Speedometer faults? Police Radar...

[LefZe]

Hi,

Today was my unlucky day... I just got busted in a police radar control riding bike, a FZ-6N (80hp).
The speed limit was 60km/h and the radar showed 87km/h (90 - 3 km/h, as they take 3km/h off), so I lost my license (loose it at 86 in 60 zone in Norway..).

The thing is that I was crusin around in 70-80km/h and my speedometer showed 82km/h when I was caught, and I admit I was crusin too fast, but not so fast I could loose my license. I explained this to the police and I asked if I could do another test in their radar to see if my speedometer actually shows such a big difference between what I saw on my speedometer compared to their radar. The first test round I did 59km/h and the police wasn't able to catch me on the radar.... In the second go I did the same speed (59), and they cought me this time and said the radar showed 65km/h. I thought a regular speedometer should show about 5% less than the actual speed, but Yamaha seems to underestimate their bikes...

Could it be that my speedometer actually shows the wrong speed at the time? Have I been crusin around 10% too fast without knowing it? Could there be any factors that could cause the speedometer showing the wrong speed when I got caught?

I haven't had the bike on service this year. It's a 2008-model, 18.000km in total, and I had it on service last season at 12.000km. It has been stored in a garage all winter (took it out about one month ago).

My tires are ok, but will be replaced soon...if I can convince the police that I should keep my license. I don't think the tires are the cause for the faulty speed on my meeter. I need proof that the speedometer actually was showing the wrong speed to be able to fight the truth.

It was very windy that day as well, but I don't remember if I had head or tail wind at the spot. Could it be that the speedometer is controlled by RPM? If I had tail wind wouldn't the bike go faster at a lower rev and indicate a lower speed?
I don't know how these speedometers works on this bike, so if anyone could explain that to me, I might be able understand this and ride again as soon as possible!

Thanks

 

[RJ2112]

The speedometer on an FZ6 is based on the transmission's output speed. If someone has replaced the final drive sprocket, or the front sprocket, the readings will be off. If the tires have a different sidewall height, the readings will be off.

For the numbers to be too low is quite unusual.

If you can find a shop that has a dynomometer, they could determine what your wheel speed is accurately compared to what your speedometer is saying.

 

[VEGASRIDER]

It's usually the other way around, regardless if it's in Km or MPH, the indicator should read higher than your actual road speed.

It's actually pretty accurate at slower speeds, but once you get over 50 mph, it will become inacurate up to 8%. But it will read higher than you are going. You're the first one who have posted that you were going faster than what was indicated. Only explanation may be that the sprocket is not stock?

Many have corrected this problem by installing a speedo healer or going by off their GPS. There are countless of threads relating to this topic about the speedometer. Just use the search tab and type in some key words and you can read up on everyone's findings.

 

[LefZe]

The speedometer on an FZ6 is based on the transmission's output speed. If someone has replaced the final drive sprocket, or the front sprocket, the readings will be off. If the tires have a different sidewall height, the readings will be off.

For the numbers to be too low is quite unusual.

If you can find a shop that has a dynomometer, they could determine what your wheel speed is accurately compared to what your speedometer is saying.

Thanks for your prompt reply. I guess "off" means "less" as well? Pardon my English

I think the sprockets are stock, but it's only a guess as I bought it second hand but from a professional shop. How do I check this?

So you don't think the wind could be a cause? I live as said in Norway, and it can get very windy here, like it was today. Don't think a GPS/Dynamo test will be accurate without wind if that could be a factor. And of course I can't drive it there either..

BTW: I fuel my bike with Shell V-Power 99 unleaded petrol only. Could that cause anything?

 

[RJ2112]

Thanks for your prompt reply. I guess "off" means "less" as well? Pardon my English

I think the sprockets are stock, but it's only a guess as I bought it second hand but from a professional shop. How do I check this?

So you don't think the wind could be a cause? I live as said in Norway, and it can get very windy here, like it was today. Don't think a GPS/Dynamo test will be accurate without wind if that could be a factor. And of course I can't drive it there either..

BTW: I fuel my bike with Shell V-Power 99 unleaded petrol only. Could that cause anything?

