Cracked 22mpg combined

[jsc7002]

tow straps and recovery straps are the same if you ever look at the, I bought one that is rated for 10000# but its breaking strength is 20000#

 

[yellocoyote]

Holy hell, someone who acutally knows something about load rating equipment.


WELL DONE SIR SHOCKED.gif


You can run your tires EASILY over 2x the "max rating" , but I'm not telling you to do it, nor would the company I work for. Liabilities are a *****.

That would be m'am, and you're welcome.

I personally don't think it's a good idea to go over the posted rating. But sometimes there are abnormal circumstances, and it would probably cross my mind to go more than maximum allowed ratings for a short - very short - time only. Not ever on a 'normal use' basis. To me, that's dangerous.

 

[incommando]

Hey guys, just thought I'd give an update on my quest for MPG in my wife's jeep.


We had 2 tanks of 20.4-20.6 and finally this tank we recorded a 22.1 MPG combined. She drives 50% city/ 50% highway. We are damned pleased, according my my scangauge we are averaging 26-27 mpg on the highway.

Mods we did:

Cold air intake
fully synthetic oil
50psi in all tires, tires brand new
not idling in prolonged periods while waiting at stoplights

Get a 6-speed, never break 1800 RPMS unless you are on the highway, PO everyone around you, and you can see #'s like that regularly.

 

[Marlon_JB2]

I discovered that I could get decent MPG numbers, city and highway, by pumping my tires to 40PSI. Seems to be a good number. I'm running the same in the WK now... might increase it a bit due to the extra weight of the vehicle. And no I haven't noticed a bit of odd tire wear.

 

[Dave]

I discovered that I could get decent MPG numbers, city and highway, by pumping my tires to 40PSI. Seems to be a good number. I'm running the same in the WK now... might increase it a bit due to the extra weight of the vehicle. And no I haven't noticed a bit of odd tire wear.

Did you get a stiffer and bouncier ride??

Dave

 

[Nursecosmo]

Tires are rated for 51 psi.

As for all the uneven tire wear BS, I've got a pair of tires on my accord with 87K on them rated for 60K. They are rated for 44 psi and have been at 60 psi for 4 years with no uneven wear.

Burst pressures on modern tires are well over 200 psi, you have been repeating too many myths which are not true. Low tire pressure leads to fatigue and blowouts, NOT high pressure.


I'm driving a 2004 Liberty 4x4 gas engine.

Amen!
Modern tires are constructed in such a way the tread surface itself has very little ability to bulge in or out like a balloon. By raising the pressure to the max rated or even slightly over, tire wear is changed very little. Many people still use the old "trick" of marking the tire with a chalk line, then driveing forward 2-3 revolutions at 1-2 MPH then checking to see if there it is rubbing off evenly. This method would work great if you drove 5 MPH in a straight line on a perfectly smooth road, but who does that? This method is flawed in that it does not factor in the way a tire changes shape at highway speed nor does it factor in the changed wear pattern during cornering or when striking bumps or pot holes. The most important method of insuring even tread wear is simply rotating them.

Folks who state that a tire will "Blow up" when inflated to max pressure or greater are also undereducated about how tires are designed and often about physics in general. This excerpt is taken from Edmonds automotive website:

"Myth: A tire may explode if you exceed the "max pressure" number on the sidewall.
Truth: The "max pressure" number found on the sidewall of a tire refers to its load-carrying capability, not its burst pressure. The burst pressure of the tire is far beyond the "max pressure" number. (See "Sidewall Graffiti: How To Read Your Tire.") When the tire is inflated to its max pressure, it will carry the "max load" weight that appears nearby on the sidewall. Especially for ultralow-profile tires on sport-utility vehicles, the tire may need to be inflated to its max pressure to safely carry the weight of the vehicle and its contents."

There are so many old and crazy myths out there about tires that it isn't funny. Many myths are even perpetrated by tire manufactures themselves because they don't want anyone inflating thier product to say, 150 PSI and getting killed because of decreased traction then blaming it on faulty manufacturing. Noise and ride harshness is also increased by higher inflation pressures which is another reason that manufacturers recomend inflating to the minimum level.

Another common myth associated with automotive tires is contact pach size VS PSI. Here is a link to some very interesting findings.
http://www.performancesimulations.com/fact-or-fiction-tires-1.htm

 

[JeepJeepster]

oh well engineers they know it all I guess

Oh an I was in the tire business before you became an engineer it looks like

Even though Im in college to become an engineer Ive found out that some of the stupidest people are engineers.

