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Alan_Hepburn
Junior Member
92 Posts
San Jose, Ca
USA
Suzuki
2007 Boulevard C50T
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 Posted - 08/25/2005 : 6:06 PM
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I don't know if this is the right place for this - if not, feel free to remove it!
Anyway, it's been noted that pretty much all motorcycle manufacturers build their product with a substantial error programmed in to the speedometer - typically 10% high is what I've seen. In the bikes I've checked myself, the speedometer reads 10% high while the odometer is reasonably accurate. Of those manufacturers that also manufacture 4 wheeled vehicles, those vehicles do not exhibit the same inaccuracy so it appears that the bikes are purposely built with this innacuracy.
My question: since there is no technical reason for the speedometers to be so innacurate, is there a legal reason?
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Mydlyfkryzis
Senior Member
274 Posts
[Mentor]
West Milford, NJ
USA
Honda
1991 Nighthawk 750
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Posted - 08/25/2005 : 7:08 PM
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My cars have varied too. My present vehicle is right on the money, my previous vehicle was off 3 MPH. (I use a GPS unit to check steady speeds). My NH750 reads 10% high exactly (30 indicated = 27, 55 indicated = 50)
Newer cars use the computer to sense speed and then operate the speedometer to indicate it to us. Most bikes, though this is changing, use a mechanical speedometer that is more difficult to calibrate and get right. My older cars were often off on the speed too. I prefer an optimistic speedo rather than one that reads too slow. I'd rather be inadvertantly under the limit than over. |
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travismhood
Junior Member
60 Posts
american canyon, ca
USA
Yamaha
xs750 sf
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Posted - 08/31/2005 : 11:33 PM
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I'd like to here some answers too.. Here's a guess. There isn't the same demand for accuracy in bike spedos as that of automotive due to the small percentage of people who ride. This is usefull for the manufactures because they can use the same internal parts (especially the spedo gear) with different modles of motorcycles and tire sizes ect. And we'll buy them any how. time, money, production, quality, yada yada. I can't find any parts catalogs around the house at the moment. Can any body help with this curiosity? I could be way off.
I see no legal reasoning for this but I'm sure the law allows for some error. |
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Cruiser
 Standard Member
127 Posts
Madison, WI
USA
Honda
ST1100
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Posted - 09/01/2005 : 9:03 AM
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quote:
Originally posted by travismhood
I'd like to here some answers too.. Here's a guess. There isn't the same demand for accuracy in bike spedos as that of automotive due to the small percentage of people who ride. This is usefull for the manufactures because they can use the same internal parts (especially the spedo gear) with different modles of motorcycles and tire sizes ect. And we'll buy them any how. time, money, production, quality, yada yada. I can't find any parts catalogs around the house at the moment. Can any body help with this curiosity? I could be way off.
I see no legal reasoning for this but I'm sure the law allows for some error.
I think you may have something there.
I've seen aftermarket speedos that are 5:1 or 4:1, etc. They are advertised as being for a certain make (i.e. Hondas, Yamahas, etc.) without regard to model. Motorcycle manufacturers do seem to make an effort to standardize some things like mirror mounts across models, so this seems like the most reasonable explanation to me.
Cruiser |
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Indiana Randy
Moderator
1758 Posts
[Mentor]
Fort Wayne, Indiana
USA
Honda
2000 Magna V4 750
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Posted - 09/01/2005 : 10:17 AM
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It was explained to me like this;
There are stiff federal fines if an imported motorcycle has a speedo that shows SLOWER than actually moving. Therefore, Honda (and presumably others) intentionally error on the safe side with about a 5% 'above actual speed' reading. The error increases as speed increases though so the Honda speedos can be 10% too high when approaching triple figures on the speedo.
Real or myth, I don't know. Twas what I've heard and been told without any verification, but it makes sense... I guess.
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Duane
Advanced Member
863 Posts
[Mentor]
Buffalo, New York
USA
Suzuki
Boulevard C90T
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Posted - 09/01/2005 : 1:16 PM
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quote:
Originally posted by Indiana Randy
The error increases as speed increases though so the Honda speedos can be 10% too high when approaching triple figures on the speedo.
