Losses to expect after a lift and big tires

Robert Bradbury · **Joined:** Wed Mar 22, 2006 10:37 am **Posts:** 132

2002 skyjacker 2 1/2" , Micky Tompson Classic bead Lock, 32 " Trxux Tires, Powertrax No-Slip, Skids and Rock Rails, ARB Bumper with 8000lb Winch .

O.k. so this is what I did to my Liberty and I felt compelled to advise not just the improvements one achives, but instead some of the losses one can expect.

Don't get me wrong, she looks great and performs good off road. I get lots of positive comments, especially with my custom color .

What I found was EXTREME reduction in fuel milage to the point where even with good highway driving I cannot make 180 miles on a tank.

I can still tow the heavy loads but with any weight at all behind the Jeep I'm down to crawlling speeds at the top of any long uphill grades . Before I could maintain highway speeds even with a heavy load in tow . I guess I'm saying expect a profound loss in torque because of the heavy tires. I can maintain highway speeds on the flat with or without a load but I
cannot run much faster than 60 mph without enduring too much noise and vibration .

Then there is the loss of braking power . I found that before the Jeep had impressive stopping ability, but now I feel there is insufficient braking to the point where I have to think ahead, againt worsted with any load in tow .

pixeldzn · **Posted:** Thu Jul 13, 2006 3:50 pm

If you are getting 180 out of a tank, you are doing something wrong.

I have 31" MT/Rs, Frankenlift, All J Skids, Rock Rails, Interior Rack and other little doo-dads weighing me down and I get 250-260 out of a tank. Heck, Wally says he still gets 230 with his SFA and 33s and he is much heavier now than any of us. Braking power may be a little less, but not substantial, and I feel the stickiness of the MT/Rs makes up for any losses.

Maybe you need to check your tire pressure. I find 35 is good for a MT tire. Air Filter and fuel injectors might be another to check.

tjkj2002 · **Posted:** Thu Jul 13, 2006 3:54 pm

I know how you feel,I also run"32's"(MT/R's) and was getting 14-15mpg on a really good day.I had to change my gears from the factory 3.73's to 4.10's and got my speedo recalibraided(it's dead on now) and now I average about 17-19mpg and pull heavy loads much better up hill.As for the brakes I had to switch to the powerslot rotors and hawk pads and now I also brake much better.As for the vibration would may need to check the tire balance,LBJ's,spindle bearings,tie rod ends,and for any loose suspension components(any of these things can cause vibrations while driving).Got any pics of your rig?

Jeepjeepster · **Posted:** Thu Jul 13, 2006 4:14 pm

pixeldzn wrote:

If you are getting 180 out of a tank, you are doing something wrong.

I have 31" MT/Rs, Frankenlift, All J Skids, Rock Rails, Interior Rack and other little doo-dads weighing me down and I get 250-260 out of a tank. Heck, Wally says he still gets 230 with his SFA and 33s and he is much heavier now than any of us. Braking power may be a little less, but not substantial, and I feel the stickiness of the MT/Rs makes up for any losses.

Maybe you need to check your tire pressure. I find 35 is good for a MT tire. Air Filter and fuel injectors might be another to check.

Heck, I get 15mpg in the city stock. Im getting some black cragar rims and 30" general grabbers mounted today. Ill get to how they do with braking and mpg. Im hopping I do not loose much if any. Its time for new rotors so ill take care of that.

DJBassman · **Posted:** Thu Jul 13, 2006 4:54 pm

Concerning breaks. When I was researching tires, someone gave me this link from another forum;

http://www.1010tires.com/TireSizeCalculator.asp

When I put my stock tires in 225/75r16 and compared them to 245/75r16 I get a warning message that states that going 3% over the stock can cause break falure. Maybe that is what your expericing with reduced breaking.

Jeepjeepster · **Posted:** Thu Jul 13, 2006 5:15 pm

DJBassman wrote:

Concerning breaks. When I was researching tires, someone gave me this link from another forum;

http://www.1010tires.com/TireSizeCalculator.asp

When I put my stock tires in 225/75r16 and compared them to 245/75r16 I get a warning message that states that going 3% over the stock can cause break falure. Maybe that is what your expericing with reduced breaking.

