Re: Repl tires other than Michelin or Continental
 

It IS totally about the combined weight of the tire and rim.

The mileage savings is because of the decrease in rotational inertia of the tire rim combination. Not alchemy, but plain old physics. Spinning up an extra 8 pounds of rotational weight ( my car has 4 tires on the ground) is expensive.

The other benefit to lighter tires and rims (called the removal of unsprung weight) is better handling and braking, and superior suspension compliance (read less shock wear) from not having the extra 8 pounds unsprung weight.

Check this out:
"
Rotational Inertia (or Momentum)

Rotational inertia is a concept a bit more difficult to deal with than unsprung weight. Inertia can be thought of as why a car wants to keep rolling once moving, or remain in place once stopped (unless you forget to set the parking brake on that hill). I believe the terms momentum and inertia are interchangeable. The term “flywheel effect” also refers to these concepts. In a car, there are a number of rotating masses which require energy to accelerate. Up front, ignoring the internal engine components like the crankshaft, we have to worry about the flywheel, clutch assembly, gears, axles, brake rotors and wheel/tire. Out back its a little simpler (for FWD) with just the brakes and wheel/tire contributing most of the mass.

The more mass an object has, the more energy it takes to accelerate it. To accelerate a rolling object such as a wheel, you must both accelerate its mass plus overcome its rotational inertia. As for braking, you must overcome its rotational inertia plus decelerate its mass. By reducing the weight of the vehicle's rotational mass, lightweight wheels provide more responsive acceleration and braking.

Before continuing with our informal analysis here, I want to point out something very important about rotational inertia. We’ve all seen the ice skating move where the skater starts spinning. She pulls her arms in and speeds up, then extends them again and slows down. Why is this? Well, the further a mass is from the center of rotation, the faster it must travel for a given angular speed (how many degrees of an arc it traverses per time unit). The faster anything moves, the more energy it has, so when the arms are pulled in, conservation of energy says that the rotation rate must increase due to equal energy being applied to the same mass over a smaller diameter. Applying this to wheels and tires, which have most of their mass spread as far as possible from the rotation center, I think you’ll agree that it naturally takes more energy to accelerate them. Example: Take a two identical masses, but one is a solid disk of diameter D, the other is a ring of diameter 2D. The ring will require more force to accelerate it (in a rotational manner). Therefore a heavier rim with a smaller diameter could have less rotational mass than a lighter rim of a larger size, and accelerate faster with the same force applied.

The effect of rotating mass can be calculated using Moment of Inertia (MOI). MoI is related to not only the mass of the rotating object, but the distribution of that mass around the rotational center. The further from the center, the higher the MoI. The higher the MoI, the more torque required to accelerate the object. The higher the acceleration, the higher the torque required.

Because of this, the weight of rotating mass such as wheels and tires on a car have a bigger effect on acceleration than static weight such as on the chassis on a car. When purchasing new wheels and tires for a performance car, it can be useful to compare the effects of different wheel and tire combinations. This is especially true when considering upgrading to larger wheels or tires on a car.

The use of light-weight alloys in wheels reduces rotational mass. This means that less energy will be required to accelerate the wheel. Given that each pound of rotational mass lost provides an equivalent performance gain as a 10 pound reduction in vehicle weight, the benefits of light alloy wheels on vehicle performance cannot be overlooked.
For example:
A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight (thats worth 0.200 in the 1/4 mile)"

Re: Repl tires other than Michelin or Continental
 

^Nice^

Re: Repl tires other than Michelin or Continental
 

Running with this idea, an 'upgrade' for those wanting to increase MPG would be to downsize their rims to a 15" wheel. Since the disc brakes are only 10" or so in diameter, there should be plenty of clearance. I see the LRR tire selection is good for a 235/75-15 size (and they're cheaper!), with minimal or no speedo error (less than 1%). Ebay has a ton of OEM Escape 15" take-off rims around from people who have "upgraded".

Re: Repl tires other than Michelin or Continental
 

Well, in my case I put MichelinA/S on my X6 a few months ago, they were out of round/defective. Tire store offered to replace but were back ordered several weeks. I had the DWS installed since they were readily available. My take is the car drives the same as with the Michelin, but the DWS tires are quieter.

Re: Repl tires other than Michelin or Continental
 

Ford did a lot of hard work designing the most fuel efficient SUV on the Planet so I'd be careful changing rims or tires of any other size. The FEH rims have stayed standard equipment for years and only the Limited FEH was given a new rim option. The Limited rims are heavier than my '05 FEH rims and I regret that they reduce my mileage ability. After seeing how much of a MPG drop just from replacing my Tours on the front of my '09 FEH with new ones, I'm going to try changing them back with all four '05 rims included.

I'm getting a noise from the rear that I thought was my old Eco-Plus tires but the noise is not as bad but still there. Putting my '09 tires and rims on my '05 FEH should rule out tire noise because they're real quiet on my '09 right now. Also, I'll have the chance to see just how much my '09 mileage is effected with the lighter '05 rims and worn Tour tires.

Tire Rack has a lot of good information on LRR tires.
http://www.tirerack.com/tires/tirete...jsp?techid=175

GaryG

Re: Repl tires other than Michelin or Continental
 

On my '09 FE window sticker it shows the 17" rims as part of the Limited Luxury Package but actually it was a seperate option available on the Limited and XLT. I have no idea why my window sticker listed them that way as the brochure doesn't and some claim to have seen them listed as a seperate option.

Re: Repl tires other than Michelin or Continental
 

The 5 spoke 17" rims were only an option on the gas XLT and Limited FE. The 6 spoke 16" rim was standard on the gas FE Limited and FEH Limited. There was no optional rims offered on any '09 FEHs and the only way to get the 16" Limited rim was to order or buy a Limited Escape. I recall seeing the optional 17" rims on '08 gas Escapes also. The FEH came with the same standard rim since the '05 FEH came out and I think it's the most fuel efficient rim for the FEH because of its lighter weight. For some reason Ford has never offered the FEH rim as an option on the gas Escape.

GaryG

Re: Repl tires other than Michelin or Continental
 

The standard rim for a '09 FEH is a 16" 5 spoke Cast Aluminum rim as is the standard rim for the FE XLS/XLT but slightly different looking. The 17" Chrome-Clad(plastic) Aluminum rim is a 5 spoke.

Re: Repl tires other than Michelin or Continental
 

I was looking at Michelin LTX M/S2 on tire rack, it shows that some tire sizes have the Green X rating but not all. Is that correct?

Re: Repl tires other than Michelin or Continental
 

^^^ Not sure about "green rating" but i bought a set of LTX AT-2 and they are amazing in wet, slush and full on blizzards. They also do very well off-road. I Jeep my beast in Moab. Best all season tire I have ever owned.