Can the 2.5L SE Handle 31 Tires?

[SSTJ]

Hi all,

I know, another thread about fitting 31s on a stock TJ, right? Besides, we already have this one. But here's why I'm posting: most threads I've found on this forum focus on matters of clearance—i.e., will the tires fit, or will they rub at full turn, etc. Occasionally, the conversation turns to whether re-gearing is needed, and usually the answer is "only for the 2.5L SE models". but I've heard a lot of different opinions.

I have 30x9.5 KO2s on AR767 steelies, and of course the Jeep runs fine with them. I almost bought 31" KO2s, but threads like this one scared me back to the 30s. Then, I recently inherited a set of stock JK 17" Moab rims, with 255/70 tires. According to this site, those are 31x10. I put them on, and so far, I notice almost no difference. If anything, the Jeep feels a little bit quicker, and I suppose that's because I'm hitting higher speeds at lower RPMs. So I'm surprised by the claims that one has to re-gear a stock 2.5L SE in order to enjoy 31" tires.

But, I haven't taken it up any steep trails, or even on a highway. I do most of my driving in a small town, so I spend about 90% of my time in gears 1–3, occasionally dropping into 4th to cruise at 35–40 on some suburban road. Will I feel differently once I hit 60mph? Or once I try to go up an off-road incline? I'm wondering if I should trade in my 30 KO2s for 31s while they're still (basically) brand-new.

 

[jeepguy03]

I think the most noticeable difference will be felt at highway speeds with a wind, or when trying to go up a hill. I would try it before making your decision though. If most of your driving is around town it might not be a big deal for you.

 

[Chris]

It can handle it, but the key will be making sure you choose a tire that doesn't weigh a ton (i.e. a A/T over an M/T), a lightweight wheel, and the proper gearing.

 

[HYRYSC]

You will definitely feel differently when you hit an incline. Even on stock size, our lack of power is evident. Not the end of the world, but it is noticeable.

I went to 33's and drove for a few days before my appointment at the regearing shop and it wasn't life-shattering. I did have to plan ahead a bit, I had to drive in the right hand lane most of the time (shudder) and I laughed when I even thought about trying to pass anyone. If I was only around town like you with most of my driving in 1 - 3 gear, I wouldn't think a thing about 31's...or even 33's.

 

[Ephry73]

To answer the question, it is not the motor that will notice the difference. You will need to regear in order to get equal performance to stock.

 

[TJ4Jim]

Hi all,

I know, another thread about fitting 31s on a stock TJ, right? Besides, we already have this one. But here's why I'm posting: most threads I've found on this forum focus on matters of clearance—i.e., will the tires fit, or will they rub at full turn, etc. Occasionally, the conversation turns to whether re-gearing is needed, and usually the answer is "only for the 2.5L SE models". but I've heard a lot of different opinions.

I have 30x9.5 KO2s on AR767 steelies, and of course the Jeep runs fine with them. I almost bought 31" KO2s, but threads like this one scared me back to the 30s. Then, I recently inherited a set of stock JK 17" Moab rims, with 255/70 tires. According to this site, those are 31x10. I put them on, and so far, I notice almost no difference. If anything, the Jeep feels a little bit quicker, and I suppose that's because I'm hitting higher speeds at lower RPMs. So I'm surprised by the claims that one has to re-gear a stock 2.5L SE in order to enjoy 31" tires.

But, I haven't taken it up any steep trails, or even on a highway. I do most of my driving in a small town, so I spend about 90% of my time in gears 1–3, occasionally dropping into 4th to cruise at 35–40 on some suburban road. Will I feel differently once I hit 60mph? Or once I try to go up an off-road incline? I'm wondering if I should trade in my 30 KO2s for 31s while they're still (basically) brand-new.

The 2.5 with the AX-5 trans can handle 31's no problem, been running similar for the last 8 years and a re-gear is not really necessary.