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2010 2011 BMW 5 Series Forum F10 BMW 5-Series (F10) Forums General 5-Series Sedan and Wagon (F10 / F11) Forum Speedometer reading off by 5 % or so...how can I fix this?
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      01-06-2022, 09:57 PM   #1
jeepzj96
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Speedometer reading off by 5 % or so...how can I fix this?

Hi All,

The snow is finaly here, so I invested in some winter tires. I found a great deal on a used pair but they are smaller than what I usualy have on the car. Normally I have 245/45R18's and the winters are 225/45R18. So slightly skinnier, and shorter...

Now I see that my speed indicator is slowing slow by around 5% vs my phonbe GPS.....which I understand why, smaller tires.

So... how can I fix this? In the old days you could change the speedo gears in the tranny, but this is all digital now.

Is there an adjustment that can be made somehow in the software to accound for this change? I've searched the forums, and it sounds like a few people are seeing this issue, but I don't think anyone has a fix for this, or at least not that I can find it.

Any ideas?

thanks,

-Hubert
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      01-06-2022, 11:16 PM   #2
Hoa
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You can code the instrument cluster (KOMBI) to match your tire size using BimmerCode.
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      01-07-2022, 09:24 AM   #3
ChiNorm
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Or you could just run the correct size tires.
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      01-07-2022, 11:41 AM   #4
Qsilver7
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Regardless of the thinner tires...your speedometer will hardly ever match your GPS and that is by design. And this is not new...I've owned BMWs since 1986 and the speedometers have always been off. And the topic isn't new...a google search should bring up many past discussions on this topic.
European cars fall under a regulation...UN ECE Regulation 39...which you can google for more details:

The European formula

The European Union requires adherence to UN ECE Regulation 39. It’s a lot of math, but the simple version is that no speedometer can read slower than the actual speed. On the high side, it’s allowed to read up to 10% above the actual speed plus four or six kilometers per hour, depending on the type of vehicle.


Japanese & American made cars usually follow the 4% rule:

The four percent rule

For ordinary passenger vehicles, there’s no law in the U.S. that regulates speedometers, but U.S. manufacturers (and most Japanese as well) subscribe to a standard called SAE J1226. Your speedometer reading must be within a range of plus or minus four percent off, but that’s four percent over the entire range of the speedometer, and that range can then be shifted in what’s called a bias.
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      01-07-2022, 09:47 PM   #5
jeepzj96
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Quote:
Originally Posted by ChiNorm View Post
Or you could just run the correct size tires.
Ahh... but that's no fun..
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