19" wheels and speedo accuracy

ZoinksM3 · 09-01-2008, 03:52 PM

This is a minor annoyance, but the speedometer seems off on my M3. The "analog" readout is a bit high for the given speed. The digital measurement seems accurate when compared to two seperate GPS devices (not BMW NAV).

This a problem? I have the 19" factory setup.

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Blake · 09-01-2008, 03:56 PM

i've noticed the same thing on mine. and when i pass a radar speed sign, it always displays a lower speed on the sign than both of the speedo's in the dash.

Sticky · 09-01-2008, 04:04 PM

Quote:

Originally Posted by blakepilot

i've noticed the same thing on mine. and when i pass a radar speed sign, it always displays a lower speed on the sign than both of the speedo's in the dash.

+1

ZoinksM3 · 09-01-2008, 04:12 PM

Some more detail...

I drove up from Austin today and had some time to test it. Once again, the digital readout on the cockpit display looks to be accurate, the "analog" dial is fast. I first noticed it when I set the cruise control, so I switched my Passport 9500i to speed display (great gizmo, btw). Matched the digital readout. I then broke out my trusty Garmin Nuvi, it showed the same.

Blake · 09-01-2008, 04:40 PM

just for shitzengiggles, i just did a run around area with my 9500i (ftw) set on speed display also. i set cruise on 30, 40, and 50. each time my passport read out 2mph lower than the digital or analog displays in the dash. very strange indeed.

sayemthree · 09-01-2008, 06:37 PM

2 to 3 mph difference? thats nothing.

ybbiz34 · 09-01-2008, 06:42 PM

All BMW speedometers are optimistic. In Germany, it is illegal to have a speedometer that reads on the low side (e.g. you are going 83 but the speedo reads 80).

This topic has been talked about A LOT on here.

GnokGnik · 09-01-2008, 07:06 PM

better err on the safe side.

rzm3 · 09-01-2008, 07:10 PM

Using the serect menu, I determined that the digital readout is about 4-5% optimistic.

KenH · 09-01-2008, 08:46 PM

19" wheels should not make a difference. The 19' tires have the same rolling radius as the 18' tires, give or take a tiny amount, as the profiles are different.

MysticBlue · 09-01-2008, 09:07 PM

As noted, 19" vs. 18" wheels have absolutely nothing to do with anything.
And it is normal for the analog speedometer to read 4 or 5% over. It is the law in some countries and the manufacturers covering their ass liability wise everywhere else. If you spend any time on car forums you'll see this subject come up on a regular basis.

09-01-2008, 03:52 PM	#1
ZoinksM3 Private First Class 9 Rep 114 Posts Drives: E90 DCT M3 Join Date: Aug 2008 Location: Irving, Tx iTrader: (0)	19" wheels and speedo accuracy This is a minor annoyance, but the speedometer seems off on my M3. The "analog" readout is a bit high for the given speed. The digital measurement seems accurate when compared to two seperate GPS devices (not BMW NAV). This a problem? I have the 19" factory setup. __________________
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09-01-2008, 03:56 PM	#2
Blake Banned 752 Rep 4,649 Posts Drives: Chevy Aveo Join Date: May 2008 Location: Parent's Basement iTrader: (7)	i've noticed the same thing on mine. and when i pass a radar speed sign, it always displays a lower speed on the sign than both of the speedo's in the dash.
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09-01-2008, 04:12 PM	#4
ZoinksM3 Private First Class 9 Rep 114 Posts Drives: E90 DCT M3 Join Date: Aug 2008 Location: Irving, Tx iTrader: (0)	Some more detail... I drove up from Austin today and had some time to test it. Once again, the digital readout on the cockpit display looks to be accurate, the "analog" dial is fast. I first noticed it when I set the cruise control, so I switched my Passport 9500i to speed display (great gizmo, btw). Matched the digital readout. I then broke out my trusty Garmin Nuvi, it showed the same. __________________
	Appreciate 0 Quote

09-01-2008, 04:40 PM	#5
Blake Banned 752 Rep 4,649 Posts Drives: Chevy Aveo Join Date: May 2008 Location: Parent's Basement iTrader: (7)	just for shitzengiggles, i just did a run around area with my 9500i (ftw) set on speed display also. i set cruise on 30, 40, and 50. each time my passport read out 2mph lower than the digital or analog displays in the dash. very strange indeed.
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09-01-2008, 06:37 PM	#6
sayemthree Major General 597 Rep 5,448 Posts Drives: ‘20 X3mC ‘20 Raptor ‘04 X3 6mt Join Date: Aug 2007 Location: usa so cal , AZ iTrader: (0)	2 to 3 mph difference? thats nothing. __________________ Fore Sale Rare 6 speed manual X3 3.oi silver over grey. PM me
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09-01-2008, 06:42 PM	#7
ybbiz34 Brigadier General 670 Rep 4,959 Posts Drives: 2023 330i M Sport Join Date: Jul 2007 Location: USA iTrader: (1)	All BMW speedometers are optimistic. In Germany, it is illegal to have a speedometer that reads on the low side (e.g. you are going 83 but the speedo reads 80). This topic has been talked about A LOT on here. __________________ Current: '23 G20 M Sport 330i Current: '20 X253 GLC300 SUV Gone: '20 W205 C43 Sedan Gone: '18 W205 C43 Sedan Gone: '13 W204 C63 Sedan
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09-01-2008, 07:06 PM	#8
GnokGnik Captain 17 Rep 936 Posts Drives: E92 335i, 997 C2S Join Date: May 2008 Location: SoCal iTrader: (0)	better err on the safe side.
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09-01-2008, 07:10 PM	#9
rzm3 Moderator 673 Rep 4,737 Posts Drives: E92 M3 Join Date: Aug 2007 Location: USA iTrader: (18)	Using the serect menu, I determined that the digital readout is about 4-5% optimistic.
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09-01-2008, 08:46 PM	#10
KenH Private First Class 3 Rep 117 Posts Drives: e92m3 f25x3 e71x6 Join Date: May 2008 Location: VA iTrader: (0)	19" wheels should not make a difference. The 19' tires have the same rolling radius as the 18' tires, give or take a tiny amount, as the profiles are different.
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09-01-2008, 09:07 PM	#11
MysticBlue Lieutenant Colonel 369 Rep 1,887 Posts Drives: '20 M5C, '09 M3 DCT Coupe Join Date: Apr 2008 Location: Eastern Oregon... They call 'em rigs here iTrader: (0)	As noted, 19" vs. 18" wheels have absolutely nothing to do with anything. And it is normal for the analog speedometer to read 4 or 5% over. It is the law in some countries and the manufacturers covering their ass liability wise everywhere else. If you spend any time on car forums you'll see this subject come up on a regular basis.
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