Tires and Gears
11-03-2019, 10:25 AM
#1
JK Newbie
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Tires and Gears
I have a 2015 Wrangle Unlimited, I just upgraded the tires to 265/70R17s and ultimately want to go to 33 when these wear out. I do not have a great deal of interest in going over 33 and will only lift it 2 ½ at the most. This is a daily driver with the occasional excursion off road to go fishing.
My question is in re-gearing the JK what ger ratio do I want to go to that will work with the 33, and give me a little more low end torque, but not kill the gas mileage..
The shop Im dealing with keeps saying need to go to 4.88s and not to worry it will only kick the RPM up about 50 at 70, but I think hes nuts. But he insists it will still be in the green eco zone
Bryan
My question is in re-gearing the JK what ger ratio do I want to go to that will work with the 33, and give me a little more low end torque, but not kill the gas mileage..
The shop Im dealing with keeps saying need to go to 4.88s and not to worry it will only kick the RPM up about 50 at 70, but I think hes nuts. But he insists it will still be in the green eco zone
Bryan
11-03-2019, 03:46 PM
#2
JK Junkie
Bryan, what the current ratio, and is it an auto or manual transmission?
11-03-2019, 04:39 PM
#3
JK Jedi Master
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Forget gears for now. Get the tires and drive it - then see what YOU think of the performance.
But, do a quick Google search on a phrase like "jeep jk rpm chart". A bunch of images of the same basic charts will come up. Pick the one with the 3.6 engine, find your transmission, and then it's just plug and play --> use actual measured tire heights if you can!!
The metric conversion for those 265/70/17's shows 31.6", so for an example we'll use 31" measured height. (though 30.5 is likely more accurate...) And for a non-rubicon, you have either 3.21 or 3.73, so easy enough to plug in. Using 3.21 in the example.
3.21, 31", auto = 2022 rpm @ 70 mph
4.88, 31", auto = 3074 rpm @ 70 mph (3074 - 2022 = 1052 rpm increase at 70)
But, do a quick Google search on a phrase like "jeep jk rpm chart". A bunch of images of the same basic charts will come up. Pick the one with the 3.6 engine, find your transmission, and then it's just plug and play --> use actual measured tire heights if you can!!
The metric conversion for those 265/70/17's shows 31.6", so for an example we'll use 31" measured height. (though 30.5 is likely more accurate...) And for a non-rubicon, you have either 3.21 or 3.73, so easy enough to plug in. Using 3.21 in the example.
3.21, 31", auto = 2022 rpm @ 70 mph
4.88, 31", auto = 3074 rpm @ 70 mph (3074 - 2022 = 1052 rpm increase at 70)
11-03-2019, 05:55 PM
#4
JK Super Freak
Build one thing at a time, and keep in mind your use. If you aren't rock crawling, don't go too low. Stick with the gears you have, and see how they do. With 2.5 lift, you will likely end up looking at 34s and 35s. (You can easily clear 35s with 2.5 even with full factory fenders. (Ask me how I know)).
Get to the tire size you want, make sure you're happy, and then regear accordingly going by the charts.
All tires run small mounted under load, so usually jumping down a size on what the chart says is appropriate. If you're looking at 33s, go by the numbers for 32s, if you're looking at 35s (315/70r17) look at the numbers for 34s.
Regearing is something you want to do only once.
Get to the tire size you want, make sure you're happy, and then regear accordingly going by the charts.
All tires run small mounted under load, so usually jumping down a size on what the chart says is appropriate. If you're looking at 33s, go by the numbers for 32s, if you're looking at 35s (315/70r17) look at the numbers for 34s.
Regearing is something you want to do only once.
