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Discussion Starter #1
I have put a 4" lift and 33" on my 302 5spd and had my mpg drop to 12mpg. I did the 6litre tune up and was upwards of 17-18mpg on 31"'s.
I am going to look at some stock diameter wheels and tires this weekend so I can run those since it will be my DD in winter and I want to be able to tow again.

Is this worth it, for 100$ I will get wheels and tires. I will save the 33" for play in the spring and don't mind swapping them when I need. I will also tow a small travel trailer next year on smaller tires for camping as the dodge is gutless.

Opinions or experiences please.



96 FSB 302, 5spd, 3:55, 33" Goodyear duratracs, eaton truetrac
 

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I have 32" on my bronco (no lift) and actually picking up the stock 235/75-15 tires and some aluminum wheels to try and gain back some MPGs.
 

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When you put the lift/tires on, did you re-calibrate the spedo and odometer? Obviously larger tires skew both and would change your mileage calcs if the larger tire diameter isnt accounted for.
Additionally, anytime you change the unsprung weight (wheels, tires, brake calipers) you will affect the mileage. More unsprung weight requires more torque and HP, and thus require more gas (and will also reduce acceleration numbers). This is why you see those little rice burners running aluminum rims with low profile tires; they are reducing their unsprung weight.
 

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Here's a good link to compare tire sizes and their effects on mph and mileage:

http://www.1010tires.com/tiresizecalculator.asp

If you compare a 31/10.5 R15 to a 33/10.5R15, you will see your spedometer reading almost 4mph lower, and you will actually travel 6% further than the odometer reads.
 

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Discussion Starter #6
No I did not update speedo. I do know per my gps I am going 5mph faster than indicated on cluster. I also added a warn 8274 up front and custom bumpers with receivers. Even with those add ons I was 17mpg consistent. That was a lot of weight but the 33" upgrade hurt more so.

Went deer hunting with dodge and trailer it averaged 10mpg holly piss I know the bronco can do better with a small 3k trailer and smaller tires
 

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When you put the lift/tires on, did you re-calibrate the spedo and odometer? Obviously larger tires skew both and would change your mileage calcs if the larger tire diameter isnt accounted for.
Additionally, anytime you change the unsprung weight (wheels, tires, brake calipers) you will affect the mileage. More unsprung weight requires more torque and HP, and thus require more gas (and will also reduce acceleration numbers). This is why you see those little rice burners running aluminum rims with low profile tires; they are reducing their unsprung weight.
How would brake calipers affect mileage? They do not rotate.

Not only rice burners benefit from lightweight aluminum wheels, any car regardless of make or country of origin benefits from lighter wheels.
 

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Discussion Starter #8
Dex that link was awsome thanks. Thinking if I might be better off spending that on re doing speedo before I jump the gun here.
 

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I'm not sure why no one else has mentioned it ... but GEARING GEARING GEARING - dont change your speedo CHANGE THE GEARING.

My bronco on 35's, 3.55's, 6-liter tune up, full exhaust and a ton of other mods still only got shit mileage when I had my AOD. After the c6 it was worse, but that's kind of irrelevant.

Gearing is a big part of your vehicles drivetrain, and is a direct corespondent with tire size. Go to 4.10's, trust me, not only will your CITY miles increase, and highway may as well depending on your driving habits. Most people drive sub-city. Some stop and go, some free open road. This WILL be effected by your larger tire and stock gear ratio. Also, keep in mind, you have just added about 100 lbs of rolling force to not only the total weight of the truck, but extra load bearing on your gears due to the increased leverage of the tire.

4.10's are basically the equivalent to a stock ratio on 29's - change the gears and let us know how it goes.
 

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How would brake calipers affect mileage? They do not rotate.

Not only rice burners benefit from lightweight aluminum wheels, any car regardless of make or country of origin benefits from lighter wheels.
My bad on the calipers, I meant to say brake discs/drums.

I just used the rice burners as an example, you are correct all vehicles benefit from lighter unsprung weight.
 

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Discussion Starter #11
Yes I plan on 4:11 my prob is I already dropped a whad of $$ on the truetrac which is limited to 3:73 at it biggest. If I want 4:11 that's new gears, bearings and a new trutrac as I love it now in 3:55.
Wondering if it's worth dropping another 1k on a rig worth 2.5k at best per insurance.
Per the link Dex provided I Might as well enjoy it as is, fix the speedo.
 

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This is from Racing, not the street. When we run the big Right Rear 102" circumference on an Aluminum Wide 5 15" x 14" wide rim we burn 4.5 gallons in 25 laps running a 6:02 rear.
Now when we go to a STEEL RIM with the 102" and change NOTHING else we burn 5.1 Gallons in the SAME distance. It is the difference in the weigh that the engine must over come to get the wheel rotating.
This would hold true in the street world as far as GETTING the vehicle up to speed BUT if you run a bigger tire and do check on teh highway your millage would be better or at lease it should be since on Rotation of the tire you would travel a longer distance.
Do not try this with your FSB might hurt it a little.
 

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Tires are a big source of drag. I once read an article about passenger cars in a wind tunnel. Engineers were able to reduce drag by more than 50% by removing the tires. This was on a passenger car with much lower drag than a truck. Truck bodies, height off the ground, and larger tires all increase drag and ruin mileage.
 

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Wondering if it's worth dropping another 1k on a rig worth 2.5k at best per insurance. .
Vehicle and the dollar value of such will usually prohibit making modifications as rarely will the initial cost of even the parts for the modifications be totally recouped when selling the vehicle.

The big question is really how well you like your vehicle and what is the ownership value to you personally and will the proposed additional modifications increase your satisfaction of the vehicle?

