Home GearStringsString Reviews Isospeed Black Fire and Baseline Speed String Review

Isospeed Black Fire and Baseline Speed String Review

by Ferenc Ferdinand Weisz

Ferenc Ferdinand Weisz is back with another guest post. This time for an Isospeed String Review of Black Fire and Baseline Speed.

Isospeed is special to me because the Isosport factory is only 20km away from my home. I’m a half-hobby stringer who does stringing for local players. I mostly work with Isospeed, because every player here knows this brand and they are using it with satisfaction. That is why I thought it was time to write this Isospees string review.

Check out the Isospeed Strings official website here.

Isospeed String Review – introduction

Isosport is located in Eisenstadt, Austria, and they are manufacturing strings for different brands from Head to String Project, and also manufacturing Innovative Plastics Solutions for other sports equipment like skis. Isospeed is their own string brand.

In this comparison, I’m reviewing the two Isospeed polyester strings that are on stock. Baseline is the cost-effective string from Isospeed. Available in 4 different gauges between 1.20 and 1.35mm, called Spin, Speed, Control and Long Life. These strings don’t have any advanced technologies. Really similar to Head Sonic Pro. Have a really nice price to value ratio, only available as reel around 50 €.

The other string that I tested is my bestseller, Isospeed Black Fire. Recommended for pros and hard hitters who are looking for control, spin and durability, available in 1.20mm and 1.25mm versions. Including some advanced technologies, Pre-Stretched, Multiple Heating, Liquid Wax and Low Friction. The result is a more flexible string with better snapback, tension maintenance, and longer durability. This string’s pricing is average, a 200m reel costs around 100-120€ and is still available in a 12m set.

The Strings in Detail

In terms of details, these strings are really similar: round, black co-polyester monofilaments, tested in 1.25 mm gauge. I strung these strings to my Head Graphene Touch Prestige S racquets, Baseline Speed at 24 kgs (53 lbs), and Black Fire at 22 kgs (48,5 lbs) because Isospeed recommended 10% lower tension for Black Fire.

Earlier I tried these strings on my friend’s different racquets: Graphene XT Radical MP with Baseline at 25kg (55 lbs), Graphene Touch Extreme MP with Black Fire at 24/23 kg (53/50,5 lbs) and Clash 100 with both on the same tension like in Prestiges. I will also lean on these experiences during this review.

Isospeed String Review – First Impressions

When I touch these strings, I feel the difference, Black Fire feels more slippery than Baseline, but this makes this string a bit fragile during stringing, so have to be careful when stringing. Black Fire stretches less than Baseline thanks to factory pre-stretching.

The first thing that appeared was vibration. I didn’t feel any with Baseline, but with Black Fire this was annoying to me. The next time I switched from a Head Pro Dampener to a rubber band, and the annoying vibration disappeared.

The difference between these is not clear after a few rallies, and the power/control factor is also very similar which means that 2 kg lower tension was the right decision.

Feel and comfort

I think Prestige with a smaller sweet spot and tighter 16×19 pattern (which is between my spin monster Artengo’s 16×19 and Ti.Radical’s 18×20) is ideal to show these strings abilities.

The feel of Baseline is simpler but nice. Black Fire is much more premium, I feel the stiffness, but this is really creamy when I hit accurately. This foreshadows the target of these two strings because Black Fire is more uncomfortable outside of sweet spot, which is anyway smaller. For me, Baseline is more comfortable, but Black Fire is also not an uncomfortable one, especially when we compare this with stiffer shaped strings.

In bigger head size and sweet spot racquets like the Wilson Clash 100, these strings show different results. I don’t hit a lot with it, but this was enough to feel extra stiffness, making this racquet much more confident, and Black Fire was the running-in after trying 6 different strings in this frame. In the Extreme MP I also felt this powerful and comfortable, which allows higher tension without lack of comfort.

Spin, power, control

I don’t miss spin despite Prestige’s not being spin machines. It is hard to decide whether there are differences or not, but differences in technology should benefit Black Fire. Height over net and ball bounce is great, both strings offer great spin among round polys.

Baseline at 24 kg in Prestige gives a good balance between power and control. This will not be the key in a bigger mid plus or smaller oversize racquet for ultimate control, then again, it’s a nice string looking for power.

Black Fire is also not the stiffest string in the market. In Prestige at 22 kg, it has a bit less power than Baseline and balance is also nice, but Extreme MP at 24/23 had a massive amount. Many clients of mine use Black Fire around 25-26 kg and nobody complained. If you are looking for massive control, it’s worth trying this on higher tension.

Tension maintenance, durability

I’m using the RacquetTune app to measure string tension. I know it’s not an accurate tool but providing useful measurements about tension loss. These measurements confirm the positive impact of pre-stretch in Black Fire, because initial tension loss is around 1 kg, and after 2 hours of play this is also close to 2 kg. During the complete life cycle, the complete loss is around 4 kg, which is incredibly good.

Baseline is average, broadly less 1.5x more tension than Black Fire. Both strings are notching, and at the end of its lifecycle, the snapback effect lacks, then string breaking. Black Fire lasts around 1 month for a hard hitter, but I can also report from drastic examples. In Blade 98S with 18×16 pattern with heavy topspin play, Black Fire lasted 4 hours but Baseline only 2 hours. This is a huge difference in durability, but when somebody is not a string breaker or using a tighter pattern racquet, Baseline can also offer average durability.

Isospeed review – Conclusion

I’m really satisfied with Baseline Speed and Black Fire. I recommend these strings for different types of players.
The Baseline range is well priced, which keeps you from considering discount brands like Pro’s Pro. With 4 different thicknesses, everybody should be able to find a suitable one for his/her game and racquet. Thinner versions offer better spin and comfort, thicker offer greater control and longer durability and have many possibilities in tension too. Great for beginners and recreational players who only look for a good price with comfort and average playing attributes. Also great for intermediate or advanced amateur players who are not really string breakers and don’t have pronounced claims. Also, a nice string for junior players.

Black Fire is another league, highly conformed for hard hitters. Offers really great durability and tension maintenance despite not a painfully stiff string, have really nice spin in round range, and also offers control and touch. Not recommended for beginners, and players with sensitive hands, but highly recommended for every hard hitter, from club players to pros.

Thanks to Ferdinand for this in-depth review! Have you tried Isospeed strings? Please comment below.

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Bryan March 15, 2020 - 17:49

Pleased to se a review of my favorite brand. I’ll definitely take a look at these models.

Chris March 17, 2020 - 09:37

I am using Isospeed Black Fire S on my Head Speed Touch MP since approx. 2 years at 25 kgs and I am very satisfied. Good price for good durability and spin. For this summer I wanna try a hybrid string on my racket in order to see if I can gain a bit of power and comfort in comparison to the poly…let’s see. Your reviews of string and rackets are always very helpful. Thanks for your work!


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