'off' means a difference from what is expected.

If someone wanted to lower engine RPM for a given road speed, increasing the number of teeth on the front sprocket, or dropping the number on the back one would make the wheels spin faster for a given RPM.... this would make the speedometer read 'low'.

 

[victorb]

Sorry to hear your license was suspended for 1 km/h above the cut off between fine and suspension.. cops don't joke around in Norway, do they?
Wind and gas will have no effect on your speed reading. Count the number of teeth on your sprockets.. stock (in the US at least) is 16 front / 46 rear. More teeth on the front and/or less teeth on the back would result in your speedometer reading being less than your actual road speed.

Good luck getting your license back!

 

[The Dude]

Lose your license for doing 54 in a 37? Wow! If they end up taking it, that should be your cue to leave Norway and enjoy the rest of your days as a free man. In my neck of the woods, just talking about requiring motorcyclists who don't wear helmets to carry more insurance is enough to cause protests. On the other hand, it's pretty cool the cops let you do a couple test runs. In the States, you're more likely to get shot or run over than to have the police even consider that you might be innocent or they could've made a mistake.

Don't worry about the wind.

Don't think it's the tire, but make sure you're running a 180/55 R17. Check the sidewall. And the fact that you're about to replace the tires only makes it less likely to be a problem. As the tire wears, the diameter shrinks and only adds to speedometer error (making the speedometer read even faster than actual speed).

I'm a bit skeptical that your speedometer would be reading too slow. As others have stated, it reads high in stock form, and even the most common mod for taller gearing just corrects the error. You would have to gear it pretty high to get it to read slower than actual speed. That would require going to a larger front sprocket AND and smaller rear sprocket. And most people change their gearing the other way, which yields an even greater speedometer error than stock configuration. In that setup, the speedometer will give you a much higher speed than you're actually moving. So yes, count your sprocket teeth front and rear, but I'll be surprised if it's your gearing that's the problem.

I suspect it's the officer's equipment that is giving the incorrect reading. But there's probably not anything you're going to be able to do about that now. Or you could have actually been going faster than you thought. Again, nothing you can do about it now.


So let's talk about your options. If I understand your situation, you've got to prove your speedometer reads too slow or else you lose your license. So here's the game plan:

1. If you determine that for whatever reason, your speedometer is actually reading too slow, go to a Yamaha dealer or reputable motorcycle shop and have them test it. If they agree it's not accurate, get them to write a letter or provide some written documentation on the problem that you can present to the court. Hopefully, that will be enough to get some leniency.

2. If you determine your speedometer is not reading too slow, find a less reputable motorcycle shop or a knowledgeable friend. You're going to need to create the problem you need. It will not be difficult to get a larger front sprocket AND a smaller rear sprocket, but it will be tough to make them look like you've been using them for some time. See if you can find some used ones, but that may be hard to do. Might as well get your new tires at the same time, that's only going to help your cause. Plan on running some miles on the new setup and get the chain and sprockets as dirty as you can. Then revert to step one and pray for mercy with the court. Once your hearing is complete, you'll likely want to switch back to stock gearing. Your FZ6 is going to feel anemic when geared as tall as you'll need it to be.


How long do they want to suspend your license for?

 

[dean owens]

crazy that the cops were able to know that you were getting a bad reading and they won't give you some sort of leeway to at least get the bike to a shop to get it checked out. i'd figure some sorta way to get it checked and challenge the ticket. and you are the first i've read/heard about who has had your problem. as others have stated, it's usually the other way around.

 

[afpreppie04]

Another possibility is that the previous shop/owner installed a speedo healer and it is miscalibrated. My speedo DRD connects under the gas tank, you can see if you have anything aftermarket under there. Good luck getting your license back!

 

[Wh0M3]

I was starting to wonder about my speedometer being off too, but in a way that it reads faster than what I'm going. I base it on traffic, but I've been wrong before.

Maybe I need to get mine checked out too. Thanks for the info. :thumbup: sorry about your license LefZe.

 

[VEGASRIDER]

Suspension for going a little too fast, very harsh.

What is the penalty for getting caught for drinking and driving, also known as driving drunk in Norway.

