you calculate the milageuntil the low fuel light comes on? how much gas is left when low fuel alert comes on?

 

Man, I just looked at 20"s with 305/55/20 Nitto Grapplers. I was set on this, but 12-14 mpg sounds terrible. I was hoping for at least 15 avg. I guess I must think about how much I want the aggressive look.

Anyone hada better experience with this size tire and wheel?

 

I get 14.7 mpg on the highway in my H2 with 13.5" wide tires, so I'd say you got something wrong

 

You have a new H3 correct? It takes a while for you to start seeing better mileage. Every single one of us has gone through this.

The larger the wheels, the worse the mileage also.

Anything over 60 MPH usually drops your mileage big time also

Did you have the AC on? That's another one.

We have found alot of reasons why collectively on here, so unless you were driving 55 with stock wheels and no AC with over 10k miles on your H3, you probably won't be seeing better mileage for a while

 

It's not just the tire width but the weight of the wheels and tires. Bigger tires and wheels are heavier, with a larger rotational mass. I hear different discussions on this, and here's one example: for each additional 10 lbs you need 1 hp to make up the performance difference. If each larger wheel/tire combination is 10 lbs heavier than stock, you've gained 40 lbs of rotating weight (and some say every 2lbs. of rotational mass added to the tires/rims is eaqual to 20lbs. of static weight added to the vehicle). More mass, more rotational mass = an engine working harder to do the same thing. Thus the drop in mpg.

I picked up the above numbers from various sources but check out this linked article, especially the numbers at the bottom of it.
http://www.tirerack.com/wheels-techpage-1/108.shtml

Here's a paragraph from that article:
[blockquote]A vehicle's total weight is the sum of all of its parts and affects its ability to accelerate, brake and corner. Reducing the total weight will enhance the vehicle's performance because less weight needs to be controlled and therefore, less energy is required. Unsprung weight is the weight under the springs which moves up and down as the vehicle rides over uneven roads and leans in the corners. Reducing unsprung weight allows the springs and shock absorbers to be more effective in controlling the suspension's movement. Additionally, a vehicle's rotational weight includes all parts that spin including everything in the vehicle's driveline from the engine's crankshaft to its wheels and tires. This affects the energy required to change speed as the vehicle accelerates and brakes. As you would guess, reducing the weight of any of these rotating components will enhance the vehicle's performance because less energy will be required to increase or decrease their speed. [conversely, adding weight increases the energy use of course]
[/blockquote]
[/align]

 

I was going to get all technical but I figure I'd make it easy. You did the dirty work! I love those wheel and tire sites. They always seem to do a good job at explaining things.

Does anybody make SUV tired that are made of special light weight material? I was thinking about getting lighter wheels next year when I replace the tires. I thought if I could decrease the amoutn of weight on the rims/tires I could boost my mileage. I just thought I'd replace the factory wheels with lighter ones of the same size, and go with the same tires, or maybe a diff brand but the same size

My stock 32" tires worked great off-roading, but having a stick helps.

 

I just finished a road trip in my 2006 H3. On the way out,..I averaged

15.8 for tank one,
18.02 for tank 2

On the way back I got stuck in slower post-Thanksgiving traffic and was moving slower. Seemed to be getting 20 mpg for the first 3/4 tank. ended up at 19.02 as the last bit was finally moving fast. ("Low Fuel" light wasn't even on at 390 miles when I gassed-up)
Second tank was less, as traffic was moving at 75-80. Tank 2 was 16.26 mpg.

So 4 tanks (about 1450 miles,..A/C off, 40-50 degree weather,..65-75 mph mostly, tires at 36 psi, fresh alignment) were;

15.8
18.02
19.02
16.06,..for an average of 17.22 mpg.

So it looks to me like the newer more realistic EPA ratings are plausable. I'd guess that at a steady 60,..it would have gotten 18.5

 

The wheel/tire combos' weight won't affect highway mileage at all,..but it will have a tiny effect on city mileage. On the highway,..the tires are maintaining a constant speed,....so their aero drag is about all you can hope to improve. Starting up from a light is about the only place that lighter wheels will show a benefit mileage-wise. Tires being the most important,..because they are farther out from the axle,...and so their "moment of inertia" is dramatically higher.

Lighter wheels and tires will help ride though. I've been wanting some 18" wheels with lighter and more street-like tires. Had been looking at the Bridgestone Duellers. Not the A/T's that are recommeded for the H3 Street,..but the Dueller L/T's. They seem to be more street like. Morelike what comes on an Explorer.

Not much selection in these sizes. No one expects to sell a high-performance street tire these days with a 65 sidewall.

I'd love to find a set of Michelin Pilot Sports or similar in a 275/65/18. LOL

 

Did you have your speedo recalibrated? Changing the final drive size will change everything. When you get bigger/smaller tires the speedometer MUST be recalibrated.

 

Here's a must read if you're going to swap tires and/or wheels.

http://www.offroaders.com/info/tech-...ng/mph-rpm.htm