odometer off

golf4501 · 03-17-2010, 01:13 PM

Going from my stock 17" to 19" 230's. Using the calculator it appears that my speedometer will read 62 at 60, which is fine. My concern is how this will effect my odometer. I'm assuming that this also means I will adding miles at a faster clip, since I'm now off 3%? Is my assumption correct? I drive almost 60 miles per day, so the less miles I can put on, the better.

remmib · 03-17-2010, 01:19 PM

The difference between 225/45/17 and 225/35/19 is only 0.906% according to the calculator when I used it.

golf4501 · 03-17-2010, 01:57 PM

Quote:

Originally Posted by remmib

The difference between 225/45/17 and 225/35/19 is only 0.906% according to the calculator when I used it.

yeah I must have fat fingered something last time and didn't notice it, thanks for pointing that out. I'm not going to worry about it with that small difference.

David1 · 03-17-2010, 02:11 PM

The car automatically compensates for wheel diameters.

remmib · 03-17-2010, 04:36 PM

Quote:

Originally Posted by David1

The car automatically compensates for wheel diameters.

How can the car know what size tires you've got on.

David1 · 03-17-2010, 08:52 PM

Quote:

Originally Posted by remmib

How can the car know what size tires you've got on.

It knows by comparing trans output shaft speed, rpms, and wheel speed from the wheel sensors to existing programming. This is why when you change rear gear ratios in the newer BMW's that you do not have to do anything to correct the speedometer. It also needs to do this to keep the stabilty programs in sync.

mycoupe · 03-17-2010, 09:12 PM

Quote:

Originally Posted by David1

It knows by comparing trans output shaft speed, rpms, and wheel speed from the wheel sensors to existing programming. This is why when you change rear gear ratios in the newer BMW's that you do not have to do anything to correct the speedometer. It also needs to do this to keep the stabilty programs in sync.

I'd like to hear more on this, because those still wouldn't make up for the different diameter of the tire, would it? If so, please give a little more info as to how.

David1 · 03-17-2010, 09:26 PM

It's all in the software.

Dackz · 03-17-2010, 10:03 PM

Interesting......Id like to find out more on this...was thinking of going 235/40/19 front and 265/35/19 rears for my next set of tires....interesting indeed

surprise · 03-17-2010, 10:42 PM

Quote:

Originally Posted by David1

It knows by comparing trans output shaft speed, rpms, and wheel speed from the wheel sensors to existing programming.

How does the wheel sensors measure wheel speed?

David1 · 03-18-2010, 12:50 PM

It uses the abs sensors.

remmib · 03-18-2010, 01:20 PM

Quote:

Originally Posted by David1

It uses the abs sensors.

I see how the car knows the rpm of the wheels, but not how far the wheels travels on one rotation, giving it the speed.

ClayMan · 03-18-2010, 02:48 PM

This is very interesting but not possible without using GPS or something to get actual LAND speed... "trans output shaft speed, rpms, and wheel speed from the wheel sensors" stay constant relative to one another regardless of tire diameter. (Wheel sensors only capture rotational speed.)

This "software" would account for rear diff changes, but it would NOT account for tire diameter changes.

deanmc · 03-18-2010, 02:52 PM

Quote:

Originally Posted by golf4501

Going from my stock 17" to 19" 230's. Using the calculator it appears that my speedometer will read 62 at 60, which is fine. My concern is how this will effect my odometer. I'm assuming that this also means I will adding miles at a faster clip, since I'm now off 3%? Is my assumption correct? I drive almost 60 miles per day, so the less miles I can put on, the better.

Correct me if I'm wrong, but I think that going UP in rolling diameter will mean that your car will be showing fewer miles, since you're getting more distance with each rotation of the wheel than the car thinks it going.

ClayMan · 03-18-2010, 03:33 PM

Quote:

Originally Posted by deanmc

Correct me if I'm wrong, but I think that going UP in rolling diameter will mean that your car will be showing fewer miles, since you're getting more distance with each rotation of the wheel than the car thinks it going.

That is correct.

03-17-2010, 01:13 PM	#1
golf4501 Lieutenant 108 Rep 587 Posts Drives: 2020 M2C Join Date: Sep 2008 Location: chicagoland iTrader: (0) Garage List 2020 BMW M2C [0.00]	odometer off Going from my stock 17" to 19" 230's. Using the calculator it appears that my speedometer will read 62 at 60, which is fine. My concern is how this will effect my odometer. I'm assuming that this also means I will adding miles at a faster clip, since I'm now off 3%? Is my assumption correct? I drive almost 60 miles per day, so the less miles I can put on, the better.
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03-17-2010, 01:19 PM	#2
remmib General 1569 Rep 29,202 Posts Drives: 2013 F10 520d M-Sport Join Date: Feb 2006 Location: Norway iTrader: (0)	The difference between 225/45/17 and 225/35/19 is only 0.906% according to the calculator when I used it. __________________ F10 520d M-Sport Alpine White \| HRE P43SC 20x9+20x11 \| Michelin PSS 255/35+295/30 \| KW V3 Coilover \| M5 Front Sway Bar + M550d Rear Sway Bar \| 3DDesign Front Lip \| BMW M Performance CF Spoiler \| BMW M Performance Diffuser \| BMW M Performance Black Grills \| BMW M Performance Pedals \|
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03-17-2010, 02:11 PM	#4
David1 Brigadier General 814 Rep 3,953 Posts Drives: 09 E92 09 X5 Join Date: Mar 2007 Location: Columbus, OH iTrader: (1)	The car automatically compensates for wheel diameters. __________________ 2021 M2 Comp Sunset Orange \|Black with orange Stitching Dakota Leather\|Executive Pkg\|DCT
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03-17-2010, 09:26 PM	#8
David1 Brigadier General 814 Rep 3,953 Posts Drives: 09 E92 09 X5 Join Date: Mar 2007 Location: Columbus, OH iTrader: (1)	It's all in the software. __________________ 2021 M2 Comp Sunset Orange \|Black with orange Stitching Dakota Leather\|Executive Pkg\|DCT
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03-17-2010, 10:03 PM	#9
Dackz Hates Speed Limits 111 Rep 2,589 Posts Drives: E92 335i Join Date: Sep 2008 Location: Northern CO iTrader: (4)	Interesting......Id like to find out more on this...was thinking of going 235/40/19 front and 265/35/19 rears for my next set of tires....interesting indeed
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03-18-2010, 12:50 PM	#11
David1 Brigadier General 814 Rep 3,953 Posts Drives: 09 E92 09 X5 Join Date: Mar 2007 Location: Columbus, OH iTrader: (1)	It uses the abs sensors. __________________ 2021 M2 Comp Sunset Orange \|Black with orange Stitching Dakota Leather\|Executive Pkg\|DCT
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03-18-2010, 02:48 PM	#13
ClayMan Second Lieutenant 19 Rep 213 Posts Drives: E36, E39, E86 Join Date: Dec 2007 Location: ON, NY iTrader: (0)	This is very interesting but not possible without using GPS or something to get actual LAND speed... "trans output shaft speed, rpms, and wheel speed from the wheel sensors" stay constant relative to one another regardless of tire diameter. (Wheel sensors only capture rotational speed.) This "software" would account for rear diff changes, but it would NOT account for tire diameter changes.
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