Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

[Bustedknuckle84]

Boat in signature, I have a lowrance elite 5 dsi. And a teleflex honda speedometer. The speed is accurate on both up to about 30mph. My WOT speed is 47 on the speedometer and 42 on the lowrance gps.

Is this normal to be off? I have a portable gps as well that i used in my car yesterday. And I was going 48mph, gps was reading 44mph. Is my car gauge off to, I do have after market 17inch on a honda accord.

 

[spoilsofwar]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

Its normal.. The GPS is right, the gauges are off a little.

 

[H20Rat]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

Is this normal to be off? I have a portable gps as well that i used in my car yesterday. And I was going 48mph, gps was reading 44mph. Is my car gauge off to, I do have after market 17inch on a honda accord.

Yes, your speedo in the car is off also. Wheel size means nothing, it is the size of the tires that matter. If your tire diameter is larger than stock, your speedo will indicate slower than actual. If your tire diameter is smaller, your speedo will read faster. (which sounds like your problem)

 

[shrew]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

On the car speed is measured on the wheel. You increased the wheel diameter, but didn't recalibrate the speedometer. This now means a wheel with a larger diameter will travel further in a single rotation than the previous wheel diamter would. Therefore the speedo will show you are travelling a shorter distance over time than you would with the smaller diameter wheel. To resolve have your speedo recalibrated in your car.

As for the boat, this more than likely uses water pressure and these are notoriously inaccurate. This is why the boating mags specify in their boat reviews that speeds are measured with GPS.

 

[Bustedknuckle84]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

Bummer I was hoping the other way around on the boat good info guys thanks!

 

[ajgraz]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

I blame the Bermuda Triangle.

 

[coastalrichard]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

Trooper once let me out of a speeding ticket when he noticed I had oversize wheels/tires on my Cherokee. Asked if I recalibrated the speedo after putting them on and, when I said no, he gave me a warning and said get it recalibrated...Nice Trooper

 

[jdlough]

Re: Speed mph is off over 30mph GPS vs. Teleflex speedometer problem??

Also current plays a factor. If you're drifting in a current, your GPS may show you moving 4 MPH, and your speedo will show that you are moving zero MPH.

Both are correct, for what they're measuring.