I must be having a brain block or something, but I'm having trouble figuring out comparative milage numbers. Running 215/75/15's, I'm getting around 22 miles per gallon according to the trip odometer and how much gas it takes to refill the tank each time. Running 33-10.50/15 Swampers, I'm getting around 17 miles per gallon when figured out the same way, by dividing the trip odometer by the gallons to refill. I know that when I'm running the swampers, I'm moving 15 miles per hour faster than the speedometer tells me I'm moving when it reads 60MPH. So how many miles per gallon am I getting running the swampers when corrected to directly compare to the 215's?

Actually the 17 MPG sounds about right.

If you really need to know, you need to
go the same # of miles, like on a trip of
say 200 miles, once with the Swampers
and once with the 215s, then refuel and
divide your gallons and miles

Other than that, if you can figure that for
every 100 miles you go say 15 miles farther
you could use the higher corrected # to figure
your MPG, but in the case you show here, you
didn't include any milage #s to be able to get
an estimate of your true MPG

Look up the gear calcs on the web site
(check the bottom of my post) and figure
your true mileage travled and gallons used

Wild

Every time I refuel, I fill the tank the whole way and reset the trip odometer. At the next fill-up, I take the trip odometer's reading and divide it by the number of gallons needed to refill the tank. That's where I got the figures of 22 and 17 for the different tire sizes. However my problem is figuring out the difference in distance travelled between the 2 sets of tires.  I don't feel it is quite right to compare the 22mpg and 17 mpg directly against each other because the 17 isn't accurate. When I'm running on the swampers, I'm travelling further than the odometer reads, but by how much, I'm not sure. So if I'm actually travelling further than the odometer is telling me I travelled, I'm actually getting more miles per gallon than the odometer is telling as well, right?

Right, that's why I suggested you
go on a trip with both sets of tires,
same distance and speed, then
compair miles and gallons

Let me try to give you a rough rule of thumb...

According to my calculator....
- P215-75-15...............27.7" diameter.........7.24' circumfrence
- 33-10.50-15..............33.0" diameter.........8.635' circumfrence

You travel 19% farther per indicated mile on the 33's than on the 215's

so your 17mpg on the 33's is more like 20mpg

Caution...you are going abouot 19% faster and farther than indicated on the speedo compared to the 215's.

Zag

According to my calculator....
- P215-75-15...............27.7" diameter.........7.24' circumfrence
- 33-10.50-15..............33.0" diameter.........8.635' circumfrence

You travel 19% farther per indicated mile on the 33's than on the 215's

so your 17mpg on the 33's is more like 20mpg...

That's what I was trying to get to. I just couldn't come up with circumference figures, I kept coming up with area instead of circumference.

So, now to compare the corrected figure of approximately 20MPG on the Swampers to 22MPG on the 215's(which I realize is kinda low, but calipers are dragging a little more than normal) I can see that a 2MPG gain is hardly worth the weird looks I'm getting from people by running around town in a rig with 6+" of total lift on stock rims/tires! Guess I'll swap the swampers back on tomorrow morning! LOL!!!

I would be willing to bet those 33s are closer to
32"  which is a 13% increase in speed, but I still
need some gallons and #s to give you an accurate
MPG with the bigger tires

which Swamper is that ??

I might be able to look up the #s

33x10.50/15 Swamper TSL Radials on 15x8" Jackman welded steel wagons.

I didn't keep track of the trip odometer reading and gals used for each fill up past the fill up, I just figured out the milage for each tank of gas, then averaged those figures to get 17 and 22...

Naw, I found it 32.7" tall (dia)
so thats 15% higher, so in 100
miles on the Odo you get 115
miles, and at 60 indicated you
are going 69.5 MPH and at 70
you are going 81 MPH be careful

Even at 15%, it's still approximately 19.55 MPG on the Swampers compared to 22 MPG on the 215's. A total gain of 2.45 MPG when rolling on the little tires. Still not worth the silly look IMHO! LOL!

More that one dude has about broke his neck
trying to get a second look at the tires on my Kick

At least 2 of them on the freeway, they caught a
glance and had to look back out of the window to
make sure they weren't seeing things 

I like it

Yeah, but that's running bigger rubber than stock, right? I got people looking twice and laughing at my really tall Tracker running little tiny tires... LOL! I liked the attention of running the 33's a lot better! LOL!

Ohh ya 33-13.5 LTBs on 2.5 BackSpace wheels
looks like a mini monster truck coming down the road

Ohh ya 33-13.5 LTBs on 2.5 BackSpace wheels
looks like a mini monster truck coming down the road

LMAO!!!