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Old 08-23-2013, 04:23 PM   #1 (permalink)
Weight Reduction
 
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Wheel height's effect on engine speed?

Hey guys,

Long time no see. I've been attempting to hypermile (somewhat successfully) on my work commute but I generally just ride my bike for local commuting (hence why I don't post much on here anymore).

Anyway, my Altima is geared poorly for highway speeds (on top of that it is a 4 speed auto). So when I'm going 60-65 or so on the highway, the engine revs pretty high (2500-2700 IIRC). I was able to get my hands on some lighter taller rims and was wondering if that might help drop the revs a little (I searched but couldn't find much on my specific question).

Old OEM rims: 16"-about 23 lbs without tires
New rims: 18"-18.2 lbs without tires

I'm assuming the lower profile tires on the 18" will weigh less than the taller tires from the OEM rims.

Thanks for the help eco-bros

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Old 08-23-2013, 04:42 PM   #2 (permalink)
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The tire diameter is what matters. It will change the revolutions per mile, and change the RPM at a given speed.
Low profile tires are not generally good for mileage nor are they cheap to buy. Keep that in mind as well. Stay with as narrow a tire as is recommended for the new rim.
Plug your info in here to see what will happen. this is one of many calculators on the web.
http://www.roadkillcustoms.com/hot-r...#axzz2cp6K0hgz
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Old 08-23-2013, 04:46 PM   #3 (permalink)
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What you want to do is increase the TOTAL diameter of the wheel and tire combo.

Assuming your tire size is 225/45/16:

Tires on your stock 16s could go up a size or 2 to 225/55 or 65/16. These sizes give you more sidewall which also induces more sidewall flex and can affect handling characteristics.

Your new 18s will help a little because of being lighter and also reducing the size of the sidewall to achieve the same total diameter of the aforementioned 225/65/16 tires. Less sidewall means less sidewall flex and better handling characteristics.

Keep in mind that tire size is a balancing act. Shorter total diameter tires require less power to get rolling, but taller total diameter tires are better for highway eco. If you go too tall, your car will accelerate like crap and possibly negate any gains made on the highways depending on your commute.

Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

Rims and tires is a good place to understand aspect ratios and tires sizes and can help you pick a larger tire.

HTH
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Old 08-23-2013, 04:58 PM   #4 (permalink)
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MANY threads on this very topic.

ignore rim size.
worry about tire diameter. The minute you said 'low-profile tire' you are headed the wrong way.
PLEASE use the search for VERY detailed discussions on the very topic.
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Old 08-24-2013, 03:13 AM   #5 (permalink)
Weight Reduction
 
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Thanks guys for the help. I guess I misunderstood the original situation. Anyway, I've got it figured out now.

Also, I just wanted to throw out that I've been doing some weight reduction to my commute also (I lost about 10 pounds of body fat, lol).

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