Speedo inaccuracies

[KoukiS14]

Anyone else notice that their speedo is off by a bunch? When I'm cruising at 80 mph on flat ground, my GPS reads 77 mph. I don't care about that so much, but I do care that the mileage indicated is actually higher than the vehicle really has, and that my MPG calcs would be off.

Interestingly, the only option I DO NOT have is VLSD. Which makes me wonder... did my QX originally come with the VLSD? Was this replaced for some reason with a rear end with different ratios? Anyone else experiencing these same differences? It's not unusual for a vehicle to be off by that much, but my 240sx was about spot on at those speeds.

[KoukiS14]

oh, to clarify...



That's not the sort of speedo I'm referring to.

[fueler]

What size tires do you have, and what is the recommended tire size as printed on your door jamb? Mine is theoretically 10% off so I just take that into account!

[Buzzman]

Fueler, you are right on. I went to a bigger tire on my Pathy, and the speedo slowed down. I wasn't concerned about it, so I didn't do the math, but I did notice a difference.

[SnowSurfLax]

If you're that concerned about it, take it to the dealer and have it reprogrammed. I'm sure they'll take you for it, but if you plan on selling your QX4 later, the extra mileage will reduce the value.

But then, if you're not going to sell it, who cares? Just calc out your service schedule diff.

[KoukiS14]

Well I'm really not that concerned. . only concerned enough to make a thread. The tires are probably stock size. . hell, they might even be the original tires :o

I haven't checked. . but good call.

I plan on driving the thing until it falls apart.

[fueler]

I know that Honda speedometers are off by about 3%, but opposite of you, their speedos read 3% faster than you are actually travelling. The symptoms u are describing can happen if your tires are slightly smaller than stock.

The dealer can not reprogram or recalibrate the speedo. It is run off a VSS, which is a small gear inside the transmission geared with respect to the OEM tire size and cannot be adjusted. VSS:

[nissandoms47]

on mine im running 4.3s with 32s and it was off at first. My VSS went out so I went and bought the gear for the SE models which have 4.6s. they have differenent tooth numbers or whatever. Now my speedo is almost dead on. Maybe off by a 1-2 mph.

[fueler]

you got just the vss from 4.6 and it changed it huh. Great point!

[SnowSurfLax]

Ha! I figured it was electronic by now. Why not? everything else is. Almost seems surreal its still detemined by a tiny little gear.

Well, "if it ain't broke, don't fix it!", eh?

[KoukiS14]

Yeah no need to really mess with it. . I don't plan on selling this thing really, hopefully just drive it into the ground.

I do have the original tire size on it. .