djdingo

I recently purchased a 2017 Jeep Wrangler Unlimited Sport and it came with the tiny tires. I'm looking to get new wheels and tires and thinking about maybe putting a 2" lift kit as well. My last Jeep I upgraded the tires to the 32" mud terrains that the Rubicon came with and I'd like to go that size or bigger if possible.

I'm reading online that if you don't have Dana 44 axles then any tire size over 32" may snap your axle shaft? I certainly don't want that to happen but I would like to know my options. I think my axles are Dana 44 but can't confirm that right now.

What's the largest size tires I can put on my JKU with it's axles and no lift? What's the largest size tires I can put on the JKU with a 2" lift?

Thanks in advance!

nthinuf

There are some FAQ's stuck to the top of the Modified area that talk about some of this.

Non-Rubicon, you should have a D30 front and D44 rear.

I wouldn't worry too much about the difference in the shafts between the front d30 and d44. The d30 has 27-spline inners, the front d44 has 30-spline inners. Both have the same 32-spline outers. If you snap a shaft in the d30, I would guess the odds are pretty good that you would also snap it in the front 44. The gears are a differnt story, though. The 44 gears are much beefier.

The front d30 and front d44 axle 'housings' are basically the same strength. Same length, tube diameter, wall thickness, same C's, same brakes, etc.

For the tire size, will you be running stock fenders, or chopping, or buying flats? Are you willing to trim at all? Will you be using the stock rims, or new rims with less backspace?

rob_engineer

If you have 3.21 gearing you will hate your Jeep if you go bigger than 32. You will feel a significant power drop. I could be wrong, but I thought all wranglers since at least 2012 come with the same size Dana rear axle. Plenty of people running 35" tires on those axles.

resharp001

Lotta fearmongering in whatever you're reading if you ask me. It's all in how it's being driven/used. Throwing 33 or larger on a D30 axle doesn't make it instantly disintegrate, but if you go out and be an idiot with it, the odds are higher than they were before that you might put a shaft at risk.....just like the odds would be higher for you to jack something else up on it. Most people don't wheel near as hard as they like to imagine in their head. There are probably more people than you can count out there running large tires on D30s that haven't snapped a factory shaft. I'd bet there are a few idiots running 40's on a D30 cuz they like the look but can't afford real axles....and unless you're talking an aftermarket D44, there's not that much of a difference between D30 and Rubi 44.

As the guys have already pointed out, gearing is going to be more of an issue with a larger tire than anything else, and the lift or lack thereof is going to dictate how large the tire can be due to clearances.

djdingo

Thanks for the responses! It looks like I'll have to go with a 32" tire and probably a 2"+ lift kit. I didn't know how complicated it can get wanting to add bigger tires.

rob_engineer

Don't forget you'll need to get the Jeep reprogrammed for the bigger tires so the speedometer is correct as well as shift points for the transmission.

resharp001

It's not "complicated" per se, but you can't touch anything on these jeeps without it affecting something else. You can slap larger tires on just fine, but without changing the gearing you're going to lose some performance. Everything is a trade off. Do you have 3.21 gearing? If you added a small spacer lift and threw 33s on there, you'd be fine. More sluggish than stock, but you'd get used to it, and you'd probably be happy with the overall appearance. I would not worry about the axle at all....that is not a concern for what you're doing. If you can afford to regear ($1500 +/- in most areas), it is almost always well worth it. Don't wanna pay for a regear? Keep your eyes open for front/rear axle set to come for sale in your area with either factory 3.73 or 4.10s, or that have been regeared lower already. Swap those in and sell your factory axles to recoup some of the cost.

Also, programmers these days (to re calibrate for new tire size) aren't that much, and simple interfaces. Most will also allow you to tweak some other settings as well.

TheDirtman

If you want 32" tires just slap them on. You don't need a lift or anything else Sahara's and Rubicon come stock with 32" tires and they are not lifted and may have the same suspension as the sport, the rubicon has a different type of shock but the fitment is the same.
Gearing is likely 3.21 since you have small tires and most newbs don't understand gears just like they don't understand suspensions (lifts). Gears are expensive and generally not a do it yourself mod but is one of the most important things in terms of performance on the jeep both on road and off.
Running to high a gear ratio will put stress on your entire driveline from the engine, transmission, and driveshafts. Improper gears for tire size will also give you poor acceleration and loss of mpg. Off road improper gears make it harder to climb steep obsiticals and you tend to have to wheel faster to have momentum to get over stuff which is why people break stuff like driveshafts and axle shafts.

If you are reading sites that push that you can't run bigger then stock tires on the factory axles you should stop reading those sites as you are getting bad information. They are likely pushing mis information to sell products for their sponsors or they are just dumb and there is certainly a lot of that on the internet.

rob_engineer

Well, you can't just slap on 32's. The programming still needs to be done for the speedo and shift points.

Creepy Neville