If you count string sales and Grand Slam Championships, Luxilon ALU Power and Babolat RPM Blast are two of the most accomplished tennis strings ever made. With their firm monofilament construction and otherworldly spin potential, these co-polyester strings have helped to unlock the explosive mechanics and raw "player power" upon which the modern tennis era is built. Like Federer and Nadal, ALU Power and RPM Blast each has a legitimate claim to GOAT (Greatest of All Time, or maybe GPOAT, Greatest Poly of All Time). But which string is truly better? Which one has greater spin potential? Which one lasts longer? Which is the true Heavyweight Champion? Indeed, a consumer faced with these eternal questions could very easily fall into paralysis - an embarrassment of riches if ever there were one. To settle the debate, the Tennis Warehouse playtest team has set up a 6 round title fight, comparing each string in the areas of power, control, comfort, spin, feel and playability duration.

If you want to find out who won, keep reading.

Stiffness

Power Control Comfort

If you want to understand how a co-poly like RPM Blast or ALU Power is likely to perform on court, don’t bother looking up words like "co-polymer" or "co-polyester" in the dictionary (unless you are a chemist). Nor is it a good idea to seek enlightenment from a string’s packaging (where you will often find marketing promises that stop just shy of the kitchen sink). In order to truly understand how a string is likely to feel and play you must know its stiffness level - a feature that not only influences how high and far a ball will fly when struck (see control), but also how much vibration and shock is likely to reach your arm (see feel and comfort).

Both ALU Power and RPM Blast are on the firm side of the stiffness spectrum, especially when compared to natural gut or multifilament strings. However, between the two, ALU Power tested 11 percent softer in our Tennis Warehouse String Lab. Chris helps us understand what this difference in stiffness means on court. He said, "Between the two, ALU Power was crisper, livelier and a tad more forgiving. I was able to get a little more zip on my shots with ALU Power, making it the winner in the power category for me.” Not surprisingly, RPM’s higher stiffness level gave it the edge in the control category. Chris explained, “I felt like I could bludgeon the ball with RPM Blast and my shots still stayed in.” Summing it up nicely, Chris continued, “When a match got tight RPM Blast was the string I wanted in my racquet. If I was riding a big lead in a match I loved grooving on ALU Power.”

For Andy the stiffness levels of these admittedly similar co-polys were cut and dry. "Right off the stringer, RPM Blast was noticeably a little stiffer." As Chris found, this difference, however small, had noticeable performance implications on court. Andy continued, "The lower-powered response of RPM lent itself to more control whereas the softer feel of ALU Power was both more powerful and more comfortable.”

Spin

Spin

A player's swing - specifically its speed and angle of attack - is the primary source of a ball's rotation (a.k.a. spin). For this reason, the world's best players could probably create impressive spin with fishing line. However, there are things a tennis string can do to make the player's job a little easier. Andy explained, "The shaped profile of RPM Blast seemed to grab the ball a bit better at impact compared to ALU Power." Of course, it's not just the grippy grabby shape of RPM Blast that won all those French Opens for Nadal. RPM's low powered response was also a crucial ingredient. Andy continued, "The lower-powered response allowed me to take bigger cuts at the ball, which enabled me to generate spin more easily with RPM Blast."

Like Andy, Chris also found that RPM Blast's lower power level enabled the higher stroke speed crucial to spin. He explained, "I got noticeably more spin on my shots with RPM Blast. Big fast swings get the ball rotating faster so I think a lot of the added spin I found came from me being able to bring more racquet head speed into my shots." Although Chris got more spin from RPM Blast, it should be noted that some of the best topspin players in the world use ALU Power. Not surprisingly, Chris conceded, "ALU Power is also a very spin friendly string, and I didn't necessarily find it lacking; it just didn't let me tap into the same amount of spin as RPM Blast."

