In the May 2010 issue of Car and Driver there was an interesting article entitled, "Plus-Size Models- Testing the Performance Effects of Upsizing Wheels and Tires." In their test, they took a Volkswagen Golf 2.5 (auto) and installed wheel and tire combinations from 195/65R-15 to 235/35R-19. They then ran the car from 0-60 mph, 0-100 mph and 1/4 mile. As expected, the bigger and heavier wheel/tire combinations proved slower. here are the results:

195/65R-15= 0-60 mph= 7.6 sec; 0-100 mph= 22.3 sec; 1/4= 15.9@88 mph
205/55R-16= 0-60 mph= 7.7 sec; 0-100 mph= 22.6 sec; 1/4= 16.0@87 mph
225/45R-17= 0-60 mph= 7.8 sec; 0-100 mph= 22.7 sec; 1/4= 16.0@87 mph
225/40R-18= 0-60 mph= 7.9 sec; 0-100 mph= 23.3 sec; 1/4= 16.1@86 mph
235/35R-19= 0-60 mph= 7.9 sec; 0-100 mph= 23.4 sec; 1/4= 16.1@86 mph

C & D summarized their test as follows: "The 19" wheels definitely look the coolest. But the 17 and 18-inch setups offer a better compromise of grip, acceleration, price, and ride harshness...If it's acceleration you're after, stick with the smaller, lighter wheels and tires...Stay away from extremely low-profile sidewalls and massively heavy wheels."

This test illustrates why Dodge chose lightweight Alcoa forged 20" aluminum wheels on the SRT.

 

I noticed a huge difference on my ram. I ran it with both 265/70R17s and 275/60R20s, the 20s weight a **** ton more than the 17s and it ran .3 faster in the quarter with the 17s 15.2 and 14.9 repectively

 

common knowledge, by going smaller you are changing the rear ratio to a lower gear when going taller you are raising it to a taller gear.

when i had my 69 coronet i was running a 3.91 sure grip but with a 29.1" tall street
my final drive was approximately 3.45 and allowed me to take the car on the highway
and run at 70 with out over revving the engine.
at the track i would swap out to a 26" tall drag radial which was the factory tire size
giving me back my out of the hole grunt

 

Always remember that the profile of the tire not the inches is where the difference lies. If you use a 20" wheel and an 18" wheel, the tire profile is where the differenc lies. The heigth of the tire. 45 profile on an 18" wheel and a 35 profile on a 20" wheel. All things being the same 45 to 45 then the 20" wheel would be taller. 315 R 35 to 315 R 45.