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Old 08-28-2013, 08:19 PM   #1
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2.5L max performance

I got a '90 YJ 4 banger with 31x10.5 tires on stock 15s, stock height. At first I had 225/70/15s on it before and I switched to these tires. I knew it would make the engine sluggish, but holy cow! I didn't know it would be that sluggish! I wanna go smaller tires with some decent tread.

Anybody got some advice? I'm thinking 235/75/15 for the size now. I'd like to hear some reviews/pics for the tires on your rig

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Old 08-28-2013, 09:22 PM   #2
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I run 235/75R15s with stock suspension. They don't rub and it moves along pretty well. I was thinking of going with a bigger tire but they line up perfectly with the stock fender flares. I have stock alloys for wheels. Good luck with your decision.

I also determined that a properly set TPS makes a big difference in drivability.

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Old 08-28-2013, 09:25 PM   #3
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I run 235/75R15s with stock suspension. They don't rub and it moves along pretty well. I was thinking of going with a bigger tire but they line up perfectly with the stock fender flares. I have stock alloys for wheels. Good luck with your decision.

I also determined that a properly set TPS makes a big difference in drivability.
Thanks a lot. I feel like I'm killing that motor with 31s
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Old 08-28-2013, 09:25 PM   #4
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Do you get decent milage with those? At least over 16?
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Old 08-28-2013, 09:41 PM   #5
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I try not to think about gas mileage (afraid to know) but I would guess 15-18 mpg. I don't like filling it to the top, I keep it between 3/4 and 1/4 of a tank. Don't know why; check the mileage in my DD all the time.
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Old 08-28-2013, 09:51 PM   #6
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Thanks a lot. I feel like I'm killing that motor with 31s
Hmm that's strange b/c I run 32's and feel that I have plenty of up and go power. The only thing that sucks is anything over 55mph, then it's sluggish lol. I used to have 30's but I feel with the 4.10 gearing the 32's work better, maybe it's just all a preference and I'm used to being the slow guy on the road haha.
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Old 08-28-2013, 10:11 PM   #7
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Gears will do more for your 2.5 than any bolt on, intake, or header ever will. Bottom line.
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Old 08-28-2013, 11:05 PM   #8
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Killing the motor with P235s?

Im running 33's 5th is useless, sometimes I hit third on the freeway when passing, or on big hills.
Only reason I have not regeared to 4:88 is because im doing a 5.2L swap eventually.

there is a Header out there, but no intake for anything below a '91 ('91 was the first year for PFI).
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Old 08-29-2013, 08:45 AM   #9
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I have often wondered what performance was like with the stock tires, read a lot about it. I have 32's on 2.5, always have had them so nothing to compare to. But rarely do I ever use 5th. gear. As it was said before, guess I as well am use to being the slowest on the road. Doesn't bother me any. Saw an appropriate bumper sticker while back, actually it was on an old VW bug, "You have been passed by a toaster", that's me.
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Old 08-29-2013, 10:30 AM   #10
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Killing the motor with P235s?

Im running 33's 5th is useless, sometimes I hit third on the freeway when passing, or on big hills.
Only reason I have not regeared to 4:88 is because im doing a 5.2L swap eventually.

there is a Header out there, but no intake for anything below a '91 ('91 was the first year for PFI).
did you say passing?
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Old 08-29-2013, 11:12 AM   #11
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glad to see that i am not the only one that needs a strong tail wind to get up to 55mph! Thinking of regearing mine as the 33s are making anyting over 55 a pipedream with the little engine that couldnt...
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Old 08-29-2013, 11:22 AM   #12
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235/75-15's:







Yes, they will rub at full flex, that's a 1" shackle lift. Anymore lift and I'd be snapping my front brake lines.

Power was not an issue, even with my 2.5L blowing oil it still motored up to 65mph without much fuss. When I had 31's it would still do 65mph. Keep in mind as your tire size increases, your indicated speed decreases. With 235's, it's only off by a little bit, maybe 2%. With 31's, it's off by as much as 11%.

If you seriously can't get to actual 65mph then you need to do a tuneup, or regear for those 35's. Swapping in a clean air filter and a fresh set of plugs/wires/cap/rotor can put as much as 10hp back into your engine that you've lost from lack of maintenance.
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Old 08-29-2013, 11:25 AM   #13
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glad to see that i am not the only one that needs a strong tail wind to get up to 55mph! Thinking of regearing mine as the 33s are making anyting over 55 a pipedream with the little engine that couldnt...
how many miles on the engine, instead of the regear maybe look at a swap..........small block anyone? Thats my plan
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Old 08-29-2013, 11:27 AM   #14
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Like RednekYJ stated above, gearing makes all the difference in the world on a 2.5. I installed 4:88's 2 years ago and WOW! Drivability, mileage and offroadability all went up. I can use 5th gear again! Should have done it 10 years ago.
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Old 08-29-2013, 11:46 AM   #15
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Only 111K on the motor... only had it about a week now. filter was just changed but i do plan on changing the plugs and wires this weekend.
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Old 08-29-2013, 12:06 PM   #16
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Thumbs up Pass What???

My little 2.5 with 33" mud terrain and 4" suspension lift", 2" body goes down the road O.K. but trying to pass anything more than an old tractor is putting your life on the line I bought it this way and had absolutely no idea what a jeep was all about, my wife and I thought it looked cool. We have a blast on the numerous old logging roads up here in New Hampshire, all I have to do is point it where I want to go and we are there. I do get to use 5th gear on rare occasions, going down a longggg hill, or wind it up in 4th on the flats without any head wind she'll give us 60-65 on a good day. Then again I didn't buy it for a highway cruiser. I like it around town and I LOVE it on the trails. This little motor has grown on me
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Old 08-29-2013, 12:09 PM   #17
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did you say passing?
Yes, if I downshift to 3rd at 60-65 MPH I can pas someone going the speed limit, but not on a hill, and yes, I hit 4500-5K RPM....

First time I forgot to shift out of 1st getting on the freeway, at 6K when i hit the clutch it sounded so bad~@ss (flowmaster), kkinda like an S-10 with a flowmaster at idle.....

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http://www.wranglerforum.com/f330/2x...ad-101879.html
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