We've pretty much all agreed that it's 8% off. This review confirms that:
'07 Motorcycle Consumer News

Ninja 650r:
Measured top speed: 129.2 mph
0-1/4 mile: 12.11 sec. @ 107.30 mph
0-60 mph: 3.84 sec
0-100 mph: 10.95 sec
60-0 mph: 128.1'
Power to Weight Ratio: 1:6.93
Speed @ 65 mph indicated: 60.1

My home-brew fix is to simply go 10% faster than what's indicated. That makes the math easy. So if I want to go 40 mph I will run it at 44 mph indicated, 50=55, 60=66, 70=77, 80=88, etc. Police will allow you to go that extra 2% over because they know that not all speedos are 100% accurate.
There's a thread here somewhere about someone who was trying to get enough people to pre-order these aftermarket gauge faces(with correct speeds)to get them into production, but it hasn't got off the ground. Any color you want!

 

It's deliberate. A speedo healer will throw off the Odo. All vehicles are the same - ussually a 5 - 7% error. While the review below is typical, other mags have given errors. Any change to gearing, tyres size, or even tyre pressure will affect it.

Don't believe the accuracy of GPS either. It's better than most speedos most of the time, but it's not perfect.

Rob

 

I dunno...I read are speedos are 6-7mph off at 60 and over. 3-4 off at 40 and under.. So far mines seem accurate. I pass one of those digital speedos every morning that cops put on the road. And its dead on....

 

But as these things aren't used to provide prosecution eveidence, maybe the cops have calibrated it to read the same as a typical speedo in order to slow the traffic down. Or perhaps I'm just paranoid.

Rob

 

I tried out my TomTom on the bike and it told me that at three or four indicated speeds (35, 40, 50, 60 Mile/hr) i was only about 3 Mile faster on the GPS than on the speedo.

 

If the GPS is saying you're faster than the speedo says, something is wrong. Have you changed the gearing? or did you just mistype what you meant to say?

Rob

 

As far as GPS accuracy goes. I have used the GPS to verify my VWs speedo before taking the car to a speedometer calibration shop (needed speeding ticket excuse). The GPS was dead on with the calibration shops equipment.

Those portable speed signs I have found to be very hit and miss with accuracy. FYI if you blow by one at 102mph it flashes an 02.

I may look into a slightly larger diameter tire to rein the speedo in a bit. Assuming that the sidewall ratio of bike tires is the same as car tires a 10mm wider tire ought to help a bit. That is still a ways off considering I have 5k on the bike and the rear tire is holding up nicely.

I have to admit I am a little disappointed my car has a higher top end than my bike. I would have thought it could actually reach 140 but alas it cannot. I am more dissappointed that the speedometer reading 140 is actually less than 130. I am guessing this inaccuracy is common in bikes?

 

Those portable speed signs I have found to be very hit and miss with accuracy. FYI if you blow by one at 102mph it flashes an 02.

It flashes 02 because they only have a two digit readout. I don't know of any place in the States that has over a 100 MPH speed limit. Explaining why they wouldn't need to have a triple digit readout.

I may look into a slightly larger diameter tire to rein the speedo in a bit.

Something like this is going to screw up your ODO If you ever resale the bike and the buyer finds out, your not going to be able to sell it for as much as you'd hoped for. Messing with the mileage is a big no no.

I am guessing this inaccuracy is common in bikes?

Yes it is...

 

My speedo seems to be wayyyy off, like 15%...is this due to having aftermarket sprockets on it?

 

Yes.

Rob

 

"Something like this is going to screw up your ODO If you ever resale the bike and the buyer finds out, your not going to be able to sell it for as much as you'd hoped for. Messing with the mileage is a big no no."

Yeaaaa..... so making the speedometer and hence forth the odometer read more accurately is illegal how?

If you put a slightly wider tire with the same aspect ratio or slightly higher aspect ratio tire with the same width on the bike it will reduce the pulses counted by the sensor per foot travelled. Making it more accurate (by a small amount).

For the sake of arguing the legality of what you mis-interpreted as odometer fraud:

Right now everyone with a speedo reading 8 MPH high is in effect being cheated by the odometer registering 8 "bonus" miles for every 100 actual miles rode. My bike odometer now reads 5000 miles 400 of which I did not ride. Now personally I don't really give a hoot if I get a few extra miles on it. I would just like the speedo to be within 3-4 MPH of actual road speed. So I can accurately judge how smarmy to be with the officer issuing my speed citation. Now everyone run out and call the fuzz on everyone who puts smaller rear sprockets on their bike. It is however permissable to "rob" themselves by putting on smaller front sprockets.

Interesting side question. How much do motorcycle tires increase in diameter at speed due to centrifugal force?

 

Yeaaaa..... so making the speedometer and hence forth the odometer read more accurately is illegal how?

If you put a slightly wider tire with the same aspect ratio or slightly higher aspect ratio tire with the same width on the bike it will reduce the pulses counted by the sensor per foot travelled. Making it more accurate (by a small amount).

For the sake of arguing the legality of what you mis-interpreted as odometer fraud:

I didn't mean to say you were attempting odometer fraud. I am sorry you took it that way. But to comment on how this would make your odometer read more accurately you are just plain wrong. The design of the odometer is spot on. The speedo is off by a small margin.

