Help me understand what will happen if I change to a 35" tire - Jeep Wrangler Forum
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Old 03-02-2014, 02:23 AM
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Help me understand what will happen if I change to a 35" tire

Current set up is Toyo Open Country A/T IIs in 295/75/16. Weight per tire is 63.7 lbs. , width is 11.61 inches and diameter is 33.42 inches.

If I change to a GY Wrangler Duratrac in 315/75/16 the specs would be 64.4 lbs., 12.4 inches in width and 34.6 inches in diameter.

Since there is negligible weight difference between the two, could I expect no noticeable loss in power?

And what about fuel economy loss? Once again the weight difference is negligible but I'm assuming the increased tire width of the Duratrac would cause an increase in rolling resistance thus affecting my fuel economy. Am I correct here in my assumption?

I'm trying to figure out if it's worth making the change or not. The 35 envy is killing me. I just need to put this thought to rest once and for all. Thanks in advance for anyone's input.

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Old 03-02-2014, 02:27 AM   #2
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You need to be thinking about the circumference more than the diameter. Let's imagine you have a GLORIOUS TJ I6 6spd Rubicon... First gear has a ratio of 4.46... Then to the Tcase... 4:1... Then through the rear diff... 4.11... Then to the tire. You get the point... A lot of reduction in rotations.

Stock is 30.5 diameter... Pi x D = 95.77" diameter. For a 33" it's 103.6... For a 35" it's 110. You're talking about a 10% increase in diameter... So it will require 10% more "degrees" or turn, for one full revolution.

This is where those couple drinks are going to really hurt me... 4.46x4x4.11 = 73.3 rotations of the engine for one rotation of the axle. With 35s, you're going 10% less than with 30.5s.

You're talking about a lot of force there... Anything less than a Dana44 and you're talking about putting a lot of stress on the axle. D35s can survive, if properly set up. But stock JEEP D35s are not a matter of if, but when.
Editted multiple times because words are hard...

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Old 03-02-2014, 04:33 AM   #3
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As long as the offset on your wheel can accommodate an extra 1" the other differences between both tires are minor. You may not even notice the difference if you adjust the speedo and the loss in fuel economy will also be minor < 1 MPG.

Since the tire differences are relatively minor so should your envy!
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Old 03-02-2014, 05:55 AM   #4
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I didn't see this addressed anywhere so I will bring it up. How much lift are you running/ do you off road or is your Jeep pretty much pavement only?

The reason I ask......similar but not exactly the same.

In addition to my JK and JKU (both stock), I have an '04 TJ (not stock). It has an OME SL a BL and 33"s on it. When I ran the 31" x 10.50" x 15"s it did great even with the stock gears and 3.73s. And my speedometer was dead on with my Gps. (kinda makes me wonder if my mileage etc was more "optimistic" in factory trim)
After switching to my 33"s yes the power was different and 5th gear was "iffy", things I had suspected from reading on the forum, but off road is where the differences really shown. Places where I used to maybe "have little trouble" when wheeling I was now getting stuck!!! I attribute it to the 33"s and not having as much POWER to spin the bigger tires, the other issue I ran into was when turning in the woods on anything other than level ground, the 12.50" wide 33"s would rub and or hit the sway bar, even when fully Discoed. Which would result in the sway-bar dropping down coming loose from being tied up/ secured so that it was up out of the way.

My "fixes" have been to regear to 4.88"s and remove the front sway bar. While this is not the ideal solution it is working, "for now". A Currie antirock is in the Plans for the front end, along with a few more mods...but that doesn't really apply to your question.

Bottom line if I never went off road, I would not have needed the regear. and if I had stayed with 10.50"s I probably wouldn't be running without front sway bar.

If your Jeep is a "Pavement Princess", as my '12 and '14 are it might not mean as much to you, if you wheel it, that is when you will really see the short comings of gears and clearance.

Sorry for long post but IMO it can not be answered with out addressing all the other aspects. Good Luck!!
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Old 03-02-2014, 06:06 AM   #5
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Quote:
Originally Posted by FloridaFeMan View Post
Current set up is Toyo Open Country A/T IIs in 295/75/16. Weight per tire is 63.7 lbs. , width is 11.61 inches and diameter is 33.42 inches.

If I change to a GY Wrangler Duratrac in 315/75/16 the specs would be 64.4 lbs., 12.4 inches in width and 34.6 inches in diameter.

Since there is negligible weight difference between the two, could I expect no noticeable loss in power?

And what about fuel economy loss? Once again the weight difference is negligible but I'm assuming the increased tire width of the Duratrac would cause an increase in rolling resistance thus affecting my fuel economy. Am I correct here in my assumption?

