Second Generation Nissan Xterra Forums banner

1 - 20 of 28 Posts

·
on line
Joined
·
54 Posts
Those of us that are running larger tires than stock are acutally sticking it to Nissan. Even if our odometers are off by 2%, i think the 285/55s are 8% larger than the 265/70s. That equates to 2400 extra miles on our 30k warrenty.
 

·
on line
Joined
·
81 Posts
Interesting article. Some of this came up in another post if the odometers were calibrated for the stock tire size they came with or if they were calibrated for the largest tire size that comes stock.

If the later is the case then those with the smaller stock tire sizes would be getting cheated.

ofcourse if you put on larger aftermarket tires you would get gains back the other way.
 

·
on line
Joined
·
1,479 Posts
hum... I noticed that in my last trip when i was using my gps gauges... I think i was running 2 miles faster on the spedo than the GPS. I am going to run some tests see what I get
 

·
on line
Joined
·
1,320 Posts
X11 said:
sneaky sneaky, I'll be testing mine against the GPS.
I've done and mine is off, however, what I beleive is that they calibrate them for the largest tire size listed in the door (i.e. 265/75r 16) therefor, having an "S" and a smaller tire you are in effect getting cheated.
It will take you guys with the 265's to confirm this.
 

·
on line
Joined
·
564 Posts
From my own tests with my gps, the OR (or at least mine) indicates about 3.4% slow. I noticed this beacause the distance driven on my odo is off by 1 mile for every 30 driven. When my odo reaches 30 miles the gps measures 31. This hold true also if you compare the differences between the 265/75-16's and the 265/70-16's. According to the tire calculator the OR's larger tires should cause the odometer/speedometer to be off by 3.4%.

Rob
 

·
on line
Joined
·
15,651 Posts
My only problem with using the GPS is that they are not 100% accurate either. I have used three different GPSr's and each one got a different MPH reading. I used a an eTrex Summit, Garmin GPA Map60Csx and the GPS puck I have on my car computer. they were all off by 1mph each. The GPS pucking giving me the highest MPH and the eTrex giving me the lowest. I used the GPS 60 to calibrate the Scan Gauge...I figure out of three, I'll pick the middle. :)
 

·
on line
Joined
·
564 Posts
Well frankly I couldn't tell by comparing speed alone. I could tell that my X speedo was off a touch, but I attributed it to paralax error. But, the distance traveled was consistantly off by 1 mile for every 30 traveled. I also am using the Garmin 60cs.


Rob
 

·
on line
Joined
·
259 Posts
robnfl said:
From my own tests with my gps, the OR (or at least mine) indicates about 3.4% slow. I noticed this beacause the distance driven on my odo is off by 1 mile for every 30 driven. When my odo reaches 30 miles the gps measures 31. This hold true also if you compare the differences between the 265/75-16's and the 265/70-16's. According to the tire calculator the OR's larger tires should cause the odometer/speedometer to be off by 3.4%.

Rob
so, you would think that if they did take the largest wheel size and use it to calibrate the odometer, that with the OR's tires which are the largest stock tires sold on our truck, would cause the odometer to be perfect, and the odometer in theory should only be off on X and S models. which is still crap. if they took the tires sizes thet they sell stock on our trucks and averaged the size and then used that number to calibrate the odometer, the difference would be so small it would be irrelevent. I think there is too much money to be made on this scam for it to be an accident or an "oversight".

interesting read Old Navy, Ive passed this on to my Altima driving freinds
 

·
on line
Joined
·
564 Posts
My guess is that Nissan would take the tire size that they would sell the majority of and calibrate all speedos to that size.


