PS reader question on motorcycle technology – tire wear on the racetrack

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PS reader question on motorcycle technology - tire wear on the racetrack
jkuenstle.de

PS reader question on motorcycle technology - tire wear on the racetrack

PS reader question on motorcycle technology - tire wear on the racetrack

PS reader question on motorcycle technology - tire wear on the racetrack

PS reader question on motorcycle technology - tire wear on the racetrack

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PS reader question on motorcycle technology - tire wear on the racetrack
markus-jahn.com

1/5
“What is the reason for the flaky, frayed way in which racing tires are destroyed??”, asks us reader Holger Gebhardt.

PS reader question on motorcycle technology - tire wear on the racetrack
jkuenstle.de

2/5
Scaly torn tire shoulder on the front wheel.

PS reader question on motorcycle technology - tire wear on the racetrack
mps photo studio

3/5
Practical, non-contact infrared measuring device for checking the surface temperature.

PS reader question on motorcycle technology - tire wear on the racetrack
mps photo studio

4/5
Tire warmer with side cover of the rim for a more efficient heating process.

PS reader question on motorcycle technology - tire wear on the racetrack
Yvonne Hertler

5/5
Mechanical, tightly closing air pressure tester.

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PS reader question on motorcycle technology – tire wear on the racetrack

PS reader question about motorcycle technology
Tire wear on the racetrack

Content of

PS reader Holger Gebhardt has the following question about tire wear on the racetrack for our technology expert Werner “Mini” Cook: “It’s about the flaky, frayed way of destroying racing tires. Why is that?”

Werner Koch

09/14/2016

Unfortunately, some racing tires disintegrate much faster during racing training than you can earn the money for them. If you look back, this phenomenon has only existed since around the middle / end of the nineties. Before, the slicks were inaccessible when they were cold and lukewarm and did not develop any grip, but they did not tear. Then the compounds became more “consumer-friendly” and you could easily warm up slicks or stroll around the rubber without falling over.

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The tearing initially occurred in cold asphalt and at low temperatures because the rubber adhered but was mechanically overloaded (too little notch toughness, i.e. too “brittle”). Now it often dismantles the tires even at higher temperatures. Probable cause: An incorrect mix that does not suit the driving style or the route and cannot cope with the resulting mechanical-thermal stress with too much slip and too high temperatures.

Too high air pressure in warm outside temperatures?

Thomas Thierolf from the Pirelli / Metzeler racing service gave us another reason for tearing racing tires: In his experience, many hobby pilots drive with excessively high air pressure when the outside temperature is warm. The tire then lies on the asphalt with too small a contact area, cannot build up enough grip in the form of surface teeth over this small area, thus producing too much slip and overheating. This sets a vicious circle in motion, because the inevitable spinning when accelerating results in even higher tire temperatures, which is why the mixture tears up sooner or later.

Therefore, the tire pressure should always correspond to the manufacturer’s recommendations. With real racing tires, the values ​​are well below those of road rubbers (front 1.8 to 2.1 bar cold, rear 1.2 to 1.5 bar cold). For all non-professionals, the cold air pressure is crucial, because the warm air pressure changes depending on the heating time, the quality of the tire warmers, the coverage of the rims, the outside temperature and the wind that cools the electric blankets. To check the heating process, tire professionals recommend measuring the temperature of the rim. When the tires have been heated for one to one and a half hours, the rim should be around 45 degrees. You can then assume that the tire pressure has increased to the optimum value due to the expansion of the heated air.

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Most tires tear on the acceleration lane

It is advisable to measure the actual hot air pressure after a turn of at least five quick, connected laps with a calibrated, tightly sealed pressure tester. The difference between hot and cold air pressure is noted in the data sheet; this value helps the tire service or manufacturer to analyze problems. Tip: compare your own air pressure tester with the professional measuring device during tire service.

The basic settings of the negative suspension travel and the damping should be checked on the chassis. Too hard springs, too tight damping and a weight distribution that is too heavy at the rear or at the front can destroy the tires, as can poor response behavior or play in the deflection levers. Most tires tear on the acceleration strip, i.e. where the rubber is stressed in the circumferential direction by the engine torque. Here, lateral forces (inclination) and circumferential forces (acceleration) overlap. In this zone, a particularly resistant rubber compound and the largest possible contact surface are required to distribute the mechanical load.

Good values ​​for the temperature of racing tires

The following values ​​for the temperature of racing tires do not have to be strictly adhered to, they can be exceeded or undercut by a small amount. They can be determined with an infrared measuring device (around 40 euros in electronics retailers). Measurements are taken on the surface, with the professionals the rubber temperature is determined by piercing the tread.

  1. Tire surface after heating / tire warmer (infrared thermometer): 70 to 80 ° C.
  2. Rubber / carcass after heating / tire warmer (measured by piercing): 60 to 70 ° C.
  3. Tire surface after a long journey at racing pace (infrared thermometer) 75 to 115 ° C, depending on the route and length of entry into the pit.
  4. Rubber / carcass after a long journey at racing speed (measured by piercing) 80 to 125 ° C depending on the route and length of the entry into the box.
  5. Maximum surface temperature during racing (infrared sensor / data recording) 95 to a maximum of 135 ° C.

An infrared sensor with data recording also reveals how high the temperature shoots when the rear tire spins: to 170 to 180 ° C.

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