tire size question
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From: Rantoul, Illinois
tire size question
On my 79 right now I have 235/75/R15, I have found some 33'' tall tires with rims for cheap. I have stock gearing in the axles and i was wondering if moving to this size tire would help me with getting a little better mileage out of my truck. I know the difference in size will affect my speedometer ( it is already 10 mph off) it says I'm going faster than I actually am going. will the bigger tire help that too or make it worse? Would 31" work better?
Last edited by Fordman79; Mar 6, 2006 at 11:53 AM.
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From: In the Middle
I have found that going to a larger tire while keeping the same gears usually gets worse MPG. There is more rotating mass and you're engine will have to work harder to move the truck. It will help fix the speedo though.
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From: Louisiana
235/75/R15 are about 29" tall, my old set was the same size.
If your gear ratio is off by 10 mph with stock tires, then you might have 4.10 gears already installed, and then 33" tires would help your gas mileage on the highway alot, while bringing down the RPMs.
Is your truck 2wd or 4wd?
If your gear ratio is off by 10 mph with stock tires, then you might have 4.10 gears already installed, and then 33" tires would help your gas mileage on the highway alot, while bringing down the RPMs.
Is your truck 2wd or 4wd?
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From: Louisiana
He did say his speedo is off by about 10 mph, so that usually happens when you go with a higher(numatically gear ratio) and stay with stock tires. So he might be running 29" tires w/4.10 gears and the 33" tires would help increase gas milage.
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Post Fiend
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From: Louisiana
Yep, the odometer would be off too. My truck shows a extra mile for about every 10 miles I go, so the gas mileage will be alittle off too.
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From: Rantoul, Illinois
It won't hurt the odometer because it quite working a couple of years ago. I had to replace the rear end gear set back in 2001 and if i remember correctly the ratio is 3.55 I drive about 40 miles round trip to work 4 days a week and about 30-35 on the weekend. I use a little less than a 1/4 tank per day. Oh and it is 4x4.
Last edited by Fordman79; Mar 7, 2006 at 11:36 AM.
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From: Louisiana
If it has 3.55 then 33s won't hurt anything to much, but you won't have as good accleration off the start and you'll get a little less gas mileage in town.
33s would look good and fill in the wheel wells nice on a 1/2 ton 4x4.
33s would look good and fill in the wheel wells nice on a 1/2 ton 4x4.
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From: New Gretna, New Jersey
Originally Posted by Bdox
There is a selection of speedo drive gears to choose from to correct the speedo reading.