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post #1 of 23 Old 10-03-2016, 06:30 AM Thread Starter
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Seeking opinions on tire size and gearing

Hello all.
I know this topic has been discussed before but not exactly to my situation. I'm having a really hard time deciding between 285/70r17 or 315/70r17 for my JKU. It's a 2008 with 265/70r17 currently and has the crap 3.8L...it's already a nightmare going up hills and merging on the highway, etc. I found an absolute steal of a deal on the 35's and would love to get them. I've read a lot that this will make the jeep even weaker and even less fun to drive on the highway. I don't do much off-roading- basically just some light trail riding on hiking trips so offroad performance is NO concern to me at all. I want to know how my highway driving and every day driving will actually be affected. I plan to purchase a tuner. The 35s are falken Rocky Mountain tires and I believe I have 3.73 gearing. I also have a 2.5" TF BB. What should I do?
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post #2 of 23 Old 10-03-2016, 06:54 AM
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Did you try the search function here? Why not post in the welcome room first and introduce yourself?

Maybe you could have googled jeep jk gearing chart. Oh wait let me do that for you.


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post #3 of 23 Old 10-03-2016, 07:01 AM Thread Starter
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Did you try the search function here? Why not post in the welcome room first and introduce yourself?

Maybe you could have googled jeep jk gearing chart. Oh wait let me do that for you.



Sorry for the quick post but I have to make my decision tomorrow morning so I needed quick advice!
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post #4 of 23 Old 10-03-2016, 07:24 AM
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Originally Posted by Chicagojeepgirl View Post
Sorry for the quick post but I have to make my decision tomorrow morning so I needed quick advice!
So what is your decision?

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If people don't take a stand now,you'll be bitches under their thumbs tomorrow.
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I think too much of a pressure variant between Earth and outer-space... lack of oxygen... something like that.
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post #5 of 23 Old 10-03-2016, 07:38 AM Thread Starter
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Originally Posted by Chicagojeepgirl View Post
Sorry for the quick post but I have to make my decision tomorrow morning so I needed quick advice!
So what is your decision?
Well...I was hoping to get some advice here. I see the chart says I shouldn't even be running the tires I am now. I'd say the chart is a little modest. I was just looking for testimonials from people with the same setup as myself. I would like the 35's, but not at the total cost of daily driving performance.
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post #6 of 23 Old 10-03-2016, 10:41 AM
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3.8 with the automatic go right to 5.13 gears with 35" tires.

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post #7 of 23 Old 10-03-2016, 12:13 PM
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I have a 3.6 manual with 3.21s with 35s. I need an incredible amount of throttle input to get going. I never stalled a vehicle so much in my life. And my jeep is lighter than yours and more "powerful" so you might be alright with your 3.73s. but I personally wouldn't go over 33s with your current set up.
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I have a 3.6 manual with 3.21s with 35s. I need an incredible amount of throttle input to get going. I never stalled a vehicle so much in my life. And my jeep is lighter than yours and more "powerful" so you might be alright with your 3.73s. but I personally wouldn't go over 33s with your current set up.
I was running 37's with 4.10 gears for over a year.

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If people don't take a stand now,you'll be bitches under their thumbs tomorrow.
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post #9 of 23 Old 10-03-2016, 01:46 PM
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We put in 4.88s on a Jeep (3.6L auto) with 35s and it's awesome on the trail (Rubicon transfer case) but rev's a little high on the freeway. I have ran 35s and 37s on 4.10s and finally installed 5.38 and love it (3.8L, auto).

If you think you will get larger tires in the future always go lower than expected. IF you think you will be running more street than trail you can be modest on your gear selection...say 4.56s.


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post #10 of 23 Old 10-03-2016, 07:44 PM Thread Starter
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Sorry I should have been more clear in the original post- I don't want to regear, ever.
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post #11 of 23 Old 10-03-2016, 08:48 PM
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Originally Posted by Chicagojeepgirl View Post
Hello all.
I know this topic has been discussed before but not exactly to my situation. I'm having a really hard time deciding between 285/70r17 or 315/70r17 for my JKU. It's a 2008 with 265/70r17 currently and has the crap 3.8L...it's already a nightmare going up hills and merging on the highway, etc. I found an absolute steal of a deal on the 35's and would love to get them. I've read a lot that this will make the jeep even weaker and even less fun to drive on the highway. I don't do much off-roading- basically just some light trail riding on hiking trips so offroad performance is NO concern to me at all. I want to know how my highway driving and every day driving will actually be affected. I plan to purchase a tuner. The 35s are falken Rocky Mountain tires and I believe I have 3.73 gearing. I also have a 2.5" TF BB. What should I do?
If you're not happy with it now, you'll want to park it with 35's.

I drove my buddies 2010 auto, 3.73, on 35's and didn't feel it was unbearable. BUT, I WANTED to like it. I was having a great time driving a "Jeep." So much so, that I went out and bought one for my self. Granted I bought a '14 Rubicon with 4.10's, I knew I was going straight to 35's.....

