Largest tires with current mods
Lead Driver
Joined: Apr 2011
Posts: 8,259
Likes: 346
From: Northern California
use the RPM calculator to see how tire size affects your rpm at a given speed
Calculators
you want to select a gear ratio that will put your final drive ratio close to what the factory setup was. that will give you close to the same MPG as the factory tire size and gear ratio.
by going to a larger tire you are going to lose some MPG from the change in wind resistance, and larger contact area of the larger tire as well as the additional weight.
your MPG while towing will always be lower simple because you are moving more weight and depending on the trailer, wind resistance.
Calculators
you want to select a gear ratio that will put your final drive ratio close to what the factory setup was. that will give you close to the same MPG as the factory tire size and gear ratio.
by going to a larger tire you are going to lose some MPG from the change in wind resistance, and larger contact area of the larger tire as well as the additional weight.
your MPG while towing will always be lower simple because you are moving more weight and depending on the trailer, wind resistance.
Logistics Pro
Joined: Jan 2014
Posts: 3,595
Likes: 17
4.30's and 37's seem to be the best match up for the 7.3. If it's already taking a lot of throttle to get moving, might I suggest delving into that first? At least ensure everything is in top shape before throwing giant tires under there.
Personally I'm on V's with a 2" drop kit and mod-B's. 35's are a good, somewhat snug fit.
Personally I'm on V's with a 2" drop kit and mod-B's. 35's are a good, somewhat snug fit.
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,246
Likes: 761
From: Houston, Texas
Largest tires with current mods
Originally Posted by 2002exPSD
But how much are 4.10's going to affect mpg? I get 14 mpg hauling my trailer.
I've found those online calculators to be wrong more than they are right. If you need to find out what gears your need for the tires you're running, the formula is very simple:
New tire size/old tire size x Desired effective ratio= correct gear ratio
In my case with Rudolph:
34.6/31.6 x 3.73 = 4.08 or 4.10 gears.
With 4.10 gears and 35s Rudolph gets good fuel economy but is also able to tow the heaviest of loads and not break a sweat or anything else. Running a 6.0 trans cooler, the temps rarely go above 150 even with it being 400 degrees outside.
37/31.6 x 3.73 = 4.36 or 4.30 gears
If you're a v10 guy who tows a lot:
37/31.6 x 4.30 = 5.03 or 5.13 gears
35/31.6 x 4.30 = 4.76 or 4.88 gears
Moderator
Joined: Jul 2010
Posts: 12,050
Likes: 1,549
From: Media PA
If you're rocking 35s, then 4.10 gears are what you should have if you want an effective ratio of 3.73.
I've found those online calculators to be wrong more than they are right. If you need to find out what gears your need for the tires you're running, the formula is very simple:
New tire size/old tire size x Desired effective ratio= correct gear ratio
In my case with Rudolph:
34.6/31.6 x 3.73 = 4.08 or 4.10 gears.
With 4.10 gears and 35s Rudolph gets good fuel economy but is also able to tow the heaviest of loads and not break a sweat or anything else. Running a 6.0 trans cooler, the temps rarely go above 150 even with it being 400 degrees outside.
37/31.6 x 3.73 = 4.36 or 4.30 gears
If you're a v10 guy who tows a lot:
37/31.6 x 4.30 = 5.03 or 5.13 gears
35/31.6 x 4.30 = 4.76 or 4.88 gears
I've found those online calculators to be wrong more than they are right. If you need to find out what gears your need for the tires you're running, the formula is very simple:
New tire size/old tire size x Desired effective ratio= correct gear ratio
In my case with Rudolph:
34.6/31.6 x 3.73 = 4.08 or 4.10 gears.
With 4.10 gears and 35s Rudolph gets good fuel economy but is also able to tow the heaviest of loads and not break a sweat or anything else. Running a 6.0 trans cooler, the temps rarely go above 150 even with it being 400 degrees outside.
