Speedometer Off By 5%

[Tim]

On bikes with chain drive, if you swap out either of the sprockets, it changes the speedometer reading. That's where the Speed-O-Healer is needed the most. But then there's the guy that "must" have his sruff perfect! 

Not if speedo is driven by the speed of the front wheel. Changing sprockets will change engine RPM for the same speed. The amount of air in the rear tire can also effect the speedo input from the front tire. Example, the local Honda shop owner saw the rear tire on my 900. He suggested I add another 3 pounds of pressure to correct tread wear. I did and noticed at 4000 RPM the speedo had raised a couple of miles per hour.

[The Pope]

Not if speedo is driven by the speed of the front wheel. Changing sprockets will change engine RPM for the same speed. The amount of air in the rear tire can also effect the speedo input from the front tire. Example, the local Honda shop owner saw the rear tire on my 900. He suggested I add another 3 pounds of pressure to correct tread wear. I did and noticed at 4000 RPM the speedo had raised a couple of miles per hour.

Point taken. But on newer bikes that are FI, "most" pick up the signal for the speedometer off of the engine.

[Shadowofshoe]

    Don't know about the newer ones ,but my(and everyone elses) BMW KLT was 10% high & I think all beemers were -yeah It often kept ya outta speeding tickets.....but I think the sales idea is/was to make you think you are faster than you are  .
 
       Mike
 

[strester]

I dont know where spedo is hooked  or what it reads, but when i put on my 190/55 my gps would show speed 55 and speed would show 54. Way better than the 190/50..

[silvermane]

A friend of mine didn't look too closely at his speedo vs. GPS.  He said during a recent run that he tucked in and rolled on during an open stretch... he said just glancing at his speedo it looked close to buring it?  Checking the GPS he maybe was close

[Conrad]

A friend of mine didn't look too closely at his speedo vs. GPS.  He said during a recent run that he tucked in and rolled on during an open stretch... he said just glancing at his speedo it looked close to buring it?  Checking the GPS he maybe was close

175mph

A 'friend' eh?   

What's that on the right of your 'friend's' bike in the pic? An Espresso machine?  I'm surprised that your friend's bike can attain that speed with all the 'stuff' on the bars.   

[silvermane]

hehehe :} left to right: iPhone case/charger, GPS, Escort via radio signal to helmet LED

[ridingfar]

Some people just like to have an accurate speedometer.  I know I wish MINE were in all my vehicles. 

You DO realize your speedometer "accuracy" will change as the tire wears...particularly with round profile MC tires. An old tire will be what....1/2 to 3/4 inch less tall than a new one...and have a smaller circumference...so it will travel less distance with each rotation...and make more revolutions in any given distance...making a change in speedo accuracy of approximately 3% over the life of the tire.

So whatever degree of speedo accuracy you have with a new tire it will be less accurate with a worn tire. True to some extent with any vehicle.

I'm just sayin'....

[RideBellChain]

Don't worry about it. Drive 5 mph (indicated) over the posted speed limit, and you're OK still.  Just forget about the difference, and don't get speeding tickets.

[Rhino]

Don't worry about it. Drive 5 mph (indicated) over the posted speed limit, and you're OK still.  Just forget about the difference, and don't get speeding tickets.

Agree! I have a gps on mine most of the time and when I am indicating 80 on the speedo the gps shows 76. Perfect for the slab. I've never been pulled over for doing 1 over.