I'm trying to figure out if it's worth making the change or not. The 35 envy is killing me. I just need to put this thought to rest once and for all. Thanks in advance for anyone's input.
You didn't mention what year you had. So I don't know what engine you have. This makes a huge difference. My 2014 does just fine turning 37s on stock 4.10s. I average 13.6mpg without really trying to get good fuel mileage. I could probably squeeze 15 if I tried. This is mixed driving city and highway
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Old 03-02-2014, 06:35 AM   #6
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Circumference, roll resistance, tire/wheel weight ,and the wrong gear ratio are the four killers to MPG.
In your case the weight is not a issue, but the other three are.........

Nobody can answer as to how much it will affect you, because your driving habits, and where you drive, will also play a major part in it..........
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Old 03-02-2014, 06:50 AM   #7
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(I have nothing to offer you technically, but your "35 envy" phrase truly made me smile {{and I feel I, too, might be catching it}}. Good post.)

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Old 03-02-2014, 08:31 AM   #8
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You will be fine. Go for the 35's

Your profile says 14 Unlimited Sahara, 2.5 inch lift, 3.73 gears, in Florida?

Go get your tires, you know you want to. Sell the old ones on Craigslist. MPG won't change enough to notice, nor will power, but that might be different for the Duratracs, since they have such awesome grip.

I have 32 inch Duratracs I put on in winter, and my MPG drops from the 35 inch Kelly Safari TSR's I run in the good weather. Even though the Kelly's and Goodyear's are "sister" tires, made in the same plants, the tread design and tire compound is just different enough to make the MPG different.

Remember, though, Duratracs aren't a "true" 35. You will lose height on the Duratracs when mounted, so you will actually only have around 33.8 mounted, depending on air pressure. See what your Toyo's actually measure mounted first.

That's a lot of coin for what could end up being a minor improvement. Oh, yeah, I would at least get gussets put on the front, too.
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Old 03-02-2014, 08:43 AM
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To clarify questions others have asked:

1. Year: 2014
2. Transmission: automatic
3. Gearing: 3.73
4. Lift: 2.5"Rubicon Express
5. Driving habits: My daily driver; on-road, mainly flat as I live in Florida; commute to work is about 15 minute drive of combined residential/interstate.
6. No immediate off-road plans. Yup it's pavement princess/mall crawler or whatever else you wanna call it but bottom line is it makes me happy driving it.

Thanks for everyone's replies thus far.
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Old 03-02-2014, 08:45 AM   #10
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Quote:
Originally Posted by FloridaFeMan View Post
To clarify questions others have asked:

1. Year: 2014
2. Transmission: automatic
3. Gearing: 3.73
4. Lift: 2.5"Rubicon Express
5. Driving habits: My daily driver; on-road, mainly flat as I live in Florida; commute to work is about 15 minute drive of combined residential/interstate.
6. No immediate off-road plans. Yup it's pavement princess/mall crawler or whatever else you wanna call it but bottom line is it makes me happy driving it.

Thanks for everyone's replies thus far.
Based on this go ahead and switch...but when or if you ever offroad plan on some changes
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Old 03-02-2014, 09:13 AM   #11
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Quote:
Originally Posted by FloridaFeMan View Post
To clarify questions others have asked:

1. Year: 2014
2. Transmission: automatic
3. Gearing: 3.73
4. Lift: 2.5"Rubicon Express
5. Driving habits: My daily driver; on-road, mainly flat as I live in Florida; commute to work is about 15 minute drive of combined residential/interstate.
6. No immediate off-road plans. Yup it's pavement princess/mall crawler or whatever else you wanna call it but bottom line is it makes me happy driving it.

Thanks for everyone's replies thus far.
I wheeled all day yesterday with a couple with the exact setup and 35s. Did just fine offroad. And he said if seems fine on road as well. Eventually you may find yourself wanting to gear up. But really the pentastar and auto trans really make up the difference quite well on their own.
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Old 03-04-2014, 12:19 PM   #12
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The Dunlop 35x12.5R15 MT's only weigh 58 lbs.
Matched to lightweight aluminum wheel you could be close to the stock Rubicon 73lb tire/wheel combo.
If weight is the major concern it might be an option.

I bought 5 of them for 1K from DTD, using Allied bead lock wheels so I'm at 85 lbs per tire mounted. 12 lbs over stock. With 4.10's, manual trans and Penstar they run fine.
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Old 03-18-2014, 11:29 PM   #13
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Got 35"x12.5r17 trail grapplers I average 15+ mpg with tire psi at 35
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Old 03-20-2014, 02:17 PM   #14
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Pros:
  • More aggressive stance
  • More clearance
  • More offroad capable

Cons:
  • 1-2 MPG less
  • Slight hit to performance
  • More wear and tear on steering components

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