I'm sure you're not speaking from experience, Randy  |
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timbo
Advanced Member
594 Posts
Uxbridge
United Kingdom
BMW
R1100S
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Posted - 09/03/2005 : 2:45 PM
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In the UK, the maximum permissible error is 10%. By law. The same law also says that speedo's must not under-read. At all.
QED.
Tim |
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marsam
Advanced Member
510 Posts
[Mentor]
Birkirkara
Malta
Yamaha
Dragstar & Vmax
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Posted - 09/05/2005 : 12:22 PM
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quote:
The same law also says that speedo's must not under-read. At all.
Makes sense to me. If speedos under-read speed by more than 10%, riders would be caught speeding by almost all properly calibrated speed cameras. I guess it is one reason why they are designed to measure the speed a little higher than it actually is.
Another thing to consider is the use of non standrard profile front tyres which would alter the speedo gearing. |
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gary
Standard Member
143 Posts
Kingston, New York
USA
Honda
1100 Shadow '99
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Posted - 10/06/2005 : 3:57 PM
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| As I posted awhile back about people riding my rear, someone said that my speedo might be saying 55 and I might be going 50. Made sense to me so I talked a NY State Trouper into following me and he said I was right on the money. I guess NYers just like driving fast. |
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Indiana Randy
Moderator
1758 Posts
[Mentor]
Fort Wayne, Indiana
USA
Honda
2000 Magna V4 750
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Posted - 10/06/2005 : 7:37 PM
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With repeated verification through testimonials of other Honda riders, I changed the speed I cruise/ride. Tis amazing how adding another 5-10 mph changes the feel of the ride. Twas funner.  I didn't say that.  |
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Boogeyman
Starting Member
1 Posts
Grants Pass, Oregon
USA
Honda
VTX1300R
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Posted - 07/26/2009 : 5:09 PM
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A speedometer error of 10% high seems to be pretty much the across-the-board error on most bikes. My GPS tells me that at a speedo indicated 25mph, I'm doing 23mph (which agrees with a radar gun, also), and at an indicated 70mph, my '07 VTX 1300R is actually going 63mph. There is an electronic device called "Speedohealer" (www.speedohealer.com) that has gotten some excellent reviews on the VTXOA boards.
As for me, I'll just do the math in my head, and compensate accordingly - it's FREE that way! |
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The Meromorph
Advanced Member
596 Posts
[Mentor]
White House, TN
USA
BMW
R1100R
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Posted - 07/26/2009 : 6:43 PM
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My BMW R1100R exhibits a strange speedo error. I always try to get an accurate validation of my speedometer on any vehicle...
I have a Chevrolet Avalanche which (checked by comparison with a police car's calibrated speedo, with more than one radar gun, with GPS, and dead reckoning - I'm a suspicious SOB) is accurate to less than 1 mph at all speeds (if the tires are new). Can't ask for better than that! The higher speed calibrations were checked at a local drag strip our owners club hired for the day. I 'wasted' some 'competitive' runs to hit and maintain a steady 80, 90 and 100 mph, just to check. 
So when I got my 'new' bike, I had my wife drive my Avalanche at a steady 40, 50, 60, and 70 on a local flat and straight section of freeway, and at 20, 25, 30, 35, 40 on a deserted level and flat country road on the way back from that, while I followed on the bike. (my wife proved susceptible to the suggestion that I have to know what my speed really is to avoid accidental speeding tickets).
The results were that my bike's speedometer was spot on accurate up to 30 mph, and exactly and consistently 5 mph fast from 40 mph (indicated - 35 mph actual) upwards. I found that difficult to understand.
I went Internet researching to find out if, how, and where I could get my speedo calibrated... I found that my speedo was a traditional mechanical electro-magnet and clock-spring device with a difficult to get at and replace calibration device that simply would affect a 'percentage error' if it existed.
I also found that the police bike versions of mine had spot-on accurate speedos at all speeds! There was/is a small company in California that could 'recalibrate' the general public version of my speedo to be just like the police version, but they wanted around a $100 and the speedo shipping to them for about a week.
In the nether regions of BMW forums, I found diagrams and instructions of DIY solutions, and one hint that if you wanted it accurate over the whole range, you had to obtain and install a 'police' version of the clock-spring, before re-calibrating it for your bike...
