10.5” vs 12.5” tire width?

KCNoDots said:
FWIW I have the Dana 44/30 with 3.73, 35s, 5spd, 4.0, and I am getting about 12mpg mixed. When i was on 31s, I was getting about 14.5mpg mixed. I think most of the drop is from the computer miscalculating rather than the actual tire. Since the tires circumference is about 110" for a 35" vs 97.4" for a 31". Which is about a 13% difference. And the 12mpg vs 14.5mpg is about a 20% difference. So most of the poorer mpg number is just the sheer miscalculation of the computer IMO.

Power is definitely different however, 5th is nearly useless on the freeway if there is the slightest grade with the 35s. I am planning on going to 4.88s.
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The drop in mpg is not caused by the computer miscalculating anything, it's caused by your engine operating inefficiently/lugging at too low of an rpm with the 35's and 3.73 gear ratio. Raise the engine rpms to a more appropriate level with lower ratio gears like 4.88 or 5.13 and your mpg will go up. I was getting an accurate sub-12 mpg with 35's with 4.88 gearing due to the too low of an rpm the 4-speed automatic transmission was causing despite the 4.88 gears.... the 4-speed automatic's Overdrive cuts the rpms by 31% which caused the engine to lug on the highway. Yes the speedometer was recalibrated to be dead-nuts on. Replacing the 4.88 gears with 5.38 last year raised my mpg to the high-14's.
 
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I should add, this is not our daily driver. It is stored in the garage for the winter. It will be a warm weather fun driver! We may take it on a trip or 2, and I think the 33’s will be much more practical. Long story short, I am personally sold on moving to 33’s, talk me out of it.
 
Yes, 33" tires will be a much closer match to your gear ratio and more in balance with your existing steering, suspension, and brakes than your existing 35's. It is a logical and well thought out course of action that would be lauded by experienced jeepers far and wide.

But your wife has spoken. Best to wait until you can get a screaming hot deal on new tires and the weather is better before you raise the subject again.
 
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Mr. Bills said:
Yes, 33" tires will be a much closer match to your gear ratio and more in balance with your existing steering, suspension, and brakes than your existing 35's. It is a logical and well thought out course of action that would be lauded by experienced jeepers far and wide.

But your wife has spoken. Best to wait until you can get a screaming hot deal on new tires and the weather is better before you raise the subject again.
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Even in marriage, sometimes better to ask for forgiveness than permission! You know, for the betterment of the TJ, of course.
 
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Jerry Bransford said:
The drop in mpg is not caused by the computer miscalculating anything, it's caused by your engine operating inefficiently/lugging at too low of an rpm with the 35's and 3.73 gear ratio. Raise the engine rpms to a more appropriate level with lower ratio gears like 4.88 or 5.13 and your mpg will go up. I was getting an accurate sub-12 mpg with 35's with 4.88 gearing due to the too low of an rpm the 4-speed automatic transmission was causing despite the 4.88 gears.... the 4-speed automatic's Overdrive cuts the rpms by 31% which caused the engine to lug on the highway. Yes the speedometer was recalibrated to be dead-nuts on. Replacing the 4.88 gears with 5.38 last year raised my mpg to the high-14's.
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I did not mean it was entirely just the computer. But it is somewhat. That is why my speedo reads 60mph when my gps speedo reads 67mph. The Jeeps computer simply thinks I am still on my stock sized tires :)
and I do agree that lugging is a definate large factor as well!
 
KCNoDots said:
I did not mean it was entirely just the computer. But it is somewhat. That is why my speedo reads 60mph when my gps speedo reads 67mph.
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That's only because you haven't changed the speedometer gear to recalibrate your speedometer which is only about a 5 minute job with a 1/2" wrench. The computer can only interpret the data that is sent to it and if the speedometer gear is generating inaccurate info, the speedometer will be inaccurate... garbage in, garbage out.

http://www.4x4xplor.com/speedo.html
 
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Jerry Bransford said:
That's only because you haven't changed the speedometer gear to recalibrate your speedometer which is only about a 5 minute job with a 1/2" wrench. The computer can only interpret the data that is sent to it and if the speedometer gear is generating inaccurate info, the speedometer will be inaccurate... garbage in, garbage out.

http://www.4x4xplor.com/speedo.html
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thanks Jerry!
 
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If I stay with the 35’s for now, what parts should I expect to wear out first? Might just roll with them for now and put money into other places on the Jeep. Eventually swap to 33’s and fix/correct whatever needs it at that time. Again, our TJ has Dana 44/30 and will see more pavement than dirt.
 
I dont like slinging shit from fat tires, its against the law here to have your wheels uncovered...

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I do lots of highway driving in bad weather. I prefer the skinnier tire as it is less likely to hydroplane. And feels much more stable when you hit standing water.

Wider tires offer better floatation at low speeds which is the only reason to buy them, if you need floataion, or a bigger aired down footprint.
 
Back to my question: If I stay with the 35’s for now, what parts should I expect to wear out first? Might just roll with them for now and put money into other places on the Jeep. Eventually swap to 33’s and fix/correct whatever needs it at that time. Again, our TJ has Dana 44/30 and will see more pavement than dirt. I have read so much on the pros and cons of tire width, no need to debate here.
 
Mikester86 said:
Back to my question: If I stay with the 35’s for now, what parts should I expect to wear out first? Might just roll with them for now and put money into other places on the Jeep. Eventually swap to 33’s and fix/correct whatever needs it at that time. Again, our TJ has Dana 44/30 and will see more pavement than dirt. I have read so much on the pros and cons of tire width, no need to debate here.
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For the mostly street use of your 35's I wouldn't be worried about accelerated wear on anything other than your brake pads. Perhaps your OE factory tie rod, in case you run into something.
 
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Ball joints, U joints, everything can wear more with bigger tires, it just depends on how you are on the skinny pedal
 
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