My review of Babolat RPM Power 1.25
Tension used for playtest:
I strung up RPM Power using the same tension profile as my regular string. After a light prestretch to remove the significant coil memory, I used 51 pounds in the center eight mains, decreasing to 39 pounds on the outer mains. And I used 46 pounds in the center five crosses, decreasing to 32 pounds for the top and bottom cross. I strung this one-piece.
Regular string set up & tension:
Tourna Big Hitter Silver 7 Tour, 17 gauge, strung as described above.
Racquet used for test:
Wilson Blade SW104, modified with several layers of heat shrink sleeve to increase the grip size to my preference. With RPM Power and a string dampener, it weighs 353 grams and is 12 points headlight.
Power/Control of test string:
Power levels overall were slightly above average among the 20 or so poly strings that I've tested this year. Groundstrokes with a flat swingpath have an initial give on contact, and then RPM Power firms up but is never that crisp feeling. There is a distinctive and loud impact sound that is higher frequency than most strings but the feel is a bit muted, which seems a bit contradictory to the loud impact sound the string generates.
Power levels with RPM Power significantly decreased with any significantly upward or downward swingpath. The feel is distinctly one where the strings aren't able to grab the ball and the ball slides on the stringbed. Consequently, the ball speed off the strings is significantly decreased when attempting loopy topspin or heavy underspin shots.
There is more than adequate power on volleys. A flatter punch results in very good directional control and putaway power. It is also very easy to take speed off the ball and hit short angled volleys.
Flat serves have a high amount of ballspeed, and the sound psychologically amplifies the effect of the ballspeed. RPM Power has a high pitched "thwack" that makes it seem the ball is going faster than it does.
Control is about average for a round poly and better than for a shaped poly. RPM Power is quite insensitive to incoming spin so a flat swingpath results in hitting the ball accurately where it is aimed. Distance control is average due in large part to the slightly higher than average power levels. Groundstrokes tend to go deep into the court as a result of the lower spin capability. Volley accuracy is high due to incoming ball spin insensitivity. Defensive shots are also easier than normal, and I was able to hit shovel shots and lobs with more accuracy than typical when on the run.
Control when attempting to hit a heavy spin shot is below average. The low launch angle and feeling of RPM Power being unable to get a firm bite on the ball results in shots falling short of the intended target. While I never had times when the ball launched high expectedly, there were consistent times when the ball would feel like it slides excessively on the stringbed and then the ball comes off with less than intended forward velocity.
Control was good for flat serves but below average for spin serves. The lack of ball grip and low launch angle translated into aiming issues on spin serves. As a righty, spin serves out wide in the deuce court never felt like the strings would grab the ball, so the serves tended to miss wide into the alley. On second serves into the ad court, the lack of grip resulted in serves that landed closer to the middle of the service box, whereas I was aiming more for the serve box sideline. All second serves suffered from a lack of topspin, which caused many double faults long until I adjusted by lowering the speed I was trying to hit the serve.
Feel (Stiff? Mushy? Muted? Crisp? Comfortable?):
For shots made with a flatter swingpath, RPM Power has an initial feel of a bit of give, and then firms up. It less crisp than an average poly, and more muted even though it makes a loud impact sound. Comfort is above average and mis-hits don't create a lot of shock.
Spin:
This is the area where RPM Power is most lacking. Spin levels are below average for a round poly, and well below average compared to a shaped poly. Launch angle is also low, amplifying the feel there is a lack of bite on the ball.
Durability:
Durability of RPM Power is about average. After 90 minutes of play, the string had worn through the external coating at the string intersections, showing the internal material, and the matte finish had worn smooth and through what seemed like the first layers of the outer coating on the cross strings.
After six hours, the strings were notched through about 40% and appeared to have about another six hours of play before they broke.
Playability Duration:
Playability duration was below average. The initial characteristics of the string changed once the string intersections wore through the external coating. At that time, the stringbed locked up and both spin capability and launch angle decreased further from their already low levels.
Tension dropped noticeably from sitting overnight after being strung, and dropped a little bit more during the first couple of times playing. After that, the tension seemed to stabilize. The loss of tension didn't seem to result in much change of the stringbed behavior, although I was struggling the entire time with the low launch angle and lack of bite on the ball.
Tension Recommendations (would you string it differently next time? Explain answer):
RPM Power seems relatively immune to playability changes with tension loss. Because RPM Power seems more suited for flatter groundstrokes, I didn't notice much of a change over the duration I used the string. The lower stringbed firmness caused by tension loss didn't increase launch angle. With better than average tolerance for tension differences, my recommendation would be to string RPM Power at the same tension used for other poly strings and change up or down from there for fine tuning.
List any additional thoughts (optional):
The coil memory of RPM Power is very significant. When opening the package, the strings exploded from the packaging and made a big coiled mess on the floor. A light prestretch was necessary to reduce the coil memory to a reasonable amount. Pulling the first couple of crosses resulted in significant string vibration on the mains, unlike any poly string I've strung up.
I've tested three other round strings this past year: Kirschbaum Proline Evolution, Diadem Flash, and Dunlop Explosive Red. The last two tests were for Tennis Warehouse. Of these three strings and including RPM Power, I would rate Proline Evolution and Flash as better strings, and Explosive Red as a roughly equivalent string. Proline Evolution and Flash both are more linear in their response from flat to spinny shots, and both offer better bite on the ball, a more normal launch angle, and a crisper feel. Explosive Red also suffered from the same problem in that once the exterior coating wore through, the playability changed noticeably.
It's difficult to understand the target market for RPM Power. It seems designed for a flatter hitter with moderate swings, where it feels very consistent in just hitting a friendly rally ball. If this is really the string that Thiem is using, it must require pro-level racquet head speed to generate high levels of spin. These levels of racquet head speed are beyond the reach of nearly all recreational level players. Also, the change in playability when the coating wears through seems at odds with recreational players, many of whom will play the string until it breaks. For singles play, I found RPM Power to cause my shots to be less effectively, forcing me to be more defensive. As a result, I couldn't use RPM Power's good volleying characteristics because I then didn't have a way to get the net effectively.
In summary, RPM Power is an average round poly, with above average comfort and power level offset by below average spin capability, launch angle, and playability consistency over its lifetime.
Thanks to Tennis Warehouse and Babolat for the opportunity to test RPM Power.