Rob
 

·
on line
Joined
·
1,479 Posts
muzikman said:
My only problem with using the GPS is that they are not 100% accurate either. I have used three different GPSr's and each one got a different MPH reading. I used a an eTrex Summit, Garmin GPA Map60Csx and the GPS puck I have on my car computer. they were all off by 1mph each. The GPS pucking giving me the highest MPH and the eTrex giving me the lowest. I used the GPS 60 to calibrate the Scan Gauge...I figure out of three, I'll pick the middle. :)
you probably want to set your trip computer to Zero on your X and use the GPS to keep track of total distance. you probably want to do this as you are getting out off a gas station into a highway and then taking the results as you get out of it. that way you won't run on the problem that the GPS spedo might not be accurate. at least keeping track of distances should be really acurate on the GPS.
that is what i am planning on doing, by the way I have the larger SE tires so I will post my results later
 

·
on line
Joined
·
20 Posts
After being tailgated many times while doing 60 mph on the speedo in a 55 zone I used my GPS to check also. Turns out when the speedo shows 60 the GPS shows 56.4 +/-. At 80 on the speedo the GPS shows 75.8 +/-. I aint no mathematician (SP) but I know its off a little. Never thought about auto manufactures doing it on purpose...Good post!
 

·
on line
Joined
·
81 Posts
robnfl said:
From my own tests with my gps, the OR (or at least mine) indicates about 3.4% slow. I noticed this beacause the distance driven on my odo is off by 1 mile for every 30 driven. When my odo reaches 30 miles the gps measures 31. This hold true also if you compare the differences between the 265/75-16's and the 265/70-16's. According to the tire calculator the OR's larger tires should cause the odometer/speedometer to be off by 3.4%.

Rob
Well since I'm running the same exact truck I think I will have to go back and do some further testing. I'm using a Garmin Nuvi 660, I drive alot for work(just past 10000 miles after just under 4 months). So I'll reset a trip guage write down the OD and reset the GPS guages. I'll report back in a day or two depending on how many miles I go.
 

·
on line
Joined
·
1,884 Posts
Mine gets tested by the friendly man with the radar gun. Seems to be right on :blackeye:
 

·
on line
Joined
·
551 Posts
I would like to know the type of GPS they used to come up with this.
Handhelds are great for rough guessing with an error of as much as +/-5% from what I have gathered.
The only true way that I see is to have the speedo certified and then check the odometer in a time-speed-distance test. That's the way we used to do it years ago. Of course with todays computers, they could probably do it all at once.
This lawyer got lucky once and is out for more bucks.
 

·
on line
Joined
·
71 Posts
What is funny is that the speedo in my truck reads 2mph faster than the speed registered in the ECM...and the speedo reads it's info from the ECM!
 

·
on line
Joined
·
641 Posts
Magic Rat said:
I would like to know the type of GPS they used to come up with this.
Handhelds are great for rough guessing with an error of as much as +/-5% from what I have gathered.
The only true way that I see is to have the speedo certified and then check the odometer in a time-speed-distance test.
Put your handheld GPS on the dash, then it's not "handheld", and the accuracy increases. Just kidding of course ;-)

The only way to measure the accuracy of your handheld GPS receiver is to compare the information it provides against a "known good source".

The 5% figure your are referring to likely is in respect to the geographic position coordinates displayed by the receiver. Doing "position averaging" is one technique that can be used to obtain better results from consumer-grade GPS receivers. It may be the case that speed reported by consumer-grade GPS receivers is more accurate than the typical use to report location when stationary, because the speed is derived from differences between locations over time, which, depending on the algorithm used, might take into account a form of averaging.

I have compared my handheld GPS's reported speed against a police laser radar, and they were virtually identical.

However, if you have a "highway test section" nearby, you could use it. To do so you don't need to 'have the speedometer certified'. Do it with a passenger, and use a stopwatch. At the start of the test section start the timing, and at the end stop the timing. Also, note your odometer readings at the start and end, and try and keep at a constant speed(based on your speedometer). If you have a GPS, you might as well use it during the test as well :)

Once you have the time it took for the test section, that's all you need in order to calculate the "true speed". Take the distance covered by the test section(in Miles or Kilometers) and divide by the time taken, in hours.
 

·
on line
Joined
·
628 Posts
Can I insist that the dealer calibrate my speedometer and show me verification? I drove around with my GPS and it shows me at 37.8 MPH when I have the CC set and the speedometer shows 40 MPH. I am not a math wizard but I know that calculates to showing more miles than I've actually driven. I've only had the X for 3 weeks now, and have put 2700 miles on it.
 
1 - 20 of 28 Posts
Top