It's my belief that BMW supplied (they now use accurate electronic speedos an all models) a clock-spring with a deliberately engineered 'weak point' that 'bound up' at between 30 and 35 mph, introducing a fixed 5 mph error above that speed. I still don't know why. I suspect that below 35 mph a fixed 5 mph error would be too noticeable, and a percentage error could too easily be adjusted out...
I simply subtract 5 mph from my indicated speed at 40 mph and above, and have provoked no speeding tickets so far.
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EH2Zee
New Member
12 Posts
Pleasanton, CA
USA
Honda
2003 750 ACE
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Posted - 07/27/2009 : 6:31 PM
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quote:
[i]
There are stiff federal fines if an imported motorcycle has a speedo that shows SLOWER than actually moving. Therefore, Honda (and presumably others) ...
Real or myth, I don't know. Twas what I've heard and been told without any verification, but it makes sense... I guess.
Indiana Randy, you are right. This topic was discussed in one of the BMW (automotive) forums.
Serious penalties (in Germany and other EU countries) go to the manufacturer if the speedometer reads LOWER than the actual speed.
As such, the speedo's are - by design - calibrated to overstate the speed (read faster than actual speed) to avoid this issue. And in this world of global trade, cars, motorcyles, etc., are sold worldwide, so the most common denominator compliance is used.
Me, I use a GPS to get a reading on the speed differentials.
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Niebor
Advanced Member
2793 Posts
[Mentor]
Highlands Ranch, Colorado
USA
Harley-Davidson
03' Superglide
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Posted - 07/28/2009 : 3:05 PM
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quote:
Originally posted by Indiana Randy
It was explained to me like this;
There are stiff federal fines if an imported motorcycle has a speedo that shows SLOWER than actually moving. Therefore, Honda (and presumably others) intentionally error on the safe side with about a 5% 'above actual speed' reading. The error increases as speed increases though so the Honda speedos can be 10% too high when approaching triple figures on the speedo.
Real or myth, I don't know. Twas what I've heard and been told without any verification, but it makes sense... I guess.
Nailed it. The feds can impose hefty fines if a speedo reads less than actual. In some cases the odo is accurate and only the speedo reads high. In others, both have the same error. If the error is the same, (as my H-D example below), both can be normalized. Keep in mind, tire wear influences the numbers, slightly.
In some cases you can actually recalibrate your own speedometer. On late model H-Ds for example, calibration mode is initiated with a series of button strokes with the ignition on and off, the same button you use to reset the trip odo.
Again, federal law forbids adjustment of the odometer by the consumer. If you would choose to do so, I would not advise much discussion of it, and certainly not on a public forum.  |
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Daddio
Senior Member
357 Posts
[Mentor]
Calera, AL
USA
Suzuki
Bandit 1250
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Posted - 07/28/2009 : 9:27 PM
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This is one of my biggest pet peeves. I believe my speedometer is off by about 10%. It reads around 10% to the high side. I believe a generous speedometer is actually as dangerous as one that reads too low.
I have several two lane interstate highways that have 70 MPH speed limits. As I righteously set my speed at 70 I find 90% of the traffic is ready to roll over me. If I run at 77 MPH, I find I flow with about 50% of traffic. There are areas that the fast traffic is running 80-90 MPH without having to get aggressive in lane positioning. If you mix someone that thinks they are going 70, actually going just above 60, you are asking for trouble. I believe there is more danger presented by differential of speed, not actual high speed progress. It is actually safer to run with prevailing traffic. Your speedometer may be saying you are over 90. In fact you are barely in the 80 MPH range.
For me, I want to know how fast I am actually going. I do not like having to mentally adjust what my speedometer is telling me. I do not like being the cause of fast moving traffic backing up because I am going much slower than my speedo is telling me. I also don't like to think running at 80-85 MPH is just average.
If LEO decides I am making too much progress, it should be because I am going too fast. It should not be the result of math errors I am calculating on the fly. Of course the error margin is not as drastic when you travel in the lower speed ranges. I have never really had a problem reading 30 MPH while actually travelling 27.
