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Hey guys. just got a reading of 55+ MPG over a course of 145 miles! besides that, how much do the speedos vary from bike to bike? My dad's '86 at 4k rpm, is ~60 mph. my 2001 at 4k rpm is 55mph. how much will new tires vs. worn tires effect it? My bike has a NEW front and rear. my dads has a NEW rear, worn front. what are some of your speeds at various rpms. I really wanna check mine with a gps.
 

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Speedometers read about 10% high. Odometers are fairly accurate.

Size,type and wear of the FRONT tire can make a difference on speedometer and odometer readings. Rear tire would not make a difference other than speed to rpm figures.... and not by much.

You can't really take mpg figures as gospel if your calculation only deals with one tank of gas. You need to find an average over several fill ups.


KM
 

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Hey guys. just got a reading of 55+ MPG over a course of 145 miles! besides that, how much do the speedos vary from bike to bike? My dad's '86 at 4k rpm, is ~60 mph. my 2001 at 4k rpm is 55mph. how much will new tires vs. worn tires effect it? My bike has a NEW front and rear. my dads has a NEW rear, worn front. what are some of your speeds at various rpms. I really wanna check mine with a gps.
According to my calculations both the 150/90-15 and the 170/80-15 rear tires have nearly identical diameters and circumferences.
At 4k rpm both should give a true speed of ~58mph.

The vn750 speedo has been reported by many riders here to read about 10% high with the stock 100/90-19 front tire.
The odometer is fairly accurate however.

Changing out to the 110/90-19 nearly corrects the speedometer, but the odometer will now read a bit low.

The ~10% difference in speedo readings between your father`s bike and your own could be explained by these different sized front tires. The worn front tire on dad`s bike will cause a few more revolutions per mile and may add an extra mph or so to the reading as well.

There is also the possible difficulty of making very accurate readings on two gauges at speed while riding. Other than these two scenarios, I`m not sure how else to account for the different readings, as all previous reports that I recall have verified the approximate 58-60 mph at 4k rpm.

Both readings seem to fall within a reasonable margin of error, given the conditions under which they were made. <shrug>

True calculated speed using gear ratios for the vn750 is 14.52 mph per 1k rpm in 5th gear, but will vary a little with tread wear.
Simple multiplcation calculations will give the speed at any rpm.
 

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Discussion Starter #4
My speedo reads 55 at 4k. If it is reading 10% high. 10% of 55 is 5.5 mph. so if it reads 55mph, really its about 50mph? that cant be right, because everyone says about 4k is 58-60 mph. I really need to just test everything with a GPS. and see. is there anything that can cause a tach to read wrong?
 

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55 mpg seems really high, I usually get about 42, but I stay on my throttle too...
 

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I've kind of resolved to the idea that no two speedometers read the same these days, especially from brand to brand, and even two bikes like yours and your dad's from different years. You'll only know for sure once you ride with a GPS, and I highly recommend it so you'll know how to read your speed off your speedo. My 750 was about 10% high like everyone has said, til I put the 110 on the front, then it ran about 3% high.
Strangely, my 1500 is really close to dead on with a GPS and I'm running the stock tire sizes. A buddy's Shadow 750 reads more than 10% high which we verified with a GPS on a road trip, so it is best to just check it yourself.
 

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My speedo reads 55 at 4k. If it is reading 10% high. 10% of 55 is 5.5 mph. so if it reads 55mph, really its about 50mph? that cant be right, because everyone says about 4k is 58-60 mph. I really need to just test everything with a GPS. and see. is there anything that can cause a tach to read wrong?
Is your front tire the stock 100/90-19 or oversize 110/90-19?

The tach reads off the front cylinder coil or plug wire.
Not sure if the tach sensor or wire could read only some of the signals or not.:confused:
 

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55 is completely doable. I usually don't hit that anymore because too much of my current commute is at 60-65, which these bikes really don't like, but 45 mph backroads for a tank can be expected to yield deep into the 50's to low 60's.
 

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I think what this really boils down to is......what does it fkn matter?

If your speedometer says you are going 90, when the cop pulls you over
And writes your ticket for going 82....you just saved yourself some green.

And most of the other times you might not even get pulled over, because in fact you aren't even speeding. They are just numbers and don't mean much
unless you are breaking the law.......and you should already know if you are doing this without looking at your gauges.

My advice is just to ride the bike and enjoy yourself, and be glad the speedometer is off in the direction that is to your advantage.

;)

KM


KM
 

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Discussion Starter #10
55 mpg seems really high, I usually get about 42, but I stay on my throttle too...

This was for 145 miles. about 90% of those were about 60mph on level highway.
 

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Discussion Starter #12

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I believe what he's saying is your mileage will go down significantly at those speeds and higher.
 

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but 45 mph backroads for a tank can be expected to yield deep into the 50's to low 60's.
Low 60's? I don't think I could get low 60's pushing my bike down the road.
 

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Got 61.1 once and 59.4 another time back when I had a lower-speed commute. 56-59 were more common. Now I'm doing well to beat 50.
 

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Discussion Starter #17
I do feel that they could have geared 5th gear up just a little bit more. This engine can handle it.
 

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I checked my 2001 with my GPS. The error is about 10% and increases a little as speed increases above 60 with 100/90 front tire. Going to change to the 110/90 next time.

Also my average mileage is around 45-50. But I have achieved a high of 62 while riding with a newbie friend at 45-55mph on a weekend trip on the back roads. My lowest was 36, but I wasn't exactly following NM laws that day.
 

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Like KM said, you really have to average mileage over several tank fulls just to get an "idea" of your miles per gallon. Problem is, unless you're on a road trip, your speeds probably vary considerably, and even filling up the small tank can vary from time to time, because just a few more or less dribbles of gas can mean several miles in either direction, and then if you're not checking while using a gps for distance traveled, it's really a shot in the dark. I got 55 mpg according to my trip meter once while traveling some back roads in the hill country going around 45 mph max, and that is nearly impossible considering my 265 lbs on that bike, but that's what it added up to be for that stretch of road when I topped off my bike. I check it once in a while just to see if everything is normal, but unless it was really low (and I think you'd know it by the trip meter anyway) I don't pay much attention to it.
 

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Discussion Starter #20
Fergy: Just a ? how does your '02 1500 compare power wise to the vn750? i mean it is twice the size, but is it SUPER heavy?
 
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