New 06 Liberty Owner - Tire Q...

[Powerslave]

On the sidewalls, it says 80psi Max COLD. I had 34psi in them, and put them up to about 42psi today. 80psi? Isn't that a little high? This is my first 4x4 vehicle, and never had tires this big, so not sure what I should be running Psi wise, for every-day driving. My MPG is far below the MFR specs too, like 13/17 MPG when it is supposed to get 18/22; and, just wondered if the low 32Psi pressure was effecting the MPG.

 

[Corwyyn]

On the sidewalls, it says 80psi Max COLD. I had 34psi in them, and put them up to about 42psi today. 80psi? Isn't that a little high? This is my first 4x4 vehicle, and never had tires this big, so not sure what I should be running Psi wise, for every-day driving. My MPG is far below the MFR specs too, like 13/17 MPG when it is supposed to get 18/22; and, just wondered if the low 32Psi pressure was effecting the MPG.

What type/brand/size of tires?

 

[Powerslave]

There are two different brands, but both the same size. 225/70/16 I think, not the OEM 235/75/16... I don't know the brands off-hand, but, both brands say the same thing for Max Psi80 lbs. The set on the rear are a knobbier tread than on the front. When I got it? The idiots (Chrysler) had one of each front, and back, so I had to rotate them to match sets for front and back.

Just seems that since I got it back after having the clock spring angle sensor replaced, the MPG has gone WAY down... They also reduced the Psi from what I had, 42psi, down to 34psi...

 

[SDLiberty]

On the sidewalls, it says 80psi Max COLD. I had 34psi in them, and put them up to about 42psi today. 80psi? Isn't that a little high? This is my first 4x4 vehicle, and never had tires this big, so not sure what I should be running Psi wise, for every-day driving. My MPG is far below the MFR specs too, like 13/17 MPG when it is supposed to get 18/22; and, just wondered if the low 32Psi pressure was effecting the MPG.

Welcome PowerSlave!!! If i didn't say it all ready? The key words here are "SUPPOSED TO". Those numbers would be new and in prime driving conditions. How many miles are on it? When was the last tune up? There are a lot of factors that will drag down MPG. Outside of dealer specs 245/70R/16 isn't one of them, i don't think? They didn't come on mine....Low tire pressure, Old plugs, clogged injectors, old air filter,.....(Talk to JJsKJ getting getting one) The list could go on and on but you get the point.

 

[Powerslave]

They are at 42PSi now, what should be in them? I had 50Psi in my former low profile 17" tires... Dealer specs are 235/75/16, these are 225/70/16, not much difference.

I will be buying an Intake from Ebay, they have a nice DUAL intake... I can really work with that.

 

[SDLiberty]

They are at 42PSi now, what should be in them? I had 50Psi in my former low profile 17" tires... Dealer specs are 235/75/16, these are 225/70/16, not much difference.

I will be buying an Intake from Ebay, they have a nice DUAL intake... I can really work with that.

I had the Goodyear Wranglers on mine when i bought it. 225/70R/16s and ran about 40 psi in them. Now some might argue this depending on what part of the country/world your in. Haven't lived in the colder elements in a while. JMO.... Do your homework on the intake first. There are a lot of conflicting stories about them and if there really worth it. By the sounds of it they could be if...... your not putting it on the 3.7. Do a search on them and see what you come up with.

 

[Ry' N Jen]

There are two different brands, but both the same size. 225/70/16 I think, not the OEM 235/75/16... I don't know the brands off-hand, but, both brands say the same thing for Max Psi80 lbs. The set on the rear are a knobbier tread than on the front. When I got it? The idiots (Chrysler) had one of each front, and back, so I had to rotate them to match sets for front and back.

Just seems that since I got it back after having the clock spring angle sensor replaced, the MPG has gone WAY down... They also reduced the Psi from what I had, 42psi, down to 34psi...