Ownership of a vehicle such as a full size Bronco is becoming more of an I own it because I want it and I like it and accept its drawbacks (such as limited mpg.) to a degree because of that. Also now as the years are rolling by super nice clean examples of these trucks are becoming more scarce in the marketplace as it has been 16 years since the last of them rolled off the Ford assembly line. It will not be so long before these vehicles will be considered a "classic" and their comes a certain pride in owning and driving a super clean vehicle that you do not see everywhere you look.

From a personal viewpoint Detroit is not making anything today that I would prefer to own over the Bronco and a nicely set up Bronco has loads more character in my eyes than any current production vehicles. That alone makes the Bronco a better choice and add in that anything new that is worth buying today will set you back 30 grand or more then the dollars I spend modifying the Bronco seems like a bargain. Add in the cheaper insurance rates and vehicle ownership taxes even increase the advantage more.

All depends on what you consider important I guess.
 

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Vehicle and the dollar value of such will usually prohibit making modifications as rarely will the initial cost of even the parts for the modifications be totally recouped when selling the vehicle.

The big question is really how well you like your vehicle and what is the ownership value to you personally and will the proposed additional modifications increase your satisfaction of the vehicle?

Ownership of a vehicle such as a full size Bronco is becoming more of an I own it because I want it and I like it and accept its drawbacks (such as limited mpg.) to a degree because of that. Also now as the years are rolling by super nice clean examples of these trucks are becoming more scarce in the marketplace as it has been 16 years since the last of them rolled off the Ford assembly line. It will not be so long before these vehicles will be considered a "classic" and their comes a certain pride in owning and driving a super clean vehicle that you do not see everywhere you look.

From a personal viewpoint Detroit is not making anything today that I would prefer to own over the Bronco and a nicely set up Bronco has loads more character in my eyes than any current production vehicles. That alone makes the Bronco a better choice and add in that anything new that is worth buying today will set you back 30 grand or more then the dollars I spend modifying the Bronco seems like a bargain. Add in the cheaper insurance rates and vehicle ownership taxes even increase the advantage more.

All depends on what you consider important I guess.
I agree 100% that the FSB is on the up and coming collection list since a LOT of them have been trashed or modified for off road or just plain rotted away from the salt and snow. We jumped on ours since it was about as perfect as you can find in a 1986.
 

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as you increase the tire size the you will decrease your MPG's mainly due to the amount of drag and weight of larger tires. two things you NEED to do to regain gas mileage (and dont expect 17mpg's with 33's)....1-reprogram the speedo or change the speedo gear (which ever yours is) and 2-spend the money and regear the truck. mileage in the teens is possible. i get 13mpg's with 35's but i'm running 4.88 gears and a manual tranny (that got me an extra 3 mpg's alone). expect to get about an extra 2-3mpg's regearing it.
 

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I have a 6" lift, 35" BFGs, steel rims, 4.10 gears, and a 3 speed auto, and I'm still getting 16.5-17.5 on highway... In town is another story though......
 

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Just using an online gear/tire calculator and assuming the stock ratio in your truck to be 3.55 with a factory 29" tire it Seems that installing a 33"tire would make your final ratio compare to be along the lines of having a 3.12 gear ratio installed compared to factory stock.

Also it would also appear that to return the final drive ratio with the 33" tires back to comparable with that which came factory with the 29" tires the gear ratio would need to be a 4.04.

As previously mentioned the larger wider tires both weigh more and have a higher rolling resistance as compared to the smaller factory tires so a 4.10 ratio would put you back with the larger tires to about where your Bronco was in relation to the final gear ratio with the factory height tires.

Another consideration would be that the factory final ratio is a general range that works best in most areas and usage of the general population, not automatically what is best for you and your usage and the type of terrain where you live.

I have owned more than one vehicle which I felt the factory gearing would be well suited if I lived in Florida or near the coast where everything is pretty well flat but where I live close to the mountains with little terrain not being up and down hills of some fashion the final gear ratio was too high for the engine to remain in its torque curve without a lot of downshifting and would have benefitted greatly from being a lower ratio from the factory.

In my area I would consider a 4:30-4:56 range good for 33's and a 4:56-4:88 range good for 35's. Your area may be different.

In the old days of kick down linkages and adjustable vacumn modulators dialing in your shift points was pretty easy. Your speedometer just told you how fast you were supposed to be going.

Todays vehicles use the speed sensor and ecm to control your shift points so the same information that tells your speedometer what to read also affects at what point your transmission will make its shifts so correcting this will put your shift points back to where they are designed to be.

Now if the online gear calculator I used is correct then installing 4.10 gears w/ 33" tires in your application will take care of the speedometer/shifting issue because the vehicle speed will be very close to being back to reading where it would with factory gears and factory sized tires.

When going to a larger tire you really need to regear your vehicle to at least a ratio that puts it back close to original. Most factory gear offerings without a trailer towing package puts the highway rpm range at about the lowest rpm range that has suffecient torque to maintain speed trying to get the best EPA mileage numbers they could get.
 

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Discussion Starter #19
I plan on keeping it as long as possible. It is a winter vehicle/camping/hunting rig that you are right I can not buy now days for what I paid for it. 2500 purchase price with another 3k in fixes and upgrades means it stays. I will start saving for 4:11 or lower perhaps with a truetrac. Figure another 1k then for gearing does that sound about right. I do my own gearing.
 

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When I first picked up this 93 I was getting between 11 and 13 MPG with 33" tires and stock gears. After maliking sure there was no drag on the brakes and bearings, 6L tune, 3g alt and e-fan I get between 14 and 17 MPG (depending on my driving habits) with the e-fan being the single biggest gain. Even with that, I only get 9 to 10 MPG while towing. The only way you're going to Chang that, is by changing your gears. Its just the nature of the beast. IMHO.
 
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