Tires: Width of tires/Weight of tires, fuel econmy, wheel drive car

Question
1. Most cars have all 4 tires of the same width.  I like to know the effects of fitting narrower front tires in a front wheel drive car.
2. Fitting narrower tires will reduce grip, right? So that's good for fuel econmy and acceleration, right? But how much narrower can we go from the stock width?
3. I have the option of 205/55R16 and 205/50R17, they are about the same size, so which is heavier? And what other differences do they have? Or should I pay a lot more for 225/40R18?
Thanks

Answer
Anthony,

1)  Tires are mostly about load carrying capacity, so you need to fit tires that are the same or more load carrying capacity.  It is possible to due that with narrower tire, but the aspect ration must go up.

2)  Grip is not only related to width, but also the tread compound.  It is possible to get grippier that are also narrower.  But grippier tires generally have worse fuel economy, and acceleration is largely unaffected.

3)  You need to consider the weight of the wheel.  A larger diameter wheel generally weighs more, even though the tire on it may weigh less. I can't tell what you are trying to accomplish.  Is it better grip or more fuel economy.  Generally these are at odds with one another.