Inacurate Speedometer
01-16-2006, 05:35 PM
#11
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My Ride: Alpine white 2004 545, cold weather package, premium sound, sport package.
Originally Posted by MidnightRider' post='224432' date='Jan 15 2006, 01:21 AM
I think my speedometer is indicating I am traveling faster than I am. It may be off by 15 mph at higher speeds. Are there ways to test this besides clocking a measured mile? If my speedo is showing a higher speed, is my odometer accumulating miles faster than I am driving them? Help! 
On my trip to Vegas I clocked mine(on cruise control) via GPS/laptop@70MPH. It was off by 2-3MPH Speedo read 70MPH, and GPS read 67/68 alternating, but it was more steady @ 68MPH most of the time. Not sure how accurate GPS really is but yeah..... If you're in Cali ask CHP to clock ya
.
01-16-2006, 06:43 PM
#12
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My Ride: Delivery 11/30/05: 2006 - 550i 6-speed, Monaco Blue, Auburn, Antracite headliner, M aero, sport, nav, HUD, cold weather, sun shades, folding seat, rearseat heat and air bags, Logic 7, Serius, SR-7 Detector, M wheels
Previous Ride - 2002 540 6-speed, sport, turning in with 114,000 wonderful miles
The problem might be that you'r driving a 550. They go fast so easily that you might not realize how fast you are truly traveling. This comes from a fellow 550 driver that often finds himself going at ultra legal speeds, sometimes without realizing it.So, follow the above threads that recommend ways to check your speedo, but don't be surprised if it is only 1-2% off.
01-16-2006, 07:18 PM
#13
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My Ride: 2004 545i Silver Gray/Black
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Originally Posted by MiStateBMRfan' post='225243' date='Jan 16 2006, 09:43 PM
The problem might be that you'r driving a 550. They go fast so easily that you might not realize how fast you are truly traveling. This comes from a fellow 550 driver that often finds himself going at ultra legal speeds, sometimes without realizing it.So, follow the above threads that recommend ways to check your speedo, but don't be surprised if it is only 1-2% off.
Will a biger tire correct this issue?
245/40/18 -> 255/40/18
275/35/18 -> 285/35/18
01-16-2006, 07:42 PM
#14
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My Ride: 2007 530i, white/black manual, sports package, nav, PDC, etc.
Why can't they just be exact? My Garmin GPS receiver gives me MPH from the satellites.
This analog speedo crap is BS
-RA
This analog speedo crap is BS
-RA
Originally Posted by MidnightRider' post='224432' date='Jan 14 2006, 10:21 PM
I think my speedometer is indicating I am traveling faster than I am. It may be off by 15 mph at higher speeds. Are there ways to test this besides clocking a measured mile? If my speedo is showing a higher speed, is my odometer accumulating miles faster than I am driving them? Help!
01-17-2006, 05:57 AM
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From what I've heard, German law says a car (as it leaves the factory) can never say it is going slower than it actually is. So to ensure no car, for example, is telling you you're going 55 mph when you're really going 57, BMW and most German car makers set their speedometers to read faster, and I guess they have to do it by a few mph to account for statistical variations. Six sigmas and all...
(They basically don't want you to be able to get out of a ticket. In Germany, the speed cameras will get you if you're going more that about 1.5 mph over the speed limit. Just ask my wife!)
Yeah, it is a bit disappointing because it means that all those times on the autobahn I was really only cruising at about 127 or 128 mph when I thought I was going 130. Oh well.
(They basically don't want you to be able to get out of a ticket. In Germany, the speed cameras will get you if you're going more that about 1.5 mph over the speed limit. Just ask my wife!)
Yeah, it is a bit disappointing because it means that all those times on the autobahn I was really only cruising at about 127 or 128 mph when I thought I was going 130. Oh well.
01-17-2006, 06:05 AM
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Originally Posted by MidnightRider' post='224432' date='Jan 15 2006, 12:21 AM
I think my speedometer is indicating I am traveling faster than I am. It may be off by 15 mph at higher speeds. Are there ways to test this besides clocking a measured mile? If my speedo is showing a higher speed, is my odometer accumulating miles faster than I am driving them? Help!
01-17-2006, 06:31 AM
#17
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My Ride: '04 545iS 6 spd, bought new via eBay, 11/05; Blk/Gry, Cold, L7, PDC, BMW Rear seatcover for pets.
First "Bumwa" was a new 1971 2002. High performance 5s since 1987. Beamer motorcycles too, currently on an 07 BMW K1200 GT; also a Moto Guzzi 1000 SP III.
They have always featured overage, at about 2 mph around 70mph. You can check your speed, while holding it at 70 by way of the cruise control, and then hitting Reset on the speed readout in the trip computer. Invariably, over several past models, the speedo was over by 2 mph, which is fine by me and the radar boys.
But what I am really asking about is the accuarcy of the GPS comparo? I thought they were dumbed down by Federal regulations so that they are off by at least 15-20 feet or something like that. It would seem that this built-in inaccuracy could compound faulty estimates. But I don't know anything about them. (Heck I just discovered my home address's GPS address playing with the iDrive; that's how high tech I am.) :'(
Cheers, Ray Hull
But what I am really asking about is the accuarcy of the GPS comparo? I thought they were dumbed down by Federal regulations so that they are off by at least 15-20 feet or something like that. It would seem that this built-in inaccuracy could compound faulty estimates. But I don't know anything about them. (Heck I just discovered my home address's GPS address playing with the iDrive; that's how high tech I am.) :'(
Cheers, Ray Hull
01-17-2006, 01:16 PM
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As the tyres wear the rolling diameter changes. Hence a speedo can never be 100% accurate 100% of the time.
As noted, the law typically says a speedo must never under-read - hence slight overead built in to be safe
As noted, the law typically says a speedo must never under-read - hence slight overead built in to be safe
01-18-2006, 04:10 AM
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My Ride: (USA) 645Ci, Silver Gray, Chateau, Cold Weather PKG, Premium Sound PKG, Sport PKG, Step, NAV [Std Equip in 645], HUD, Satellite (SIRIUS) Radio, Aux Input, Bluetooth enabled using iPhone 3GS w/ adapter cradle - Build date - 01/05, Baby delivered 2/24/05
Mine is as many are here; off by 2 MPH high. Using clocked mile markers on I95, FHP radar, and Cape & Kennedy Traffic Radar - all consistant.
01-18-2006, 08:26 AM
#20
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My Ride: 2007 530i, white/black manual, sports package, nav, PDC, etc.
As the tires wear, they become smaller and spin faster, accentuating the over read.
Originally Posted by new-kid' post='225610' date='Jan 17 2006, 02:16 PM
As the tyres wear the rolling diameter changes. Hence a speedo can never be 100% accurate 100% of the time.
As noted, the law typically says a speedo must never under-read - hence slight overead built in to be safe
As noted, the law typically says a speedo must never under-read - hence slight overead built in to be safe