Admin
05-14-2001, 03:50 PM
Scrub-a-dub-dub
by Jason Black
Sport Rider Magazine August 1996
With all the frightening stories about it, scrubbing in new tires at the racetrack (or on the street) can be f/at-out scary for the novice. Without the knowledge of a few vital procedures, getting those intimidatingly shiny new tires ready for traction becomes a guessing game. But it doesn't have to be.
http://www.parts411.com/articles/scrub/scrub1.jpg
First of all, let's dispel a few myths. The new tire at left looks shiny because it has not been scuffed or heated up. Many riders believe a shiny appearance is the sole component that creates a slippery tire. The main factor in the tire's inability to provide adequate traction is its low temperature, whereas the new surface may contribute to a new tire's slipperiness. There are up to 15 different chemicals (depending on the tire) that make up a compound. Heat breaks down those compounds and makes them react with each other, and the tread and compound "come together." A racer using tire warmers on fresh tires can go into the first corner at 90 percent of race pace since his tires are at operating temperature.
Another trend that many riders like to follow is weaving in order to warm tires, but most consider this more of a risk than it's worth. Heat, generated by carcass flex, rotational speed and gradually increased lean angle, is the main ingredient for new-tire traction.
http://www.parts411.com/articles/scrub/scrub2.jpg
There is a procedure to follow during scuff-in: Keep entry speed Iow so you're able to get off the brakes before turning the motorcycle; be smooth and avoid quick, aggressive movements; use moderate lean angle to begin with; crack the throttle off-idle and begin gradually accelerating as soon as possible. Don't rush into corners using high-entry speeds and trail-braking--this overloads the new tire and can result in a low-side crash. Notice the brake light of the rider in the second photo; he's braking while still straight up-and-down.
http://www.parts411.com/articles/scrub/scrub3.jpg
Demonstrated here on the track, the rider has finished his braking and then turned the motorcycle. The front tire is a/ready managing the traction deficiency caused by cornering; to add braking to that could overtax a new, cold tire.
Once the throttle is cracked, the front tire is less likely to push (slide). The weight of the chassis shifts and settles and the load is no longer biased toward the front end. Bending the bike into the corner relatively slowly a/lows the rider to apply the throttle a/most immediately.
This photo demonstrates the desired smooth, arcing line upon entry to the corner, compared with a more aggressive, squared-off line that would be used in a racing situation. As the rear tire comes up to temperature, the throttle can be applied harder at the corner exits, thus increasing the tire's temperature.
http://www.parts411.com/articles/scrub/scrub4.jpg
You'll hear racers talk about a tire "coming in." This term refers to the tire reaching optimum temperature and becoming adherent, and a rider can actually feel this with experience.
Your lean angle should increase as the tire comes up to temperature. When the tire is cold, it's going to feel loose and will tend to move around a bit. There will be a point when the tire stabilizes and feels p/anted; this is the tire "coming in." Be aware that a racetrack or road mostly consisting of right-hand corners will heat the right side of the tire, but the left side will not reach the same temperature as quickly and should be treated more carefully for the first few laps. Give tires extra time to come in if the track/road surface is colder than normal.
Scuffing in new tires shouldn't be a lesson in fear. Approach it thoughtfully and with care, and the anxiety that once accompanied the thought of breaking in new rubber will soon be rep/aced by a mental checklist that brings you and your tires up to speed.
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by Jason Black
Sport Rider Magazine August 1996
With all the frightening stories about it, scrubbing in new tires at the racetrack (or on the street) can be f/at-out scary for the novice. Without the knowledge of a few vital procedures, getting those intimidatingly shiny new tires ready for traction becomes a guessing game. But it doesn't have to be.
http://www.parts411.com/articles/scrub/scrub1.jpg
First of all, let's dispel a few myths. The new tire at left looks shiny because it has not been scuffed or heated up. Many riders believe a shiny appearance is the sole component that creates a slippery tire. The main factor in the tire's inability to provide adequate traction is its low temperature, whereas the new surface may contribute to a new tire's slipperiness. There are up to 15 different chemicals (depending on the tire) that make up a compound. Heat breaks down those compounds and makes them react with each other, and the tread and compound "come together." A racer using tire warmers on fresh tires can go into the first corner at 90 percent of race pace since his tires are at operating temperature.
Another trend that many riders like to follow is weaving in order to warm tires, but most consider this more of a risk than it's worth. Heat, generated by carcass flex, rotational speed and gradually increased lean angle, is the main ingredient for new-tire traction.
http://www.parts411.com/articles/scrub/scrub2.jpg
There is a procedure to follow during scuff-in: Keep entry speed Iow so you're able to get off the brakes before turning the motorcycle; be smooth and avoid quick, aggressive movements; use moderate lean angle to begin with; crack the throttle off-idle and begin gradually accelerating as soon as possible. Don't rush into corners using high-entry speeds and trail-braking--this overloads the new tire and can result in a low-side crash. Notice the brake light of the rider in the second photo; he's braking while still straight up-and-down.
http://www.parts411.com/articles/scrub/scrub3.jpg
Demonstrated here on the track, the rider has finished his braking and then turned the motorcycle. The front tire is a/ready managing the traction deficiency caused by cornering; to add braking to that could overtax a new, cold tire.
Once the throttle is cracked, the front tire is less likely to push (slide). The weight of the chassis shifts and settles and the load is no longer biased toward the front end. Bending the bike into the corner relatively slowly a/lows the rider to apply the throttle a/most immediately.
This photo demonstrates the desired smooth, arcing line upon entry to the corner, compared with a more aggressive, squared-off line that would be used in a racing situation. As the rear tire comes up to temperature, the throttle can be applied harder at the corner exits, thus increasing the tire's temperature.
http://www.parts411.com/articles/scrub/scrub4.jpg
You'll hear racers talk about a tire "coming in." This term refers to the tire reaching optimum temperature and becoming adherent, and a rider can actually feel this with experience.
Your lean angle should increase as the tire comes up to temperature. When the tire is cold, it's going to feel loose and will tend to move around a bit. There will be a point when the tire stabilizes and feels p/anted; this is the tire "coming in." Be aware that a racetrack or road mostly consisting of right-hand corners will heat the right side of the tire, but the left side will not reach the same temperature as quickly and should be treated more carefully for the first few laps. Give tires extra time to come in if the track/road surface is colder than normal.
Scuffing in new tires shouldn't be a lesson in fear. Approach it thoughtfully and with care, and the anxiety that once accompanied the thought of breaking in new rubber will soon be rep/aced by a mental checklist that brings you and your tires up to speed.
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