tire size vs speedometer

Reply Subscribe

Thread Tools

Search this Thread

Nov 10, 2014 | 09:42 PM

speedybill

Thread Starter

Trailering

Joined: Nov 2014

Posts: 16

Likes: 0

tire size vs speedometer

I have a 99 F-350 crew cab
I just put new tires on up 2 sizes from stock , stock=215r85/16, now 235 will this make the speedo off? & by how much, any 'formulas'??

Thankx, Bill

Nov 10, 2014 | 10:16 PM

Ltngdrvr

Lead Driver

Joined: Nov 2005

Posts: 8,459

Likes: 4,955

Speedo is off from the factory, you might have made it closer to being right with the new tires.

Tire size calculator here: Tire Size Calculator - Tire & Wheel Plus Sizing

Nov 10, 2014 | 10:32 PM

EXv10

Post Fiend

Joined: Mar 2009

Posts: 11,798

Likes: 14

From: Mt. Shasta California

Quote:

Originally Posted by speedybill

I have a 99 F-350 crew cab
I just put new tires on up 2 sizes from stock , stock=215r85/16, now 235 will this make the speedo off? & by how much, any 'formulas'??

Thankx, Bill

That is now the same diameter as the 265/75-16 on the stock Ex. My speedo is accurate but I guess you could just guess at it and not get a ticket.

Nov 10, 2014 | 10:58 PM

351Cleveland C4

Lead Driver

Joined: Jul 2011

Posts: 8,679

Likes: 191

From: On the Edge of the Desert

It should be right on now actually.

Nov 11, 2014 | 04:34 AM

redford

FTE Leadership Emeritus

Joined: Sep 2000

Posts: 23,174

Likes: 1,678

From: Stephensville WI

Do you have a smart phone? Get a GPS Speedometer application to find out how far off your truck speedometer is.

Nov 11, 2014 | 06:03 AM

ATC Crazy

Hotshot

Joined: Jun 2003

Posts: 12,340

Likes: 4,361

From: SW VA

Quote:

Originally Posted by redford

Do you have a smart phone? Get a GPS Speedometer application to find out how far off your truck speedometer is.

This is a good idea. I downloaded one (Speed bot) a few months ago and it seems to be pretty dang accurate.

At an indicated 35mph, I was doing 39mph. At 60mph, I was actually going 67mph.

Stock on mine was 245/70/17...I went to 285/75/17.