Check the sticker in the "B" pillar door jamb, it will show you what tire sizes came stock on your KJ and what the recommended tire pressures for the size.( Then you can use that value as a start point for your tires. Until via trail and error you choose what pressure works best for you on road and off road!)
And yes, 235-70-16 did come as standard fitment on KJ's.
Also, why did you buy your KJ with two tires from one manufacture and two more from another manufacture?
To me that's the same as having a Nike on one foot and New Balance on the other foot.
All tires wear differently and if you have four the same make, model, size, it will make a difference as to how they wear on your vehicle. Not to mention that you will have the same traction properties on the front and the rear! Also, even though a tire has a size on it of lets say225-70-16, no two tire manufactures tires are the same size.

 

[Powerslave]

Also, why did you buy two tires from one manufacture and two more from another manufacture?
To me that's the same as having a Nike on one foot and New Balance on the other foot.
All tires wear differently and if you have four the same make, model, size, it will make a difference as to how they wear on your vehicle. Not to mention that you will have the same traction properties on the front and the rear! Also, even though a tire has a size on it of lets say225-70-16, no two tire manufactures tires are the same size.

I didn't, it CAME that way, wow, didn't you read?

There are two different brands, but both the same size. 225/70/16 I think, not the OEM 235/75/16... I don't know the brands off-hand, but, both brands say the same thing for Max Psi80 lbs. The set on the rear are a knobbier tread than on the front. When I got it? The idiots (Chrysler) had one of each front, and back, so I had to rotate them to match sets for front and back.

So, where did you get the idea that I put two different brands on? I said that was the way I got it. I also looked to be sure, and they are 225/75/16, Enduro HT(Fr), and Mesa A/P(Rr). when I got it, as I SAID, one of each was on the front, and one of each was on the back, dunno why Chrysler didn't catch and remedy that... The Mesa A/P are a more aggressive tread than the front ones, and are like new.

I also noticed today, that my speedo is also off by a few miles. I know it's 20 miles to work, and 20 from work, and after one round trip, I am at a 37 mile reading on the trip ODO. I have a Motorcycle, and the prior two other vehicles before this, and it is 40 miles round trip. I believe these tires are a little taller than the OEM... Hence the low MPG and ODO difference, though not by much...

The tire size I also quoted as OEM, 235/75/16 is on the door jamb, I looked, which is why I posted it as such. I am no fool, I don't arbitrarily post numbers.

 

[ATXKJ]

a 225/70 would be an unusual size - stock - they normally come 225/75 and 235/70 so it's smaller than stock - so 1st off your odometer is further off than normal - and it wasn't accurate to begin with. (235/75 would also be unusual)
225/70/16 - 28.5 tall
225/75/16 - 29.4
235/70/16 - 29.1
235/75/16 - 29.84

http://www.jeepkj.com/forum/showthread.php?t=26358


Second - the Max tire pressure is for the max load that tire is capable of - a tire with a 80psi max - is probably a load grade E and rated for ~2000lbs/tire - or an 8000 lb vehicle at the 80psi limit.

you should have about 4200/4400 lbs - so 40 is probably a good starting point.

The generic pressure calculation is a chalk line - pump up cold tire - a little closer to max - draw chalk line across the tread - drive 2-3 wheel revolutions - if the chalk on the center of the tire is gone - the pressure is too high. if the chalk on the edges is gone - the pressure is too low. adjust and retest - you want the highest pressure where the line disappears all at the same time.

also if you have mismatched front/read tires - a Select trac 'NV242' transfer case - may or maynot go into 4wd. Even though the tire sizes are the 'same' different manufacturers, different pressures, different wear - make them different enough the front and rear driveshafts won't turn the same speed.

 

[ATXKJ]

As to the original question about mileage - pressure will make a difference, but you should also look at a general tuneup - including running Seafoam though the engine and putting new plugs, air filter and all oil changes.

(general principle used car stuff)

 

[SDLiberty]

I didn't, it CAME that way, wow, didn't you read?

So, where did you get the idea that I put two different brands on? I said that was the way I got it. I also looked to be sure, and they are 225/75/16, Enduro HT(Fr), and Mesa A/P(Rr). when I got it, as I SAID, one of each was on the front, and one of each was on the back, dunno why Chrysler didn't catch and remedy that... The Mesa A/P are a more aggressive tread than the front ones, and are like new.

