OT: Will increasing the tire size (16 to 18) affect the speedometer?

Longoo · 01-25-2008, 12:34 AM

I thought I read somewhere (and it seems to make sense) that changing from 16s to 18s will affect the speedometer and odometer readings. Is this true?

If so, is it noticeable? Right now, my GPS always says I'm going slower than the speedometer. I know the GPS isn't perfectly accurate, but there seems to be a fairly big discrepancy between the two reading.

Sorry for asking in the

classified, but this is where people are looking for (and talking about) wheels.

cbad335 · 01-25-2008, 02:10 AM

For what it's worth, I was told by a vendor that going from 18" to 19" wheels would affect speedometer only very slightly, and that odometer would measure slightly less than actual miles covered (i.e., in my favor).

Nikos335i · 01-25-2008, 08:06 AM

Quote:

Originally Posted by Longoo

I thought I read somewhere (and it seems to make sense) that changing from 16s to 18s will affect the speedometer and odometer readings. Is this true?

If so, is it noticeable? Right now, my GPS always says I'm going slower than the speedometer. I know the GPS isn't perfectly accurate, but there seems to be a fairly big discrepancy between the two reading.

Sorry for asking in the

classified, but this is where people are looking for (and talking about) wheels.

Actually there is a wheel and tire forum BTW. And to answer your question as long as you retain the same overall diameter 205-55-16 = 225-45-17 = 235-35-19 (not 100% perfect but very close).

Later,

discoboy1 · 01-25-2008, 09:35 AM

Speedometers are already off 10% in our cars with stock wheels...

Longoo · 01-25-2008, 10:44 AM

Is there a way to calibrate the speedometer (or any other method) to make it accurate?

01-25-2008, 12:34 AM	#1
Longoo New Member 0 Rep 17 Posts Drives: 2009 328i x drive coupe Join Date: Jan 2008 Location: New York iTrader: (0)	OT: Will increasing the tire size (16 to 18) affect the speedometer? I thought I read somewhere (and it seems to make sense) that changing from 16s to 18s will affect the speedometer and odometer readings. Is this true? If so, is it noticeable? Right now, my GPS always says I'm going slower than the speedometer. I know the GPS isn't perfectly accurate, but there seems to be a fairly big discrepancy between the two reading. Sorry for asking in the classified, but this is where people are looking for (and talking about) wheels.
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01-25-2008, 02:10 AM	#2
cbad335 Lieutenant Colonel 63 Rep 1,739 Posts Drives: '09 E92 335i Join Date: Jan 2008 Location: Cardiff-by-the-Sea, CA iTrader: (17) Garage List 2009 BMW 335i Coupe [7.34]	For what it's worth, I was told by a vendor that going from 18" to 19" wheels would affect speedometer only very slightly, and that odometer would measure slightly less than actual miles covered (i.e., in my favor).
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01-25-2008, 09:35 AM	#4
discoboy1 Lieutenant Colonel 128 Rep 1,558 Posts Drives: E82 1M VO/F30 328D Join Date: Mar 2005 Location: Montreal iTrader: (3)	Speedometers are already off 10% in our cars with stock wheels... __________________ 2011 E82 1M VO 2013 F84 35i VO
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01-25-2008, 10:44 AM	#5
Longoo New Member 0 Rep 17 Posts Drives: 2009 328i x drive coupe Join Date: Jan 2008 Location: New York iTrader: (0)	Can we do anything about it? Is there a way to calibrate the speedometer (or any other method) to make it accurate?
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