The Specialized Turbo Cotton is a road bike tire optimized to provide the lowest possible rolling resistance, highest grip, and most comfortable ride at the cost of tire life and puncture resistance. The Turbo Cotton comes with a 320 TPI cotton casing, and the Specialized GRIPTON compound which they claim is the best compound in the world. It also has a layer of Specialized BlackBelt puncture resistance material to get the puncture resistance to an acceptable level.
I'm testing the 24-622 version of the Turbo Cotton as that comes closest to the other tires I've tested previously and will test in the future. A slightly bigger 26-622 version is available as well. The main competitor of the Turbo Cotton is the Continental Grand Prix TT (read review) that I've tested recently as well. Both the Turbo Cotton and Grand Prix TT are tires that provide the ultimate performance in speed. Both these tires are not made to last thousands of miles or provide a very high puncture resistance.
As the name suggests, the Turbo Cotton has a cotton casing with skin-colored sidewalls (a black version isn't available). Some people swear by cotton tires like the Turbo Cotton and Vittoria Corsa because they are supposed to offer a more comfortable ride. I can't do a complete road test of every tire I test, but I'm very curious how the Specialized tires perform on our tests...
|Tire Type||Tubetype (clincher)|
|Supplied By||Bought in store|
|New or Used||New|
|Price Range||Very High|
|Specified Weight||220 grams|
Size and Weight Measurements
|Size and Weight Measurements (Bike Wheel: 622x17C, Pressure: 100 psi / 6.9 bar)|
|Specified Weight||220 grams|
|Measured Weight||224 grams|
|Measured Width||25 mm|
|Measured Height||22 mm|
|Total Tire Thickness Center||2.1 mm|
|Total Tire Thickness Sidewall||0.75 mm|
Specialized claims the weight of the 24-622 to be approximately 220 grams; my sample comes in at a nice 224 grams. With a maximum width and height of 25 and 22 mm respectively, the Turbo Cotton comes close to its rated size, but measures smaller than tires from other manufacturers. I'm not sure why Specialized has gone with the non-standard tire sizes, the 24 comes a lot closer to 23 mm tires from other manufacturers. The 26-622 Turbo Cotton should be similar in size to 25-622 tires from other manufacturers.
Just like the Continental Grand Prix TT, the Turbo Cotton is a very thin tire. Total measured thickness at the center of the tire is 2.1 mm, which is a bit more than the Grand Prix TT (1.9 mm). Most other all-round tires come in closer to 3 mm thickness at the center of the tire. The low thickness of the tires means they will wear out quickly. Because the cotton casing is constructed in a different way when compared to nylon casings, the 0.75 mm sidewall thickness is the average between the bottom half of the sidewall (1.0 mm) and top half of the sidewall (0.5 mm).
Rolling Resistance Test Results
|Rolling Resistance Test Results (Speed: 29 kmh / 18 mph / 8 m/s, Load: 42.5 kg / 417 N)|
|Inner Tube||Conti Race28 (100gr butyl)|
|Rolling Resistance 140 psi / 9.7 Bar||
CRR: Not Tested
|Rolling Resistance 120 psi / 8.3 Bar||
|Rolling Resistance 100 PSI / 6.9 Bar||
|Rolling Resistance 80 PSI / 5.5 Bar||
|Rolling Resistance 60 PSI / 4.1 Bar||
|Use the formula: RR (watts) = CRR * speed (m/s) * load (N) to calculate rolling resistance at a given speed and load|
As expected from a tire that is supposed to be one of the fastest tires in the world, the Turbo Cotton has a very low rolling resistance. At an air pressure of 120 psi, rolling resistance is 10.1 watts, which is just 0.2 watts higher than our current fastest tire: Continental Grand Prix TT 25 mm (read review). At lower air pressures, the relative performance of the Turbo Cotton is a bit worse when compared to its performance at very high air pressures.
Because the 24-622 Turbo Cotton measures small compared to the 25-622 Grand Prix TT, It might have been better to test the 26-622 Turbo Cotton as it should be the same size as 25-622 tires from other manufacturers. I expect the 26-622 Turbo Cotton to slightly outperform the 25-622 Grand Prix TT at 120 psi (~9.7 - 9.8 watts) and close the gap a bit at 100 and 80 psi. Keep this in mind when buying Specialized tires: 24 = 23, 26 = 25.
Puncture Resistance Test Results
|Puncture Resistance Test Results (higher is better)|
|Puncture Resistance Tread||9|
|Puncture Resistance Sidewall||4|
Does the Specialized BlackBelt puncture resistance material provide enough puncture resistance? With a score of 9 points in the tread puncture test, puncture resistance is slightly better than the Grand Prix TT which scored 8 points. Compared to the more all-round tires which mostly score 11-12 points in our test, performance is as expected from a tire with a very low rolling resistance and thin tread.
At 4 points, sidewall puncture resistance is similar to most other high TPI tires which generally come in at a sidewall puncture resistance score of 4-5 points.
Just like the Continental Grand Prix TT (read review), the Specialized Turbo Cotton is a very, very fast tire with limited puncture resistance and tire life. These tires will save you 5+ watts for a pair of tires when compared to the most popular all-round tires that provide better puncture resistance and will last a lot longer. If you fit these with latex tubes, I'm convinced it will be very hard to find faster tires.
Most bicycle shops don't sell the Specialized tires, but they are available at (local) Specialized dealers at prices that are a bit higher than the Grand Prix TT (read review) or other top-of-the-line clincher tires. Have you used these tires or have any experience with the Specialized GRIPTON compound? Please consider writing a comment as I'm curious to your opinion.
TEST VERDICT: Highly Recommended
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