Lostfisher1

Ok there is always talk about MPG on here and there is always a responce " well ur mpg is not the actual MPG because of ur tire size.
So does anyone have the numbers on the miles.
Lets take the tire size go 1000 miles on stock... not sure what is the stock tire size is but u get the idea.

Stock x 1000mi = 1000 mi
28" tires x 1000 = ?
29" x1000 =?
30
31
32
33
I believe those are the most common sizes but if anyone has the info im sure everyone would appreciate the info.

Drewjharper1900

I know that 33's are 11% larger than stock. Theres a website that can give you the percentages and what speed you are actually going and stuff like that. I cant find it now though.

OnlyInMyXJ22

Just buy the correct speedometer gear. Problem solved.

Lostfisher1

It is easier for me 2 ask. Rather than spend. $70 on a gear and install it drive around for a few days. 2 find out.

So if 33's r 11% bigger than stock than in theory i'll get 11% more mialage. So for every 1000 miles I will get an additional 110mi than my spedo claims.

Drewjharper1900

Exatly.

purplegrocerygogetter

Prolly woulda been easier to do this too, there are several threads on this subject.....

Lostfisher1

used the search feature with no avail. But I did find out some other info that helped. The stock tire size for the cherokee was 27.5" so if you have a set of 28's it is 1.8% bigger
tire size|percentage|x100mi
28= 02.8%= every 100mi= 102.8
29= 05.2= 105.2
30= 08.4=108.4
31=11.3= 111.3
32=14.1=114.1
33=16.7=116.7

So I average 16.2 right now with a set of 29's on, but that is with my improper gearing on my jeep. so 16.2 x .052= .84 so in reality I am getting 17.04mpg

Drewjharper1900

My bad on the incorrect info. Not sure how i got it wrong. Guess ive been getting a little better mileage! haha

peep

I run 31 x 10.5 -15 on stock 7x15 rims. My speedo is right on, right on!
Speedo was never correct on the stock tire. Used to get 24 to 26 mpg Canadian gallon, 150000 miles ago.
Stock 3.55 geared. AW4 trans with convertor lockup.
Today on 31's Peep gets 21 mpg Canadian gallon. Corrected to US gal, I get 17 mpg.
Your mileage is what you get, what you pay to play at the cash register.
I'm still bartering with a friend for a set of 4:10 gears, that would help my torque and mileage at about +2 mpg max. A bigger gear without also a bigger tire would not get me a mileage gain. I don't expect to see the stock mileage ever again without a fresh engine.

kikstand454

Awesome. This means I'm averaging 17.34mpg.

Makes me feel 8.4% better.

no rdplz

$70?!? Where are you looking? Quadratec has 'em for about $40 and install is incredibly easy.

motorcharge

It varies by far more than tire size. Age/condition of plugs, wires, air fuel and oil filters, oil viscosity, condition of fuel system/injectors, gears, driving habits, vehicle weight, tire psi, ect all have a significant effect on your mpg's.

Lostfisher1

No: I have only seen the gears online thru a link on the Cherokee web sight. I have not searched for the best deals out there. I am not sure about the best prices out there.

Motor: I am just going by distance if u have stock gear in ur spedo. If u average out ur MPG with the stock mialage all you have 2 do is multiply it by the percentage than add it to you MPG and than if my numbers and ur calculations are correct than that should give u ur real life MPG.

Calculate at ur own risk because I am not sure how accurate this is. All I did was calculate the percentages of how much larger the tires are than stock. But in theory mu formulas should work. Or u can just get a gps and drive around a few hundred miles and compare the 2 distances and see what u get.

motorcharge

This only tells you what you're getting, not what you can get.

All the OP is going to figure out is what bearing tire size has on mpg, and even then it's not all that accurate because it can vary among different tires/tread patterns, drivers, ect.