Carbon fiber used at Silverstone even if it rains

8/24/2021

Not much force but lots of braking feeling in the British MotoGP Grand Prix. Discovering brake fluid.

The British GP is back after a year's absence. It also skipped 2018 due to flooding. In the past, MotoGP riders used steel discs when it rained, but lately, they have been turning to carbon fiber, thanks to the latest generation of discs suitable for use in the wet.

According to the Brembo technicians who work closely with all the MotoGP World Championship riders, the Silverstone Circuit is a moderately demanding one for brakes. On a scale of one to five, it earned a three on the difficulty index, identical to Misano Adriatico and Valencia.

Brembo brake fluid can rise to 300°C without reaching boiling point

In addition to brake calipers, discs, pads, brake master cylinders and clutch master cylinders, Brembo also supplies all the MotoGP riders with brake fluid. Two types are available: HTC64 brake fluid has higher heat resistance but lower hygroscopic properties. This refers to its ability to absorb the water (moisture) in the atmosphere.

For this reason, if humidity is high, the brake fluid has to be replaced once a day. LFC 600 brake fluid that teams opt for when temperatures are low needs to be replaced much less frequently and is more stable in terms of compressibility and more hygroscopic. They also have different dry boiling points: approximately 315°C for the LFC 600 fluid and 335°C for the HTC64 fluid.

Brake fluids for road motorcycles

LCF 600 Plus fluid is commercially available, although it is recommended for track use: since it has a high hygroscopic level, it has a limited lifespan. This depends on several factors, but it usually ranges from 2,000 to 4000 km (1242 to 2485 miles). It can be mixed with other DOT3 and DOT4 racing fluids but should not be used in brake systems with magnesium parts.

The Brembo Sport Evo 500++ DOT4 fluid, on the other hand, has a dry boiling point of 270°C (518° F) and is recommended for road use without compromising performance. Its excellent properties help it to reach a high mileage before it has to be replaced, usually from 12,000 to 24,000 km (7456 to 14912 miles). However, it is not for brake systems designed for mineral fluids.

You can see the characteristics of Brembo brake fluids here.

Relaxed arms when braking

Despite exceeding 300km/h at one point on the track, the riders use the brakes ten times per lap, although, in three of these cases, the deceleration is less than 50km/h. No fewer than six braking procedures take longer than three seconds, making a total of 33 seconds of brake use per lap, or 28 per cent of the race duration.

Calculating all the force a rider applies on the Brembo brake lever from the starting line to the checkered flag, the result comes in at more than seven tons, the lowest of this year’s races. The reason for this is that there are no individual forces of at least 4.7 kg; a threshold reached at all other tracks with one braking procedure per lap, sometimes two, and at Spielberg three.

200 km/h deceleration in 4.5 seconds 

Of the ten braking sections at the Silverstone Circuit, three are classified as very demanding on the brakes, four are of medium difficulty, and the remaining three are light.

Due to the higher top speed, Stowe (Turn 7) is the most challenging: the MotoGP bikes drop from 318 km/h to 118 km/h in 4.5 seconds covering 253 meters, thanks to a 4.5 kg load on the lever and a 1.5 g deceleration. Brembo HTC 64T brake fluid pressure hits 9.6 bar.