[alee]

Just started reading my April 2002 Car and Driver. Check out the article on 108-109 titled "Speedometer Scandal!"

Here's a taste:
... by manufacturer, GM's domestic products are the most accurate, and BMW's are the least accurate by far

BMW speedometer needles read notoriously high, typically overstating speeds by 2 to 9 mph at 70 mph

I always knew BMW figures in about 10% error, but it appears they are one of the worst offenders.

-Al

 

[node21]

hmm, i've passed by those mobile "Your Speed Is" signs and my speedo reads spot-on against what those signs display.

 

[alee]

hmm, i've passed by those mobile "Your Speed Is" signs and my speedo reads spot-on against what those signs display.

Sounds right if you're talking about the local speed signs... a ~10% error should translate to a tiny error at low speeds, and large error at higher speeds.

 

[vexed]

Just started reading my April 2002 Car and Driver. Check out the article on 108-109 titled "Speedometer Scandal!"

Here's a taste:
... by manufacturer, GM's domestic products are the most accurate, and BMW's are the least accurate by far

BMW speedometer needles read notoriously high, typically overstating speeds by 2 to 9 mph at 70 mph

I always knew BMW figures in about 10% error, but it appears they are one of the worst offenders.

-Al

Hmmm...maybe's that why I did not get a ticket from the nasty traffic cam van the other night...

 

[ALEX325i]

Damn Al,

I don't even want to think about how fast you drive then... :lmao:

 

[alee]

Damn Al,

I don't even want to think about how fast you drive then... :lmao:

:lmao: :lmao:

Maybe I don't need that V1 after all.

 

[ALEX325i]

:lmao: :lmao:

Maybe I don't need that V1 after all.

No, you don't. I'll trade ya my recently acquired Cobra ESD 9110. That should give you enough false alarms... Let the V1 help who really needs one.

 

[ESS]

Can the odometer be trusted? I've tested my spedometer accuracy using the odometer and a stopwatch and it seems to be right on at 60 MPH.

 

[nate]

OBC reads the same as speedo :dunno:

 

[Magna]

not to cause trouble, but the OBC and the analog speedo could be linked.

by the way, no problem driving 100 in New Orleans? never get the chance to go that fast here in the boston area unless i travel to the rural areas which at least 100 miles away.

 

[nate]

not to cause trouble, but the OBC and the analog speedo could be linked.

by the way, no problem driving 100 in New Orleans? never get the chance to go that fast here in the boston area unless i travel to the rural areas which at least 100 miles away.

That's out in the swamps in western LA :lmao: I wouldn't want the state police to find out

I probably cruied for about 15 minutes at that speed. Also the speed blindness from the top speed run probably got the best of me, I felt parked :eeps:

Another place in NOLA you can go that fast is on the Causeway. 24 straight miles and rare crossovers :eeps:

 

[Cal]

Sounds right if you're talking about the local speed signs... a ~10% error should translate to a tiny error at low speeds, and large error at higher speeds.

True Al, but even at 30mph, 10% is 3 mph, so the speed traps would still display 27 mph when your speedo reads 30 mph. I've gone through some as well, once at about 40, another at about 55, and my speedo was right on with the trap display.

This issue has been of a lot of interest to me in the past couple of months since C&D reported this on their M3 and 540 tests. I've actually "tested" my speedo against plenty of cars on the freeway (yeah, a little dangerous, but done carefully). The ones with digital speedos (present in some Caddys, Buicks, etc) are the easiest to compare against. I've found out that the ONLY cars that have shown my speedo to be optimistic were two Caddys (one displayed 74, mine was at 75, and another Caddy display 76, mine was at about 78). In other words, at most 2 mph by about 80. All other cars I've compared with are either right on the mark with mine or too optimistic compared to mine. Hondas seem to be quite optimistic, especially Civics and Accords.

Any ways, several people equipped with GPSs have measured their speedo accuracies, and have noted that they are off by about 2-3 miles at 80, and about 3-6 mph at around 128. (Done by some people at the Mohave. Check bimmer.org archives.)

 

[Cal]

not to cause trouble, but the OBC and the analog speedo could be linked.

by the way, no problem driving 100 in New Orleans? never get the chance to go that fast here in the boston area unless i travel to the rural areas which at least 100 miles away.

I thought this would be the case too, but I've tested it numerous times. At anything below 80, my OBC reads nearly 2 mph higher than my speedo. I took it once to about 100 on an open deserted road, and the OBC was now only 1 mph higher than my speedo. SO, it looks like they are not linked (at least in my car). Seems like the speedo was becoming optimistic as speeds increased, albeit only 1 mph.

 

[bol]

I've checked using a GPS unit and my speedo was only off by ~5mph at the govenor... :dunno:

 

[DougDogs]

hey nate.....

is that photo touched up in photoshop????

if not, how does the OBC display current MPH ?????

I do not have that display on my OBC

 

[Guest84]

"Overstating..." Okay, help me out here, is CD saying that if I am doing 70, I may be actually doing 72-79 mph? Or are they staying "overstating" meaning that if I'm doing 70, its actually doing 61-68 mph?

 

[Guest84]

Also, does BMW compensate for the 17" tires when you get the SP (from the 16" standard) for calibration?

 

[jdlsc]

Also, does BMW compensate for the 17" tires when you get the SP (from the 16" standard) for calibration?

I haven't checked the tire sizes on the 3er specifically, but typically when a manufacturer offers different diameter wheels, they adjust the tire profile so that the combined wheel and tire diameter changes very little, if any. Hence, low profile tires on the 17" wheels, and probably even lower profile tires on the 18" wheels.

 

[Spiderm0n]

"Overstating..." Okay, help me out here, is CD saying that if I am doing 70, I may be actually doing 72-79 mph? Or are they staying "overstating" meaning that if I'm doing 70, its actually doing 61-68 mph?

They make it look like you are going faster then you actually are. According to C&D tests, on the average BMW you have to set your speedometer to 73.18 MPH to actually be going 70 MPH

 

[Guest84]

Thks for clarification gentlemen.!