY for non cable operated speedos.

I'm quite grateful that the Thruxton now has a speedo drove on the front wheel, rather than from the gearbox as per the 900 Thruxton. Although my speedo is about 5kph optimistic at the speed limit, I can easily compensate by running at asn indicated 105 kph. But the big advantage was that when I changed rear sprockets from 42 to 37, my speedo reading was not affected by the change.
 

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Discussion Starter #5
Speedo recalibration software is available, but ONLY for non cable operated speedos.

I'm quite grateful that the Thruxton now has a speedo drove on the front wheel, rather than from the gearbox as per the 900 Thruxton. Although my speedo is about 5kph optimistic at the speed limit, I can easily compensate by running at asn indicated 105 kph. But the big advantage was that when I changed rear sprockets from 42 to 37, my speedo reading was not affected by the change.
Interesting Thanks although I'm not sure I want to spend quite that much to fix it.

Doesn't make sense why motorcycles are so far off my design and cars can be very accurate when compared to a GPS. My expedition is always within +/-1mph when compared to the gps.

Thanks all
 

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Cars are NOT so accurate!

The accuracy of vehicle speedos is covered by Australian Design Rule 18.

Until July 2006 this rule specified an accuracy of +/- 10 percent of the vehicle’s true speed when the vehicle was traveling above 40km/h.

That is, at a true vehicle speed of 100km/h the speedo was allowed to indicate between 90km/h and 110km/h.
An odometer accuracy of +/- 4 percent was also a requirement.

From 1 July 2006 newly introduced models of a vehicle available on the market must comply with ADR 18/03. Also, from 1 July 2007 any newly manufactured vehicle(excluding mopeds) must comply with this rule

This new rule requires that the speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4 km/h. Significantly, this change means that speedos must always read 'safe', meaning that the vehicle's true speed must not be higher than the speed indicated by the speedo.

That is, at a true vehicle speed of 100km/h the speedo must read between 100km/h and 114km/h. An alternative way to look at it is; at an indicated speed of 100km/h, the vehicle's true speed must be between 87.3 km/h and 100km/h.
 

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Although my speedo is about 5kph optimistic at the speed limit, I can easily compensate by running at asn indicated 105 kph.
Yair I do that, and every bastard on the road goes past me at 120, usually in a massive dual-cab. I wonder if the police have ever considered having cars on the road?

Not sure if they still have it but there used to be overhead gantries on some freeways telling you what speed you were doing. As a result everybody went faster after realising they were under what their speedo said. :LOL:
 

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Discussion Starter #8
I'm not saying that the law doesn't allow discrepancy in automobiles, but in my experience they are generally pretty accurate. In the US it allows a 5 mph discrepancy at 50 mph. I've not EVER had a car that's been that far off.

In my rather limited experience with motorcycles, they are generally very inaccurate.
 

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My wifes brand new Hyundai reads 4% low at 100 kph. My T100 was about the same until I changed to an electronic speedo.
 

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My AC Bonnie is wildly optimistic too. Like 10%. The error is in the correct direction, it helps prevent speeding tickets.

But I use a GPS speedo from my phone, mounted on my bars, most days now. You CANBUS guys may be able to adjust it, not sure. But my is physical. It is what it is.
 

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Hmm. My T120 is pretty close to the gps speed reading. Within a mile per hour or so. On a 2500 mile trip last year, the GPS and the odometer were within 20 miles at the end. Is each bike calibrated differently at the factory?
 

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I'm not saying that the law doesn't allow discrepancy in automobiles, but in my experience they are generally pretty accurate. In the US it allows a 5 mph discrepancy at 50 mph. I've not EVER had a car that's been that far off.
My '96 and '03 Miatas both read high by around 10% at freeway speeds. Judging by various threads in the old miata groups, they all did. My parents' GM vehicles are all read dead-on accurate according to my Garmin GPS. My Infiniti was very accurate as well. My BMW 228 reads high by 1-1.5 mph at freeway speeds.
 
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