Lab test: A comparison test on the brake performance of the carbon wheels

By: kiritozhang　　Translator: alanyu

Introduction

The technology of the carbon industry has developed rapidly in the recent decay and it updates to a new generation each several years, including the frame and wheelset. The stiffness, strength and weight has improved in each update and the carbon products are very reliable nowadays, whose strength is more than alu alloy, and even DH frames and wheels has used carbon fiber.

There are many points for a wheelset, such as weight, stiffness, strength and aerodynamics. However, compared to professional closed road race, another point is more important for most riders: brake performance. A better brake performance means you have a better control and you are safe in a more complicated environment where there is full of motors and people.

The craft was not high enough in the early time, resulting in quite a lot damage of the carbon wheels, while nowadays most carbon wheels with a good QC have a good strength, which means it won’t be damaged within the normal use, but there is still one problem, the brake track failure due to the high temperature during the long time braking, which is one of the significant difference between different brands.

This lab test focuses on the brake performance based on several aspects including peak brake power, brake performance in dry and wet, and continuous braking test.

MythBusters

1, The tubular wheels won’t be damaged due to long time brake

Of course, No. There is no carbon wheel (rim brake) which will never be damaged due to long time brake. The composites of a carbon wheel include carbon fiber and resin, some kind similar to reinforced-concrete structure.

Resin (epoxy) is amorphous, which doesn’t have a melting point and it will turn soft, decrease the density and finally become a liquid while the temperature increases. Resin is continuously turning soft slowly before T_G and the strength of the wheel will drop significantly when it reaches T_G. TG is the glass transition temperature. (Translator’s note: you can find here for more info: http://www.epotek.com/site/files/Techtips/pdfs/tip23.pdf) Thus, the wheel will be damaged if you keep on increasing the temperature.

2, Why the clincher/tubeless wheel is prone to damage due to brake?

This is the problem of the structure. Clincher and tubeless tires have more pressure on the brake track after inflation, which makes the brake track easier to be damaged under the same strength of the resin compared to the tubular wheel.

More air pressure has more force on the brake track, which makes it easier to be damaged at high temperature. Thus, it is not good to inflate the tire to a too high pressure.

3, Is there any 300 degrees super high T_G resin?

It’s a trick here. What is the detailed unit of degree? Fahrenheit degree °F or Celsius degree °C? 300 °F is around 150 °C. Some brands are playing tricks on the words, while other brands claim that they use the high temperature material such as basalt. However, this can’t avoid the damage due to high temperature. Before the basalt is broken, the resin will be too soft. It’s the buckets effect.

Although there exists 260 °C T_G resin, it’s too expensive and complicated to store, and the production craft of the wheel is different. As far as I know, there is no factory using it to make a bike wheel in China mainland. It is only used on military equipment currently.

Method

All the wheels in this test were the clincher/tubeless type rear wheel and mounted with clincher and inner tube. All were Vittoria Corsa Speeds 25mm and Kenda inner tube, 100psi and 70kg load. The brake pads were the original ones coming with the wheels.

Why not the same brake pad?

There is no absolute best pad, since the material is different and you should pair a good combo of the pad and the wheel. For example, Swiss Stop black prince is appreciated by a lot of riders, but it can be very weak on some wheels such as Giant SLR series.

Brand	model	Depth (mm)	Outer Width (mm)	Inner Width (mm)	is Tubeless	Brake Pad
ZIPP	404 NSW 2018	58	27.8	17.25	×	Stocked grey
CAMPAGNOLO	Bora One 50 AC3	50	24.2	17	×	Stocked red
ROVAL	CL50	50	29.4	20.7	√	Swiss Stop black prince
GIANT	SLR0	42	25	17	√	Stocked grey
MAVIC	Ksyium Pro Carbon SL	25	25	17	×	Swiss Stop yellow king
VORTEX	N6	60	27	17	√	Stocked grey
ECC	N84	40	27	17	√	Stocked blue
UNAAS	Team 55	55	26	17	√	Stocked grey
FARSPORTS	Ventoux C5 MK1	45/50	25	17	×	Stocked grey
FARSPORTS	Ventoux C5 MK2	45/50	26	19	√	Stocked grey
FARSPORTS	Ventoux S6	50	26	19	√	Swiss Stop black prince

*Most of the test products for the above experiments were purchased at my own expense.

