new tires
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Hotshot
Joined: Dec 2005
Posts: 10,253
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From: Chino Valley, Arizona
new tires
I have just purchased a '97 F250 PSD 4X4 and I need new tires so my question is what is the best size tire to get my RPM's down at highway cruise,
ZF5 trans<O
4.10 gear ratio? <O
at 70 mph I am at 2700 rpm<O
I would like to slow down the engine and try to get better mileage<O
ZF5 trans<O
4.10 gear ratio? <O
at 70 mph I am at 2700 rpm<O
I would like to slow down the engine and try to get better mileage<O
Posting Guru
Joined: Apr 2004
Posts: 1,424
Likes: 0
From: AZ
What size do you have on it now?
I think with my 265-75-r16 tires I am right at 2500 rpm at 70 mph. Same set up as yours (97 f-250, zf-5, 4.10, 4x4)
If you want to lower the rpms you will have to go with a taller size, but because of this added resistance you will probally not see any increase in fuel milage.
I know that with 265-75 tires my speedometer is off 1-2 mph, the original size 235-85 tires are just a hair taller.
What kind of mpg are you seeing now?
I think with my 265-75-r16 tires I am right at 2500 rpm at 70 mph. Same set up as yours (97 f-250, zf-5, 4.10, 4x4)
If you want to lower the rpms you will have to go with a taller size, but because of this added resistance you will probally not see any increase in fuel milage.
I know that with 265-75 tires my speedometer is off 1-2 mph, the original size 235-85 tires are just a hair taller.
What kind of mpg are you seeing now?
Postmaster
Joined: Aug 2004
Posts: 3,948
Likes: 2
From: SHELTON, WA
i have a similar setup except an f350. i run 33's and my rpms at 70 are 24XX.
i have my speedo calibrated exactly also. i run bfg all terrains. 33X12.5x16.5.
the only problem you may have is the 250's sit about 2" lower than a 350. i am sure you can fit em with a little shimming of the front bumper. if you decide to go with them let me know and i will get my psom code for you so you dont have to do the guess work.
i also get 16 mpg mostly. i also have quite a few mods that help that though too.
i have my speedo calibrated exactly also. i run bfg all terrains. 33X12.5x16.5.
the only problem you may have is the 250's sit about 2" lower than a 350. i am sure you can fit em with a little shimming of the front bumper. if you decide to go with them let me know and i will get my psom code for you so you dont have to do the guess work.
i also get 16 mpg mostly. i also have quite a few mods that help that though too.
Postmaster
Joined: Apr 2004
Posts: 3,658
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From: Ellensburg, Washington
you can stuff a 35 under a stock height 250. you just need to buy a bumper relocation kit that moves it out about an 1'' or 2''. looks good i think. I run 265 bfg all terrains and i love em. i had the 235 tires and scrapped em the first day, to small i thought. you can easily fit a 285, which is the same as a 33'' tire, by getting a set of add-a-leaves up front. bought 80 bucks or so. I got a buddy who did this, looks really nice. goin from a 235 to a 265, you really wont notice a diffrence in mileage or rpm really. just my .02 cents worth. I am a tire guru if i do say so myself, lol, dad owns a rim and tire business so i been around it my whole life. like it matters im sure, lol. i would go with 265's personally b/c you wont have to spend any money on suspension or bumper mods. hope this helps
Thread Starter
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Hotshot
Joined: Dec 2005
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From: Chino Valley, Arizona
This helps a lot, I am looking for the most for my money and everything I have found makes me believe that any mileage change will be lost in the cost of the rims and the higher priced tires, so I am off tomorrow to buy new tires. 1 week too late as the left rear threw all of the tread off at 70 MPH and did about $1000.00 damage to the bed. Than today I started to get a pull to the left and a vibration so I took back roads home and drove slow. When I got home my right front was severely separating. Gotta love those Generals
Originally Posted by powerstroked162
you can stuff a 35 under a stock height 250. you just need to buy a bumper relocation kit that moves it out about an 1'' or 2''. looks good i think. I run 265 bfg all terrains and i love em. i had the 235 tires and scrapped em the first day, to small i thought. you can easily fit a 285, which is the same as a 33'' tire, by getting a set of add-a-leaves up front. bought 80 bucks or so. I got a buddy who did this, looks really nice. goin from a 235 to a 265, you really wont notice a diffrence in mileage or rpm really. just my .02 cents worth. I am a tire guru if i do say so myself, lol, dad owns a rim and tire business so i been around it my whole life. like it matters im sure, lol. i would go with 265's personally b/c you wont have to spend any money on suspension or bumper mods. hope this helps
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Hotshot
Joined: Dec 2005
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From: Chino Valley, Arizona
Ok I am guilty I like big tires so I went with the 285/75R16 Dunlop AT 8 ply rating on 8X16 Eagle rims, I do believe I sat a little higher in the seat on the ride home
Lead Driver
Joined: May 2000
Posts: 9,236
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From: Senoia, GA
i run 315/75R16 and its about the perfect tire size. i drive interstate at least twice a week and my mileage (if i stay below 75MPG) is about 18-19.
the only time i wish i had a touch smaller tires is pulling up the real steep hills of N. Carolina and Tenn. she will really bog down with 8K lbs on my g/n heading up some of those hills but thats why i got my chip! that really helped too!
-cutts-
the only time i wish i had a touch smaller tires is pulling up the real steep hills of N. Carolina and Tenn. she will really bog down with 8K lbs on my g/n heading up some of those hills but thats why i got my chip! that really helped too!
-cutts-