Speedo question

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Apr 12, 2025 | 06:33 AM

yeet

Thread Starter

Tuned

Joined: Feb 2023

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Speedo question

Hi Guys,
95 F 150 4x4. I'm running the stock tire size of P235-75R15 on the truck now. I'm going to be getting new tires soon and will be putting on 31x10.5 R15's. What effect will this change have on the speedometer readings?

Thanks,
Jeff

Apr 12, 2025 | 07:08 AM

tjc transport

i ain't rite

Joined: Mar 2005

Posts: 65,446

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From: Marlboro Mental Hospital.

going to a 31 inch tire will make your speedometer read about 60 when actually doing 64. the good thing about your 95 is the speedometer can be recalibrated easily for the new tire size. if i remember correctly you can recalibrate the PSOM 6 times.

Apr 12, 2025 | 09:25 AM

yeet

Thread Starter

Tuned

Joined: Feb 2023

Posts: 278

Likes: 86

Quote:

Originally Posted by tjc transport

Thanks!!

Apr 12, 2025 | 10:08 AM

Conanski

FTE Legend

Joined: Jun 2006

Posts: 31,930

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From: Ottawa, Ontario

The speedo in consumer vehicles tends to read a bit fast by design so before recalibrating test it against a GPS app to see if it really needs any adjustment, in my experience the move to 31" tires should just bring it closer to actual.

Apr 13, 2025 | 07:05 AM

manicmechanic007

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Joined: Jul 2020

Posts: 10,331

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From: Near Salt Lake City

I would reprogram it with one of these Ford NGS scan tools
It'd take me about 5 minutes with mine
Not sure of how many times it's allowed myself, either 5 or 6, I think 5 times