Speedometer Accuracy

[BLACK WIDOW]

A funny thing when I checked my speed with the GPS, at a true 70 mph, the speedometer reads approximately 68-69 mph. What's funny is that with the old tire it was a good 5 mph fast, now with the Toyo its just off 1-2 mph. Cool.


Michael:doorag:

 

[2spyders]

I guess the speed measurement that I'm most interested in is the one on the cop's radar gun.

 

[BillGargan]

I guess the speed measurement that I'm most interested in is the one on the cop's radar gun.

That, consistently, would be what the GPS says.

 

[BLACK WIDOW]

Radar

That, consistently, would be what the GPS says.

:agree:

Michael:spyder:

 

[pitmon]

I noticed this as well, my GPS was about 2 miles faster than my speedometer. Don't know what's up with that. :shocked:

 

[NancysToy]

I noticed this as well, my GPS was about 2 miles faster than my speedometer. Don't know what's up with that. :shocked:

That is typical for most vehicles, especially motorcycles. Most speedos are calibrated to the actual inflated diameter of the tire (or largest standard tire for autos), without load. Under load the bottom of the tire flattens, making it effectively smaller. You don't go as far as calculated for each revolution, making your speedometer read higher than your actual speed. Lots of bikes are worse. Some of the older BMWs average 12% optimistic.

 

[3wheeldemon]

My Spyder consistently shows 5% over the radar gun. But according to Scotty's explanation the larger your a.. the bigger the percentage!

3WD

 

[NancysToy]

My Spyder consistently shows 5% over the radar gun. But according to Scotty's explanation the larger your a.. the bigger the percentage!

3WD

Actually, the other way around...smaller tire, larger discrepancy. :roflblack:

 

[MarkLawson]

I tested my wife's against my Zumo 550 & at an actual 45, the speedometer read 43.

 

[BLACK WIDOW]

Speedometer

I tested my wife's against my Zumo 550 & at an actual 45, the speedometer read 43.

With the Stock rear tire?

Michael:doorag:

 

[durango kid]

I have tried two different gps units and my speedometer is 2 mph faster then gps.