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OT/Tire Advice

Discussion in 'Uncategorized Threads' started by esoxhunter, Feb 18, 2008.

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  1. esoxhunter

    esoxhunter Well-Known Member

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    Hey gang. I need some advice on tires. My SUV has 235/70/16 tires on it. They need replacing. I was thinking of going up a size. (245/70/16) Would this be advisable? I am thinking with a bigger tire it would give a little better gas mileage. (The engine would turn less RPM's) I understand my speedometer will be a little off and my acceleration might suffer a little; but 90% of my driving is highway driving anyway. Or will the gas mileage gain be negligible and not worth the effort? Thanks. Ed
     
  2. porky

    porky TS Member

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    You could get 235/75/16 tires and the mileage would be better and your speedodometer would be off, but not that much. In going to a larger( 245 vs 235) you would not gain due to the increased tire width gaining more friction and causing the engine to work harder due to the increased tire surface contact. Hilly country would be even worse with the larger tires. If you have ever seen any of the contests where the drivers are given a premeasured amount of gasoline and drive until the gasoline is gone, the tires that are used are tall skinny tires, not big fat ones. Big fat tires are used for traction and that is only practical when you have a lot of weighht on them to keep them from hydroplaning in water and on slippery surfaces. But the fact is that big fat tires cause the engine to work harder and decrease milage considerably.
     
  3. miketmx

    miketmx Well-Known Member

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    In my Jeep Cherokee, I went from 225/75 R15 to 235/75 R15. The gas mileage is probably about the same but now my odometer registers a tad less miles for the same distance traveled and now my speedometer is more accurate because it used to show a higher speed than it was really doing. Not much difference either way but I had more options in light truck tires by going to the larger size. I bought a new Jeep Patriot and so far there are very few tires made in the new size 215/65 R17. I hope there are more options when it's time for new tires.
     
  4. RGS Guy

    RGS Guy TS Member

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    We have a 2003 Yukon, that came with the 70 series tires. They are all the "P" series, meaning passenger. The vehicle was a little hard to keep on track at highway speeds. Others I talked with had similar experiences. The SUV’s are all truck frame vehicles, and no way a truck should have “P” passenger car tires. They put them on for the soft ride. I put on a set of the same size tires, but as they don't make an "LT" (light truck) in those 70 series tires, I opted for the highest speed rating I could find, to cut down on tire side wall squirm. It worked, and the vehicle is a lot more highway friendly.

    If I was doing it over though, I would definitely put on a 75 series “LT” of close to the same diameter. you can find the diameter on most tire sales web sites. The slightly narrower tire would also be a little better in the snow, and far better handling.
    You can find 8 ply "D" rated LT tires that will give a good ride, with far better handling.
    Best pricing was tirerack.com or tiredepot.com

    I also have an 05 Sierra pickup, that I tried putting the next size up tire on, and the truck was always searching for gears on the highway. Going up even a small grade, it downshifted. Found no improvement in mileage either. Put those on one of my other trucks & went back to stock size. Better.

    My diesel truck had no problem with larger tires, because the high low end torque of the diesel has no problem with the higher gear ratio an oversize tire duplicates.

    Nick
     
  5. Bruce Specht

    Bruce Specht Well-Known Member

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    You could move up one size with out any problems as far as your ABS, or ECM.
    Anti Lock Brakes, Engine Control Modual. Your thought about increasing in size helping gas milage all though well thought out is flawed. The flaw is that as the tire increases in diameter it all so increases in over all width. The increase in width will have an adverse effect on your gas milage. One of the posters, suggested changing sizes to a 75 series aspect ratio tire which would increase gas milage. Be advised that you should not alter O.D. overall diameter by more that 10% or there could be problems with the electronics on your vehicle. If you want to find good tire sizes for your vehicle check at www.tirerack .com the site is a wealth of information. Or stop by a tire dealer and they can advise. Beware of mass merchandizers NTD,Sears,Pep Boys etc as their staff are not well trained.
     
  6. trapshootin hippie

    trapshootin hippie Well-Known Member

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    If you are looking for increased mileage, put larger tires on the back the back than the front. By raising the back end the vehicle will always be going downhill, there fore the better mileage.

    Gne J
     
  7. sako2115

    sako2115 TS Member

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    Feb 4, 2008
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    I'd not go up in size; if you want more load capacity, get an LT tire in the same factory size. Also consider: Going up in size raises the height of the vehicle. That also hurts fuel mileage due to more air drag, not a lot, but some.
     
  8. perazzitms

    perazzitms TS Member

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    The difference in sidewall height is 6mm (that's millimeters) from a 235/70 to a 245/70. In other words, it ain't squat. You won't gain fuel mileage, or anything else for that matter. I have to ask -- why change? I could see going from a 235 to a 265 if you drove in loose sand or dirt, but otherwise........

    Also, the 245/70/16 is not a common tire. That's the OEM tire size for my SUV. Tire choices (especially when they're on sale) is more limited than the far more common 235/70 series tire.
     
  9. spitter

    spitter Well-Known Member TS Supporters

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    I'm in the same boat. I have Michelins 235 70/16s. I spoke at length to my tire guy and he gave me his wholesale price guide.

    Going to a 235/75 does a couple things.

    1) Tires are less expensive going to a 75 series
    2) 75 series profile, will increase load bearing capacity (nominal)

    Also to increase tire life, inflate t0 85-90% of inflation maximum

    Jay
     
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