Montego

The question will be - should I do 33" or 35" tires.....
I just got a 2017 JK Rubicon. No lift, factory wheels & 32" MT tires. 4.10 gears, 5 speed auto trans, and the 4:1 transfer case. .
Those (brand new) 32" factory spec tires are about 31.25" diameter when I measured them.

For comparison, my previous 98 Jeep TJ had 32" BFG A/T tires, 4.10 gears, regular 2.72:1 transfer case, a 3 or 4" suspension lift, ARB Air lockers, and all that.
I'm in a 4x4 club and I will be doing various trails, some tough. Just for comparison, about half of the guys in the club are running 35" tires, about half are 37", 3 have 33" tires, and a couple have 39" & up. Mostly desert trails, but also some big rocks.
This is also my daily driver, so whatever I do has to work out good for the city & highway as well as offroad in the deserts & mountains.
So - how to choose which tire size?

I do plan to replace the 32" Mud MT tires I have now with either 33" or 35" AT. And get rims with correct backspacing/offset.

My neighbor has 35s and let me borrow them. Here's a photo as I was swapping tires - you can see both the 32s & the 35s. (I don't have any 33s handy). After a few days of driving on pavement I can report that the 35" tires are not rubbing on anything. Probably would rub in real trail situations though. But if they only rub on plastic flares, that doesn't seem like a big deal.


Man, the 35s look good, maybe even a little too big. 33s would probably be fine as well. But for 35s I really should change out the gears to 4.56 or 4.88 to make things right. I will for sure get the right wheels with the right backspacing for the tires.
So the question is how should I decide between 33s or 35s?

Here are some considerations ....
Unsprung weight. Those 35s are heavy! 33s are heavy too, but not that heavy. My tailgate has the factory "swing gate reinforcement" so I epxect it can support a heavier tire. And it has for the past week.
Gears - The 35s are driving ok around town today, but I know upgrading the gears to match the tire diameter needs to happen. OTOH if I just went with 33s the 4.10 gears are fine.
MPG - of course MPG is obviously not a top consideration for Jeeps. But with the factory tires, this JK is getting about 19 MPG highway, and only 16 while trying on the 35s around town. Different yardstick, I know. Can't really compare those, plus the tire size affects the odometer directly and I didn't tell the computer about the different tire size. So the math is off too. But anyway - MPG.
Steering - feels mostly ok, but it was slightly tighter with the 32 factory tires(?).
Ride, little bit softer & squishier with 35s than 32s.
Look – Not a big factor to me.
Cost- I'm trying to ignore cost and instead focus on the other decision points. The 35's will cost more, and deeper gears will be part of that.
Clearance – would probably need to trim or replace the fender flares and/or add a 2" lift for 35" tires. But 33" tires ought to fit without issue.
Performance – Unknown for sure, but seems like 35s would do better on more extreme trails. Since the guys in the club mostly have 35s & 37s I can see it might be a good idea to have similar size tires to keep up more easily? Also, I do pull a small camping trailer on & off road a lot. I did mostly OK pulling that with 32s on the old Jeep TJ, but traction is always a consideration. Where is the point of diminishing returns?

So – after all that – what and how do you think about it?

Jay2013jk

Good thought process.. FWIW We run 35s (really measure on 34") on a '13 JKU Sport with 4.10s and 6 speed man trans.. Mostly a DD. IMO you should be good on the tailgate with the reinforcement.. 35 might hit the bumper .. Ours weigh 67lbs for the Falken AT3s.
37s vs 35s is about 1" increase in ground clearance for the axles. We could go to 37s on the JKU BUT the COST Difference does not support the improved look & in reading the Forums 37s put much more strain on drivetrain components.

CJ7nvrstk

35s hands down.

TheDirtman

A "C" rated 35 and I would look for a light wheel with 4.5" aoc back spacing vs using the factory wheel. Tires are all over the place size wise depending on the model. Your jeep with 35's is going to go just about anywhere but buggy lines if you can drive. Most people that run bigger than 35's are doing it for looks.

MrClortho

I went from 33's on factory steel wheels and E rated tires with wheels spacers to 35's on 4.5" BS aluminum wheels with lighter rated tires. The 33 combination and spacers weighed almost identical to the 35 combination on my home scale (91 lbs). Even with 3.73 gears, the Jeep runs acceptably for the most part on the 35's. It rides smoother as well, but the brakes are not quite as strong. Overall, I certainty would not go back to 33s.

I have a 2" front, 1.25" rear lift with no rubbing on the street but no doubt they will rub on the rear off-road. For a bandaid, I am adding 1" spring spacers and geo brackets this week until I can put together the funds for a complete new kit hopefully next year.

Sixty4x4

I'm with Dirtman - if you are buying anyway then spring for the 35s in C rating. Also the lighter wheel will offset some of the accelleration losses. I upgraded my brakes to ceramic pads and they work pretty darn good. Way better than stockers so where I am going is if I change to 35's then I am going 15" wheels and they clear the calipers just like my son has ordered for his 2016 JKUR.

Montego

Good points everybody.
Yes, I do notice that the brakes are not as good with the 35s as they were with the 32s.
It's so great being able to try on some tires before committing to them! I was out yesterday looking for something to get a wheel up on to check for rubbing. I saw a high curb where a storm drain went low. so there was maybe a 10" difference. Put it into 4Low so I could disconnect the sway bar & see. Not a great test, but going in the right direction anyway. For what its worth, the 35s did not rub on anything - but it was close, I could just barely squeeze a finger in between the tire tread & fender flare. This curb was maybe 10" off the asphalt, So the tire might rub when on a bigger rock. But, hey it's just plastic. I know this test is too small, but I'm still pretty surprised it is going so well. I'm also surprised that the 5 speed auto transmission (4.10 gears) seems ok with driving the highway on 35s. I expected some serious lagging. Haven't tried pulling the trailer yet though.


side view on 10" curb, Sway bar disconnected. 35s not rubbing but close



front view. sway bar disconnected. 35s not rubbing

Sixty4x4

I would add that under some pretty good articulation your front inner tires will rub the sway bar when turning. My 33's did prior to a puck lift I had then it went away and now have MC springs etc.

MrClortho

Stock bump stops and 35's with a 2.5" lift. Say good by to the rear fender flares if you wheel.

Yesterday, I found some rocks to crawl up to verify clearances after going from 33's to 35's. In this picture, my tire is wedged into the fender flare but my stock bump stock is not contacting yet. I do not want to install longer bump stops to limit the travel as the shock still had some stroke, so off come the flairs.

Montego

Great research! (Same size tires, same year JK & same color paint even!) Thanks! Please post a photo when you do whatever you're going to go about those flares.
I don't see a rock, so maybe the other rear wheel on this axle is in a hole?

Good point. I can understand that taller bump stops prevent excess wheel up-travel so the tire wouldn't hit the fender flare. While still allowing wheel droop to stay in contact with the ground. What's the downside to taller bumpstops?

What's the deal about bump stops vs lift? Can we talk about that?