Edit - Have you ever been asked by LEO, "Do you know how fast you were going?". On my bike I really and honestly could answer,"NO"! |
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gdickelman
Moderator
1144 Posts
[Mentor]
Annandale, VA
USA
Moto Guzzi
CA & Ducati MS1100s
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Posted - 07/28/2009 : 9:54 PM
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| This certainly explains the many phalangeal expletives that I have witnessed (directed at me) as I traverse the fast lane at the posted speed limit. |
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falcon1
Standard Member
247 Posts
Colorado Springs, CO
USA
Indian
Chief
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Posted - 07/29/2009 : 5:30 PM
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To keep manufacturing costs and model design down, speedos need to be able to handle various size tires and transmission gearing, so they are set to a standard at the factory, and the auto manufacturer chooses the one that is the closest calibration match to their vehicle setup. Used to change the matching tranny gear to calibrate the one in a few of my old cars and trucks if they were off too far. On others, a change back to stock tire size would take care of it. Nowadays, there are other ways, on both bikes and autos.
The Autometer speedometers that came stock on the 2002 - 2004 Indian Chiefs were all 10 mph slow. But, contacting the company, instructions were provided on how to use the reset button and the ignition key and travel to recalibrate them (and change them over to kilometers if wanted). Came in handy when changing tire size, too. Same thing with the VDO speedos put in earlier Indians and other models - a check with the manufacturer, and the instructions for recalibration were obtained.
For instance, for the Autometer:
Ride the bike to an area that you know is two miles plus in distance
Pull up to the first mile marker and stop the bike, turn the ignition OFF
Next, hold the speedometer reset button down and while continuing to hold it down THEN turn the ignition key on. You will notice the odometer number will change to O------O.
Release speedometer reset button and start engine; depress the button a second time. Note the speedometer will not operate. Follow the pace rider or car at 45 mph for two miles non-stop (any speed over 25 will do as long as you aren't so fast that the tires get too mis-shaped).
At the end of the two mile ride, stop the bike BUT KEEP THE ENGINE RUNNING. The odometer will display a lot of numbers, this is the number counted by the speedometer from the transmission pulse gear.
Depress the reset button again then turn the engine off with the KEY.
Restart the engine and check the odometer reading to insure that the correct mileage is present. You are done calibrating.
For the VDO speedo,the process was somewhat similar, although if you knew what the code was to match the speedo to the bike, you could just input that code into the speedo using the reset button and the right mode.
So if you think your speedo is off, contact the manufacturer. Likely they know a way for you to calibrate it. |
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sporty
Senior Member
286 Posts
north liberty, ia
USA
Harley-Davidson
Dyna & Sportster
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Posted - 07/30/2009 : 7:22 AM
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quote:
Me, I use a GPS to get a reading on the speed differentials.
Why not simply use it as your speedometer
(at least until the battery heads south :-O)
-W
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Redbeard
Junior Member
48 Posts
South Ogden, UT
USA
Triumph
Sprint ST
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Posted - 07/30/2009 : 1:07 PM
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quote:
Originally posted by timbo
In the UK, the maximum permissible error is 10%. By law. The same law also says that speedo's must not under-read. At all.
QED.
Tim
Aha! That must be why my Triumph speedo reads 8% high (verified against GPS) while the odometer is accurate. It's intentional! *cue dramatic music* |
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Niebor
Advanced Member
2793 Posts
[Mentor]
Highlands Ranch, Colorado
USA
Harley-Davidson
03' Superglide
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Posted - 07/31/2009 : 11:04 AM
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quote:
Originally posted by Redbeard
[quote]Originally posted by timbo
In the UK, the maximum permissible error is 10%. By law. The same law also says that speedo's must not under-read. At all.
QED.
Tim
Aha! That must be why my Triumph speedo reads 8% high (verified against GPS) while the odometer is accurate. It's intentional! *cue dramatic music*
LOL, Nailed It! |
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Texasphotographer
Advanced Member
746 Posts
[Mentor]
Copperas Cove, Texas
USA
Suzuki
2008 C50T
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Posted - 08/09/2009 : 5:19 PM
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I complained about the Speedo when I first bought the bike. Dealership took it for a ride and commented it was within tolerances. Did not like the answer, but accepted it.
Now ride with a GPS and it's about 8% to high side.
Understand there is a mod you can install to make the speedo accurate, but it throws off the odometer.
Can't win. |
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