 

[novaks47]

Take them to court, and make sure that they can PROVE without a doubt, that the radar was calibrated THAT DAY(assuming this is even possible in Oslo). I'm willing to bet money that the radar gun used is way out of tune. What radar guns were they using? Were they using laser? Ka, K, X band?

 

[LefZe]

Suspension for going a little too fast, very harsh.

What is the penalty for getting caught for drinking and driving, also known as driving drunk in Norway.

Yes, 6 months (as I had 3 violations previously) and about $1400 in fine...

"Drunk driving" equals jail and an even bigger fine. I hope that is valid in other countries as well?

 

[LefZe]

Take them to court, and make sure that they can PROVE without a doubt, that the radar was calibrated THAT DAY(assuming this is even possible in Oslo). I'm willing to bet money that the radar gun used is way out of tune. What radar guns were they using? Were they using laser? Ka, K, X band?

I will be in court soon.. I think it will be a waste of time, but I really feel I'm innocent. I still think my speedo is faulty and will check this asap, or the shot was taken in some conditions that could have an effect on the speed reading.

It was a laser gun on a stand and the shot was on top on a hill over a small turn. Not sure of the model of the Laser, but they said it recently was calibrated..

 

[clunk]

If you look at your test run, you were clocked at 65 when you were reading 59. If you apply that same ratio to the 82 that you thought you were running, you end up with a speed of 90. That test run data should prove to the court that you weren't intentionally running 90, but I don't know if that will make a difference in your outcome.

Good luck.

 

[novaks47]

I will be in court soon.. I think it will be a waste of time, but I really feel I'm innocent. I still think my speedo is faulty and will check this asap, or the shot was taken in some conditions that could have an effect on the speed reading.

It was a laser gun on a stand and the shot was on top on a hill over a small turn. Not sure of the model of the Laser, but they said it recently was calibrated..

Laser is pretty straight forward, as far as conditions are concerned. There's really not much that would alter the reading, other than the gun being out of tune. If it wasn't calibrated that day, there's no way to tell if the thing is accurate or not. Even if it was done the day before, there's no guarantee that it didn't drift out of spec by the next day. I just have a tough time believing that it's your speedo's fault. I'm much more inclined to think it's the officer's equipment that's out of whack.

 

[TownsendsFJR1300]

If you already don't have a GPS, borrow one.

Mount it near the speedometer and go for a ride. Have a passenger, with a camera take a picture of both (in ONE PICTURE) with the difference in speeds and bring it to court. You'll probably get the speed amount reduced, possibly a lesser charge, faulty equipment, etc and keep your licence. Your conversation checking the speedometer with the officers equipment helps your case as well.

While checking the speed at 60, note the difference and get a SPEEDOHEALER. I have mine adjusted so it is DEAD ON, no guessing what so ever.

And as noted above, the speedometers read high, NOT LOW from the factory. Taking pic's of after market sprockets on your bike (if equipped) and what's supposed to be there can also help you in court... Show what the what bike is SUPPOSED TO HAVE and what you ACTUALLY HAVE...

As a retired LEO(25+ years), thats radar certified, all I noted above, at least in the Florida court system, would definitly get the speed lowered if not dismissed. Should I be testifying against you and you brought all this up, I'd personally opt to the judge to dismiss the charge, that is, if you fixed the problem since then..


Good luck

 

[FinalImpact]

You might take a look at this thread too.

You can do the calculation based upon the facts and get the speed based upon RPM, Rear Tire Size, and the sprockets on the bike (tooth count). This will get you it pretty close. You'll need to convert to metric tho.


http://www.600riders.com/forum/fz6-...ead-rpm-gear-sprockets-tire-actual-speed.html

Also I have an Excel spread sheet which you can enter the data into and change all of the variables on the fly if you like. If someone wants to host it PM me and I'll send it out. My ISP makes this painful to share without giving the whole world my account password.

Here is the original post:

All,
After seeing all the threads about correcting the speedo error, top speed, tires, and how fast will an FZ go, I had to look a bit deeper. With that here is a formula that should give you the corrected speed based upon gear selection, sprocket choice, and tire diameter.

