another validation of the "fast" speedometer

[Thud]

Took a weekend trip to NC last weekend.... with the cruise control set at 84mph, my TomTom GPS indicated 79-80mph. Until now I've never had a car that was more than 1-2mph off at 80 mph.
So it looks like the speedo in my 135 reads about 5% faster than actual speed. Looks like the speedometer was calibrated using larger wheels??

[atr_hugo]

See this thread: http://www.1addicts.com/forums/showt...ht=speedometer

[Tom K.]

Checked mine on a recent trip against the OBC, Navi and clock. The result was that the speedometer reads 61~62 at an honest 60 mph - a 2~3% error. And after repeatedly checking it against interstate mileposts, I was surprised to find that the odometer is actually just under 2% slow. Corrected gas mileage on the trip (mostly mountain roads with some interstates) was 29.8 mpg. Like they say YMMV!
Tom

[mistermojorizin]

the odometer is slow, meaning that the odometer is showing less miles than the car actually traveled?

i wouldn't think the interstate mileposts are that accurate.

[jeremyc74]

Originally Posted by mistermojorizin

the odometer is slow, meaning that the odometer is showing less miles than the car actually traveled?

i wouldn't think the interstate mileposts are that accurate.

You'd be surprised. Over a 100 mile stretch they'll be within a very small percentage. Keep in mind they're placed by surveyers as reference points, and newer ones are done with pro GPS systems with military accuracy. If there were a lot of inaccuracies, it would show up over long distances, so they have to be pretty close. I wouldn't think you could use one or two and expect it to be dead on, but over a long distance the OD and milemarkers should be right on.

[Jack in Jax]

The E46 wiki offers a link to how you can adjust your speedo.

http://www.bimmerfest.com/wiki/index...ed_warranty.3F

Jack

[mistermojorizin]

Originally Posted by jeremyc74

You'd be surprised. Over a 100 mile stretch they'll be within a very small percentage. Keep in mind they're placed by surveyers as reference points, and newer ones are done with pro GPS systems with military accuracy. If there were a lot of inaccuracies, it would show up over long distances, so they have to be pretty close. I wouldn't think you could use one or two and expect it to be dead on, but over a long distance the OD and milemarkers should be right on.

ok. how bout as to my first question, is the odometer showing less miles than it should? thanks

[Tom K.]

Originally Posted by mistermojorizin

the odometer is slow, meaning that the odometer is showing less miles than the car actually traveled?

i wouldn't think the interstate mileposts are that accurate.

I measured it on 5 different interstate stretches totalling about 100 miles and the odometer is 1 3/4% slow. In other words, when travelling 100 miles, it reads 98.25 miles.

First BMW I've seen with a measurable odo error, but on the other hand, the 1er is the only BMW I've owned which has an accurate (within 1%) avg. mpg readout on the OBC.
Tom

[mistermojorizin]

thanks. sounds like bmw is trying to protect their lease residuals by misleading used 1er buyers into paying more. lawsuit waiting to happen. but i'm not complaining.

[Tom K.]

Originally Posted by mistermojorizin

thanks. sounds like bmw is trying to protect their lease residuals by misleading used 1er buyers into paying more. lawsuit waiting to happen. but i'm not complaining.

Personally, I think it's more likely that my odo was mistakenly set up for the 16" wheels which sometimes (but not always) come with the non ZSP 128i - even though I have the SP.

Although it won't help me as my mileage will be lower, it would actually extend the warranty by 875 miles if I were to average better than 12,500 miles per year - so I doubt that it's intentional on BMW's part.
Tom

[Steve135i]

Originally Posted by mistermojorizin

the odometer is slow, meaning that the odometer is showing less miles than the car actually traveled?

i wouldn't think the interstate mileposts are that accurate.

If the speedometer shows you are going 84mph but you are actually going 80mph, your miles on the odometer will add up faster for less miles traveled. Not good, the 50,000 mile warranty isn't a full real 50,000 miles.

[jeremyc74]

Originally Posted by mistermojorizin

ok. how bout as to my first question, is the odometer showing less miles than it should? thanks

I'm doing a 1000 mile trip (each way) this week. I'm going to check it on some open stretches in FL and I'll report back. I've got GPS, and I'll take note of the mile markers, and see how closely everything jives. It will give me something to do on my 15 hour drive

[jeremyc74]

Originally Posted by Steve135i

If the speedometer shows you are going 84mph but you are actually going 80mph, your miles on the odometer will add up faster for less miles traveled. Not good, the 50,000 mile warranty isn't a full real 50,000 miles.

The speedometer shows you are going 83MPH when you're actually going 80. If the OD was also off that would be in our favor, but that's not the case on these cars. The speedo error is intentional. The car knows exactly how fast it's going (you can pull it up somehow), and displays it with the error. The OD is typically dead on according to everyone who's checked it.

[Steve135i]

OK so the mileage odometer is correct but the speedo needle is off. Thats OK.

[Bilsko]

I'm a bit new to this conversation so please correct me if I'm way off...but I wouldn't think a GPS would give you very accurate measurements to go by. The satellite technology that all of the TomTom and Garmin services use is really old (like 30+ years old) and isn't accurate to more than a couple meters - over a distance of several miles this could conceivably add up to the kinds of differences you're talking about.

[ARES45]

At any given point it is accurate to a couple of meters. However, if you started at x+/-2meters then drove 600miles and arrived at y+/-2 meters it would be pretty accurate distance wise.

[hbiscuit]

my e36 328i had a similar speedometer error... it is nothing new.

it grow as speed increases.

[jeremyc74]

Originally Posted by Bilsko

I'm a bit new to this conversation so please correct me if I'm way off...but I wouldn't think a GPS would give you very accurate measurements to go by. The satellite technology that all of the TomTom and Garmin services use is really old (like 30+ years old) and isn't accurate to more than a couple meters - over a distance of several miles this could conceivably add up to the kinds of differences you're talking about.

GPS is very accurate. The positioning really has nothing to do with it, because they use the Doppler effect in calculating speed.

[Thud]

Originally Posted by Bilsko

The satellite technology that all of the TomTom and Garmin services use is really old (like 30+ years old) and isn't accurate to more than a couple meters - over a distance of several miles this could conceivably add up to the kinds of differences you're talking about.

The locational errors aren't cumulative... if you have travelled 10 feet, there will be a significant margin of error in the distance reported by the GPS, but if you have travelled several miles, the margin of error will be almost zero.

GPS systems are very accurate at determining speed, as long as you're traveling in a relatively straight line at a constant velocity.

http://www.ncbi.nlm.nih.gov/pubmed/15519597

[Mad Dragon]

My Nuvi moved almost 0.1 miles just sitting on my toolbox.:biggrin:

[pghollysprings]

My speedometer consistently reads
2-3mph less than my GPS readout.

[mistermojorizin]

Originally Posted by Steve135i

If the speedometer shows you are going 84mph but you are actually going 80mph, your miles on the odometer will add up faster for less miles traveled. Not good, the 50,000 mile warranty isn't a full real 50,000 miles.

yes, but the guy above was saying the odo shows less miles. also, the car knows that its showing a fake speed on the speedo. it doesn't use the fake speed to calculate the odo. (you can check fake speed and accurate speed in the secret menus).