I'm putting together my build for the upcoming 2020 Diesel Wrangler and I'm going back and forth about 35" vs 37" tires. I've scoured various forums, but trust this one the most (most reasonable and down to earth people who are least prone to flame wars). Any advice from those living with 35's vs 37's. This is both my overland/offroad rig and my daily driver. I plan to tow a turtleback expedition trailer as well. I'm considering this clearance, mechanical wear on the vehicle, availability of replacement tires you end up needing more after you use you spare, overall weight, etc. Any advice, especially experiential advice of how its been if you lived with both would be great. Thanks in advance to any replies!
35" vs 37" tires for Jeep Rubicon Unlimited w/ Turtleback Trailer
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Pathfinder I
I've researched this as well over the last year or so and came to this conclusion: if money weren't an issue, I would go 37's. That little bit of extra height is nice and the Jeep's rolling on 37's always catch my eye.
However the jump up in necessary mods to accommodate the extra 2"s is close to double. I say that from the perspective of building out everything to make as stable as possible.
Considering that, 35's are 95% as capable as 37's with significantly less strain and less cost. You're probably not rock crawling with your trailer, maybe you're towing it to a location that you'll unhitch and crawl for the day?
My opinion on 37's: not enough tangible gain for the cost. However, if I had the money to do it right? Yeah, I'd roll on 37's because I like the look.
However the jump up in necessary mods to accommodate the extra 2"s is close to double. I say that from the perspective of building out everything to make as stable as possible.
Considering that, 35's are 95% as capable as 37's with significantly less strain and less cost. You're probably not rock crawling with your trailer, maybe you're towing it to a location that you'll unhitch and crawl for the day?
My opinion on 37's: not enough tangible gain for the cost. However, if I had the money to do it right? Yeah, I'd roll on 37's because I like the look.
Everything Tupenny just said... I loved my jeep on 37s, but they're so much more expensive, little harder to find, and the accompanying mods really add up.
I used to wheel on 35s and DD on 37s, as it was much safer on my JK drivetrain.
Our GX470 is on 35s and I think I'll be stopping there, lol.
I used to wheel on 35s and DD on 37s, as it was much safer on my JK drivetrain.
Our GX470 is on 35s and I think I'll be stopping there, lol.
It's a rubicon. I was planning on having to upgrade the differential and possibly the transmission for 37's.
You won't have to do anything to the transmission but you'll want a re-gear for 37's
Pathfinder I
4.56 with a manual trans will probably(?) give you a close to stock feel with all the extra weight. Manual trans is much more forgiving than auto when going big. If it were me, going 37's, and a trailer and an auto trans, I would def be looking at 4.88. Anything to reduce strain...
I don't think a manual transmixer is going to be available on the deezil. I know it isn't going to be available with the deezil Gladiator. The 8 speed ZF though is a very forgiving transmission and I agree that with 37's 4.88 or better will be required.
Enthusiast III
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I know the JL 44s are a newer generation then my JK 44's, just not sure how much stronger they are. I stuck with 35s due to the costs associated in upgrading the front 44 to handle my type of wheeling. If you are just running light trails, you might be able to get away with 37s, but I would be saving to beef up the front or to pay for repairs.
My plan is to slowly start modding my front 44 while running 35s. Once the mods are completed and I got full life out of the 35s I will look into 37s.
My plan is to slowly start modding my front 44 while running 35s. Once the mods are completed and I got full life out of the 35s I will look into 37s.
Advocate I
That's really not the case on JL/JTs, especially since the diesel will be auto-only. The 8 speed auto has a very deep first few gears, the total spread runs: 4.71 1st, 3.13 2nd, 2.10 3rd, 1.67 4th, 1.28 5th, 1:1 6th, 0.84 7th and 0.67 8th. The stick DOES have a deeper 1st (5.13) but from 2nd on it's not as deep going 2.63 2nd, 1.53 3rd, 1:1 4th, 0.81 5th, 0.72 6th (so I guess the six speed's 2nd overdrive is deeper than the auto, lol). Combined with an unlocked torque converter at low speed and the crazy torque the diesel will produce down-low, I think an auto diesel JL will be WAY more forgiving than a gasser with the stick when "going big." I honestly expect people to find the stock Rubicon 4.10s to be fine on 35"s with the diesel, in fact, it'll be interesting to see if Jeep still fits 4.10s to Rubis with the diesel, or if they go with something like a 3.73 to better-suit the powerband.
So, that said, if I was building a diesel JL/JT the practical side of me says "stay with 35"s." They'll likely run fine with the stock gearing, stock trans, etc. With a 35" tire there will be a bit less drivetrain wear and tear, but I think people are attributing too much of that to SIZE alone. Wheel offset (and therefore scrub-radius) and overall wheel/tire combo weight will have as much or more to do with wear and tear and driving "feel" as the 1" radius difference between a 35" and 37" tire. For example, a heavy 35" M/T on a set of steelies with beadlocks is going to be harder on things than a lighter 37" A/T on a high-quality, light set of non-beadlock AL wheels. A 37" on a wheel that doesn't much increase scrub-radius will have less impact on steering components and hubs than a 35" pushed way out with a wild offset.