Obviously tire pressure and speed will change the rear tires rolling distance but I'm not going to get into that! In short if you have Stock Gearing and the manufactures recommended rear tire; If you hold your RPM's at 6,000 you should get the Speeds listed in Bold in all Six Gears (27, 40, 50, 59, 66 and 72mph)! There are other variables, but this should be pretty close. If you change sprockets or Tire diameter, use the formula to punch in the correct values so you can see how far off your speed is.

Formula is:

RPM * PIE * Tire Diameter (inches)
---------------------------------- = Speed in MPH
1056 (constant) * Actual Drive Ratio


So now we add in all the variables:

TIRE:
Stock Tire: 180, 55 ZR17 73W
Hint: Z rating is rated at 149mph with a max speed of (W) = 168mph
Tire Diameter: 24.8"
Circumference: 77.9"
Revs Per Mile: 813.39
- - - - - - - - - - - - - - - - - - -

RATIOS:
Primary Ratio: Engine to Trans (PR): 86/44 = 1.9555
Secondary Ratio: Sprockets (SR): 46/16 = 2.8751
- - - - - - - - - - - - - - - - - - -

TRANSMISSION RATIOS:
G1 = 37/13 = 2.846
G2 = 37/19 = 1.947
G3 = 28/18 = 1.556
G4 = 32/24 = 1.333
G5 = 25/21 = 1.190
G6 = 26/24 = 1.083

- - - - - - - - - - - - - - - - - - -
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

RPM * PIE * Tire Diameter (inches)
---------------------------------- = Speed in MPH
1056 * PR * SR * GX

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

1st Gear @ 6000 RPM:
6000 * 3.1415 * 24.8
---------------------------------- = 27.6MPH
1056 * 1.9555 * 2.8751 * (G1) 2.846


2nd Gear @ 6000 RPM:
6000 * 3.1415 * 24.8
---------------------------------- = 40.4MPH
1056 * 1.9555 * 2.8751 * (G2) 1.947


3rd Gear @ 6000 RPM:
6000 * 3.1415 * 24.8
---------------------------------- = 50.6MPH
1056 * 1.9555 * 2.8751 * (G3) 1.556


4th Gear @ 6000 RPM:
6000 * 3.1415 * 24.8
---------------------------------- = 59.0MPH
1056 * 1.9555 * 2.8751 * (G4) 1.333


5th Gear @ 6000 RPM:
6000 * 3.1415 * 24.8
---------------------------------- = 66.2MPH
1056 * 1.9555 * 2.8751 * (G5) 1.190


6th Gear @ 6000 RPM:
6000 * 3.1415 * 24.8
---------------------------------- = 72.7MPH
1056 * 1.9555 * 2.8751 * (G6) 1.083


haha! Confirmed! :thumbup: Speedo was correct!

2nd Gear @ 14,000 RPM:
14,000 * 3.1415 * 24.8
---------------------------------- = 94.3MPH
1056 * 1.9555 * 2.8751 * (G2) 1.947


Plug in the numbers for the variables on your bike and watch the tach! This should tell you pretty close to what your actual speed is!


To get the tires diameter use this!
Remember there are many variables so this is to get us "close"!

********************************************
Using a stock Tire Size of: 180/55 R17
The first number is the Tire's indicated section width in millimeters, measured from sidewall to sidewall. {180}/55R17

Section Width: 180 is converted to inches!
180mm / 25.4 = 7.0866"

Profile or Aspect Ratio: 55
The second number 180/{55}R17 is the tire's aspect ratio or profile.
55% or add a decimal point 0.55

Sidewall Height (SH):
SH = 7.0866" X 0.55 = 3.897"

Wheel Diameter (WD): 180/55R{17"}
WD = 17"

Tire Diameter in Inches:
SH + SH + WD = Tire Diameter
3.897" + 3.897" + 17" = 24.8"

********************************************

 

[TownsendsFJR1300]

A GPS will take all those variables into account, simple check/fix...

 

[Kazza]

Pretty strict in Oslo!

Out of curiosity, what is your road toll like? Are the roads quite safe due to this?