Somebody correct me if I am wrong, but your speedo and odometer are linked together. With that in mind considering if the ODO is spot on and you correct the speedo, your ODO is now not tracking correctly. Thats all I was saying.

 

650R Rider is right. The ODO is spot on, even though it runs off the same transmission output shaft sensor as the incorrect speedometer, it has it's own little processor. Don't ask me why they made one accurate and one not though...It could be because if the speedometer reads slow even by the slightest fraction they could be held liable for accidents in BS court cases. Or it could have something to do with giving dealers some headroom should they need to fit slightly taller tires than expected sometime in the unforseeable future. It also could have something to do with the speedometers processor having to translate the signal to an analog needle gauge, the ODO doesn't have to do that. Dunno...
Just let the next buyer know what the approximate actual mileage is if you get a Speedo-Healer, change sprockets, or get a taller tire. A clear conscious is priceless.

 

Ahhhhh so the ODO is accurate. I never even bothered to check. I am guessing you paced the mile markers on the highway? If that is true then I am sure there is a way to recalibrate just the speedometer inside the cluster itself. The last thing I want is an ODO that reads low! In three months I will have about 6k miles on her.

650r: I wasn't offended. I don't take the internet seriously. Hopefully no one will take me seriously as well.

 

I do believe I have heard of a face plate you swap out in the speedo guage that has the tick marks in a more accurate position... either that or you can pretty much figure 5 miles indicated over the posted speed. I always drive 5-10 over posted anyway no matter what I'm driving, unless I'm in California where I need to floor it to keep from getting run the he!! over....

 

I do believe I have heard of a face plate you swap out in the speedo guage that has the tick marks in a more accurate position...

I have heard of this as well. Although you have to remember a new face plate is not 100% accurate either. Every bike is different and you have to factor in so many different things for one to be 100% accurate. Although, this would display a more accurate reading then what it is now and I would hope a face plate is a heck of a lot cheaper then a speedo healer... It would pry be a good way to go if you could find one.

 

I like the placebo effect of the optimistic speedometer; it is a very cost effective way for manufacturers to improve to 0-60 times.

 

No it isn't. You can't possibly get an accurate 0 - 60 time using the bike's speedo. For that you use electronic 'off the bike' timing gear.

I do like having the speedo read a little high as it provides a cushion against speed limits. This speedo is neither significantlt better or worse than every other speedo on every vehicle I've ever owned - car or bike.

Rob

 

i was woundering if i was one of the only ones who seems to be going slower than what it tells me. says im going 65 but more likely around 60. or even a little less.

 

I didn't get a real good feel for it due to lack of mile markers in N.C. but the ODo seems a bit optimistic as well.

 

The ODO is spot on, unless it has been messed around with. (i.e. Speedo Healer, Different size tires, Aftermarket Sprockets, ect.)

 

I know what placbo effect is. I donb't belive that anyone riding the bike can get a number that feels anywhere near accurate while riding, so the effect can only exist for the very easily fooled.

No one with any sense accelerates hard looking at the speedo anyway - although keeping half an eye on the tacho is useful, and the rest on the road in front.

Rob.

 

I know what placbo effect is. I donb't belive that anyone riding the bike can get a number that feels anywhere near accurate while riding, so the effect can only exist for the very easily fooled.

You are right, of course, the placebo effect of an optimistic speedo is likely temporary and only the very easily fooled could be influenced by the obviously inaccurate speedometer reading. :agree:

I do like having the speedo read a little high as it provides a cushion against speed limits.

Errrr........:stooges:

 

if you want to check it at 60MPH, one way is easy. pin the bike at 60MPH, you should cover exactly one mile in one minute. or pin it at 120 and do the mile in 30 seconds.

 

The portables are accurate. I was referring to those placed on the roadside by law enforcement in florida.

 

The portables are accurate.

Portable GPS?

They're reasonably accurate, but nowhere near 100%.

Rob

 

too bad the radar guns have triple digits haha

 

I did a little math but I am unsure if it is applicable to bike tires.

A 170/60/17 tire should be about a .5" larger in diameter than a 160/60/17

Should drop the speedo a little bit.

 

I'm finding my 09 with ~200 miles is off by around 2-3 mph. I used two different GPS units and received the same reading.

 

Who the he!! looks at their speedo anyway?oke: If it's off by 5-10% then take a pill for for OCD and look up at the traffic jacka**! I've been driving in California for 30 years (yea that's right, and I'm still alive) and the spped to drive is always the safe speed. 9 times out of 10 that is dictated by crazy SOBs all around you. If I look down at my speedo and it says I'm doing 75 and I decide I'm going to be a good little girl and slow down to 65 like the nice officer told me, then I'll have every other driver riding my behind like they want to marry me! My car gets nervous when other cars try to give it a rectal exam, my bike gets down right upset!

Now I don't have a lot of years on 2 wheels but I've learned one thing REAL fast, the speed to drive is the speed that keeps you alive. I may have to argue that philosophy with the judge one day, but I think I can be pretty convincing.

I like to keep my eyes on the traffic around me or the scenic view if I'm out of the city. I check the speedo every now and then just to see if I'm way off in ticket land or if I have a liitle room to spare.

Keep your head up! Enjoy!

 

Good advice. :agree:

But the point of the tread is to point out that these odometers are frequently inaccurate - Nothing more.

 

True that...:agree: