http://sports.yahoo.com/nba/news?slug=ys-nbarims110608Here's an article on the subject from back in 2008
“I think it’s hard for two rims to be alike everywhere,” said Utah Jazz point guard Deron Williams. “Some are dunked on more than others, some have more jump shots than others.
“They’re just like cars. All models don’t break down at the exact same time even though it’s the same parts in each car.”
Christopher Arena, the NBA’s vice president of apparel and sporting goods, said every rim is thoroughly tested and measured. A contractor named Drew Sorensen travels to all 30 NBA arenas in the preseason to set each rim. Sorensen uses something called the ERTG Rim Tester, which measures the “rim flex,” a computation based on energy absorption. A weight is dropped from each rim and a tiny microprocessor calculates the flex. The higher the rim-flex number, the softer the bounce, and the more likely your shot will roll in when maybe it shouldn’t have.
Each NBA team is required to buy new rims at the outset of every season – new backboards must be purchased every five seasons – and the league mandates a rim-flex reading of 20 to 35. Once Sorensen signs off on the measurements, he theoretically locks that number in place for the season by placing pieces of tape over the brackets that connect the rim to the backboard brace. Those pieces of tape each have a seal with holographic imagery. If a visiting team were to complain about the flex, the NBA can “go to the tape” to discover whether the rim has been illegally altered.
Sorensen returns to each arena once during the regular season, once during each playoff round and then resets the rims for every NBA Finals game.
Sounds fairly foolproof, but it doesn’t explain why our small sampling of NBA players believes rims feel different in different arenas.
Raja Bell, resident marksman of the Phoenix Suns, said today’s NBA rims are “the same (in) that they are the same dimensions. But act the same and give the same? No.”
“They’re supposed to be the same,” Jazz guard Kyle Korver added, “but they’re not.”
Rim-flex issues can occasionally, but rarely, work against the home team. Last January, Tracy McGrady of the Houston Rockets complained that the rims in his home arena, the Toyota Center, were too tight. McGrady shot 43 percent on the road but only 40 percent at home. His 3-point percentage was not great on the road (32.7 percent), but he was a much-worse 25.7 percent at home. Free throws? Also better on the road (71.4 percent) than at home (63.4 percent).
