I realize that this particular subject is not specific to any year or type of vehicle. I also know that it's probably been addressed many times in the past. However, I'm still trying to get the hang of how things work on this web site! I just wish I had enough time to check out everything else that's available!

I recently replaced & upgraded the tires on my truck. I don't really remember the name of the manufacturer of the tires I replaced. However, I do remember that the size of my old tires was LT 245/75 R16. The new set of tires I put on my truck are Michelin LTX A/S, size LT 265/75 R16.

This is what I think I know about tire sizes:

The "LT" indicates that it's a "Light Truck" tire.
The next three numbers "265" indicate height of the tire.
The next two numbers "75" indicate the width of the tire.
The "R" means it's a "Radial" tire.
The last two numbers "16" indicate the inside diameter of the tire.

Please feel free to correct me if any of the information I've provided is incorrect!

This is what I don't know about tires:

Q: What was the original size of the "standard" tires Ford put on these trucks?

Q: How much does increasing the height/diameter of tires affect the speedometer/odometer readings?

Q: What affect does increasing the tire size have on MPG?

Since increasing the size of my tires, my odometer is now registering .85 mile for every actual mile that I travel.

Q: What do I need to do to correct this problem?

Many thanks to everyone for your patience with all my questions & especially for all of the great assistance you have already provided!

I noticed that I've finally been promoted from a "New User" to a "Freshman User". I guess this means that I'm going to have to get on the stick & learn the correct area's to ask my questions in the future!

"LB"

 

(25.4mm to the inch)

P265 is the metric width (tread) of the tire = 265 mm

That is like a 10.5 " tire

75 = the height of the tire as a % to the width
Otherwise known as sidewall aspect ratio

ie: 75 is 75 % of 265 mm = 198.75mm from road to rim

R is Radial

16 = 16" rim size


Tires also have speed rating & side ratings
~~~~~~~~~~~~~~~~~~~~~~~~~~

Q: What was the original size of the "standard" tires Ford put on these trucks?

On 4x2 F250's ....anywhere from 7.50 -16 to 9.50 -16 depending on GVWR


Q: How much does increasing the height/diameter of tires affect the speedometer/odometer readings?

The taller the tire the slower the speedometer reading

Q: What affect does increasing the tire size have on MPG?

at highway speed ,,,lowering the Rpm of the engine ...should increase fuel economy (all things considered).

although, it takes more consumption to start off

Since increasing the size of my tires, my odometer is now registering .85 mile for every actual mile that I travel.

Q: What do I need to do to correct this problem?

Change the transmission speedo gear

http://www.tciauto.com/tech_info/speedo_gears.htm

 

Your original tires were on 16.5" rims.

Tire section approx equivalents:
================================
195 = F = 7.75"

205 = G = 8.0"

215 = H = 8.5"

225 = J = 9.0"

235 = L = 9.25"

Old tire size data:

http://www.coker.com/
Just enter the tire size in the search box and check the details.

The 9.5 x 16.5 was 31" in diameter.
The 8.75 x 16.5 was 29.4" in diameter.

Check the Read First: FAQ thread at the top of the 73-9 forum for additional info.