I recently purchased a Garmin GPS V, to add a navi to the car that was very simple. One of its features, of course, is to tell you your speed and direction. This evening I left the screen up the whole time which shows your compass direction and speed. First off all, the compass showed that my Mirror compass was off by 45 degrees! Then, the speed... At 20 or so it was dead accurate. However, 50 on my speedometer was 51 to GPS, 60 was 61.6 to the GPS, and 70 was 72 to the GPS! My usual 74 cruise setting was acutally 76.3 MPH! When I opened her up 100 it was really 103.9!

I have a 2k3 6speed with 4k miles.

Just letting you know, I constantly cruise at 74 and was dismayed that I was in the 10+ ticket category. Anybody else notice any inaccuracies?

I had gone by one of those radar things in town and was always dead on, but of course I was only going 30 or so. Gave me a safe feeling that it was accurate. I was wrong...

 

I have just the opposite experience in my 2K2 GXE which comes w/16" wheels unlike your SE. On my Magellan Map 330 GPS unit, when I'm going 70 on my speedo, my GPS unit says I'm going about 68.

 

yeah, I've got a GPS V as well (and a Vista), both my Pathfinder and Maxima show 68 on the GPS while 70 on the GPS. However, I recently put 2k2 rims on my GLE that came with the 5 spoke 16's. Now in the max, I read 70 on the speedo and right under 72 on the GPS. :/ Thats hard getting used to as I was padding my speed alittle. If you are on a perfectly flat, straight road and have a good lock, you can pretty much trust the GPS. Garmin uses an averaging algorithm that will be very accurate. As for my rim change, that was pretty much what the tire calculator said it would be.

Most Nissans I have been in read 2 mph too fast. I assumed it was a liability thing, better to read alittle fast than alittle slow. I've been in other cars where they had changed rims and couldnt figure out why they were getting stopped so much, when in fact they were as much as reading 6mph too slow The worst was an SUV, you'd probably notice a 6mph diff in most cars.

I'm kinda surprised yours is reading too slow.

 

Mine reads 3 mph fast at 70mph ( Says 73mph). But at 30, it is only about 1mph off. robably saved me a ticket or two.

I've timed it, compared to those roadside radar signs, and used a GPS.

 

I bought a Garmin out of curiousity, after all of the "you didn't go 130 plus, your speedo's out of whack" posts. Did the same thing you did, and...at 80 my speedo is 0.2 mph fast. At 100 it's...0.3.

Criminy (can you say that on the .org?), at 130 it must be out by...0.5 - or even 0.6!!!

sorry, BTW - not sniping at you, just minor residual annoyance from the previous threads.

 

Keep in mind all of you that radar is innacurate like this also. It all depends on the car. You may look down and say, ok I'm going 45 in a 40, and then the cop pulls you over for doing 48 or 49 saying his radar said 49. Just because ur speedometer says 45, doesn't mean your speedometer could be just a bit off. I wouldn't really worry about it though...

 

Mine is a minimum of 6 MPH slow. So when I'm going 40 MPH on the speedometer, I'm really going 46 MPH. I got pulled over by a cop who said I was going 52 in a 35 when I was driving at just a hair over 40. It seems that it gets worse the higher up I go. I took the car to the dealer, and they ordered me another speedometer. I'll get it put on this week and see if it changes any.

 

i can't remember which one, but one of the car mags did an article about this, comparing actual speed vs. speedometer measured speed, and most of the car companies read about 1 or 2 mph fast at 70 mph, and bmw led the pack with around 3.5 mph fast i belive. maybe to help keep us safe and save on tickets?

 

2002 Altimas have this problem as well, as you get proportionally faster the actual speed becomes more inaccurate. Just Nissans little flaws

 

It was Car and Driver quite awhile back (somewhere between 3-9 months ago).