Gas milage issues
#1
Gas milage issues
I recently purchased a1985 Ford Bronco with the 300 I6 and Np 435. I was getting about 18-23 mpg at first. Now I get about 7-9 mpg. The only thing I changed was the tires. At first I had 235/75/15. Now I have 31x10.50/15. The tires are about a 1/2" taller than the factory tires. I have never been much on Ford but I fell for this one . Would the tires change the mpg that much? Is there anything I can do to get better gas mileage that won't cost over a few hundred dollars. I bought the truck for $700 and have invested $4000 in small repairs. Windshield, clutch, tires, wheel bearings, fluids, etc. Any info will be greatly appreciated. Thanks for your time.
#2
235 is 9.25 inches
6.9 inches high, 15 inch wheel
15+14=29 inches diameter
So you went from 29 inches to 31 in the diameter
and you went from 9.25 inches wide to 10.5 inches wide
and your new tires might weigh significantly more than your old ones.
29 pie=91 inches, 63360/91=696 revolutions to go 1 mile
31 pie=97 inches, 63360/97=653 revolutions to go 1 mile
odometer reads 1 mile at 696 revolutions
Odometer with new tires reads 1 mile but actual mileage is
6 percent more
6.9 inches high, 15 inch wheel
15+14=29 inches diameter
So you went from 29 inches to 31 in the diameter
and you went from 9.25 inches wide to 10.5 inches wide
and your new tires might weigh significantly more than your old ones.
29 pie=91 inches, 63360/91=696 revolutions to go 1 mile
31 pie=97 inches, 63360/97=653 revolutions to go 1 mile
odometer reads 1 mile at 696 revolutions
Odometer with new tires reads 1 mile but actual mileage is
6 percent more
#3
235 is 9.25 inches
6.9 inches high, 15 inch wheel
15+14=29 inches diameter
So you went from 29 inches to 31 in the diameter
and you went from 9.25 inches wide to 10.5 inches wide
and your new tires might weigh significantly more than your old ones.
29 pie=91 inches, 63360/91=696 revolutions to go 1 mile
31 pie=97 inches, 63360/97=653 revolutions to go 1 mile
odometer reads 1 mile at 696 revolutions
Odometer with new tires reads 1 mile but actual mileage is
6 percent more
6.9 inches high, 15 inch wheel
15+14=29 inches diameter
So you went from 29 inches to 31 in the diameter
and you went from 9.25 inches wide to 10.5 inches wide
and your new tires might weigh significantly more than your old ones.
29 pie=91 inches, 63360/91=696 revolutions to go 1 mile
31 pie=97 inches, 63360/97=653 revolutions to go 1 mile
odometer reads 1 mile at 696 revolutions
Odometer with new tires reads 1 mile but actual mileage is
6 percent more
#4
what gear ratio do you have? I bet its 3.08's in which case you could probably swap over a later year bronco front/rear diff to get 3.55's and see a great boost in performance. anytime you increase the tire size though your going to loose mpg not just due to tire size but also the vehicle being taller.
#5
what gear ratio do you have? I bet its 3.08's in which case you could probably swap over a later year bronco front/rear diff to get 3.55's and see a great boost in performance. anytime you increase the tire size though your going to loose mpg not just due to tire size but also the vehicle being taller.
#6
#7
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#8
Just bought a 2 barrel carburetor. What do I need to do to swap it out. I have read to use efi manifolds. What's the difference in the manifold that I already have. I was just planning on using a flat plate 2 to 1 adapter. The carburetor is a 9T motor craft. I'm hoping I can just swap it with no problems. Any suggestions are greatly appreciated. Thanks for your time.
#9
I have an 83 Bronco, 6 cyl, NP435, 3.55 gears (stock) and 31" tires. I'm still getting in the high teens on the freeway.
You have something wrong with your truck and its not the tires. Too large a drop in mileage to be from tires alone.
If your truck is not running pig rich you must have a fuel leak somewhere. Brakes dragging?
You have something wrong with your truck and its not the tires. Too large a drop in mileage to be from tires alone.
If your truck is not running pig rich you must have a fuel leak somewhere. Brakes dragging?
#10
I have an 83 Bronco, 6 cyl, NP435, 3.55 gears (stock) and 31" tires. I'm still getting in the high teens on the freeway.
You have something wrong with your truck and its not the tires. Too large a drop in mileage to be from tires alone.
If your truck is not running pig rich you must have a fuel leak somewhere. Brakes dragging?
You have something wrong with your truck and its not the tires. Too large a drop in mileage to be from tires alone.
If your truck is not running pig rich you must have a fuel leak somewhere. Brakes dragging?
#11
#12
Thanks for the advice. I have a 1648 alumacraft boat. I pulled it to the lake for the first time the other day. The lake is in the mountains of Henry county. The hills are terrible, by the time I got to the top I was in first gear. Do you think a 2 or 4 barrel carb would help out on the pulling power.
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Big John Hance
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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02-23-2013 04:24 AM