Tire size upgrade question

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Oct 27, 2024 | 09:13 PM

wmeads

Thread Starter

3rd Gear

Joined: Feb 2024

Posts: 3

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From: Mt. Juliet

Tire size upgrade question

Hi, I am new to the F250 Super Duty group. I have just upgraded my wheels and tires to 35's. Do I need to change anything in the computer or tell it anything so that it knows? I have a 2017 with a 6.2 4 door with an 8ft bed. Thanks

Oct 27, 2024 | 11:43 PM

Ltngdrvr

Lead Driver

Joined: Nov 2005

Posts: 8,465

Likes: 4,958

Do you need to?
Only need to reprogram the pcm if you want the speedo to be correct.

Oct 28, 2024 | 08:44 AM

CBEllis

Fleet Mechanic

Joined: Dec 2012

Posts: 1,566

Likes: 537

From: DFW

With 35's, the speed may be closer to accurate than when it rolled off the dealer lot. Find a good app that tracks your speed and compare the two. You might be surprised.

Oct 28, 2024 | 09:48 AM

greenno

Tuned

Joined: May 2016

Posts: 385

Likes: 197

From: San Diego

I have some 35’s on my 19’ f350 and the speed is off 10%.
So if I’m doing 70 on the speedo I’m actually going 77.

You can go into forscan and change the #’s to get a correct reading if you want to.

Oct 28, 2024 | 09:56 AM

WXboy

Logistics Pro

Joined: Sep 2002

Posts: 4,411

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From: Central KY

I have 35x12.50R18 on my '19 and GPS shows that I'm 3 MPH off at interstate speed, 2 MPH off on slower highways. Not a big deal. As the tread wears down it'll get closer to reality.

Oct 28, 2024 | 10:06 AM

ZooDad

Retired guy fixn stuff

Joined: Mar 2009

Posts: 3,220

Likes: 1,230

From: East TN

Ford’s “acceptable “ speedometer variances are 7% plus or minus.

ZooDad

Oct 28, 2024 | 10:07 AM

ZooDad

Retired guy fixn stuff

Joined: Mar 2009

Posts: 3,220

Likes: 1,230

From: East TN

Quote:

Originally Posted by wmeads

Try the tire size calculator in the ForScan sticky. It will get you close.

ZooDad

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Oct 29, 2024 | 07:42 AM

Florit17

Mountain Pass

Joined: Sep 2016

Posts: 243

Likes: 33

From: Montana

Been running 35/12.5/20's on my 2017 since 200 miles on the clock. MPH has always been within about 1-2 mph, accurate enough for me. I run about 60 pounds of pressure so I used Forscan to eliminate the low pressure TPMS notification.