At the end of the day a JLUR on 35"s with an appropriate lift and fenders allowing full-flex and a good driver will go further and do more than 99% of Overlanders want to even consider. The ~1" of extra ground clearance from a 37" and slightly longer contact patch isn't going to be a night-and-day difference on the trail. You're far, FAR more likely to get stopped by an obstacle that neither a 35" or 37" (or your gut, or other body parts a bit lower...) will allow than you are likely to get stopped by the "perfect" obstacle that just can't be passed with 35"s and a winch, but is just that RCH bigger/harder that 37" WILL do it.
Of course, on the bulky JLs (I love them, don't get me wrong, they're just big vehicles) a 37" just looks way better, so because I'm an idiot I'd ignore all of my advice above and get 37"s. :p
-TJ
Advocate I
Not to toot my own horn, but:
If I'm hearing that right, 3.73s for the diesel even in the Rubicon. Of course, that takes away a little of what I said about 35"s or maybe even 37"s being fine with stock gears, since they're not 4.10s. I suspect 35"s might be okay on the stock 3.73s, but you'd probably want to gear (maybe just to 4.10s) for 37"s.
-TJ
I'm betting they did that for fuel mileage numbers.
Advocate I
I doubt it. Jeep does what they can for fuel mileage, but the fact that they put 4.10s in the gas Rubicons proves they're willing to pick the "right gear" and give up a little MPG. You have to remember they have a .67 8th gear in the auto too. The EcoDiesel (according to the Jeep engineer in that vid) is going to make 442 lbs-ft of torque in the Wrangler, and it makes it way down low. The EcoDiesels actually rev out pretty well compared to say my 6.6L Duramax in my pickup, but they still have a lower redline and make peak torque much lower than a gasser. That's why they've put a higher (numerically lower) gear in it the diesel models.
This article is about the RAM-spec 3rd Gen EcoDiesel which seems to have a bit higher peak numbers (480tq) but should give us a decent idea what to expect:
With that kind of torque available at just 1600 RPM, there's no reason to gear it to get revved up as quickly.article said:
-TJ
Influencer II
Advocate I
Influencer II
So you may know that the jk was sold with a diesel from factory in Europe, whilst having lower power (200hp) has a lot more torque (325ftlb if I'm right).
So I have this one with factory 3.73 gears, the auto transmission, which is the same as the one you know from the pentastar and 33" tires.
It's overall still a bit short for highway, would fit perfectly with 35" tires.
With a diesel you always need to remember, you have way more torque earlier than a gasser but your usable rpm range is smaller so you need to run longer gears or you end up revving the engine to death on the highway.
So I have this one with factory 3.73 gears, the auto transmission, which is the same as the one you know from the pentastar and 33" tires.
It's overall still a bit short for highway, would fit perfectly with 35" tires.
With a diesel you always need to remember, you have way more torque earlier than a gasser but your usable rpm range is smaller so you need to run longer gears or you end up revving the engine to death on the highway.
Member III
TJzO6 had some great points. The JL is much different than the JK. 37 are the new 35s. You have the strength in axles and in the 8speed auto where 37s will be fine. Look at some YouTube videos from way of life and lite bright. How they wheel there vehicles is pretty hard with nothing breaking. Like I said the 35 is a safe upgrade for the JK with minimal upgrades as the 37 is a safe upgrade for the JL. Just my opinion from my research.
More importantly I cannot wait to hear about you diesel. I am thinking of selling my JKU on 37s!
More importantly I cannot wait to hear about you diesel. I am thinking of selling my JKU on 37s!
Fantastic breakdown. I REALLY appreciate all the feedback...and the video. Mildly jealous.
Advocate I
So diesel JLU? 4 door? but not a pickup?
The big question is what will you do with it?
Where will you go?
How much highway?
How long will the trips be?
33s/35s/37s/40s
Each choice reduces fuel economy, range.
Add airing down, each choice might increase capability, depending on use.
The bigger the tire, the higher the unsprung weight, the rougher the ride.
"I'm considering clearance, mechanical wear on the vehicle, availability of replacement tires after you use you spare"
Where are you going that you worry about getting a new tire? If that is a concern, buy a world wide available commercial tire, set yer rig up to work with that. AND guaranteed, if you go for a bigger than stock tire WILL increase mechanical wear, but beyond wear, even after regearing every big, bigger tire choice increases the likely hood of breakage. mechanical wear is .... a polite way of saying stranded.
The big question is what will you do with it?
Where will you go?
How much highway?
How long will the trips be?
33s/35s/37s/40s
Each choice reduces fuel economy, range.
Add airing down, each choice might increase capability, depending on use.
The bigger the tire, the higher the unsprung weight, the rougher the ride.
"I'm considering clearance, mechanical wear on the vehicle, availability of replacement tires after you use you spare"
Where are you going that you worry about getting a new tire? If that is a concern, buy a world wide available commercial tire, set yer rig up to work with that. AND guaranteed, if you go for a bigger than stock tire WILL increase mechanical wear, but beyond wear, even after regearing every big, bigger tire choice increases the likely hood of breakage. mechanical wear is .... a polite way of saying stranded.
