MPG Drop After New Tires?

ups4 · **Posted:** Sun Jan 03, 2010 5:11 pm

What in the world would cause my MPG to drop from about 18 to 15 after getting new tires?
The new tires, Goodyear Wrangler Silent Armor 235/70/16, replaced the original OEM Goodyears.
Scratching my head on this one :roll:

.

Paul

nightdrv · **Posted:** Sun Jan 03, 2010 5:38 pm

235/70 is a smaller overall diameter than 225/75. Simple as that. More rotations per mile required to go the same distance (ie, more gas). 225/75/16 is really only comparable to 245/70/16.

Don't feel bad. I have the same size tires (not by choice, mind you).

Diggerfreek · **Posted:** Sun Jan 03, 2010 6:44 pm

Are they LT rated tires?

Elt31987 · **Posted:** Sun Jan 03, 2010 8:20 pm

After putting these junky Treadwrights on my gas mileage dropped HORRIBLY. I think its cuz they are Load Range E and weigh about 48 Pounds each instead of the stock tire which is like 28. Gotta get rid of these

Diggerfreek · **Posted:** Sun Jan 03, 2010 8:30 pm

Elt31987 wrote:

After putting these junky Treadwrights on my gas mileage dropped HORRIBLY. I think its cuz they are Load Range E and weigh about 48 Pounds each instead of the stock tire which is like 28. Gotta get rid of these

That is the reason I asked if they were LT rated tires.....

To bad you were so far away, I'd take your tires.............

Rick K · **Posted:** Sun Jan 03, 2010 9:06 pm

Looks like I lost about 1 mpg after I put on the All-Terrain T/As. On the other hand, compared to the Wranglers I'll take it.

Elt31987 · **Posted:** Sun Jan 03, 2010 9:25 pm

Dont get me wrong, they tear up the trail great, but just weigh too much

tjkj2002 · **Posted:** Sun Jan 03, 2010 9:54 pm

Elt31987 wrote:

Dont get me wrong, they tear up the trail great, but just weigh too much

You want my tires? They only weigh 89lbs each and are only load range "C" tires,yeah there 35" tall but most other 35" are about 55lbs-65lbs in load range "C".

ups4 · **Posted:** Sun Jan 03, 2010 10:08 pm

nightdrv wrote:

235/70 is a smaller overall diameter than 225/75. Simple as that. More rotations per mile required to go the same distance (ie, more gas). 225/75/16 is really only comparable to 245/70/16.

Dang, it looks like they're only .3" smaller than the 225/75's.
Would it make that much of a difference? :furious:

Oh well, at least they look/drive better :lol:

.

Paul

Edit: Digger, yes I believe they are LT rated. Couldn't find anything definitive about the rating.
Nope...it looks like they are rated "P" which I guess is Passenger?

Elt31987 · **Posted:** Sun Jan 03, 2010 10:31 pm

tjkj2002 wrote:

Elt31987 wrote:

Dont get me wrong, they tear up the trail great, but just weigh too much

You want my tires? They only weigh 89lbs each and are only load range "C" tires,yeah there 35" tall but most other 35" are about 55lbs-65lbs in load range "C".

Sure let me go outside real quick with some Fiskars scissors and trim a little off the fenders and ill take em

Diggerfreek · **Posted:** Sun Jan 03, 2010 11:19 pm

ups4 wrote:

nightdrv wrote:

235/70 is a smaller overall diameter than 225/75. Simple as that. More rotations per mile required to go the same distance (ie, more gas). 225/75/16 is really only comparable to 245/70/16.

Dang, it looks like they're only .3" smaller than the 225/75's.
Would it make that much of a difference? :furious:

Oh well, at least they look/drive better :lol:

.

Paul

Edit: Digger, yes I believe they are LT rated. Couldn't find anything definitive about the rating.
Nope...it looks like they are rated "P" which I guess is Passenger?

OK, my 3 guesses....

1. You let your wife drive the KK who has a lead foot
2. winter gas
3. The tire weights more and has more rolling resistance because of the tread design....

