Just thought I'd share:

https://www.greenhybrid.com/share/fi...8/HCH-2006.jpg

Here's what 17x7 O.Z. Superleggera rims look like on a 2006 HCH. The tires are 225/45HR-17 Continental ContiTouringContact CH95 from Tirerack.

MPG calculation really gets messed up though. I was doing about 48 mpg and it fell to the 30s in a very short time on the same tank of gas. I guess I'll have to measure the tire circumference and figure out what the real mpg is.



-- Frank

 

That's a very sharp look! What did it run you?

Don

06 HCHII Mag Pearl w/o Navi

 

Try this - tyre(tire) size calculator (2/3 down the page)

 

According to my tire sizing calculator, the stock 195-65-15 has a calculated overall diameter of 24.98 inches. A 225-45-17 has a calculated overall diameter of 24.97 inches. They are for all purposes, exactly the same diameter. If your fuel economy dropped off by that much, it's definitely not due to any difference in size, since there is none. What tire pressure do you run in your new tires? Has the weather and your driving conditions been the same, or have temperatures suddenly dropped off right around when you got your new wheels and tires?

If you saved your old wheels and tires, you could always do a controlled test and pick some road where you'll drive at a set speed for some distance and log the fuel economy, do it one or two more times to make sure the results are about the same, then go home, swap wheels and do it again.

 

Sweet! That looks *really* nice.

BTW, other folks have mentioned strange behavior of the mileage display on their 2006 HCH's, so your issues may not be related to the new rims/tires.

 

Those tires are one of GreenSeal's recommended ones, so I seriously doubt they are causing the lowered mileage as such, but in the picture they do look larger than the normal ones to me... even though AZ calculated they're identical. And even though the stock rims are supposed to be extra-aerodynamic, I seriously doubt that would affect anything by more than 1 mpg, if that.

Why don't you measure the tire diameter yourself? If they are larger then that would reduce mileage, and not just the computer's calculated MPG or MPH... it's harder to accelerate when the wheels' radius is large but you can go faster and the ride is smoother, which is why 15" wheels are used on the hybrid and optionally 18" wheels are available for the Si.

 

I pretty sure that those rim + tires weighs a lot more than the standard OEM combo... which was designed to be light and offer minimal rolling resistance.

I would say that alone is contributing to your poor FE.

 

Good point, livvie -- the rims probably weigh a good deal more than the stock ones. I think it's alot safer just replacing the tire than replacing the rims and the tire.

It looks like the Superleggeras weigh 16 lbs. Does anyone know what the stock rims weigh?

Of course, wheel weight only affects FE during acceleration -- it should have no affect whatsoever on cruising FE. And heavier wheels should actually help the car's ability to coast... essentially they act like flywheels.

 

Keep in mind that tires in that profile tend to be oriented towards performance and not low rolling resistance. So that is also a contributing factor... not just weight.

 

On the contrary, GreenSeal lists them as having very low rolling resistance in their report. Almost the lowest there is, in fact.