I just went up an inch and it says that. I do not believe my brakes are going to fail with just a 30" tire.

05kjrenny · **Posted:** Thu Jul 13, 2006 6:03 pm

i lost respect from my grandma,and aunt because they have libbys also and they are not supposed to look like that?

jason thompson · **Posted:** Thu Jul 13, 2006 6:51 pm

all your losses are related to tire / gearing
you will never see factory fuel mpg again even with the lift you loose some mpg wider tires and you loose taller tires changes the # of rev's per mile ie a small tire will do more rev's over one mile vs a taller tire in return every thing down the line turns slower wich makes the engine work harder than it did with those short skinny street tires
you can get much of your milage back with a regear to 4.10 also your trail preformance will go up as well

i still cant under stand why we cant put 4.56's in the front i thought that it used the same tru-trac as the standard dana30?
that is what the ring gear bolts to so that means the problem is with the pinion but what is the problem? has any body tryed?

sure with 4.56's you would be cranking out close to 3000 rpm at 70 but thats what my TJ does and i am not worried i just drive a little slower on the highway and realy slow on the trail

tjkj2002 · **Posted:** Thu Jul 13, 2006 7:32 pm

Quote:

jason thompson

all your losses are related to tire / gearing
you will never see factory fuel mpg again even with the lift you loose some mpg wider tires and you loose taller tires changes the # of rev's per mile ie a small tire will do more rev's over one mile vs a taller tire in return every thing down the line turns slower wich makes the engine work harder than it did with those short skinny street tires
you can get much of your milage back with a regear to 4.10 also your trail preformance will go up as well

i still cant under stand why we cant put 4.56's in the front i thought that it used the same tru-trac as the standard dana30?
that is what the ring gear bolts to so that means the problem is with the pinion but what is the problem? has any body tryed?

sure with 4.56's you would be cranking out close to 3000 rpm at 70 but thats what my TJ does and i am not worried i just drive a little slower on the highway and realy slow on the trail

The problem with pinion is that our Dana30A's use a longer pinion than standard Dana30's,the ring gear is the same though.

jason thompson · **Posted:** Thu Jul 13, 2006 7:50 pm

tjkj2002 wrote:

Quote:

jason thompson

all your losses are related to tire / gearing
you will never see factory fuel mpg again even with the lift you loose some mpg wider tires and you loose taller tires changes the # of rev's per mile ie a small tire will do more rev's over one mile vs a taller tire in return every thing down the line turns slower wich makes the engine work harder than it did with those short skinny street tires
you can get much of your milage back with a regear to 4.10 also your trail preformance will go up as well

i still cant under stand why we cant put 4.56's in the front i thought that it used the same tru-trac as the standard dana30?
that is what the ring gear bolts to so that means the problem is with the pinion but what is the problem? has any body tryed?

sure with 4.56's you would be cranking out close to 3000 rpm at 70 but thats what my TJ does and i am not worried i just drive a little slower on the highway and realy slow on the trail

The problem with pinion is that our Dana30A's use a longer pinion than standard Dana30's,the ring gear is the same though.

no way to cut or maby shim to make it work?
i need to get on that steel housing thing i been thinking about

Robert Bradbury · **Joined:** Wed Mar 22, 2006 10:37 am **Posts:** 132

tjkj2002 wrote:

I know how you feel,I also run"32's"(MT/R's) and was getting 14-15mpg on a really good day.I had to change my gears from the factory 3.73's to 4.10's and got my speedo recalibraided(it's dead on now) and now I average about 17-19mpg and pull heavy loads much better up hill.As for the brakes I had to switch to the powerslot rotors and hawk pads and now I also brake much better.As for the vibration would may need to check the tire balance,LBJ's,spindle bearings,tie rod ends,and for any loose suspension components(any of these things can cause vibrations while driving).Got any pics of your rig?

I didn't have any vibration or issues before the new tires and rims went on, but now I do. The tire balancing guy said it took a LOT of weight to balance two of the tires and he suggested for me to put those on the back.

Thanks for the tip on the gear change, where did you get the 4.10 ratio gearing ?

I just did up the brakes so I will wait for them to wear out before replacement, but I will look for bigger and better than stock the next time around .