Is it really a "nightmare" or is it a "Jeep?" They're not built to be an autobahn cruiser. Everything on them is a compromise. Price we pay to have folks glaring enviously at us when the weathers nice and the top and doors are off.

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post #12 of 23 Old 10-04-2016, 06:00 AM
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Originally Posted by Chicagojeepgirl View Post
Sorry I should have been more clear in the original post- I don't want to regear, ever.


If you don't want to regear then expect quite a bit of drop in power when you go to the 35's. On my old '07 JK I had 35's w/ 4.10 for 3 or so years and it wasn't a nightmare to drive but I wasn't winning any races. However if your not happy with your power now, then you really wont be happy with the power after you go to 35's.

There are small things you can do to retrieve some of the lost power, but in the end re-gearing is your best bet. You can do the programmer, cold air system, exhaust system, throttle body spacer.

Or....
Go ahead and do the tires you want and save up to regear. I'm not sure what you have against regearing, but that will be the best way to give it the pep you want. I had 5.13's with 37's in my '07 when I sold it and it wasn't too bad. If your scared that re-gearing will screw up your jeep, just make sure you do your homework and find a good reputable shop that stands behind their work.

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post #13 of 23 Old 10-04-2016, 12:18 PM Thread Starter
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Quote:
Originally Posted by Chicagojeepgirl View Post
Hello all.
I know this topic has been discussed before but not exactly to my situation. I'm having a really hard time deciding between 285/70r17 or 315/70r17 for my JKU. It's a 2008 with 265/70r17 currently and has the crap 3.8L...it's already a nightmare going up hills and merging on the highway, etc. I found an absolute steal of a deal on the 35's and would love to get them. I've read a lot that this will make the jeep even weaker and even less fun to drive on the highway. I don't do much off-roading- basically just some light trail riding on hiking trips so offroad performance is NO concern to me at all. I want to know how my highway driving and every day driving will actually be affected. I plan to purchase a tuner. The 35s are falken Rocky Mountain tires and I believe I have 3.73 gearing. I also have a 2.5" TF BB. What should I do?
If you're not happy with it now, you'll want to park it with 35's.

I drove my buddies 2010 auto, 3.73, on 35's and didn't feel it was unbearable. BUT, I WANTED to like it. I was having a great time driving a "Jeep." So much so, that I went out and bought one for my self. Granted I bought a '14 Rubicon with 4.10's, I knew I was going straight to 35's.....

Is it really a "nightmare" or is it a "Jeep?" They're not built to be an autobahn cruiser. Everything on them is a compromise. Price we pay to have folks glaring enviously at us when the weathers nice and the top and doors are off.
It is my opinion that it is indeed a nightmare as it is now. When I can barely reach 60mph to merge on to the highway or pass someone without having to slam on the gas and watch the RPMs skyrocket, I'm not that happy. I had a grand Cherokee v8 for 5 years previously and that thing was a powerhouse. Don't get me wrong, my jeep is the love of my life, but I'm not trying to make it not enjoyable to drive. I want to find that balance of performance and looking BA :-) (without having to regear because it's just not in the budget any time soon and the jeep is 8 years old with 161k miles on it already)
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post #14 of 23 Old 10-04-2016, 12:49 PM
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In reality you should be looking into going down to a 30" tire not up. I ran 33's on 3.21 in my 07 JK with the 6 speed and it sucked. Thats when I was in Champaign and the biggest hill was a bridge overpass. No way would I run 35's and off road will be just as bad as on road.

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post #15 of 23 Old 10-04-2016, 12:58 PM
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Originally Posted by Uncle Sams Misguided Child View Post
Did you try the search function here? Why not post in the welcome room first and introduce yourself?

Maybe you could have googled jeep jk gearing chart. Oh wait let me do that for you.

is there a chart like this for the 3.6?
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post #16 of 23 Old 10-04-2016, 12:59 PM
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yes there is.

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post #17 of 23 Old 10-04-2016, 02:11 PM
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If you don't want to re-gear and hate the way it drives with the tires you have, you certainly shouldn't be considering bigger tires. At this point, you have two alternatives: buy smaller tires (and have your Jeep look like a scared cat with the 2.5" BB) or buy bigger tires and re-gear.

If you want 35s, get 35s. Just understand your Jeep will be a gutless wonder around town and will be constantly shifting in and out of OD on any highway with the slightest grade. Drive it for a while, roll your pennies, and re-gear later.

Or, buy the 285/70R17s, which are only slightly taller than the 265/75R17s you have, drive it for a while, roll your pennies, and re-gear later.

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post #18 of 23 Old 10-04-2016, 02:33 PM
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Quote:
Originally Posted by mvjeeper View Post
is there a chart like this for the 3.6?

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If people don't take a stand now,you'll be bitches under their thumbs tomorrow.
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I think too much of a pressure variant between Earth and outer-space... lack of oxygen... something like that.
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post #19 of 23 Old 10-04-2016, 03:15 PM Thread Starter
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Lol yeah I would never go smaller...
I think 33s and a tuner is where I'll head.
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post #20 of 23 Old 10-04-2016, 03:51 PM
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Don't expect anything from a tuner they really don't do much.