I also noticed today, that my speedo is also off by a few miles. I know it's 20 miles to work, and 20 from work, and after one round trip, I am at a 37 mile reading on the trip ODO. I have a Motorcycle, and the prior two other vehicles before this, and it is 40 miles round trip. I believe these tires are a little taller than the OEM... Hence the low MPG and ODO difference, though not by much...

The tire size I also quoted as OEM, 235/75/16 is on the door jamb, I looked, which is why I posted it as such. I am no fool, I don't arbitrarily post numbers.

(popcorn)Take it easy there big guy....... This is a friendly environment and no one said you were a fool. kopkrab.gif

 

[Powerslave]

a 225/70 would be an unusual size - stock - they normally come 225/75 and 235/70 so it's smaller than stock - so 1st off your oodometer is further off than normal - and it wasn't accurate to begin with.
225/70/16 - 28.5 tall
225/75/16 - 29.4 What I have now
235/70/16 - 29.1 What it calls for on the pillar
235/75/16 - 29.84

Second - the Max tire pressure is for the max load that tire is capable of - a tire with a 80psi max - is probably a load grade E and rated for ~2000lbs/tire - or an 8000 lb vehicle at the 80psi limit.

you should have about 4200/4400 lbs - so 40 is probably a good starting point.
I am at about 42Psi right now, mileage is better. Pillar calls for 33Psi in the 235/70/16. I run higher for better MPG anyway.

The generic pressure calculation is a chalk line - pump up cold tire - a little closer to max - draw chalk line across the tread - drive 2-3 wheel revolutions - if the chalk on the center of the tire is gone - the pressure is too high. if the chalk on the edges is gone - the pressure is too low. adjust and retest - you want the highest pressure where the line disappears all at the same time.

also if you have mismatched front/read tires - a Select trac 'NV242' transfer case - may or maynot go into 4wd. It does go into part-time on the fly, and the other two; HI & LOW, from neutral or park. Even though the tire sizes are the 'same' different manufacturers, different pressures, different wear - make them different enough the front and rear driveshafts won't turn the same speed.

Pressures are the same, just the TREAD is different. Yeah, I know about 4wd and the tire issue, but since the rear ones are like new, they are turning slightly slower than the front worn 50% ones. I wanted the aggressive tread on the back.

I did change the air filter the day before taking it in for the sensor repair, and since THEN, the mileage has dropped. They disconnected the battery, so maybe all the learned stuff was erased, and needs relearned.

I will change the oil when weather permits, as well as put in iridium pluigs, or split-fire platinum. I used them on my Dodge, ran smooth as could be. I think I have some SeaFoam at home. I have used it on my Avenger a few times, along with Marvel Mystery Oil.

I will be customizing the intake. A snorkel would be nice, but the wife is STRONGLY against that... There is plenty room behind the grille to mount an intake funnel.

It is a little out of toe also, so I need an alignment. Though, it was fine with the tires the way they were originally, as the newer one was on the front right, the other worn one, on the front left. As, the oher newer on the rear left, and worn on the rear right. That's the way they sold it to me at the dealer, so when the tires were rotated, they criss-crossed it all. They didn't bring the front ones directly back, then cross the rears to the front; Else the tires would not be mismatched like they were. I just can't believe the dealer let that by, AND, were going to charge me 12.00 to rotate them right! That was just wrong... They did fix the clock spring angle sensor for free though.

So, my MPG is about 1.5 miles more than listed, per 20 miles traveled, due to the tires or whatever inaccuracy there is. My GPS also shows me going slower than what the Speedo says; but, was pretty ACCURATE in my Dodge Avenger... It is also off a few MPH off in my Vibe; about the same as the Jeep.

I guess I was a little foolish, I put the wrong OEM numbers in the previous post, when I read it THREE times. Damn type-os!!!

 

[Ry' N Jen]

Sorry if I pissed you off. Maybe I was out of line or maybe it was too many pain killers!
What ever... I apologize!

 

[Powerslave]

Sorry if I pissed you off. Maybe I was out of line or maybe it was too many pain killers!
What ever... I apologize!

No, didn't piss me off in the least... It's only the internet...