*Product sponsors: Votrex, ECC and UNAAS.

Device

A 1500W motor drove the crankset directly. The brake was controlled by the adjustable pump on the lever to satisfy the real situation. The computer read the brake time, brake power, temperature, etc.

There was a fan but the wind speed was much smaller than the real situation, which could be neglected. Thus, the condition in the test was harsher than the real ride on the road, and it was easier to damage a wheel in the test as there would be more air flow to bring away the heat when you ride outside.

There are four tests in this test: brake time in dry, brake time test in wet, mid force brake test and continuous braking test.

1, Brake time in dry

The cranks span at 130-135 round per minute, 1:1 gear ratio, brake force 100N. This force is more than enough to provide more than 1500W brake power, which exceeds the power of the motor. The computer recorded the time from the pad touching the wheel to the wheel stopped spinning. There were 10 round tests for one wheel and separated 5 seconds each. This test will give the result of the brake performance in dry

2, Brake time in wet

The cranks span at 130-135 round per minute, 1:1 gear ratio, brake force 100N. There was water spraying on both side of the wheel at 90° position. This force is enough to stop the wheel. The computer recorded the braking time. There were 10 round tests for one wheel and separated 5 seconds each. This test will give the result of the brake performance in wet.

3, Mid force brake test

The cranks span at 160-165 round per minute, 1:1 gear ratio, brake force 50N. This force produces the brake power lower than 1500W which let the wheel spin. There were 10 × 10 seconds tests for one wheel and separated 5 seconds each. This test will give the result of the brake performance under the medium brake force.

4, Continuous braking test

The cranks span at 160-165 round per minute, 1:1 gear ratio, brake power 1000W. Since different wheels have different brake power under the same force on the lever, here we tested under the same brake power, which is lower than the motor’s 1500W and let the wheel spin. The computer recorded the time and temperature. This is similar to the descend where you need to keep on braking. This test started from 10 seconds and increased 10 seconds each until the maximum time of 100 seconds. If there was no damage on the wheel, the test went on to next round after the rest of 30 seconds, which could reduce the temperature of the wheel.

Results

1, brake time in dry

Most wheels have a good result and the difference between these wheels is not too large. A good rim brake wheel can be locked and start skidding if you apply too much force on the level.

2, brake time in wet

The pad needs to remove the water film on the brake track before it can stop the wheel. Thus, many brands have added the groove on their rims, which is definitely useful. In this test, the wheel with groove is much better than the traditional wheel. The AC3 groove on Campagnolo Bora One is the shallowest one and the it has the longest brake time in the similar products.

However, when we tried to spray A LOT OF water on the wheel, which was a simulation of the pouring, even the performance of those wheels with the groove decreased significantly. This is the disadvantage of all rim brake wheel. (Translator’s note: how many people are willing to ride in a pouring rain?)

Here we have a short conclusion that, the groove on the brake track is useful while the rain is not heavy and its performance is much better.

3, Mid force brake test

In this test, we compare the brake power when there is the same force on the lever. Here, Zipp is far ahead, which is unmatchable. Even under 40N on the lever, the brake power on Zipp was more than the power of our motor which is 1500N. At last, it only needed 32N to provide 1100W brake power.

Other wheels who score high in the brake time in dry test also have a good result here. However, due to the material of the pad, there is a big difference under the mid force brake while there is not much difference under a high force on the lever. This is like the feeling of “Oh! The pads are too soft at first but they lock the wheel if I squeeze the lever more”.

Mavic, Giant, Roval and Vortex wheels has been damaged due to the temperature in this test.

4, Continuous braking test

In this test, there is a big difference between different wheels. The lab test is much harsher than your real ride and it can magnify the problem: Only Zipp 404 NSW and Farsports Ventoux C5 mk2 can survive our 100 seconds test, in which ZIPP reached 210°C and Farsports Ventoux C5 mk2 reached 200°C. There were only the charred pads remaining on these two wheels but the wheels themselves are not damaged. They are the winner in this test.

According to the principal of SRAM China, there has been no customer service due to the high temperature failure of NSW so far, while there is few customer service of C5 mk2 due to the high temperature failure.

