Taller tires / gearing question

[100acrehuphalump]

v_man
I found what you posted earlier. I'm really really math anxious. I kinda glanced it over at first. My bad. So I just need to pick a tire size and then change the gearing accordingly? I really didn't want to go higher than 33" tires, and I definitely wanted to go taller as opposed to wider. I didn't consider added weight to be an issue either. Especially going with an E rated tire. Thank you, that's a huge help.


Old Gear Ratio × New Tire Size ÷ Old Tire Size = New Gear Ratio

So you have 3.55 gears, you have 30 inch tires right now , and let's say you want to move up to 35 inch tires ...

3.55 x 35 / 30 = 4.14 , so 4.10 gears would be a good starting point when considering a re gear for the 35" tire size...

 

[1stDeuce]

If you want a quick and dirty answer, you'll be fine bumping 1" or even 2" unless you're constantly towing the max rated capacity. If you're towing or hauling, and use the towing mode, it should do a pretty good job of managing shifts better. Or if you're driving and it's very hilly and you find it shifting a little too often, just pull it out of OD until things level out. Certainly not worth the expense of regearing for 1-2" of tire size increase. Staying with a narrow tire will minimize the loss in performance. Don't forget to get the speedo corrected though. I think most Ford dealers will do it for free if you bump tire sizes, but not sure. Worth asking at least!!

 

[100acrehuphalump]

Thanks Deuce. What deuce do you have? Are you on SS? I am under the same name.

 

[tommudd]

Interesting answers, I always regear when going to larger tires to keep the engine in the area they most like to run.
Pays for itself usually in 50,000 or less miles with less wear and tear on the engine and transmission.
Of course i build all of mine to last a long time since i never trade / sell until they have at least 275,000-300,000 miles
Since the OP is going to be hauling a camper ( if I remember right) and on hilly area etc I'd think it would be beneficial as well
But then maybe thats why I hear so many complain that with lifts and larger tires they lose so much gas mileage ( they never regear)

 

[100acrehuphalump]

Interesting answers, I always regear when going to larger tires to keep the engine in the area they most like to run.
Pays for itself usually in 50,000 or less miles with less wear and tear on the engine and transmission.
Of course i build all of mine to last a long time since i never trade / sell until they have at least 275,000-300,000 miles
Since the OP is going to be hauling a camper ( if I remember right) and on hilly area etc I'd think it would be beneficial as well
But then maybe thats why I hear so many complain that with lifts and larger tires they lose so much gas mileage ( they never regear)

.

Wow that's great to know. I'm learning as I go. So I'm guessing with lifts, larger tires and regearing you will gain clearance and mpg will either stay the same or decrease only a little because of the higher COG and taller = more wind resistance. But with proper gearing it will be less wear and tear on the transmission/engine, and not as bad mpg loss. Awesome!

 

[chet6.7]

http://tire-size-conversion.com/gear-ratio-calculator/

 

[100acrehuphalump]

http://tire-size-conversion.com/gear-ratio-calculator/

Awesome thanks Chet!

 

[verdesardog]

My truck has 3.73 gears and I'm running 315-70-17's about a 32" tire. I have recalibrated the speedo, the truck tows fine. I do use tow haul mode when in hilly areas. Of course a diesel has better torque characteristics than a gasser.

 

[oldblue]

The most common stock tire size for this F150 with the 5.0 and 3.55 gears is a 275/65r18 - a 32.1" tire.

Since you have 17" wheels and want E rated tires you could get a 275/70r17 tire which is a 32.2" tire and readily available in an E rating.

No need to regear as Ford already uses this diameter stock.

 

[MR. ED]

I got a 13 super crew XLT with 3.55 ratio this fall. It had P rated 265-70-17s and I was getting 19.3 MPG. I threw on some 255-8-17 ST MAXX and my mileage dropped to 17.3. When I brought it in to have the computer re-calibrated for the bigger tires I still was getting 17.3 MPG. So to answer your question-Yes those gears will work. I'm planning on getting a tuner to try and get back those 2 MPGS.

I think it's the weight of the burlier tires that affects the mileage. Old tires were 42 LBS (I think) and the new ones 54(?). I also can't tell any difference in performance. Good luck.

 

[Buliwyf]

Tires are heavy. If you do go bigger and need to regear, go bigger than the 4:10 that the calculators recommend. That's the correct gear, but if you're going to spend serious $$$on gears, minus well get something with some pep. Start at 4:30. Get a locker for the rear at the same time.