1996 Jeep XJ, tires & wheels, and fuel economy

fuel-economy

#1

Hi everybody,

I have a 1996 Jeep Cherokee that I use basically in the same way Mom uses her Subaru: hauling groceries, back and forth to work, taking the kids around, and so on. The transfer case gets some work only in the snow because we live on a hill–we don’t get outdoors much any longer. I want to keep this rig because I really like it and it’s very comfortable for me to drive. The trouble is that the mileage is rough for street driving, well under 20mpg. That, and it’s getting harder to find tires to fit 15" rims… the Goodyears I have on there now are just awful, like driving on jellyfish. The current ones are American Racing rims that a previous owner painted black. I had to replace two tires last week and it took the tech seven hours to get the beads seated properly on these things. I think it’s time to try something else.

My idea is that by replacing the tires in a certain way, I might be able to get better mileage and solve the tired old rim problem too, at least for street use. Stock tires are 215/75/r15, and there’s a 1.5" lift on this thing; the current offset is +40mm, and I’m not sure but I think the rims are 8" wide. OK. This means I should be able to get 17" rims with tires at, say, 215/60/r17, which should have approximately the same total diameter as the stock tires had. (These happen to be the wheels on most Jeep Patriot/Compass Latitude models, which happen to have the same 5x4.5 lug pattern, should I happen to find them used on craigslist.)

I’d like to know if this is a stupid idea or one worth pursuing. Would this have an impact on mileage or performance? Might I save time and money in the long run shopping for tires with more contemporary rims to work with?

Thanks!

ps: here’s a picture of how the XJ looked before I got to work cleaning her up.


#2

That “jellyfish” condition could be the result of reduced caster from the 1.5" lift. And the lift also increased wind drag which negatively affected fuel consumption. Changing to 17" wheels, regardless what tires are installed can’t improve fuel mileage but it might worsen it.


#3

+1 to @Rod Knox, Across the boards The 17 inchers may make it easier to find the new “high mpg” tires tires but that is the best you can expect. The lower profile of the 60 series tires will make it ride a bit harder but should help the jellyfish feeling.

BTW, I doubt those 15 inchers are 8 inches wide given the 215 wide tire and the picture. If you can find take-offs from a Compass, be sure the offset is correct for your Jeep. That 40mm seems to be negative (wheel centerline moved outboard) rather than positive. Your current wheels look to be too far out of the wheelwells. Tire rack shows wheels that are zero offset for your Jeep and about +40 for a Compass. That means they won’t fit your Jeep. Tire rack does show nice aftermarket wheels, though.


#4

This is all helpful stuff, thank you.


#5

There is very precious little you can do the change the mileage. Getting the largest circumference tire you can fit under wheel well could theoretically help if you never pass or went up hills. This is not an Eco car. Do what you can to minimizing trips or fall out of love with it and get 4 cylinder compact.


#6

Some thoughts:

First, tires have a relatively small affect on fuel economy. And a tire’s affect on fuel economy is greatest with long commutes - short trips (like to the store and short errands) only minimally.

Also, tires are subject to a technology triangle involving fuel economy, treadwear, and traction. In order to get improvements in one area, one or both of the other areas has to be sacrificed.

As time goes on, smaller wheel diameters tires are going to be harder and harder to find.

But changing to a larger diameter wheel would put you in an area more likely to stay available.

So you should change wheels for reasons other than fuel economy. There’s not much to be gained there.


#7

I used to own a '96 model Jeep Cherokee with the 4.0 engine. The best mileage that I ever got with it was about 19mpg around town and 24mpg on the interstate. I owned it for years and kept it tuned up and the mileage never changed after replacing tires at least 3 times. I used Goodyear Viva II tires from Walmart. The ride was great and they wore great…and lasted about 50K on all 3 sets.