Gps Vs Odmeter

I've just mounted a TomTom One on my '04 vfr and in doing a little field testing I noticed that the GPS is between 3-5 mph slower than the odometer. I kind of think the GPS is correct, what do any of you think it? If the bikes odometer is off, is there a way to adjust it? The GPS is a bottom end factory refurbished model, could it be that the GPS is off? I plan on clocking a test mile, but I was just curious if anyone else has noticed this?

Doesn't Honda allow up to a 10% error on their speedometers?

I noticed that when using a TomTom 130S on my '02 the speedo is almost exactly 10% off across the speed range up two about 100mph.

The speedos are optomistic as to your rate of travel, most Hondas are about 7% high on avarage.

The motorcycle manufacturers calibrate them higher in order to avoid penalties that can be imposed in some countries when testing a new motor vehicle for road approval. If the speedometer reads less than the correct speed, the manufacturer can be fined and/or the vehicle approval can be rejected.

So, just to be sure, they jack the speedo reading a bit.

My speedometer/odometer matched my GPS exactly when my 06 had new oem tires. Of course, as the tires wore down, the difference increased.

Not sure if its just my unit, but my TomTom 125 has been on the fritz lately. Losing signals, speed varying by 8mph. But back when it was working right, it followed the 10% rule.

I was under the assumption that the speedos are off, but the odometer was correct. I'm not sure how that was suppose to work. When I reset my tripmeter after every fill up I also reset the fuel trip on my Zumo. There is about a 10 mile disparity that the GPS indicates that I traveled farther, which I think is more accurate than the stock speedo.

[image: View Post]hondalover, on Jul 20 2009, 03:06 PM, said:

I was under the assumption that the speedos are off, but the odometer was correct. I'm not sure how that was suppose to work. When I reset my tripmeter after every fill up I also reset the fuel trip on my Zumo. There is about a 10 mile disparity that the GPS indicates that I traveled farther, which I think is more accurate than the stock speedo.
Well that answers my question.... Seems as if trip, and speed are both off........
PLUS 1.... on error mines of 3, 4 miles depending on speed I'm going, around the higher speeds it moves up one mph...... And then my GPS starts beeping, and I feel something smacking me in the back of the helmet...... Funny thing is, I don't carry a pillion.... :blink:

Just did 713 miles indicated by the GPS this weekend. The GPS was off on both speed and distance but that is no surprise. For every 100 miles it seems my trip odometer was off by about 1 mile compared to the GPS. Speedometer has always been a "guestimated" speed and I definitely go by the GPS for that. To compare you can always put the GPS in the car and it is pretty much dead on (at least for my Corolla) as long as you have stock sized tires.

Considering if you have changed your sprockets or have worn tires the effects are more easily noticeable on bikes.

For some people, the real issue is indicated speed vs. radar indicated speed....right, Baileyrock?? :goofy:

[image: View Post]Bent, on Jul 20 2009, 07:27 PM, said:

For some people, the real issue is indicated speed vs. radar indicated speed....right, Baileyrock?? :goofy:


I had my Zumo in my RV for vacation and coming back from Virginia Beach there where a few radar trailers along the way. The Speedo indicated 66, the gps 62, and the radar van about 64. On the bike it's always 10% off on speed and about .8% off on distance traveled. This could be attributed to the gps registering a few mph for a hot second even when I'm sitting still in the driveway or redlight. Once my max speed was 363mph and there have been some other computer glitch speeds so I don't know how the GPS accounts for these little hiccups for the trip odometer. I can usually get them when I turn the Zumo off and back on while moving. my .01$ anyway..