Feel

Dead, grippy, muted, extremely controlled Soft, dead, muted Chris Andy Crisp, clean, firm, controlled, responsive Crisp, lively, more elastic

Like the faint and fruity notes that mark a Pinot Noir from the California Central Coast, RPM Blast and ALU Power each comes with its own subtle but wholly unique feel. Known for his advanced polyester palate, Chris found ALU Power to be more ripe (gut-like) on shorter strokes and touch shots. He said, "ALU Power has more 'feel' to it in a traditional sense. I really enjoyed it on touch shots such as droppers, soft volleys and rolling lobs.” The flip side came with the firmer RPM Blast, where the ball occasionally died on the vine. Chris added, "RPM Blast played with a more muted feel. It also felt deader with not as much jump off the racquet face.” Make no mistake though, our resident fan of stiff polys is keenly aware of RPM’s virtues. He said, "With RPM Blast I would just take a rip at the ball and watch it dip with savage spin and pace. Could I feel the shot as well? No. Did it matter? Not at all! I hit some bloody nasty angles with RPM Blast thanks to the spin and control I found with it.” Scoring this round a draw, Chris appreciated the feel of both. He said, ”To sum it up, with ALU Power I felt like I was part of the experience. When hitting with RPM Blast I was more of an observer. I took a big swing at the ball before sitting back and watching it spin crazily inside the lines."

Andy discovered some significant differences between these strings in the feel department. He said, "The feel of the two strings was distinctive and noticeably different. RPM Blast had a soft, more muted feel to it whereas ALU Power was a bit crisper and livelier.” Unlike Chris, Andy found RPM Blast to feel softer than ALU Power, despite the fact that RPM posted a higher stiffness score in our string lab. He said, "Even though the string is actually stiffer and lower-powered, the soft, muted sensation that I got from RPM Blast gave me the impression that it was the softer of the two strings, although in actuality that’s not really the case.”

Tension Maintenance/Playability Duration

Tension Maintenance Playability Duration

When it came to tension maintenance, our team didn't find much daylight between RPM Blast and ALU Power. Both strings lost a noticeable amount of tension over time (a universal affliction of tennis strings, especially co-polys). Although both lost their fair share of tension, it is important not to view tension loss in a vacuum. The real metric for evaluating tension loss comes in the area of playability duration. That is, at what point does tension loss compromise a string's feel and responsiveness? When does the ball start to spray or the crisp feel turn to flaccid mush?

According to Chris, RPM Blast's firm and controlled response better inoculates it against the ravages of time. He explained, "Despite RPM Blast dropping more tension than ALU Power, its overall deader response meant the tension loss had less impact on playability. Even after two weeks of hitting, RPM Blast still offered me lots of control and spin." Ultimately, though, Chris scored this round a draw. He concluded, "With both of these strings I can get a solid three weeks of hitting on them before I'm ready to cut them out. I don't expect to get more out of these kind of strings so they both fulfill my needs here."

Andy scored this round a tad differently than Chris. For him, RPM Blast's original playability faded more noticeably over time. He explained, "Similar to the tension maintenance, I thought the ALU Power was softer initially but held that playability for a longer period of time. Conversely, RPM Blast's playability changed gradually over time, which was quite a bit more apparent to me over the course of the test."

Overall Winner

Chris' Pick Andy's Pick

Coke or Pepsi? De Niro or Pacino? London or New York? Wrigley Field or Fenway Park? Choosing between two of the best strings we’ve ever hit was a difficult task. Chris lamented, "I love both of these strings so picking one over the other was not easy.” Ultimately, though, a choice needed to be made, and for Chris it came down to which string he trusted more when the pressure was on. He said, "The fact that I want RPM Blast in my racquet when the points are big, the muscles tight and the nerves are on edge means it's the winner for me. I can get most of that back with ALU Power at a higher tension, but with all things equal RPM Blast is the string that gives me the confidence to keep swinging with lots of racquet head speed."

It was a tough decision for Andy as well, but in the end he came to a similar conclusion. “Picking an overall winner between two of my favorites strings of all time was very difficult,” he said. “On one hand, I can’t help but love the silky smooth and comfortable feel of ALU Power that left me feeling completely connected and in control of the ball as it left my strings. On the other hand, I loved the ball grab and spin potential that RPM Blast provided me, allowing me to get the ball diving at the court and moving in all directions. In the end, I found that I preferred the feel of the shaped feature of RPM Blast biting into the ball and allowing it to sink into the stringbed for just a fraction of a second longer than it does with ALU Power. Couple that with the level of control and spin I was getting from it, I’d have to give RPM Blast just the slightest edge overall.”

Article date: August 2016. If you found this article interesting or have further questions or comments please contact us. All content copyright 2016 Tennis Warehouse.