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Speedometer calibration

ScottRNelson

ScottRNelson

Adventure and Dual Sport
Joined
Aug 3, 2002
Location
Meridian, ID
Moto(s)
Honda XR650L, KTM 790 Adv R
Most of the motorcycles that I've owned over the last decade have had fairly accurate speedometers. The Ducati 888, however seemed to be off by about 20% such that if it said you were doing 100 mph you were really only doing about 80. Surprisingly, the odometer on that bike was much more accurate. The only way to calibrate that speedometer would have been to measure speedometer cable rotation for a carefully measured distance then take it over to Palo Alto Speedometer and have them cut it open and calibrate it.

When I got my KTM at the end of August I was annoyed to find that the speedometer was off by about 10%. If the speedometer says 66 I'm really doing 60. It's as bad as my wife's VW beetle and a bit annoying. But after reading some hints over in the Orange Crush section of AdvRider, someone mentioned that on some KTMs you can change the speedometer mode by pushing the right sequence of buttons.

I tried it and now my speedometer is much more close to reality. You have to get in the "F" trip meter mode (miles since fuel light went on), hold both buttons down for ten seconds, then you can cycle through settings for 21", 19" or 17" wheels. The bike has a 21" wheel on the front, but if you lie to it and tell it that it has a 19" the speed is much more accurate. This was verified using my Garmin Zumo 550 GPS for speeds up to 60 mph. I still have to go make a ten mile run in a straight line to check the odometer accuracy.

I just think that it's too bad that all cars and motorcycles don't have an easier way to calibrate the speedometers for accuracy.
 
ScottRNelson said:
I just think that it's too bad that all cars and motorcycles don't have an easier way to calibrate the speedometers for accuracy.
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thank the used car salesmen back in the day that would roll back odometers as a matter of course. it's a federal crime to tamper with them now. adjusting accuracy is fallout from that i bet
 
auntiebling said:
thank the used car salesmen back in the day that would roll back odometers as a matter of course. it's a federal crime to tamper with them now. adjusting accuracy is fallout from that i bet
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Which makes it interesting that while modern speedometers are typically off by as much as 10% (stock), odometers are still accurate.

The speedo error on my bike throws me off when I drive a car. In a 35 I'll do an indicated 45, which is an actual 41. When I get in a car I'll catch myself doing an indicated 45 which is an actual 45.
 
On my KTM, I can adjust my speedometer by changing the value for my front wheel circumference, down to the millimeter. It's kind of a hidden setting, though, and requires a connector be disconnected before it can be accessed. I'm surprised yours isn't similar.
 
OldFatGuy said:
On my KTM, I can adjust my speedometer by changing the value for my front wheel circumference, down to the millimeter. It's kind of a hidden setting, though, and requires a connector be disconnected before it can be accessed. I'm surprised yours isn't similar.
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Maybe it is. How does one find out where the secret connector is at?
 
On mine, it's one of the two connectors that go to the speedo (the 3-wire one, I think). Yours might be different.
 
This is a design feature. Once again the manufacturers are saving you from yourself. The logic is;

If we report to you that you are going faster than you really are, then you will not speed.
If you are not speeding, you will not get yourself killed.
If you don't get yourself killed, in a few years you will buy another bike from us.

I made that top part up.

It is very common for the speedo to be off by a significant %. Ducati is known to be the most off.
 
OK, so for most bikes, how can you get the speedometer to show the correct value? I always thought me bike was fairly accurate until I recently went by one of those fixed speed radar signs and it showed me as doing 65 even though my indicated was over 70.

And my Accord is off by about 10% which is real annoying.
 
DaveT319 said:
OK, so for most bikes, how can you get the speedometer to show the correct value? I always thought me bike was fairly accurate until I recently went by one of those fixed speed radar signs and it showed me as doing 65 even though my indicated was over 70.

And my Accord is off by about 10% which is real annoying.
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I guess I'm confused. :loco

If your indicated speed is higher then your actual speed, why is this a big deal? You won't get a ticket if your speedo says 70 and you're actually doing the 65 mph limit for example.

Unless you are looking for bragging rights that you were actually going 130 mph. :dunno
 
I'd just like to be able to see in an instant just how fast I'm really going without having to do some quick mental math.
 
TheRiddler said:
Which makes it interesting that while modern speedometers are typically off by as much as 10% (stock), odometers are still accurate.
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I have never precisely calibrated the odo on my R6, but I know from the radar signs that the speedo is off by a set 10% at all speeds. Like, exactly 10%, always, which makes me think it's by design.

However, if I plot my route to work on google maps, it tells me the route is 3.3 miles whereas the odo advances 3.5, which, after rounding, could also be exactly 10% too.

Interesting to think whether the maintenance schedule was calibrated for actual miles or indicated miles...
 
From the Ducati owners manual

On the electronic section of the manual for my Multistrada

"The instrument panel receives information about the actual
speed (calculated in km/h) and displays the number
increased by 8%."
 
The speedo on my ZX-6R is really off as well. But it makes me think I'm going fast and keeps the chance of getting a ticket down.
 
I really don't get this policy of intentionally elevating the reported speed. What's the benefit? If their speedo says 75 but they're only doing 68, then it'll keep them from speeding? Nope, people will figure out how much it is off and adjust their speed accordingly so that they are actually doing the 75 they want to be doing. This is why I wish my speedo were accurately displaying the speed I'm going.

BTW, I went by two of those automated radar speed limit signs yesterday. One showed my speed as being just 1 MPH below what my speedo was displaying (36 indicated, 35 on the sign), but the other showed a 4 MPH difference (38 indicated, 34 shown on the sign). So even THOSE aren't accurate to help you figure out just what your speed really is.
 
DaveT319 said:
I really don't get this policy of intentionally elevating the reported speed. What's the benefit? If their speedo says 75 but they're only doing 68, then it'll keep them from speeding? Nope, people will figure out how much it is off and adjust their speed accordingly so that they are actually doing the 75 they want to be doing. This is why I wish my speedo were accurately displaying the speed I'm going.

BTW, I went by two of those automated radar speed limit signs yesterday. One showed my speed as being just 1 MPH below what my speedo was displaying (36 indicated, 35 on the sign), but the other showed a 4 MPH difference (38 indicated, 34 shown on the sign). So even THOSE aren't accurate to help you figure out just what your speed really is.
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It's probably to keep you from blaming them if you get a speeding ticket. You have to be going past the indicated speed limit to get a ticket for exceeding 60mph for example.
 
The old Smith's magnetic drive speedometers had an adjustment that allowed the magnetic drive parts to move closer together or farther apart, which altered the displayed speed. A reasonable level of consistency was available by using that adjustment.

I don't know if any other mechanical speedometers have that capability.

Electronic speedometers? The ones they make for bicycles can be set when you install them to take into account the circumference of the wheel/tire. Maybe there's some variable you can plug into the ecu to do that on modern motorcycles.

Or you can just ride around for awhile with a GPS, and calibrate the speedo in your head.
 
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