Real Problem with over size tires

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Aug 15, 2019 | 01:03 PM

msmith55

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Real Problem with over size tires

In June I purchased a 2011 F150 4x4 3.7. When I took it for the test drive I noticed that the speedometer was off. After checking it with a GPS app I found that it was off by 12 to 15 mph. The kid I was buying it from had the thing recalibrated from the factory size 235/75/17 to the ones he had on which were 265/70/17 which was fine. That was until last week when I had to clean the battery terminals. It went back to being off again. After research I learned about Forscan. I picked it up and followed the spread sheet info. I found the BCM line 726-12-01 mine looked totally weird. It was as follows ( 0000-000F-4F) . When I changed the middle set it said invalid. I thought that the code sequence was to be 4 characters in each. Please if someone could give me the correct sequence, I really need your help.

Aug 15, 2019 | 02:09 PM

driximus

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From: Auburn, Wa

Not all of the 09-14 trucks will change in Forscan. I was trying to get my 14 to change tire sizes also but mid 2014 and up have better success when trying to change tire sizes.

Aug 15, 2019 | 03:21 PM

00t444e

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From: Southern OH

Something wasnt calibrated right, a 235/75/17 is roughly 31" in diameter and a 265/70/17 is about 32". That's less than a 4% difference in diameter, for you speedometer to be off 12-15 MPH just from the tire change you would have to be going over 150 MPH.

Aug 15, 2019 | 04:38 PM

steve(ill)

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00t444e is right........ those two tires would be a difference of 2 MPH at 100 MPH.... not even worth a reprogram.

Aug 15, 2019 | 05:20 PM

Siberexpress

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From: Clinton TN.

I think you need to check what you have in it for rear end gears and see what they are or ask the guy what he changed them to.

Aug 15, 2019 | 09:53 PM

cmorningstar01

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From: New Lisbon NJ USA

As those above have stated the speedometer error for the difference in the 2 tires is negligible.

Speedometer Difference

Speedo ReadingActual Speed

20 mph (32.19 km/h)20.47 mph (32.95 km/h)

25 mph (40.23 km/h)25.59 mph (41.18 km/h)

30 mph (48.28 km/h)30.71 mph (49.42 km/h)

35 mph (56.33 km/h)35.83 mph (57.66 km/h)

40 mph (64.37 km/h)40.94 mph (65.89 km/h)

45 mph (72.42 km/h)46.06 mph (74.13 km/h)

50 mph (80.47 km/h)51.18 mph (82.37 km/h)

55 mph (88.51 km/h)56.3 mph (90.6 km/h)

60 mph (96.56 km/h)61.42 mph (98.84 km/h)

65 mph (104.61 km/h)66.53 mph (107.08 km/

https://www.tacomaworld.com/tirecalc...5r17-265-70r17