CX/Gravel Tire Test: CST E-Series Reach 37

The CST E-Series Reach is an E-bike tire from the world's largest bicycle tire manufacturer. CST (Cheng Shin Tire) is a Taiwanese company with factories in Taiwan and China. There's a big chance you've ridden on CST tires without knowing, a lot of tires from smaller brands are actually rebranded CST tires. They also own the Maxxis brand, which is their high-end brand. The CST branded tires are marketed as the more value-oriented tires.

The E-Series Reach comes with a 22 TPI carcass, single compound rubber, ECE-R75 certification (up to 50 km/h), and the CST APL technology. The APL system is basically a 1 mm thick layer of rubber that is harder to penetrate. Although 1 mm is better than nothing, there are also tires on the market that come with 3 - 5 mm thick AP layers. Maybe this layer is extremely hard to penetrate while at the same time keeping rolling resistance at a low level? Let's put this tire on the test bench.

Manufacturer Specifications

Manufacturer Specs
Brand	CST
Model	E-Series Reach
Year	2015
Supplied By	Supplied by Continental
New or Used	New
Mileage	0 km
Price Range	Med
Buy At
Manufacturer part number
TPI	-
Compound
Bead	Wire
ETRTO	37-622
Specified Weight	734 grams
Max Air Pressure (psi)	75
Made In	Pro Data
Available Sizes	37-622 (28x1.40)

CST E-Series Reach 37 Test Results

Size, Weight, and Thickness Measurements

Size, Weight, and Thickness Measurements
Specified Weight	734 grams
Measured Weight	734 grams
Measured Width Casing	37 mm (un-round)
Measured Width Tread	mm
Measured Height	Pro Data
Tire Circumference	Pro Data
Measured Knob Height Center	0.0 mm
Measured Knob Height Edge	0.0 mm
Measured Total Thickness Center (excluding knobs)	4.40 mm
Measured Total Thickness Sidewall	Pro Data
All size measurements are taken at high air pressure on a 18 mm inner width rim.

CST specifies the weight should be close to 715 grams, my sample comes in at 734 grams. On a 17C rim, at an air pressure of 60 psi, the 37-622 E-Series Reach measures 37 mm wide and 34 mm high. It's nice to see a tire actually measure close to its rated size.

The E-Series Reach comes with an almost slick tire profile, there are only some slight grooves at the edge of the tire. I've measured these grooves at 1.1 mm deep. This definitely is less that most other touring tires that come closer to 2 mm tread depth. The total tire thickness at the center of the tire is also quite thin with a thickness of 4.4 mm. The sidewalls do are thick with a measured thickness of 1.8 mm.

Rolling Resistance Test Results

Rolling Resistance Test Results
Inner Tube	Conti Tour 28 (170 gr butyl)
Measured Width	37 mm
Rolling Resistance Real tire width in mm: 30-32 = 66 psi/4.6 bar 33-35 = 60 psi/4.1 bar 36-38 = 54 psi/3.7 bar 39-42 = 50 psi/3.4 bar 43-46 = 46 psi/3.2 bar 47-50 = 42 psi/2.9 barHigh Air Pressure (54 psi / 3.7 bar)	Pro Data
Rolling Resistance Real tire width in mm: 30-32 = 55 psi/3.8 bar 33-35 = 50 psi/3.4 bar 36-38 = 45 psi/3.1 bar 39-42 = 42 psi/2.9 bar 43-46 = 38 psi/2.6 bar 47-50 = 35 psi/2.4 barMedium Air Pressure (45 psi / 3.1 bar)	Pro Data
Rolling Resistance Real tire width in mm: 30-32 = 44 psi/3.0 bar 33-35 = 40 psi/2.8 bar 36-38 = 36 psi/2.6 bar 39-42 = 33 psi/2.3 bar 43-46 = 31 psi/2.1 bar 47-50 = 28 psi/1.9 barLow Air Pressure (36 psi / 2.6 bar)	32.9 Watts CRR: 0.00986
Rolling Resistance Real tire width in mm: 30-32 = 33 psi/2.3 bar 33-35 = 30 psi/2.1 bar 36-38 = 27 psi/1.9 bar 39-42 = 25 psi/1.7 bar 43-46 = 23 psi/1.6 bar 47-50 = 21 psi/1.4 barExtra Low Air Pressure (27 psi / 1.9 bar)	Pro Data
The CX/Gravel section is a multi tire size section, air pressures have been adjusted to the measured casing width. All numbers are for a single tire at a speed of 29 km/h / 18 mph and a load of 42.5 kg / 94 lbs. Use the formula: RR (Watts) = CRR * speed (m/s) * load (N) to calculate rolling resistance at a given speed and load.

At the maximum rated air pressure of 75 psi, rolling resistance comes in at a low 19.0 watts. This is actually the lowest rolling resistance of all touring tires that have been tested to date. At 75 psi, it outperforms the Schwalbe Marathon (read review) by 0.6 watts. At lower air pressures, rolling resistance starts rising much faster than comparable tires. At an air pressure of 60 psi, the Schwalbe Marathon already has a 0.6 watts advantage which increases to 5.6 watts at 30 psi.

Rolling resistance is close to what I expected from the E-Series Reach. It's just unfortunate rolling resistance increases so much at higher air pressures. It's nice to be able to lower air pressure to increase comfort, 60 psi on 37-622 tires already gives quite a bumpy ride.

Puncture Resistance Test Results

Puncture Resistance Test Results (higher is better)
Total Puncture Score Tread	61 Points
Total Puncture Score Sidewall	Pro Data
Tread Puncture Force Sharp Needle	10
Tread Puncture Force Blunt Needle	Pro Data
Tread Total Tire Thickness	4.40 mm
Sidewall Puncture Force Sharp Needle	Pro Data
Sidewall Puncture Force Blunt Needle	Pro Data
Sidewall Total Tire Thickness	Pro Data

While performance in the rolling resistance test is strong, the E-Series Reach performs very poorly in the puncture resistance test. In the tread puncture resistance test, which is the most important measurement, it's the lowest scoring tire to date. It does perform much better in the sidewall test, but I'm sure 90% of real-life punctures are in the tread area.

Puncture Factor Tread also comes in very low because the tread is not only easy to puncture but also very thin. With a score of 44 points, it scores less than half what the Schwalbe Marathon scores (102). Just like the puncture resistance sidewall score, Puncture Factor Sidewall is on the high side as well because the sidewalls are quite thick compared to other tires.

Hard Surface Static Grip Test Results

Static Grip Test Results
Wet Grip Average	No Data
Wet Grip Center	No Data
Wet Grip Edge	No Data
Measured Knob Height Center	0.0 mm
Measured Knob Height Edge	0.0 mm
Grip in points = coefficient of friction * 100 CX/Gravel grip test rim width = 23.0 mm
Wet Grip Test and Off-Road Tires (info)

Conclusion

Rolling resistance at very high air pressures is very good. At lower air pressures, rolling resistance starts rising faster than comparable tires. In the puncture resistance test, the E-Series Reach performs awfully with the lowest tread puncture scores to date. On top of that, it doesn't have much tread depth. We do rate the CST E-Series Reach recommended 3/5 because.. this is Bicycle Rolling Resistance.

There still doesn't seem to be a tire that comes close to the Schwalbe Marathon (read review) in both the rolling resistance and puncture resistance departments. The Schwalbe Marathon is still our nr 1 recommended tire for a low rolling resistance and high puncture resistance. On top of that, you also get a decent tread profile and tread depth.

RATING: 3.0 / 5
TEST VERDICT: Recommended

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