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post #31 of 36 Old 11-13-2013, 09:39 PM
WidowYj91
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Ive also never had a problem knockin it over to 5th at 45 mph and cruisin around 1900 rpm... And my jeep is heavy with the winch, bumpers, spare, sliders and a hardtop in the winter.


'91 YJ,2.5L, 5spd, 1.25" BL, O.M.E 36r springs, 32x11.50 km2's,
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post #32 of 36 Old 11-14-2013, 10:30 AM
GrantYJ
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There's more to it than just the tire diameter. Different styles and brands of the same tire size weigh vastly different amounts which has a huge effect on drivability. Wheel weight also plays a big role. My Jeep with the MPFI 2.5 and 4.10 gears does better now with 33" 12.50 15 Hankook Dynapro MTs on aluminum 8" Centerline Hellcat wheels than it did with 31" 11.50 15 Kumho MTs on aluminum 10" American Eagle wheels.

Also, My nephew has 33" 12.50 15 Baja Claws on steel wheels on his 2.5 TJ with about 150k less miles than my YJ and I can run off and leave him.

“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values
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post #33 of 36 Old 11-14-2013, 08:31 PM
Tom95YJ
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31's w/o regearing anything larger you'll have to regear. 33's & 4.88 are great 4.88's and 35's are ok but 5.13's would be better. My buddy Brian has been running 37's and 5.38's behind his 2.5 for about 10 years. And his Yj is a heavy sob. Running Psc crusher corners , rochochet rockers , tube fenders with 6" flares , full cage Waggy D44's ........ It drives fine on road and better offroad

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post #34 of 36 Old 11-14-2013, 10:18 PM
GrantYJ
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Originally Posted by Tom95YJ View Post
31's w/o regearing anything larger you'll have to regear. 33's & 4.88 are great 4.88's and 35's are ok but 5.13's would be better. My buddy Brian has been running 37's and 5.38's behind his 2.5 for about 10 years. And his Yj is a heavy sob. Running Psc crusher corners , rochochet rockers , tube fenders with 6" flares , full cage Waggy D44's ........ It drives fine on road and better offroad
I understand that he's running d44s, but 4.88s are as low as you can go with the d30. As for needing to change gears above 31s ...there are plenty of folks running 33s with 4.10s (me included). I live in the Ozarks. Very steep large hills. I've got tube fenders, rock sliders, and bumpers all built from 3/16" steel (and of course tube for the fenders) as well as an 8274 up front. The little 4 banger isn't a rocket ship, but I can run 70+ on the interstate. The only time I have problems maintaining speed is with a strong headwind while going up a long hill.

I'm not saying that 4.88s wouldn't help, but saying that you "have to regear" to run 32s or taller seems a bit excessive.

“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values
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post #35 of 36 Old 11-14-2013, 10:51 PM
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Quote:
Originally Posted by GrantYJ View Post
I understand that he's running d44s, but 4.88s are as low as you can go with the d30. As for needing to change gears above 31s ...there are plenty of folks running 33s with 4.10s (me included). I live in the Ozarks. Very steep large hills. I've got tube fenders, rock sliders, and bumpers all built from 3/16" steel (and of course tube for the fenders) as well as an 8274 up front. The little 4 banger isn't a rocket ship, but I can run 70+ on the interstate. The only time I have problems maintaining speed is with a strong headwind while going up a long hill.

I'm not saying that 4.88s wouldn't help, but saying that you "have to regear" to run 32s or taller seems a bit excessive.
Once you drive a 4 cylinder that has been re-geared your thought process of running stock gears and 33's will drastically change !

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post #36 of 36 Old 11-15-2013, 12:13 AM
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Once you drive a 4 cylinder that has been re-geared your thought process of running stock gears and 33's will drastically change !
I have. It drove alright. Not exceptionally, but acceptably (much like mine with stock gears). My "thought process" is still intact and unchanged.

My daily driver is a Charger R/T. It doesn't get a whole lot more "drastic" than going from 350 hp & 400 ft lbs of torque in a car that weighs less than my Jeep to the 4 angry squirrels.

Regardless, it doesn't change the fact that on 33s I can drive interstate without issue (and I'm not a "flat land" guy). For guys out West in areas like Nevada where the speed limit is 80+ and there are mountains, I can see where there'd be a problem, but at that point 4.88s aren't going to cut it either. To do that every day, you'd want a minimum of 6 cylinders and 8 would be far better...

It's comical that people talk about changing from 4.10s to 4.88s as though it'll feel like you added another 50 hp. With 4.10 gears and 33" tires, every rotation of the drive shaft will move you approximately 25.29". With 4.88s it is 21.24". Will it give better driveability? You betcha! Will it feel more powerful? Yep. Will it "drastically change", no. It will not. You won't have to work as hard to maintain speed, but it's still a naturally aspirated 2.5 liter engine. You can only do a certain amount of work per given unit of torque.

Rotating mass is a big deal here. If you have a limited ability to do work (i.e. the torque from a 2.5) the wasted "work" from spinning a heavier wheel/tire combo can zap you of driveability. If you bump up a few posts, you'll see where I was talking about wheel and tire selection. If you have a wheel and tire combo that weighs less, it will feel (acceleration and top speed) similar to a regeared Jeep running steel wheels and heavier tires. As a side benefit, it will stop better too.

“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values
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