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Help with tire size

1468 Views 17 Replies 13 Participants Last post by  rickwhoo
I have an ‘09 Unlimited X with 35” tires and a 4” lift. I need new tires for the harsh winters. I found a deal on 37” tires. Will these fit?
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Why does a harsher winter require larger diameter tires?


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I think she just found a deal on 37s and wants to know if they will fit. They will clear the fenders with a 4" lift, but depends on the backspacing of the wheel if they will rub on sharp corners.
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Just so she ain’t buying that size for better winter traction as all else equal it would be worse or no better for winter traction

But a higher center of gravity does make vehicle roll over easier if you slide and hit something


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It is probably not as good of a deal as you think.....
37s put a lot more load and stress on the steering, brakes, and drivetrain. Do you have the right gears, Is your Jeep a Rubicon with Dana 44? There are many things needed to make a jeep safe and/or comfortable to drive with 37s. I would think with a little time you should be able to find a good deal on 35s.
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First picture is my jeep with the 35” and second and third pictures are the 37” I’m looking at
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First picture is my jeep with the 35” and second and third pictures are the 37” I’m looking at
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That extra 2” of tire is expensive. The cost to properly run 37’s is dramatically higher than the cost to run 35’s.
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That extra 2” of tire is expensive. The cost to properly run 37’s is dramatically higher than the cost to run 35’s.
It’s more or less a pavement princess
I get this feeling you are already set on getting these tires. Yes....you can put them on. But as others have said.....to do it right will be expensive. If you run these tires you run the risk of breaking things. Wearing out items quickly. To repair these will cost you more. Just be prepared if you do get them.
Your Jeep could handle the tires but how are you geared (3.73, 4.10, 4.56)?
The answer to your question is, yes, they will fit.
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@Peyton S have you ever ridden a 10 speed bike of any kind? If you have, you know how difficult it is to start off from a dead stop in a taller gear. The same applies to larger (taller and wider) and heavier tires. The amount of stress placed on the engine, transmission, drive shafts, differentials, brakes and axles multiplies pretty significantly. While it seems an easy question, "will they fit" the mechanical side of that question is not so easy. The upgrades required to keep form breaking things rather quickly and the ability to stop is really compromised.

In addition, "will they fit" is not just will they fit in the wheels wells with your setup, since it is a wider tire as well, are your wheels offset enough to allow the additional width? Factory wheels absolutely do not. Some might say use a spacer between the wheel and hub. Bad idea. All of that rotating mass moving, flexing, turning will break an axle rather quickly.

Unless you've got somewhere in the ballpark of $10k to upgrade everything to run that big a tire, then no, they wont fit.
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The new larger tires may fit. But you may have clearance issues at the front bottom corner of the rear fender wells, where your tube step bar is. If you have adjustable control arms for the rear axle you can adjust them to move the axle back a little.
If your only concern is "will they fit" and not how well they will work, there is the answer. They should fit aside for an area of concern at the bottom front corner of the rear fender well. There is also the question of backspacing, do the wheels have enough backspacing to fit tires that wide? Since you have not indicated how wide the 37's are, or what backspacing the wheels have, it would be impossible to answer.

That said, you may find that, even on the street, they 37's don't work well. They will make your gearing, whatever it is now, taller. That will reduce the performance of the Jeep, making it slower and putting more load on the engine and transmission. They will also reduce the effectiveness of your brakes. They will make steering, turning the wheels left and right, harder. That will be more noticeable at a stop or at lower speeds. They will put more loads on the wheel bearings, axle shafts, and ball joints. And it will put more load on the steering linkages and steering box.
If none of those things matter to you, have at it. Don't get me wrong, I like 37's, and run them. But I have spent a lot of money to do it right. I have regeared, upgraded the D30 front axle, added hydro-assist steering, upgraded to larger brake disks, upgraded the ball joints, replaced wheel bearings, upgraded axle shafts, have adjustable control arms, and more. I did all that to make the 37's work as well as I can. But you do what you want. I can't see it from my house.
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not to mention that those do not look like they would work very well on the street in the snow.....just judging by the tread blocks and not know what tire that is. I actually put on smaller all terrain tires in the winter.
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Something I just noticed, you have a 2009. This means you have the 3.8 V6 and possibly the 4 speed automatic. The tires will fit, but that is not the issue. You absolutely HAVE to regear the axles to run 37's. You also have the weaker Dana 30 front axle. You cannot practically gear that Dana 30 low enough for 37's. With the 3.8 V6, you need to go to at least 5.38 gears for 37 inch tires. Even 5.13 gears are pretty weak in a Dana 30. Even if someone was giving you a set of brand new 37 inch tires, you would still need to spend thousands of dollars to upgrade your front axle and regear. 2 inches doesn't sound like much, but it's a huge jump from 35's to 37's!
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I think I will convince her stay at 35 or under for her winter tires and wheels... I'm the one who works on all our vehicles and I don't want to replace more than we have to. The whole front end has been completely replaced with bigger and better parts already. Not sure of the gearing currently in it. I'll figure that out. Thanks for the help tho...
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