So I am in the market for new tires since mine are beginning to wear down. I am trying to figure out what is the biggest I can go on stock 3.73 gears. I have lifted it 2.5 inches and I have also came to the conclusion from the previous forum I wrote that, I will need wheel spacers with the stock wheels. I was originally looking at 285/70/17 tires. But I found some 285/75/17 for a good price but they are all E rated. I also came across some 315/70/17 for a good price as well. I live in Texas and this is my DD. My drive is usually 12 mile round trip to work and back in the suburbs. I occasionally get on the highway and drive longer that 30 miles to visit family. A handful of times a year I go on road trips with my wife to camp. This summer we plan to go to Moab, Ouray, and Rockies on a road trip and I would like to have set of tires that will me able to manage all these trails. My questions can my stock 3.73 gears handle 315/70/17? What is the biggest I can go on 3.73 gears? My main concern is that it can do everything I talked about wanting to do. I have read people who said they run 35's on that gear fine, but some say that they have to take the OD off and still struggle to go up hill. I can't afford to re gear yet so that is not an option. Most of my budget went towards moving recently. I am new to the forums so any input that would be great.

 

I live in Texas. Have a similar drive too. And have a house in Pagosa Springs. So I do the "Colorado thing" too. I have 3.23 gears and 35x12.50-18's. Works fine for me. Haha. Could it better? Of course. I will eventually re gear to 4:56 or something, but, for now it works. I pull a 2000 lb boat daily. No problems there either. So, in reality, any size will work. You will lose some gas mileage for sure. And lose some useable power, really for sure. Lol. But it can work. I have a 12 with a 3.6 auto. Gas mileage REALLY SUCKS!!!!

 

You didn't say if you are running an auto or manual or if you have a 3.8 or 3.6. I have a 3.6 man. with 3.73 gearing. I'm running 305-70-16s which measure out to be 32 1/8 in dia. At 70 mph in 6th gear (with the speedo recalibrated) I'm turning 2100 rpms. For my set-up it's just about right. I talked on this forum with a couple guys that had the stock set up (225-75-16 tires with 3.21 gears man. trans) and they said at 70 mph they turn 2100 rpm. 315-70-17 measure out around 34.4 in. if you go that size with 3.73 gears IMO your going to have problems with it being geared to low even if you recal your speedo. Do a search in this forum there is all sorts of info. Good luck

 

I have a JKU with automatic with a 3.8 engine. So I am wanting to know what is the largest tires size I can put on this setup with out re gearing and losing dramatic power. I understand ill lose some but do not want to not be able to off road it. I want to keep it capable of doing stuff. Also is an E-rated tire ok for a JK.

 

I have a 10 JKUR with 410s and I struggle with 35 toyos on the highway here in colorado for sure.

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Where in Dallas are you? If relatively close, we can meet up and you can see how things change just from stock rubicon tires to 33s.

4.88s would put me back to stock + the extra weight of bumpers and roof rack. Regear will be in my very near future to be when I go up to 35s (if it is still a daily driver.) if not then stock gearing will be marginally adequate.

Sent from some string and a few tin cans.

 

I have 4:10s with 37s and i avg 12-16 mpg.

 

And you are wanting a definitive answer? There isn't one. It is personal opinion based on engine, transmission, model, specific location, specific driving style, specific usage, etc, etc, etc.

What about just pressing the OD button until you save the money for gears?

Stuck right to the top of this modified area are some FAQ's. If you scroll down to the drivetrain section you will find the rpm charts. When plugging numbers in, use 'measured' tire height, not mfg spec, and to get the OD/Off rpm, divide the number you get by .69

Start by finding what the rpm's will be with your current 3.73's and the new tire size. (if you don't know the measured size, go 1" less than spec for a ballpark).

The rpm's will be low, right? So, to simulate you reaching down and pressing the OD/Off button, divide that number by .69 and see what you come up with. And then, look at 5.13's with that new tire size and compare the numbers.

A 3.8 auto with 3.73 and 35's running OD/Off is fairly close to a 3.8 auto with 5.13 and 35's running OD/On, right? Pressing that button while on the freeway can get you by until you come up with the money for a regear.



Or, since you are going to over-think it and worry and stress, just stick with the stock tire size...

 

Well I am not looking for a definite answer.

I just wanna know were i am going to see a change. Now riding with the OD off is that going to put any extra stress on the transmission and engine? Will re gearing it put extra stress on the transmission and engine? Do i need the OD off when driving in the city?

I am not concerned about MPG to much if it drops a couple of MPG ill be fine but if it is going to drop it by 5 to 7 MPG that is different. I am not worried about acceleration or MPG really. I am worried about being able to go 70mph for a long period of time when I need to. I want to know if I can still hit trails in Moab and Ouray. I drive a Jeep not a ferrari.

 

Then you will be fine.