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Discussion Starter #1
Got my GPS wired up and did a road trip this weekend. Noticed the Speedo has a 6 mph optimistic error everywhere from 65 mph (indicated as 71 mph) to 85 mph (indicated as 91 mph).

Don't know if that's common to all our bikes, but I would assume so.
 

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The only bike I've ever had that was close to accurate is my Harley Police Electra Glide with the certified speedo. My Japanese sportbikes have usually been the worst of the bunch.
 

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Saddlebag, It's common practice for manufacturers to make their speedos optimistic by about 5%. If I recall correctly, I read that the Feds limit that optimism to 15%. That 6mph you mention will really be a percentage. The 2 examples you provide give differing percentages. The first is a gain of 9% and the second is 7%. It's gotta be one or the other, or maybe there's some sorta glitch going on in that dial.
 

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Discussion Starter #4
Saddlebag, It's common practice for manufacturers to make their speedos optimistic by about 5%. If I recall correctly, I read that the Feds limit that optimism to 15%. That 6mph you mention will really be a percentage. The 2 examples you provide give differing percentages. The first is a gain of 9% and the second is 7%. It's gotta be one or the other, or maybe there's some sorta glitch going on in that dial.
Which is what I thought was odd too. At an indicated 55 mph the error was maybe 2 or 3 mph IIRC, but from 65 to 85 mph it was a pretty consistent 6 mph. In fact, there was a couple of times I set the speedo to 90 and saw 85 mph on the GPS, indicating that the speedometer was re-gaining accuracy at the higher speed.

Makes you wonder how that affects the odometer readings. If they correspond, and I don't see why they wouldn't, the guy riding highway miles is logging miles considerably faster than the city rider despite the actual distance traveled.

Anyway, it was just general info for people not to get too panicked if they see a cop when their speedo reads over 70 mph in a 65 zone. Hell, even a speedo reading of 80 mph is probably within the hard eye range.
 

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My previous bike (Kawasaki) was off exactly 10%. I installed a device called a Speedo-Healer to recalibrate it because the error bothered me so much.

Surprisingly, my XC speedo matches exactly with my GPS speed reading.
 

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Mine is also off calibration and I have read that it may have something to do with the stage 1 download. If I have a PCV, can I reset my mph calibration or is this a dealer adjustment only? I purchased my bike with a stage 1 download so I haven't had a before and after comparison.
 

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Got my GPS wired up and did a road trip this weekend. Noticed the Speedo has a 6 mph optimistic error everywhere from 65 mph (indicated as 71 mph) to 85 mph (indicated as 91 mph).

Don't know if that's common to all our bikes, but I would assume so.
I use a GPS all the time. My 2011 XC is more accurate, at 70 (per GPS) it indicates 72 or so.
 

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Discussion Starter #8
Mine is also off calibration and I have read that it may have something to do with the stage 1 download. If I have a PCV, can I reset my mph calibration or is this a dealer adjustment only? I purchased my bike with a stage 1 download so I haven't had a before and after comparison.
Interesting, I hadn't heard this before, but mine also has the Stage 1 mods.
 

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Discussion Starter #12
It has nothing to do with S1, but variance is changed by selected gear, and tire pressure. Mine is S1, and in 6th gear it is 1 mph off

Your what? All the measurements I monitored were in 6th gear and above about 65 mph indicated they were all off ~6 mph.

I don't understand how the Stage 1 has anything to do with it either, but what else explains the wide variance between bikes? Maybe our GPS' our off? Mine is a Garmin, what's yours?
 

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Discussion Starter #14

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This is a little bizarre given Kevin answered both ways???
Well Kevin is simply mistaken :cool: Consider this, I noticed the difference within 5 miles after I left the dealership after the recalibration and then I run across this thread over a month later. Case Closed.

BTW the Tire pressure theory is almost laughable.
 

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Well Kevin is simply mistaken :cool: Consider this, I noticed the difference within 5 miles after I left the dealership after the recalibration and then I run across this thread over a month later. Case Closed.

BTW the Tire pressure theory is almost laughable.
Mistaken....Now that's interesting. Wrong but interesting. My 11 XC has had a GPS on it since the second day I owned it. On the 4th day I added an S1 download. Funny thing is.....My speedo was the same BEFORE and AFTER. At the same time I have customers that have stock bikes, and they are off by 5%. For evidence you call into play QNE bike, and I made my statement from observing dozens. So enjoy your closed, but mistaken case.

As for laughable....Use a little brain power here. I know it's hard, but give it a try. The speed is read off the output shaft in the trans, and calculated by the ECM for a signal to the speedo. Allow your tire to be deflated, and the tires is shorter. Multiply the ratio change through the gearbox, and you get significant variance in the speed reading. Simple physics friend. The rules of life.
 

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Mistaken....Now that's interesting. Wrong but interesting. My 11 XC has had a GPS on it since the second day I owned it. On the 4th day I added an S1 download. Funny thing is.....My speedo was the same BEFORE and AFTER. At the same time I have customers that have stock bikes, and they are off by 5%. For evidence you call into play QNE bike, and I made my statement from observing dozens. So enjoy your closed, but mistaken case.

As for laughable....Use a little brain power here. I know it's hard, but give it a try. The speed is read off the output shaft in the trans, and calculated by the ECM for a signal to the speedo. Allow your tire to be deflated, and the tires is shorter. Multiply the ratio change through the gearbox, and you get significant variance in the speed reading. Simple physics friend. The rules of life.
I don't need all of your calculations, all I need is common sense. If you are running your tires low enough on air to change the diameter, you're gonna know it. After all, were talking about a motorcycle not an 18 wheeler :rolleyes:.

BTW, On my original Thread there is one comment saying that it is possible that the recalibration was the cause of my speedometer variance. It was made by YOU !!
 

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Discussion Starter #18
I don't need all of your calculations, all I need is common sense. If you are running your tires low enough on air to change the diameter, you're gonna know it. After all, were talking about a motorcycle not an 18 wheeler :rolleyes:.

BTW, On my original Thread there is one comment saying that it is possible that the recalibration was the cause of my speedometer variance. It was made by YOU !!
Which raises the question why the fuel/air mix table should have anything to do with the speedometer.

An interesting corollary is Corba's new PowrPro. Instead of providing an open loop fuel/air map that is fine tuned with O2 sensor feedback, it bases the amount of fuel on what propels the wheels with the most spunk. I've also heard that Victory uses Cobra as a vendor. I'm not saying that Vic uses PowrPro technology, but in that case, at least it would make sense that the fuel map is somehow tied to the speedometer reading.
 

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My tires are checked every couple weeks and are inflated to Victory specs.. When my speedo reads 75, three other guys I ride with tell me their bikes indicate 70. All these bikes are different brands so I don't think they are the ones with a calibration issue. I have not checked mine against a GPS but am willing to bet that it will indicate the same amount of error. Picked the bike up new with S1 download already installed so I have no before and after comparison. Since the ECM is in the speedo loop, I believe this is where the problem exists.
 

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I don't need all of your calculations, all I need is common sense. If you are running your tires low enough on air to change the diameter, you're gonna know it. After all, were talking about a motorcycle not an 18 wheeler :rolleyes:.
Common sense says that the low air on the 18 wheelr would still be suported by the tire next to it, and would not change it. Last time I looked. There was no dually made by Vic
BTW, On my original Thread there is one comment saying that it is possible that the recalibration was the cause of my speedometer variance. It was made by YOU !!
Possible, but not probable
 
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