Boblemoche · **Posted:** Mon Jan 04, 2010 1:20 am

i had those tires in a 245/70 16 and I didnt notice a diffrence in mpg. They were p rated. I also dont think the slight diffrence in rev per mile can affect mpg since going to 4.56 gear made little diffrence in my mpg when I had these tires and I still get around 19/16 mpg hiway/city with my LT 285/75 16. there must be something else that affect your mileage

hrogi · **Posted:** Mon Jan 04, 2010 4:51 pm

Give the tires a few hunder miles to break in...

Then fill up and look at the new numbers.

Do not forget to reset the counter and maybe see the dealer about adjusting for the new size in the computer.
if they do it for free.

racer1 · **Posted:** Mon Jan 04, 2010 10:15 pm

Here is a handy tire size calculator:

http://www.miata.net/garage/tirecalc.html

Dave

stripesace · **Joined:** Sat Oct 18, 2008 1:25 pm **Posts:** 54

18MPG mostly city or highway? I think I need to slow down on the HWY before I'll see any kind of jump in my MPG. On my drive to louisiana for thanksgiving I was getting almost 100 miles per quarter of tank. I can barely get 160 out of half a tank during a normal week.

jeeplikens · **Posted:** Wed Jan 20, 2010 6:06 pm

MODS: If you think this is in the wrong place, please move it. Thanks

Well, it's been a LONG while since I've posted here but stop by to read from time to time. I see some nice posts about tires but I'm in need to replace the stock goodyear's that came on the KK. I got my Liberty last feb of 2009. Took it in today for it's 30k mile service. It really had 35k but figured, what could a tune up hurt right? Well, long story short and 371.00 later, tune up, throttle body cleaning (hey, their ASE cert tech said it was "pretty dirty"), fuel system cleaning done, oil change and tire rotation (cupon, yey) and dif service (they said the oil was "dingy" and I could wait till it hit 40/45k but I went ahead and did it. While I was there, had the rear hatch window seel replace (mine, like the 04 KJ I had, was leaking a little). Oh, and they looked into why my tire warning low air light was coming on and staying on (this had been a on going issue from back in the summer). Well, 35k on the orig tires put them close to replacement so instead of having them pull the nail they found (oops) and the gash down to the steel belt (all on the same tire), I'm looking for a set of tires for the KK.

I do go off road from time to time and have had it covered in mud. But those standard GY tires are not for anything other then a little mud slinging and nothing serious. I don't want some Richard Cepek(sic?) style mudders. I'm looking for something that is great for onroad and good for off. I had a nice set of Cooper M+S tires on my 04 and loved'em. That might be about as aggressive as I want but putting M+S's on now is over kill. I figure I'll spend around 100/120 a tire before all the fees, coverages, etc...
Some of the tires I'm looking at:
Bridgestone Dueler H/T (want a little wider tire then stock 225's) (These got so/so ratings from what i've read so far)
Bridgestone dueler APT IV With Uni-T (on sale at sears for about 100.00 a tire)
Dunlap Rover A/T (108.00 a tire)
Kumho Road Venture A/T (113.00 a tire) LT225/75R 16 to stay within my same size. Rated at 115/E load

I know there are MANY tires out there. I would like something that will give me a little edge when I do go down some trail or drive in crappy weather.

OK. Enough rambling for now. You guys are great and keep up the good informative postings. I've enjoyed reading them over the years.

oops.. forgot to mention. This 09 is a big improvement over the 04. My MPG is above average. The BEST I've gotten was 26.7. 2 tanks of gas. One going to Chicago, a little local driving, then back to Detroit. City seems to be around the 16/17 mark. I do have a K&N air filter but I dont' think that's helped much at all. Did seem a little faster out of the gate. So, before I got todays tune up, I was hitting 22.9 hwy at 2k rpm or higher (70+). My 26.7 came when I FORCED myself to drive at 1800 rpm (or around the 64mph mark) both ways. The best I ever got with my 04 was 19 hwy, and city was 12 :furious:

.

Elt31987 · **Posted:** Wed Jan 20, 2010 7:39 pm

Well i cant vouch for them yet but im ordering Bridgestone Dueler AT REVO 2's this weekend. Best rated tire for 245/75/16 All Terrain and Off Road on TireRack

MPG Drop After New Tires?

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