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post #21 of 23 Old 10-04-2016, 06:00 PM
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Lol yeah I would never go smaller...
I think 33s and a tuner is where I'll head.
You're not going to be happy without re-gearing. Not sure why you're so opposed to getting the correct r&p in those axles, but be warned... you're not going to dig 33's if you already hate it with the stock tires/ gearing. Re-gearing for 33's will make driving so much less frustrating... well worth the expense if set-up correctly by a qualified shop. I would also make sure to look at some lifted JKU's on 33's... proportionally speaking.

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post #22 of 23 Old 10-04-2016, 06:36 PM
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Don't expect anything from a tuner they really don't do much.
X2

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You're not going to be happy without re-gearing. Not sure why you're so opposed to getting the correct r&p in those axles, but be warned... you're not going to dig 33's if you already hate it with the stock tires/ gearing. Re-gearing for 33's will make driving so much less frustrating... well worth the expense if set-up correctly by a qualified shop.
X2

Quote:
Originally Posted by Chicagojeepgirl View Post
Hello all.
I know this topic has been discussed before but not exactly to my situation. I'm having a really hard time deciding between 285/70r17 or 315/70r17 for my JKU. It's a 2008 with 265/70r17 currently and has the crap 3.8L...it's already a nightmare going up hills and merging on the highway, etc. I found an absolute steal of a deal on the 35's and would love to get them. I've read a lot that this will make the jeep even weaker and even less fun to drive on the highway. I don't do much off-roading- basically just some light trail riding on hiking trips so offroad performance is NO concern to me at all. I want to know how my highway driving and every day driving will actually be affected. I plan to purchase a tuner. The 35s are falken Rocky Mountain tires and I believe I have 3.73 gearing. I also have a 2.5" TF BB. What should I do?
From your OP, it doesn't sound like you "need" tires right now, just found "an absolute steal" on some 35s that would look really "BA" on your rig. Looks won't be very satisfying when you hate to drive it because it's a dog (worse than it already is). And those looks won't pay for the repairs you're going to have to do down the road because you overworked/overstressed your drivetrain from trying to turn those really "BA" 35s with improper gearing. Think transmission repair or replacement; not pretty.

IMO, a better approach is to create a long term plan and work toward that plan in steps you can afford and that meet your current needs. If you don't "need" the tires yet, then do the gearing now then replace the tires when yours wear out. I'd be surprised if even your "absolute steal" is much less than the cost of a gear swap at a competent shop. Tell them what you want to accomplish and let them advise you on gearing; they're the pros and they're in your area. All of us on here could give you our opinions, but they don't come from the same place and so may be totally invalid.

Or, you could do what so many of us find so difficult -- you could do NOTHING right now and SAVE that money you'd be spending on the 35s, add some more to it while you're wearing out those awful looking tires that are on it now, and then when the need arises go for those "BA" 35s and the PROPER gears to make "the love of your life" more fun than you've ever known it to be.

For comparison, I ran 37s on 4:10s for about a year, but that was on a 3.6 Unlimited so it's already inherently more peppy than the 3.8. It was just barely workable and I was constantly concerned for my auto trans. In the hills and mountains here in California, it would "search" for the right gear too much. So to make it more fun to drive, but more importantly, to save my transmission, I bit the bullet and regeared. The 3.6 gear chart shows 4.56:1 to be the "good" daily driver gear for 37s, with 4.88s and 5.13s being "performance" gears. I went with 5.13s for a handful of reasons. 1) I intended to do most of my wheeling in the Sierras and I drive to the trails -- no trailer queen. 2) I pull a relatively heavy trailer, often on those wheeling trips into the Sierras, and the lower gears will more easily pull that load. 3) At the recommendation of my gear shop, who brought up the real situation that those 37s create a greater flywheel effect than 35s or 33s, and so have a bigger impact on drivability than a person might first think. The 5.13s definitely cost me some top end on the freeway, but I can still get above legal speeds pretty easily, so it's kind of a moot point. I'm running 200-300 rpm higher at 70 MPH now than I was with the factory 4.10s and stock rubicon tires (whatever size those were -- can't remember).

Your area and your goals may require a different approach, but I would suggest that with your 3.8, your drivability with 35s and 4.10s might compare to mine with 37s and 4.10s. So it will be even worse if you leave your 3.73s in place. Bottom line to what I understand is a long post, is that I would urge you to re-think your plan and not make a spur-of-the-moment decision that you may regret later on. And the worst case scenario would be that you regret it and don't know why it happened so you dismiss your Jeep as "a piece of junk," when a better-thought-out plan could have REALLY made it the love of your life.

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post #23 of 23 Old 10-05-2016, 07:08 AM
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Don't expect anything from a tuner they really don't do much.
What dirtman said. No noticeable difference from my flashpaq. It did a great job turning off the TPMS light and calibrating the speedo when I went to 35's. I do run the 93 octane tune, it's not my DD, and my perception is that it runs a little better on this tune. Again, zero discernible power gain (on 35's).

If I was unhappy with my on-road performance as it sits now I would not go with larger tires without either a gear or LS swap......

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