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Discussion Starter #1
Yesterday I was finally able to install my GPS, so today we went on a 108 mile ride to check the speedometer. I have a 2006 B400. Here is what I found. Up to 40 mph the difference is about 2 to 3 mph, with the GPS showing me going slower than my speedometer said I was. The difference increased slowly as the speed of the bike increased, so that at 40 mph indicated on the bike my GPS showed 36. By the time I reached 65 on the bike speedometer, the error was more apparent in that it was now 5 mph off. It stayed that way up to 70 where I decided not to go past. So the error is NOT 10%, which is what I have heard they were off, but still it would be nice to know what our REAL speed was. Well, at least it is in favor of less rather than more because I wouldn't want to try to fight a ticket where my speedometer was showing me going slower than I really was going. Here is a picture of my GPS setup, for those interested.
 

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True your error is closer to 8-9%, but it does increase as speed goes up. To be on the safe side and make corrections easier, most round up to 10% and then just subtract the first digit of indicated speed from the total. It is simpler, easier and gives you a little wiggle room if you happen to be in one of those radar trap towns that will get you for even 1 mph over.

On my 650 the error is 9-10% and it has routinely been 5-10% off every bike I have ever owned all the way back to the mid 60's. I have long since stopped fretting over it and have used the 10% rule on any bike I get on. If the industry has not changed it in 50 years they darn sure are not going to do it now.
 

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Discussion Starter #3
I have seen my share of bike riders go into traffic court and try to convince the judge that they were not speeding in a speed trap town. This pretty much confirms that they couldn't have been speeding if they showed a certain speed and were instead going SLOWER, not faster. One of those towns....Mobile, Alabama to be exact, had some pretty shadey things happen at the end of the month when the cops were told that they needed to write more tickets. In one case I had to go to court to show the judge a video I had taken of two cops who were manipulating the school zone light manually to write more tickets. The judge was NOT impressed by their antics and ended up dismissing about 2 dozen tickets, including several of us who were on bikes at the time. There are a lot of those types of towns in the South. So it is good to have GPS as a backup if we had to prove our case.
 

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In one case I had to go to court to show the judge a video I had taken of two cops who were manipulating the school zone light manually to write more tickets.
Sounds like a couple of dirt-bags with a gun & a badge,
that have no business having a gun & a badge.
 

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The "error" factor is effected by many different things. First of all some of it is engineered in by design, but tire and belt wear can and will factor in too.
The actual tire height on the different brands can be different too. And of course if you mount over or under sized tires the "error" factor changes accordingly.
But the best thing you can do is stay out of small towns in Alabama! :D
 

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Speedometer error

My 2013 650 has a speedometer reading that is about 7% optimistic and the odometer is about 3% higher than actual, on new tires. My Honda Pacific Coast has been/is always virtually "on the money" on both.
I, too, use the 10% process to gauge actual speed and 3% when I want to be accurate in calculating MPG at fill-up.....MPG reading on the instrument panel has always been quite pessimistic......50 MPG shown usually calculates to more like 55+ MPG when I do the math....don't much care one way or the other.......

TW
 

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It seems that this is a challenge that Suzuki would have wanted to fix coming out of the factory with the OEM tires/wheels on. Having said this, is there any easy way (for the layman) to adjust the speedo and odo so that they do their job correctly?
 

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Discussion Starter #8
That is a question that I am interested in too. As was noted earlier, this has been going on for many years. With all this modern technology why couldn't this have been addressed many years ago?
 

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After getting a speeding ticket I am just going to look at the speedo and stay within reason to what it says. I don't think its that far off. It does seem odd to me though when I pass those your speed is signs on the side roads or freeways they almost always peg what the speedo says. Sometimes my TomTom doesn't agree but also fluctuates so much I am not sure how accurate that is either.

I know the cop clocked me at 2mph under what the speedo said when I saw him :(
So it seems to be only 2 or 3 mph optimistic.
 

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In Suzuki's "mind" it is not something to be fixed; they deliberately designed the speedometer system to read 9 to 10% faster than actual vehicle speed. It could have been just as easily engineered to be accurate to 1 to 2%; they just chose not to do so.

Tire wear and tirss from different makers are of course factors in the system's accuracy, however such variances are typically in the 1/2 to 5/8 inch range--tire diameter would have to vary by over 2 inches to create a 10% error...
 

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Discussion Starter #13
Knowing that my speedometer is off by 2 - 3 mph until I get to 40 is acceptable, but being 4 - 5 mph off after that is really the problem. I get on the freeway with mine and when I think I am keeping up nicely with the traffic it is disconcerting to realize that I am slowing everyone down or might get run over by those going the allowed speed. Still, why would I have to pay $117 to correct Suzuki's lack of quality control?
 

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It's not about quality, it's about deliberately lying to you, to make you happy that your scooter is faster than promised.
:sign3::lol::lol:
 

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Knowing that my speedometer is off by 2 - 3 mph until I get to 40 is acceptable, but being 4 - 5 mph off after that is really the problem. I get on the freeway with mine and when I think I am keeping up nicely with the traffic it is disconcerting to realize that I am slowing everyone down or might get run over by those going the allowed speed. Still, why would I have to pay $117 to correct Suzuki's lack of quality control?
It has nothing to do with quality control. I've had 14 or 15 motorcycles/scooters over the last 40+ years. They have been BMW, Honda, Kawasaki, Yamaha and Suzuki. They have all been off about 10% on the speed but normally within 1 or 2% recording the miles ridden. If it was a quality control issue, the error should vary and sometimes be inaccurate the other way. It must be an industry conspiracy of a government "suggestion".
 

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Discussion Starter #17
So now I ride with my GPS on. Well I guess that is a good thing. If I decide to continue riding after a short run, at least I won't get too lost. :)
 

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Yesterday I was finally able to install my GPS, ...................................., so that at 40 mph indicated on the bike my GPS showed 36. ........................... So the error is NOT 10%,.....................(quote clipped for effect).............
I guess things have changed since I was at school, then:D


The error will change across the speed range, and from vehicle to vehicle. On yours, the error is 10% at 40mph indicated, and around 8% at 65mph.

For mine, (taking multiple readings at various speeds, over a period of several days), I've had results varying from 7% to 13%, but taking an overall average of 10%, is fair (at least for my bike), and makes the mental calculations of actual speed much simpler.

But if you need to be more accurate, I wouldn't take figures from a single run to be completely representative...try repeating the test under different conditions, and you could find your results vary.......but either way it should improve the reliability and accuracy of your findings.
 

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.MPG reading on the instrument panel has always been quite pessimistic......50 MPG shown usually calculates to more like 55+ MPG when I do the math....don't much care one way or the other.......

TW
Earlier 650s would only show MPG up to 50 (if you did better, it would still show 50 MPG). I seem to recall that's been fixed, but I don't know when they did it (and am not absolutely certain that they did).
 

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Discussion Starter #20
Well, I have been on multiple test runs since that first one and they always have the same results. It stays at about 10% until after 50 mph. Then, for some reason the error remains at 5 mph off. So, at 60 mph indicated on the speedometer, the GPS shows 55 mph. At 65 mph, the GPS still shows 5 mph error, and I have 'bumped' 70 mph for only a minute or two but it was still off by only 5 mph, meaning 70 on the speedometer showed 65 on the GPS. Interesting. I wonder if it would change if my speed was any higher than 70? I have no intention of testing that.
 
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