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Old 02-18-2019, 07:59 PM   #1
AL in NY
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Default Speedometer correction with 16" Ford rims

I just purchased a nice set of 16" Ford wire wheels. After viewing several threads for recommended tire sizes for these rims, I have a couple of questions. The manufacturer for the Model "A" 4.47/5.00x19 tires startes the tire diameter as 29.5 inches. The recommended size I find for use on the 16" rims is 205/70R16, which have a diameter of 27.3 inches. That equates to a speedometer error of -3.7 MPH at 50 MHP. The recommended rim width for these tires is 5 to 7 inches. The 35 Ford rims are only 4 inches wide. A better tire size is 205/80R16 which measures 28.9 inches in diameter with a speedometer error of -1.0 MPH at 50 MPH. This tire also is recommended for a 5-7 inch wide rim. Sorry for the ramble, but here are the questions. Is it a big problem putting tires recommended for 5-7" rims onto 4" rims? (AND) What have folks done about the speedometer error when changing to 16" rims?
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Old 02-19-2019, 07:40 AM   #2
BRENT in 10-uh-C
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Default Re: Speedometer correction with 16" Ford rims

Al, if you have a Peterbilt or Kenworth dealer nearby, you can check with them to see if they still have any speedo correction boxes on their shelf. These little boxes have gear sets inside that can change the output to input ratio by percentages. In the interim, download the speedometer as for your smartphone.
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Old 02-19-2019, 12:36 PM   #3
Jim Brierley
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Default Re: Speedometer correction with 16" Ford rims

I have run the 205/70's on stock 4" rims with no problems.
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Old 02-19-2019, 05:39 PM   #4
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Default Re: Speedometer correction with 16" Ford rims

Just go with 19” Radials. Problem solved.
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Old 02-19-2019, 08:55 PM   #5
papanick
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Default Re: Speedometer correction with 16" Ford rims

hay if you find that your speedometer is off I can reset it to mach your speed needed.
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Old 02-19-2019, 09:09 PM   #6
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Default Re: Speedometer correction with 16" Ford rims

Quote:
Originally Posted by BRENT in 10-uh-C View Post
Al, if you have a Peterbilt or Kenworth dealer nearby, you can check with them to see if they still have any speedo correction boxes on their shelf. These little boxes have gear sets inside that can change the output to input ratio by percentages. In the interim, download the speedometer as for your smartphone.
Google 'Speedo Ratio Adapter'. Or check with Glenn at Flat-o products. http://www.flat-o.com/accessories/speedcable.htm
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Old 02-19-2019, 09:19 PM   #7
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Default Re: Speedometer correction with 16" Ford rims

youre gonna be too happy with the ride to worry about how fast your going..
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Old 02-19-2019, 10:14 PM   #8
Chris Haynes
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Default Re: Speedometer correction with 16" Ford rims

https://www.ebay.com/sch/i.html?_fro...apter&_sacat=0
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Old 02-20-2019, 02:36 PM   #9
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Default Re: Speedometer correction with 16" Ford rims

Thanks Chris, I'm going to check into this vendor.
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