37/31.6 x 3.73 = 4.36 or 4.30 gears
If you're a v10 guy who tows a lot:
37/31.6 x 4.30 = 5.03 or 5.13 gears
35/31.6 x 4.30 = 4.76 or 4.88 gears
I'm a V-10 guy that pulls 11,000lbs about 70% of my EX's miles, the combination of my 35" tires and 4.88 gears is great, much better performance AND (towing) mileage!
Lead Driver
Joined: Apr 2011
Posts: 8,259
Likes: 346
From: Northern California
If you're rocking 35s, then 4.10 gears are what you should have if you want an effective ratio of 3.73.
I've found those online calculators to be wrong more than they are right. If you need to find out what gears your need for the tires you're running, the formula is very simple:
New tire size/old tire size x Desired effective ratio= correct gear ratio
In my case with Rudolph:
34.6/31.6 x 3.73 = 4.08 or 4.10 gears.
With 4.10 gears and 35s Rudolph gets good fuel economy but is also able to tow the heaviest of loads and not break a sweat or anything else. Running a 6.0 trans cooler, the temps rarely go above 150 even with it being 400 degrees outside.
37/31.6 x 3.73 = 4.36 or 4.30 gears
If you're a v10 guy who tows a lot:
37/31.6 x 4.30 = 5.03 or 5.13 gears
35/31.6 x 4.30 = 4.76 or 4.88 gears
I've found those online calculators to be wrong more than they are right. If you need to find out what gears your need for the tires you're running, the formula is very simple:
New tire size/old tire size x Desired effective ratio= correct gear ratio
In my case with Rudolph:
34.6/31.6 x 3.73 = 4.08 or 4.10 gears.
With 4.10 gears and 35s Rudolph gets good fuel economy but is also able to tow the heaviest of loads and not break a sweat or anything else. Running a 6.0 trans cooler, the temps rarely go above 150 even with it being 400 degrees outside.
37/31.6 x 3.73 = 4.36 or 4.30 gears
If you're a v10 guy who tows a lot:
37/31.6 x 4.30 = 5.03 or 5.13 gears
35/31.6 x 4.30 = 4.76 or 4.88 gears
I've found those online calculators to be wrong more than they are right. If you need to find out what gears your need for the tires you're running, the formula is very simple:
/QUOTE]
The formula for rpm is also simple math but you need to know the gear ratios in your transmission to calculate it. But to demonstrate how a diff gear change affects your engine rpm the one I linked to is close enough for government work
Senior User
Joined: Feb 2013
Posts: 135
Likes: 0
From: Port Coquitlam, BC
I've done a custom 4" lift with the larger block from an F-350 in the rear and I run 295 70 18s and the only adjustment I had to do was create a bracket to suck the front inner fenders back a bit to stop the rub. I have the same offset the truck came with so I'm tucked nicely and I clear all around. With 4", 37s would be a real pain for me.
I pull heavy so I had 4.30s installed giving me an effective 4.0 and I'm in the fat of the power. I do lose out on top end speed so I don't push the Ex beyond 70mph but where I live, 60mph is the common. I'm happy with the choice to re-gear to cope with the larger tires.
I pull heavy so I had 4.30s installed giving me an effective 4.0 and I'm in the fat of the power. I do lose out on top end speed so I don't push the Ex beyond 70mph but where I live, 60mph is the common. I'm happy with the choice to re-gear to cope with the larger tires.
Posting Guru
Joined: Feb 2015
Posts: 1,092
Likes: 0
2" bigger diameter.
Good looking EX!
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Senior User
Joined: Jan 2012
Posts: 309
Likes: 0
I have 285.70.17s if that helps the OP. I have no mods yet but will be doing modded x/b codes. Supposed to be around 4inch but we will see. iv got the leafs, just gotta get springs and other parts before i do the mod.
Thread
Thread Starter
Forum
Replies
Last Post
98cobra1064
1973 - 1979 F-100 & Larger F-Series Trucks
34
Jul 5, 2006 02:28 PM