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[mitch.smith]

When I use my ZUMO GPS it shows I am always 2 mph slower than my bike speedometer.  I have a 2012 CVO Streetglide.  Just wondering if anyone else has noticed this!!!

[Midnight Rider]

When I use my ZUMO GPS it shows I am always 2 mph slower than my bike speedometer.  I have a 2012 CVO Streetglide.  Just wondering if anyone else has noticed this!!!

Very common.  The GPS is correct, the HD speedometer is incorrect.

The only "fix" I am aware of is if you have the TTS Mastertune tuner which allows you to offset the electronic signal to the gauge to correct it.

[willyB]

I rent a ton of cars while traveling on business. Nearly 99% of all the cars I rent are between 2-4 mph faster than my gps.

[grc]

I can't get over how so many people seem to think optimistic speedometers are something unusual.  It's been this way for as long as speedometers have been installed, and in the "old" days they were off a whole lot more than they are today. 

I seriously doubt there will ever be a truly 100% accurate vehicle speedometer.  If you consider all the variables involved, such as manufacturing tolerances, tire size variations due to manufacturing tolerances and wear, etc., the fact that most speedometers are within "only" 3% these days isn't a big deal.  Maybe when the world, or at least our country, incorporates military quality GPS and then uses that technology for regular vehicle speedometers we will be able to eliminate much of the variation.  I don't see that being worth the cost, however.  Btw, the consumer grade GPS is fairly accurate, but it is not 100% accurate.  If given a choice between the reading from the GPS and the reading from the speedometer, I'd always give priority to the GPS.  But I wouldn't go so far as to tell anyone the GPS is always right.

I'm trying to figure out where a 2 mph error is going to create a real problem.  While it may make a difference in elapsed time on your next coast to coast ride, I don't think it's something most folks really need to worry about.

JMHO - Jerry

[Ghost Rider]

I'm trying to figure out where a 2 mph error is going to create a real problem.  While it may make a difference in elapsed time on your next coast to coast ride, I don't think it's something most folks really need to worry about.

JMHO - Jerry

Exactly.  If it doesn't matter to the state trooper, then it doesn't matter to me.   

[110tHunDer]

 
The analog and digital guages in my two Chrysler vehicles are dead nuts to their factory GPS and my portable 660.  If they can do it, why can't everyone else?

[sadunbar]

The analog and digital guages in my two Chrysler vehicles are dead nuts to their factory GPS and my portable 660.  If they can do it, why can't everyone else?

My Lincoln MKS is dead nut accurate too.  As long as everything remains stock (gearing, tire size etc.) there is absolutely no reason why there should be any error.

But then again, in the MOCO world, within 3% is probably exceptionally within their target zone...

[mitch.smith]

My only complaint is with it showing faster than actual with a period of time I will show more miles than really on bike.!!

[dayne66]

At an indicated 100kph...GPS says 98kph...radar sign says 97kph.

[110tHunDer]

My only complaint is with it showing faster than actual with a period of time I will show more miles than really on bike.!!

You're only talking 3 or 4% error here.  What's the difference between a 50,000 mile bike and a 52,000 one?  I know, I know ...... 2,000 miles.  So, maybe you do an extra oil change during that time that you didn't need to.

[tweeter13]

One thing I have noticed.  At 35 mph my gps is right with the speedo.  At 60mph it's off by about 2 or 3 mph.  As Jerry stated above that tire size has a effect on the speedo.  Now I am not sure about this and have no backing to prove this, but with the tires being bias ply and the most noticed at higher speeds I just wondered if the tires might grow a millimeter or two at 60 plus miles per hour to account for the difference in the speedometer. 

Then again this could be MOCO just calibrating it this way so they don't have every Tom, Dick and Harry coming in every time they get a ticket saying that their speedometer is off and they should pay for their ticket.  Just a CYA type of thing for them to save some headaches in the attorneys office.   Just a thought from a very tired man today.



Todd

[jagerbomb]

If the tire grew it would indicate a slower MPH. Speedos are normally calibrated to read fast as previously stated with a brand new recommended size tire. This prevents speeding tickets being blamed on the manufacturer . as the tires wear they become smaller and the error increases.

[tweeter13]

If the tire grew it would indicate a slower MPH. Speedos are normally calibrated to read fast as previously stated with a brand new recommended size tire. This prevents speeding tickets being blamed on the manufacturer . as the tires wear they become smaller and the error increases.

Yep.  I do believe you are correct my mistake. 

[mitch.smith]

Thanks I buy it!!