Comments on each wheel

Champion: Zipp 404 NSW

Pads: Stocked grey Swiss Stop

Brake time in dry: 1.8s

Brake time in wet: 1.9s

Mid Force Brake: 1100W (32N)

Continuous Braking: 210°C @ 100s, pass

Comments: the champion in our test, scores the best in all four tests, the special TiN brake track.

Runner-up: Farsports Ventoux S6

Pads: Swiss Stop black prince

Brake time in dry: 2.0s

Brake time in wet: 2.3s

Mid Force Brake: 1200W (50N)

Continuous Braking: 200°C @ 90s

Comments: the new carbon spoke S6 with the third-generation rim. The brake track performance is always an important point and Farsports has proved themselves. The improvement of each generation is clear.

The temperature increased quickly in our test due to the black prince. Though it was not damaged at 90s when it reached 200°C, the brake track was split at the rim bed under the 100 seconds test when it reached 210°C.

The third: UNAAS TEAM 55

Pads: Stocked grey

Brake time in dry: 2.0s

Brake time in wet: 2.4s

Mid Force Brake: 1200W (50N)

Continuous Braking: 160°C @ 80s

Comments: a Norway brand with the founder and the registration in Norway. There is also a workshop in Norway, but the products in China is different from those in Norway. What important here is not the brand name. The result in our test is very good and only lose a little compared with Farsports S6.

The overall performance is quite satisfactory. However, in the continuous braking test after 160°C, the inside was also split and the brake track bulged, which is a bit dangerous if it happens while you are descending.

The fourth: Campagnolo Bora One

Pads: Stocked red

Brake time in dry: 2.0s

Brake time in wet: 2.9s

Mid Force Brake: 1200W (50N)

Continuous Braking: 160°C @ 90s

Comments: Bora series are popular worldwide and have a good reputation. The overall performance is above average. As the first brand to release the grooved type brake track, its influence in the wheel field can not be neglected. (Bora One, Bora Ultra, Bora WTO and Fulcrum shares the same AC3 tech)

The performance of Bora One is a bit special. In our test, the temperature increasing speed and decreasing speed were both slow. The heat capacity of the resin is suspected to be quite high. Although the maximum working temperature is only 160°C, it passed the 90 seconds test as the temperature increasing speed is low. However, it couldn’t survive the 100 seconds test in which the brake track delaminated.

The fifth: Vortex N6

Pads: Stocked grey

Brake time in dry: 2.3s

Brake time in wet: 2.4s

Mid Force Brake: 1200W (50N)

Continuous Braking: 160°C @ 70s

Comments: The first domestic (China) brand to use the carbon spokes. The founder is Dr. Huang of Tongji University, so people usually call it “Doctor wheels”. The results are also quite satisfactory. However, it encountered its Waterloo in the high temperature problem. The first wheel was broken in the test 3 and we thought it was a defective product, but the second wheel was broken at the same situation. Including the one tested for test 4, the brake track of the three wheels was stretched at 160°C with creaking.

We suspect that the craft of the brake track machining is the main problem.

The sixth: Farsports Ventoux C5 mk2

Pads: Stocked grey

Brake time in dry: 2.2s

Brake time in wet: 7.7s

Mid Force Brake: 900W (50N)

Continuous Braking: 200°C @ 100s, pass

Comments: The second generation of Farsports C5. Though the brake performance in dry and brake power under mid force is around average, the brake performance in wet is far worse than those wheels which has the groove. It’s a big surprise that C5 mk2 and Zipp are the only two wheels which survived our continuous braking test.

The seventh: Roval CL50

Pads: Swiss Stop black prince

Brake time in dry: 2.0s

Brake time in wet: 8.3s

Mid Force Brake: 1300W (50N)

Continuous Braking: 160°C @ 70s

Comments: An upstart in the wheel field, the sub brand of Specialized. A lot of riders like it due to its aerodynamic and light weight. Roval CL50 and CLX50 share the same rim. Several hundreds of dollars are used to upgrade the spokes and CeramicSpeed bearings. However, in our test, the overall brake performance is at the average level.

Before the test, I had already suspected the performance of CL50. Since it is too light weight, the strength of the brake track is compromised and prone to be damaged due to high temperature. As predicted, the brake track does not only delaminated but also is filled with a lot of bump points at 160°C.