I bumped my psi back up to 36psi and it rode pretty rough compared to 30-32psi. While the air is cooling down I usually put air in them around 2-3 times before it levels off and stops dropping due to cooler temps. Im looking at getting a nitrogen tank and filling them up so the drop isnt so big.. I can get the stuff for free so it doesnt matter... Only thing is I cant keep the tank so if I need to top off it will be with, gasp, air..

Usually keep 36psi in the WK and it does ok with that big hemi. Cherokee gets ~33 since its kinda light and the ZJ gets ~34-36 psi since it tows some.

 

[LibertyTC]

Did you get a stiffer and bouncier ride??

Dave

I run with about 50 lbs of gear in the rear and have a push bar up front. When I tried taking my silent armor tires that are rated at 45 cold to 40 it was quite a bit stiffer, felt all the bumps, occasionally a shudder through the wheel on pot holes, but also got way better mileage. Today I leave them at 37.5 but know I am sacrificing mileage, butt not my tail bone.
If I wanted that premium mileage I would run with a half a tank, take the stuff out, and fill the tires back to 40, drive like a grandpa.
Now does that really sound like fun in a Jeep?
To heck with worrying about the mileage, I got to go to my friends waterlogged back woods farm tonight...throwing in another 100 lbs of gear and beer !! Cheers!

 

[UTRacerX9]

I am not sure if my KJ would hit 22mpg, right now I am getting 17.5, but I am doing 100% city/rush hour traffic driving. I have the 3.7, 2WD version. (Yes, I meant to only get 2WD.)

I just posted a thread for the AEM CAI, where I saw a 6.7% increase in gas mileage, check it out if you're interested.

http://www.jeepkj.com/forum/showthread.php?t=37165

 

[Marlon_JB2]

Did you get a stiffer and bouncier ride??

Dave

Yes, this is a good thing. Now it doesn't float around so much.

 

[04liberty4x4]

Last several tanks have been about 20.5 average in these cold temps.

Forgot to mention, car is a v6.

Driving was 53% city / 47% highway in 30 degree weather

 

[Cableguy]

Right. People like me? Oh you mean Educated beings, aka a Tire Engineer. I've been an Engineer since 1976, what the **** have you done?

We put warnings on tires for idiots like you, obviously they are needed.

If you seriously think tires will self implode at the side wall max, or even OVER IT, you sir, are an IDIOT.

Some of the dumbest people i've ever met are engineers. (no offense jeepster) I also think it's funny that a "Tire Engineer" doesn't know the difference between an implosion and an explosion in a tire. I've seen photos and videos of the aftermath of several exploded tires. (blarg)

Yes, you may be able to run your tire at 50psi and not have it explode instantly, but doing that for anything other than short, usually emergency periods of time is plain stupidity. That's like saying hrrmmm... i've got a 15 ton overhead hoist, but i'm going to lift 20 tons with it because it'll do it! Those ratings are just there for idiots!!!!

I personally don't think it's a good idea to go over the posted rating. But sometimes there are abnormal circumstances, and it would probably cross my mind to go more than maximum allowed ratings for a short - very short - time only. Not ever on a 'normal use' basis. To me, that's dangerous.

Amen.

 

[Nursecosmo]

There is of course no obligation for anyone to run their tires at the proper pressure (fully inflated) but since this thread has to do with MPG gains it has been proven to be a good way to achieve more efficiency. Many thousands of drivers have been doing it for many years without catastrophic blowouts.

 

[tulsa]

I keep mine at 34 PSI. It's the only PSI I can run where I don't get a low pressure alarm in the morning, and a high pressure alarm in the afternoon.

That's interesting, I run my tires at 38-39PSI cold and do not exceed the high pressure alarm point when running.

 

[kjpilot]

I ran my BF Goodrich long trail t/a at 44 psi for a while, & the handling characteristics scared me back down to 36 psi. I experienced much less control.

Granted I prefer sports car control over truck wallowing on the road, so I may be more jittery than some, but I think the way the KJ handled at 44 psi was approaching dangerous.

 

[Shpotty]

My first tank of gas...

came in at 22.5 MPG. My commute is nearly all highway driving and
I kept the cruise control set for 68-69 MPH. I picked the Jeep up Monday night so I haven't really had a chance to do a thing to it. I am hoping that with the careful driving and some future tuning I can do even better.