round town maybe a hair drop in mpg

slight gain on hwy mpg due to "taller" tire and lower rpm on motor on flat highways.

i'd say you won't notice much. keep the tires at 35 psi for top mpg. if you are worried about mpg, remove your roof rack cross bars, take all the junk outta the back, and keep tires at 35 psi, along with top quality high flow air filter, for your stock rig.

 

Honestly, I think with size a little difference in size and weight. I doubt you will see a change.


I dont have expirence with this size jump so you can wait for someone who has done it.

 

the change, if any, would be so small you prob wont even notice, maybe a mile per gallon loss, i did the same change to my jeep back in the day, didnt notice at all

 

1 mile per gallon loss is definitely more than I want to experience if I make the shift. Can anyone else confirm this? If it were something like 1/10th or 2/10ths of a mile per gallon loss, than perhaps I will do the switch, but a mile per gallon adds up really fast. At 12,000 miles per year, that is about 50 extra gallons of gas per year.

 

dude im poor and cheap but are you serious, 1 mpg was a guess it prob wont even be that much

 

I had 225's on mine, and averaged 18-19 on highway. Switched to 235's and did a tune (plugs,wires,cap,rotor) and first 200 mile trip I did 22.7. You'll be fine - Go with the 235's.

 

same thing happened for my dd. keep it running in top shape and you should get over 20 mpg on the highway. and dont flex the skinny petal. i get 22 mpg @ 65-70 mph.

 

I am going to do 30's on my DD. But as stated you should gain on highway. Also why would it matter? You are driving a Jeep and I can think of no reason to have one if you are concerned with Fuel Economy.

 

Because it is the vehicle I own. I bought it when gas was cheap. Now I'm trying to save on fuel with high gas prices.

 

If you are that concerned about mpg get tall skinny tires with street tread or sell you jeep

 

From exprience I'd have to say that yes you are going to see a negative change. It may not be much, but if as little as a 1/10th of a mpg is going to be an issue then you'd be better off sticking with where you are at.
Its a Jeep.

 

I just changed from 225 to 235 and I did lose about half to 1 MPG. I also noticed a lil bit off pulling power lost when I tow a small boat at lower speeds. If its your DD I'd keep it stock.

 

Your behavior will do more to affect mpg than that tire difference. The right-foot-boogie on the skinny-minnie pedal has done more harm and gotten less blame than almost anything else I can think of.

At $3/gallon (we're about $2.92 around here as of today), driving 12,000 miles per year, going from 21mpg to 20mpg will cost you exactly $85.71. For the entire friggin year.

And those tires are going to run you, what?, -- apiece, more than that.

So, for at LEAST four (4) YEARS, your tire cost will have made your "loss" in fuel economy insignificant in comparison. And that's IF you keep those tires for four years.

In proper perspective, your focus may be the bigger problem here.

 

Going from 16 MPG to 15 MPG for 12,000 miles will take an extra 50 gallons of fuel exactly. I do a lot of stop and go driving. This is my DD, and I don't average any more than 16 MPG right now; maybe even a little less. On the highway, I get around 19 or so, but I'm not on the highway that much. At $3.25 gas, that turns out to be about $162.50, for four years, adds about $650 dollars to the cost of those tires, if I really will loose 1 MPG.

Their are only two reasons, I'm thinking of moving up one size. First, because, interestingly enough, the cheapest place I can get the tires I want (michelin ltx) sells the 235's for about $10.00 less than the 225's. And because, I was wondering if one size up might look better on the soft 8's I just purchased. However, I don't want to save $10.00 up front, if it will end up costing me $650 more over the life of the tire, or a lot more should gas prices shoot back up over $4.00, as I expect.

 

I've looked into the idea of buying a more fuel efficient vehicle, but it just isn't worth it even with $4.00 a gallon gas. Gas would have to go to around $7.00 dollars a gallon before I could justify the expense of buying a different vehical. I like my Jeep, but I don't see why I shouldn't be trying to get the best fuel economy I can.

When you mention that my Soft8's will have a bigger impact than the 235's, why is this? Are they much heavier than the steel wheels I have on there now? They are the same size (15X7).

Thanks.

