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Man with Car
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228 Posts
Discussion Starter · #1 ·
Has anyone else picked up this month's Car and Driver? There's an interesting if brief piece on speedometer and odometer error across automotive lines. Practically all speedometers are set at the factory to read slightly high above 55 mph. European manufacturers are the worst about this, with some BMWs reading as much as 9 mph over at 70 mph.

The most interesting point as relating to our '02 Altimas reading high, however, is the SAE standard to which manufacturers of U.S. automobiles voluntarily adhere. Among other things, the standard allows for a four percent (+) error above 55 mph. And get this: The percentage isn't a relative to indicated or actual road speed, but to the speedometer scale. Applying the standard to our 160 mph Altima speedometers allows for a +6.4 mile per hour reading at speeds above 55 mph. So, according to the SAE standard, our speedometers, many of which read about five mph high at 70 mph, are within tolerance. :rolleyes:

Bureacracy at its finest, fellas.

Jarrod K. Wright
'02 3.5 SE 5-speed
'98 SE 5-speed
 

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Yeah, I read this article too. What was also interesting was the ODOMETER reading. The benchmark was 1,000 miles and they listed the diff't manufacturers' odometer readings after that 1,000 miles. Nissan, the only Japanese car company, hit it right on the dot with 1,000 exactly! Hmmm....

And yeah, those BMW speedometers exaggerate the most out of any manufacturer they tested. They said European cars tend to have a higher speedometer reading, while GM was the most steady. Go figure....
 

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Man with Car
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228 Posts
Discussion Starter · #3 ·
Yes, I was surprised about the accuracy of Nissan's odometer readings. Honda's readings were *way* out of whack if I remember, something like an average reading of 1021 miles for every actual 1000 miles driven. The worst of the bunch. And lowly GM, which puts out products like the Aztek thinking buyers will flock, apparently has the best speedometer engineering team on the planet. :confused:

I thought the bit about Porche "engineering" in optimistic speedometer readings under the assumption that most of its owners would put on taller aftermarket tires and wheels was enlightening. The funny thing is, in my part of the country I don't see very many modified Porsches -- nearly all of them have the stock wheels and tires. Go figure x2.

Jarrod
 
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The SAE information is what nissan gave me when I complained about my speedo being off about 7mph at an indicated 60mph. Two times back to the service department without any relief. On the other hand, the odometer was totally accurate. As soon as mentioned that "I was very concerned about my safety driving down the road at an indicated 75mph while only going 65mph and the possible implications with getting rear ended or not begin able to accurately tell my speed and picking up a speeding ticket, a call was made to Nissan and the following week I got an accurate speedo. Because I put on 215-60-17 snow tires that are a little larger then the stock tires, I am reading just a slight bit lower then true speed. Also, I am off about 125 ft/mile. In other words, I am going about an extra mile every 100 or so miles the odometer lists.
 

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Future Z Driver
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215 Posts
Seriously, if I bought a Porsche, I would hope there would be no need to upgrade the wheels and tires!

I saw a new 911 Turbo on the street the other day, which has those cool hollow-spoke forged aluminum 18s on it. Man, that car is sweet!
 

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M W S
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386 Posts
If a speedometer is off by 5%, and it is documented by the dealer as such, and the odometer is also off by 5% as a result, does that mean the warranty expires per the odometer reading or by the ACTUAL miles?
 

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Man with Car
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228 Posts
Discussion Starter · #8 ·
I don't know if that scenario exists except in extraordinary cases, marks.

The C&D article indicated that while speedometer error is widespread, the vast majority of odometers are very accurate. The worst odometer offender was Honda, and their average was only an indicated 1021 miles for every 1000 actual miles driven, or +2.1 percent. So at 36,000 actual miles, Honda's odometers would read 36,756. Not much of an impact on the company's 3/36 warranty.

Interestingly, while BMW's speedometers were the most optimistic of the bunch at an average of 73.18 mph while traveling a true 70 mph, their odometers were the *only* ones to indicate fewer than actual miles traveled. (For every 1000 miles, the BMWs' odometers indicated an average of 993 miles. Drive your BMW 100,000 miles and your odo reads a dainty 99,300!)

Jarrod
 

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Future Z Driver
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Just got my C&D yesterday. One thing I found interesting about that article was how the trip computers are much more accurate than the speedos. This confirms what we've been seeing in our Altimas, when we set the cruise control at an indicated 75 and reset the average speed display on the trip computer to determine how inaccurate our speedos are.
 

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My plan

One of these days, I will take my GPS out for a ride and find out just how far off the thing is and different speeds, and just deal with it. I'm guessing it probably won't be that much.

Personally, I think people making a bit too much out of this. I would much rather have the "factory" installed speedo with a bit of error than turn my car over to ANY dealer to let them try to dismantle the dash assembly to put a new cluster in. The chance of getting the car back with fewer problems than it went in with are next to zero. Plus, I just cringe at the thought of some ass taking my car out for a spin to make sure new speedo works (and you know they will).
 

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04-05 Pedal Insert
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Max

U the man! I feel that way exactly, that is why I still have a clunk, and have not had my coils replaced.
 

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Man with Car
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Discussion Starter · #14 ·
Re: My plan

Max Power said:
Personally, I think people making a bit too much out of this. I would much rather have the "factory" installed speedo with a bit of error than turn my car over to ANY dealer...
Agreed. The speedometer error doesn't bother me one bit. And the one (and only -- I hope) time I took my Altima back to the dealer for work was to clear out the rattles and squeaks, which they did. They also put 43 miles on the car and broke the rear seatback release button. :angry4:

Jarrod
 
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