With the success of the Model X under their belts, the Granville brothers set out to produce and market a new line of aircraft in the Sportster series. They were billed as "The fastest and most manoeuvrable licensed airplane for its horsepower in the United States" - and they were all that and more. The Gee Bee Sportsters were frequently shown off at airshows by their owners, attracting much attention wherever they appeared.

The prototype models for the D and E were retained by the Granville brothers for a time, and were very successful in production class racing. The Model Y, known as the Senior Sportster (a two seat version) was also very successful in competition - said to have won more money and races than the purpose built, better known Gee Bee's. However, the marketing of these aircraft could not have happened at a worse time. The Great Depression was entering its dismal peak and the sales of personal aircraft were almost non-existent. There were only a handful of these aircraft ever produced; Only two Model X's, one Model C (later converted to a Model D), one other Model D, four Model E's and two Model Y's.

With the Great Depression taking its toll on sales, the only true venue of hope left to the Granville brothers was racing. An amazingly large sum of prize money was being offered at the Cleveland National Air Races and the Granvilles were convinced to build a racer that could win the Thompson Trophy Race. The Gee Bee Model Z was created - and in 1931 won the Thompson Trophy race in Cleveland, Ohio, showing the world that the Granville Brothers could build the fastest airplanes in America. That same year, during a speed dash attempt, the Model Z shed a wing and rolled into the ground, killing pilot Lowell Bayles. This was the beginning of a run of bad luck that would plague the Granville's racing aircraft.

With the 1932 races just a half year away, Granville Brothers Aircraft hired a new engineer, Howell W. "Pete" Miller, a performance specialist fresh out of school and brimming with innovative ideas. Led by the elder Granville Brother, Zantford "Granny" Granville, the four brothers and Miller set out to build two new planes for the upcoming races. The racers would be designated the Model R-1 and R-2 and powered by engines on loan from Pratt & Whitney. The R-1 was designed and built around the new R-1340 ci nine-cylinder, supercharged engine which produced 800 hp.

Built for the Thompson Trophy race, a pylon course, it would be a short-range airplane built for all-out speed. The R-2, on the other hand, was built for the Bendix Trophy race, where long-range and speed were needed. Consequently, the R-2 was powered by the R-985ci Pratt & Whitney engine developing 535 hp. Burning less fuel than its bigger brother, the R-2 could fly the race with fewer stops, giving it a better overall speed. The main difference between the two airplanes, other than engines, was that the R-2 held 302 gallons of fuel versus the 160 gallons of the R-1. There were other slight differences as well, such as the shapes of the vertical fin rudder, and the R-2's fixed tailwheel versus the R-1's steerable tailwheel.

In the hands of Jimmy Doolittle, the R-1 won the 1932 Thompson Trophy race. At that time Doolittle also set a new world landplane speed record of 296 mph in the Shell Speed Dash, a straight line course. Lee Gehlbach, flying the R-2, finished fourth in the Bendix due to oil leak problems and fifth in the Thompson. Once again, the Granville Brothers brought home the trophies. They were on top of the world. Then in 1933, in the hands of pilot Russell Thaw, the R-2 stalled on landing approach at Indianapolis, rolled, and hit the wingtip.

Although he recovered with only wing and landing gear damage, the R-2 was out of that race. Russ Boardman, pilot of the R-1, was shaken by Thaw's accident and, pulling the R-1 off prematurely, stalled and caught a wingtip, flipping the plane onto its back. Boardman died from the injuries. The R-2 was repaired and while landing at Springfield in 1933, James Haizlip found himself floating too far down the 2,000 ft runway. As was done with most airplanes of that period, he kicked the rudder to sideslip and kill the speed. This caused one wing to stall, and once again the R-2 found itself rolled into a ball. Haizlip escaped without serious injuries, barring his pride.

Granville Brothers Aircraft used parts from both crashed airplanes to build the R-1/R-2, a hybrid model initially flown by Roy Minor. During a test flight out of Springfield, he made thirteen landing attempts before finally getting it on the deck; whereupon he slid off the end of the runway with the brakes locked.

The airplane caught its wheels in a ditch, performed a complete somersault, and landed upright on the road. After another trip through the shop, the R-1/R-2 ended up with Cecil Allen. Despite warnings from Miller and Zantford Granville, Allen Granville installed a large fuel tank well aft of the center of gravity (cg). The two designers feared the cg would be moved so far back that the plane would be impossible to fly. Ignoring their warnings, Allen took off with the tank full, lost control, crashed, and was killed. Thus ended the R-1 and R-2 racers, as well as the Gee Bee line of aircraft.

The Granville Brothers Aircraft, Inc., liquidated in the fall of 1933. They built a total of 22 aircraft - including 9 biplanes, 8 Sportsters, 2 Senior Sportsters, 3 Super Sportsters, and one long-tailed racer. They had a large, cantilever monoplane under construction that disappeared into history. After liquidation, the workforce went on to build the QED for the 1934 England-to-Australia race and Time Flies, a racer for Frank Hawks.