 

I've always run 235s and stock my '94 got around 18 mpg. Now I've moved them to the wife's '90 and yup--18 mpg. Get rid of the steelies and go alloy--you'll make up for the extra tire weight. Gas is 2.77 here now--not so bad, eh? Of course, gas mileage takes a nose dive as it gets colder--winter mix, more idleing. When all is said and done, I don't think there will be any net difference. 235s are, of course, illegal on the XJ in Maine so you need to pick your inspection station carefully

 

235s are, of course, illegal on the XJ in Maine so you need to pick your inspection station carefully

Shock! Thanks for the heads up. Are you serious? How come I see Jeeps with huge tires driving around?

 

Hello,

I am currently using 225/75R15, but am considering moving up to 235/75R15 with the new crager soft 8 rims I bought. The 235's are each six pounds heavier than the 225's, and are a half inch larger in diameter. If it will effect my fuel economy negatively, I'm going to stick with the 225's.

Thanks!

I wouldnt do it

your jeep would fold like a taco

 

its more then likely that it wont even be a full mpg difference, this shouldnt even be an issue. MY buddies geo metro cost him 400 bucks and it gets over 30 mpg. something to consider.

 

Your driving habits, tire inflation, and tire design will change it more than that small size diff.
If everything else was equal, probably it would depend on your personal driving habits if better or worse, but doubt you could see the diff either way.

Softer rubber, worse fuel mileage.
Wider footprint, worse mileage.
alloy vs. stock? I don't know how much diff in unsprung weight their is in this size range, but I doubt much. Aluminum is a lot lighter, but they also have to make it a lot thicker.

HTH, YMMV (Pun Intended)
--
dw

 

Up until this year when they changed the law, you could not LEGALLY lift a vehicle with ABS (nothing to do with tires) in Maine.

BTW, a vehicle equipped with ABS that does not work will not LEGALLY pass inspection, either (though, again, it's up to the inspection mech to spot it).

I believe the original stock tire size was 205, with 215s and 225s coming on some models. Thus, 235 would be three sizes over. Again, the worst you will need to do is be aware of where you are getting it inspected.

I DO know that places like Wal-Mart/Sams Club Tire dept. will NOT mount them--they WILL rotate them if they are already on there, though. Just make sure that wherever you buy them will actually put them on the Jeep for you.

Not sure exactly where you are in "Central" Maine, but I can recommend Jeep friendly inspection stations in the Waterville area via PM, if the need arises.

 

Up until this year when they changed the law, you could not LEGALLY lift a vehicle with ABS (nothing to do with tires) in Maine.

BTW, a vehicle equipped with ABS that does not work will not LEGALLY pass inspection, either (though, again, it's up to the inspection mech to spot it).

I believe the original stock tire size was 205, with 215s and 225s coming on some models. Thus, 235 would be three sizes over. Again, the worst you will need to do is be aware of where you are getting it inspected.

I DO know that places like Wal-Mart/Sams Club Tire dept. will NOT mount them--they WILL rotate them if they are already on there, though. Just make sure that wherever you buy them will actually put them on the Jeep for you.

Not sure exactly where you are in "Central" Maine, but I can recommend Jeep friendly inspection stations in the Waterville area via PM, if the need arises.

My Jeep says 215 in the door, so I imagine I'll be okay with the 235's. Another question: Will Sams Club/Walmart mount Tires on Rims without knowing what vehical they are going on? I have new Crager Rims as well. What I planned to do is just bring all the stuff down there in the bed of a pick-up, as I want to torque the lug nuts myself.

Thanks.

 

Not to thread jack. But will 30x9.5x15 tires fit the stock alloy rims of a 1988 XJ?

I have 225/75/15's on there now.

 

Yes, they will fit fine. You may get some rubbing, though, on the LCAs. You can add some backspace with spacers, adj. your steering stops, or just be aware of it and live with it.

 

Your obviously not too concerned with money if you just bought new soft 8's

 

Well they are the cheapest wheel you can find pretty much..

 

I can tell you that the Wal Marts in central CA will put whatever tires you buy from them on your vehicle, my 83 Ranger has 225/70/14s from them and stock is 185s. You got the moola they mount the tires. Phil

 

If you are that concerned with gas mileage you are in the wrong hobby.

And most shops will mount and balance any tires and rims as long as they are within the fitment for each other.

 

Umm... It's not a hobby. Unless you consider a vehicle a hobby. I specifically explained that at the start of this thread. It's my only vehicle.