The eighth: Giant SLR1 42

Pads: Stocked grey

Brake time in dry: 2.3s

Brake time in wet: 10.3s

Mid Force Brake: 1050W (50N)

Continuous Braking: 160°C @ 70s

Comments: SLR should be the most in the world among the wheels we tested, because it is the stocked wheel of some Giant road bikes. The overall performance is below the average. It is observed that quite a lot second hand Giant SLR wheels selling online has some indication of delamination, maybe because the wheel has reached a high temperature but not high enough to damage the wheel. The author reminds the readers be careful of the second hand SLR series as there will be no custom service. (SLR1 and SLR0 shares the same rim)

Although the stocked pads can provide a good brake power, the temperature increases quickly. The wheel itself also cannot be used under high temperature. The limit temperature is only 160°C, so the damage is significant.

The ninth: Farsports Ventoux C5 mk1

Pads: Stocked grey

Brake time in dry: 2.8s

Brake time in wet: 12.6s

Mid Force Brake: 750W (50N)

Continuous Braking: 180°C @ 80s

Comments: The first generation of Farsports C5 was popular due to its 12K weaver carbon and the good ride feeling. However, the shitty brake performance blew away it then and the overall performance in the test is the third from last. However, it is strange that it scores high in the continuous braking test, while we hear about the damage due to high temperature quite often. The author thinks it is because many riders have this wheelset and the news spreads fast via the internet, which makes people think there are a lot of failure of Farsports C5 mk1.

Also, Farsports replied us that the QC of the early product is not good enough, which is improved later.

The tenth: Mavic Ksyium Pro Carbon SL

Pads: Swiss Stop yellow king

Brake time in dry: 2.5s

Brake time in wet: 9.1s

Mid Force Brake: 1100W (50N)

Continuous Braking: 160°C @ 40s

Comments: The old big brother in the wheel field, “the light of France”. However, it is outdated in the carbon wheel age nowadays. In the test it is almost the bottom in every aspect. Moreover, it created the shortest time in the continuous braking test. Less and less people are buying Mavic Carbon wheels nowadays.

The performance is very disappointing though Mavic is a big brand. The yellow king not only left a lot of yellow marks on the track but also increases the temperature quickly. The brake track reached 160°C in no more than 50 seconds and delaminated.

The eleventh: ECC N84

Pads: Stocked blue

Brake time in dry: 3.5s

Brake time in wet: 11.7s

Mid Force Brake: 780W (50N)

Continuous Braking: 160°C @ 70s

Comments: one of the basic-level wheels. It has a very low price. (Translator’s note: about 600 USD on Taobao) Its performance is at the bottom in the test and after we changed to the new pad provided by ECC, its performance is about average. Considering that its price is only 1/7 of Zipp 404 NSW, the performance is just acceptable. You can’t expect more for this price and at least, it is not prone to be damaged.

The performance is very disappointing if not considering its price. The brake power is weak while the high temperature endurance performance is OK. The biggest problem comes from the blue pad, which can’t provide a good brake power and is to be melt, remaining the ugly blue trace on the brake track. The rim structure was destroyed from internal after it reached 180°C.

ECC had sent us a pair of new brown pad for test after they got the test result. The brake performance is improved significantly but it will howl. ECC also claim that the stocked pad will be changed to the brown one and those who bought their wheels in 2019 can get the new brown pads in free.

Scores

How do we score? The best in each test is set to 100, and others are scored by the percentage. E.g., in the dry test (test 1), Zipp 404 NSW scores 100 whose result is 1.8s; Farsports S6 scores 90 whose performance is 90% of Zipp. In the continuous braking test (test 4), how many seconds equal to the score.

It is no doubt that the winner in our test is Zipp 404 NSW, which is the flagship in every aspect. The third generation of Farsports proved themselves that the brake performance of the Chinese brands can be matched with the big brands in the world after several times of R & D. Moreover, Farsports, UNAAS and Vortex are the three of the top five.

Campy’s Bora One acts as a guardian, scoring above average in every aspect, while the overall performance of Roval and the Farsports’ second generation C5 is above the pass line.

It is clear that the performance of the brake track of the carbon wheels from different brands is varied no matter whether it is the big brand or the Chinese brand. Some people’s bias that the Chinese brands’ carbon wheels are worse is obviously wrong.

Keep in mind that, China can produce good carbon products, but it doesn’t mean that the cheap products are good. Be careful when you want to buy some carbon products with an extremely low price.