It is not unusual for automotive and motorcycle manufacturers to calibrate the speedometers to read a few MPH faster than the actual speed.
Speed is the measurement of distance over time. But a speedometer doesn’t actually measure how fast you travel from Point A to Point B. Speedometers usually work by measuring rotation of the axle or wheel. They then use some basic maths to extrapolate that rotation and determine how fast you are traveling.
However, if the diameter of the wheel/tire alters, the calculation will be incorrect. For example, the diameter will increase if you put on new tires (more tread, which wears down over thousands of miles) or increase the tire pressure. This means that, for each revolution of the wheel, the vehicle is traveling further, meaning your speed is greater. This may only be a few millimeters but it is a significant amount at higher speeds.
This margin for error is taken into account in how the law is applied, and how manufacturers calibrate their car speedometers.
Sorry got a little long winded on the subject.
There are devices out there to correct the reading like the Speedohealer.
Do not own your model so hopefully some other members who do will contribute their expertise.

 

Pretty sure they use the rear wheel speed sensor for speedometer on our Vulcan S as well as many other Kawasaki models currently. The speedo healer worked great when there was a transmission mounted sensor, not sure if they have anything for wheel speed sensor calibration. Many motorcycles read high, my opinion is they want them to read high in hopes of riders going a little slower, but if you search just about any current motorcycles they are all pretty much 5-10% higher than actual.

 

Nope, sensor is on front sprocket. It will read about 6.7% higher because our Vulcan has 15t in front while it is engine from bike that has 16t as stock, Ive changed to 16t anyway to calm down revs at moderate speeds and it is near perfect now. Highly recommend doing so, she feels smoother now.

 

I've never had a Japanese made vehicle that did not read 5% - 10% high on the speedo. It doesn't bother me as long as I know that's what's happening.

 

I have found that going up one tooth on the front sprocket gets the speedo as near as correct as I think you can make it.
I have done this anyway with several modern bikes as I don’t like the standard sprocket which seems to make the bike too high revving in the lower gears.Also calms down the aggressive engine braking.

 

It's weirder that your car speedo shows the same as GPS than the bike showing a few mph off. I have never had a vehicle which shows exactly as the GPS. They are always a little off.

 

Those speedo's being off is one of my pet peaves on bikes. My previous 900 was off almost 5mph at 55. When I got my Nomad, which read high by 6%, I added the SpeedoDRD calibrator. This was in 2015. Now my speedo is accurate but my odo is low by 6%! I can live with that. I see they make one for the 2015-16 Vulcan S. Maybe they just didn't update the compatibility list. (You don't say what year model you have.) They also make a "universal" kit. Might be worth checking out.

SpeedoDRD

 

Just think of it like this -
Your going 60mph.
But really only 55mph.
As you go buy the patrol guy with his radar gun - YOU are not speeding on the 55mph freeway!

 

I just don't look at the speedo. [emoji2369]

 

Thanks all for your replies. I guess I'll just go with it for now and just know it's always a few over.

 

Back in the late 70's/early 80's Suzuki's speedometers were 10% over on the clock, so 70mph was actually 63mph.

 

Yea, I always go 5 mph over the limit according to the speedo!

 

Step up the size of the front tire and it will probably correct the speedo being “off”. I’m pretty sure it’s intentional from Kaw but in the case of my bike moving from a 100 to a 110 front tire will sync the speedo. I have not done this because I’m ok with knowing it’s off and I judge by whatever traffic situation I’m in but I have thrown on go’s to compare before and I notice the variance is higher at higher speeds. Meaning 32 on my speedo may be close to 30, but when I’m doing 70 it’s more like 63-64 as mentioned

 

Speedo takes info from the sensor at front sprocket tho. Front tire wont change it

 

noticed yesterday also that I think my speedo is off. Was showing 55mph in a 55 zone and had a line of cars behind me and the cars in front of me were pulling away.

 

The size of the tire will still change the rotational speed of the wheel. The sensor will still be in the same location, but the time it’ll take to complete a revolution should slow down. If the bike in stock configuration bumps up the speed reading, then slowing the rotation with a larger wheel/tire combo will be closer to the actual speed. Physics doesn’t care if it’s a 750, an S, or if it’s a tricycle

 

I think what they are saying is that the sensor senses the rotation of the front sprocket, and unless you change the size of the rear tire, the speed of the sprocket won't change if you change the front tire size.

 

The odd thing is a non-ABS Vulcan S does not have a speed sensor or ring on the front wheel, only the rear wheel....

 

Decided to check the service manual and yes the sensor is on front sprocket, I could not find information on why the non-ABS model still has the ring and sensor on the rear, though some bikes do use that to compare to the gear indicator an ensure it's accuracy but that would seem unnecessary with the normal speed sensor at the sprocket.

 

My 2004 Nomad was 10% off in speed and distance. Not only did this make speed calibration inaccurate, for every 9 miles I Road the Odometer showed 10 (9000 = 10,0000). Kawasaki needs to do better. Japanese products are known for quality and this is a tolerance limit acceptance issue at the factories putting this crap in the consumer’s hands. To answer your question, I don’t know if a solution other than buying a different motorcycle that doesn’t allow this much error.

 

all metric motorcycles that I kno
w of at the same issue it must be a tool to get motorcyclist to slow down my buddies full dress Harley reads Dead on

 

all metric motorcycles that I know
Have the same issue it must be a tool to get motorcyclist to slow down my buddies full dress Harley reads Dead on

 

Read this about the speedo accuracy problem - Weekend WTF: Your Motorcycle's Speedometer Is Probably Wrong
AND relax. If the speed limit is 60 you can go 65 and be right on.
No reason to fret about it or spend $$$ to try and fix it.
Us old riders just live with it!

 

I agree, us old farts can live with it however, the actual miles driven and thus mechanical service points should be kept in mind. I have a vulcan 900, i changed to a larger Baron drive pulley and smaller rear wheel pulley , in addition to a larger 170/180/16 rear tire to reduce rpm at highway speeds. These mods reduced the speed and mileage by 18%. Not a big deal but at a 15,000 mileage service date for adjusting valves, that equals 15,000 miles x 1.18% = 17,700 actual miles driven. A small problem to realize the benefits of cruising at 70 mph @3500 rpm vs. a teeth grinding , bone rattling , eye blurring 4500 rpm. Not to mention i get 55 mpg now. Just be mindful !

 

It's a bit annoying. My Lexus does the same.