cleorn

Don't get me wrong I love the way the car looks but I don't get the same lanch off the line with the 20's on the car. I figured I was going to lose a little but not this much. any ideas?

joshoowa

iTrader: (1)

well yeah your going to loose take off performance because of the weight, unless you have some light weight forged wheels. i know my car is slower at a stop and i know i've lost MPG too...

Ice350

iTrader: (1)

It's not a little slower just because of the weight. The larger circumspherence also makes it take longer for the wheel to reach high speed. Larger wheels makes it easier to maintain higher speeds though and your car uses less energy to stay at high speed. Then it takes longer and more energy to stop from high speed.

Lexbox

I cant stand the MPG loss...I only get 300 miles to the tank whether all highway or not.

baba

I get about 250 miles to the tank on my GS 300 with 20's on but I don't run it dry. I fill up when the gas light comes on.

tonysofly

wow, you guys get horrible gas mileage

i got 20" wheels also, and i noticed mpg decreased, but i still get around 340 miles to the tank.

but it is a lot slower off the line with 20"s

joshoowa

iTrader: (1)

i normally get around 275-280 per tank that mixed highway and city driving. one time i ran my car after the gas light and got 300mi then refilled 17gal. so thats about 17.5mpg

tonysofly what kind of gs do you have?

corkycal

iTrader: (8)

it called rotating mass. yes the larger the wheels, the slower off the line.

300-320 on a tank sounds right.

GWELEX

Not being a physicist or anything close and disrearding the possible weight differences. I would think as long as you maintain the same overall diameter of the wheel and tire as close to stock as possible, shouldn't acceleration and decelleration stay the same?

HI98GS

You guys are lucky, I am getting about 15 MPG. but then again, it may be my driving style or just that the twin snails eat too much.

corkycal

iTrader: (8)

stock rims with 70 series side wall will be shorter than 20's.

bottom line is 20" wheels are tall even with rubber band 25 series side walls.

HI98GS

Diameter does play a role, but you also have to remember width of the tire. If more contact patch, more resistance, then you will need more power to overcome the resistance.

Also, inertia (rotating mass) is increased since the distance of most of the weight (tire) is farther from the center of the wheel. So starting and stopping the tire rolling will require more force.

GWELEX

Not true, stock tires are 225/55/16 with an overall dia. of 25.7", you can get 20" tires at 245/30/20 with a overall dia. of 25.8".

GWELEX

Thanks!! That makes sense and I understand what you're saying. I didn't consider the extra width in my thinking.

Chpsk8

Width has far less to do with it than the physical weight of the wheel (rim and tire) Although in theory the width will add to the rolling resistance, it is too small to measured by a butt dyno and with MPG.

Size Matters
http://www.wam.umd.edu/~greghess/sizematters.pdf

Tire weights
http://www.tirerack.com/wheels/tech/...jsp?techid=108


Just a couple to get you started. I could add about 20 more.