I don't have any pics yet as I was waiting to finish up the last few details. I have to say though, the color I picked looks so classy on the ole Lib and I have
had many Liberty owners and non owners for that matter tell me how very nice the Jeep is in this color.

Tokyojoe · **Posted:** Thu Jul 13, 2006 8:31 pm

Just remember the 02 has a smaller gas tank than the 05 and newer models. Those 32's and the beadlock wheels weigh a lot more than our MTRs and Rubi wheels. Throw in an ARB bumper and the winch. That's a huge amount of weight gain.

You could remove the power doors, windows, AC, carpet, plastic interior molding, rear seats and passenger seats, radio, speakers, make the doors removeable, chop the roof into a convertible AND then you will lighten up the load to what you had added to make it hardcore trail worthy.

:-)r

tjkj2002 · **Posted:** Thu Jul 13, 2006 8:52 pm

If 2 of the tires took alot of weights to balance try and have them rotate the tire 180 on the rim and try rebalancing them.I got a whole new front diff from a dealership with the 4.10's and got the rears from 4WHEELPARTS.What color did you paint it?Here is a pic of my custom painted KJ.Hope all goes well!

USAFCOP · **Posted:** Thu Jul 13, 2006 11:07 pm

Even a good Shop will have trouble balancing TRXS tires, but it is possible. As mentioned, the heavy part of the tire could be on the heavy part of the rim...

As for the bad mileage, do not forget to take into account your Odometer is reading low now because your tire covers more ground as it rotates... Your mileage will shrink, My worst has been 9 mpg hauling a 24 ft trailer up the rockies!

Jeger · **Posted:** Thu Jul 13, 2006 11:21 pm

9MPG!!! We had a 454 that could get mileage that good. Of course thats what it got whether you were going up the mtn or down the mtn.. Man I love my CRD :lol:

tjkj2002 · **Posted:** Thu Jul 13, 2006 11:26 pm

Quote:

Jeger

9MPG!!! We had a 454 that could get mileage that good. Of course thats what it got whether you were going up the mtn or down the mtn.. Man I love my CRD

Heck 9mpg would have been a dream when I had my '84 F150,I only saw 2mpg highway(valves nearly floating doing 75mph) and 4mpg city.Maybe those 4.88 gears with stock size tires was a bad idea,awsome offroad and could pull anything but real bad gas mileage.I miss that old Ford :cry:

.

alljeep · **Posted:** Fri Jul 14, 2006 7:42 am

Jeger wrote:

9MPG!!! We had a 454 that could get mileage that good. Of course thats what it got whether you were going up the mtn or down the mtn.. Man I love my CRD :lol:

That's for sure! I don't have anywhere near 32s for tires, but mine are pretty wide and really increase my rolling resistance. Look at all the crap in my signature and I'm still getting 24-25mpg.

But, the gassers will have the last laugh when their transmissions are still going and we have gone through 3 or 4 torque converters due to the constant high torque of the CRD above 1600rpm...

Sport · **Posted:** Fri Jul 14, 2006 9:11 am

So if I regear to 4:10 I will actually increase my mileage? Would I do this to the front and rear? I don't want to jack the thread, I need to learn about regearing.

tjkj2002 · **Posted:** Fri Jul 14, 2006 10:43 am

Quote:

Sport

So if I regear to 4:10 I will actually increase my mileage? Would I do this to the front and rear? I don't want to jack the thread, I need to learn about regearing.

Yes it will if you went to 245/75 R 16's or bigger,and yes you have to do the front and rear so you don't waste the tranfer case.The bigger the tires the lower the gears so you will be back in your useable torque range and it will make spinning them bigger tires easier,thus better fuel mileage.

Sport · **Posted:** Fri Jul 14, 2006 12:25 pm

tjkj2002 wrote:

Quote:

Sport

Yes it will if you went to 245/75 R 16's or bigger,and yes you have to do the front and rear so you don't waste the tranfer case.The bigger the tires the lower the gears so you will be back in your useable torque range and it will make spinning them bigger tires easier,thus better fuel mileage.

Thanks I will have to check into it a little more, I am running 31x10.5 on steel wheels now and I know that regearing will increase the torque I just always thought that more power meant more fuel burn.

What you said makes sense though.

Losses to expect after a lift and big tires

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