When I first got my Scion I noticed the threads about the gearing on the highway an dfound that mine would do 72 at 3000rpm-not too bad. I had 215/35-18s but have since traded the wheels and gotten 205/40-17s and now I understand a little better. On 1010tires thay have a tire size calculator and it turns out these are even a little smaller in diameter than stock.

I was already plannning on getting into 215/40-17s which should help.

I immediately noticed when I changed wheels that the box was much quicker both going and stopping (lighter wheels as well as shorter).

Looks matter and I know that most people like me have an ideal picture of what would look just right but given the power restraints and gearing provided I think just a small difference in tire size can still look great without resorting to new transmissions, various and possibly complicated and un-reliable gear swaps-etc.

If you want the acceleration go with a lighter smaller wheel/tire set up. Highway travelers maybe a little taller to quit the buzzing.

To me it seems like an easy way to adjust things especially when the car is still under warranty and to each his own as far as desires and requirements.

 

Since the majority of the weight is in the rim of the wheel (not the tire sidewall or the spokes), the biggest advantage in smaller wheels is not the raw weight savings, but the decrease in the radius of the weight. This decreases rotational inertia... There is a reson that practically no race car on the planet runs wheels bigger than 17", nor do they use rubber band tires. Big wheels and skinny tires are purely a cosmetic application and a band aid to bad handling. Good tires of higher aspecte ratios and identical widths will easily match and outperform them with the advantage in rotational inertia. You can read an entire book on this subject, and very few "tuners" are even aware it exists.

 

Oh yeah? there is plenty of weight in the tire tread, and being that far out from the hub makes it very important weight. Your average wheel and tire package is around 50/50 in terms of percentage of weight.

(edit* I originaly interperted your statement too mean there is more weight in the rim of wheel vs. any other element of the wheel/tire package. I see that's not what you meant. You meant: All things being equal, it's better to have the wheel rim closer to the hub. I agree)

Not exactly true. You haven't seen the American Le Manns Series P1 and P2 class then. They run , like 22s"

True, also causes your final drive gear to feel shorter as pointed out by OP.

 

Notice I said tire sidewall, not tread! If you want to scrutinize what I say with a microscope, try READING my post first.

Most people should not be messing with their final drive ratios by adjusting their total wheel diameter. Assuming the total wheel size is the same, tire weight does not change much, since the sidewall weight is minuscule and insignificant next to wheel weigt and tread weight.

And I'll double check on LeMans. AFAIK, they do not exceed 17, but I will check. The rule of thumb for racing wheels is to find the smallest wheel possible that will fit over the brakes. So if they had to run brakes in excess of 17", they would have to up the wheel size (not by choice, but by necessity)

*edit* I see you edited my post after rereading.

 

does that mean a scion wiht stock 15" alloyswill smoke guys with 18's?

 

All else being equal, yes.
Asuming the 18s are heavier and the weight is being spun farther out from the hub.

 

It's the big v-b style cars that can run the really wide and heay wheels without too much loss but running heavy wheels (chromed, big sized, etc) on our cars isn't really a smart idea as far as performance.

Lower inertia in the wheel (lighter having less inertia) also allows a car to stop, corner and accelerate better as well as allowing the suspension to absorb road imperfections better due to unsprung weight.

Quality wheels and tires are constructed better and with better materials so they usually weigh less as well. That's why Enkeis or Volks are expensive but worth it to someone who is really using the performance of a car.

The touring cars from a few years ago were running 19 inch wheels with almost rubber band tires (215/40-19)-on a road these actually hurt your cornering performance especially with a lowered and stiff car-the variations in the road allow the car to be unsettled due to nothing taking up the jolting.

Watch somebody on a bumpy corner when their car is running lo pro tires and on the bump stops-it's all over the place

 

And even if you want higher profile tires with minimal flex, they can be attained. It just takes a well built tire with the ability to tolerate higher inflation pressures.

All the wheel/tire newbs always compare a cheap OEM high profile tire to a high end (usually wider) low profile tire, which is not an apples to apples comparison.