Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Lone Rider]

GPS shows 100 km/h but my speedo shows 108 km/h.

In other words 62.1 mph GPS vs 67.10 mph speedo.

8 km/h over is enough to receive a bill in the mail.

Has anyone else noticed it…which is accurate?

[GregKhougaz]

Satellite based gps is likely more accurate than you speedometer.  An under inflated tire (among other things) could raise your speedo speed.  Taxis do for the odometer.   

[imoo6170]

Satellite based gps is likely more accurate than you speedometer.  An under inflated tire (among other things) could raise your speedo speed.  Taxis do for the odometer.

Plus 1

[FLSTFI Dave]

I have found that most Harleys  have owned the speedometer reads about 3 mph faster than its really going, same with friends bikes and my wife's bikes.  This is using two different GPS to check.

[kiro]

I have found that most Harleys  have owned the speedometer reads about 3 mph faster than its really going

That's about right for my bike also. Checking indicates the GPS read-out is correct.

[pkl]

Government allows mfgs a margin for inaccuracy and most mfgs err on the faster side. Probably saves some on speeding tickets. Not that anyone on this site would do exceed speed limits.

[Ripcord]

My Prius reads exactly 2 mph slower than my GPS .... no wonder I get inpatient people behind me! Will have to check the bike.

[Para Bellum]

Here in the U.S., federal law prohibits manufacturers from building the speedometer to read lower than the actual speed.

Edit: I went back and checked my source; it only says that Motor Vehicle Regulations prohibit manufacturers from building the speedometer to read lower than the actual speed.  So I retract my statement, since the source doesn't provide any references.

One car I have is exactly right, but other car reads 5% faster than actual. 

[GregKhougaz]

Here in the U.S., federal law prohibits manufacturers from building the speedometer to read lower than the actual speed.

    U.S. Code of Federal Regulations (CFR)  § 393.82: Speedometer:

Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).

[porthole]

Which is accurate….GPS or CVO speedo?

Because of the way most GPS units works, the simple answer will be 99+% of the time the GPS will more accurate. GPS units are capable to .01 knot accuracy.
There are a lot of variables including the quality and sophistication of the GPS, how many satellites are being used and at what relative position they are to the GPS (above or nearer to the horizon).

How well the GPS handle errors is another factor.
"Multipath errors" can cause spikes in speed recordings, but, since the "displayed" speed is averaged out over 1-2 seconds (typical), we don't see those errors.
For example, my GPS 478 will sometimes display a max speed of well over 300mph, and sometimes over 500mph

You can do your own test with one of those road side speed warnings.
Go with the GPS reading if the speed readout is required.

[Lone Rider]

For example, my GPS 478 will sometimes display a mx speed of well over 300mph, and sometimes over 500mph
Go with the GPS reading if the speed readout is required.

Thanks for that porthole….but WTF…..500 mph?

[Para Bellum]

   U.S. Code of Federal Regulations (CFR)  § 393.82: Speedometer:

Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).

This true and correct, but it is for commercial vehicles.

I went back and checked my source; it only says that Motor Vehicle Regulations prohibit manufacturers from building the speedometer to read lower than the actual speed.  So I retract my statement, since the source doesn't provide any references.

[GregKhougaz]

This true and correct, but it is for commercial vehicles.

I went back and checked my source; it only says that Motor Vehicle Regulations prohibit manufacturers from building the speedometer to read lower than the actual speed.  So I retract my statement, since the source doesn't provide any references.

No retraction necessary.  That's just all I could find on the subject. 

[Trapperdog]

I've used speed DRD and speed healer's on other manufactures bikes.  You can manually adjust the speed shown on the speedometer in percentages ( +3%, -4%, etc). If the odometer works off the same signal as the spedo though, it is also changed by the same percentage. I seem to remember they used to be available for HD's.

[porthole]

Thanks for that porthole….but WTF…..500 mph?

Had me wondering, I hadn't checked the max speed since getting back from Maggie Valley. I believe this is the highest so far in the 7 years I have been using this unit.

1243.6 mph