A Slick (English for "smooth" ), is a profile of loose tire that is suitable at the right temperature because of its very adhesive tread compound for use on dry or slightly damp roads.
Slicks in the motor vehicle racing
Unlike slicks are wets and intermediates having a profile. While slightly molded Intermediates the same rubber compound as slicks have to operate on dry roads still wet tires have strong profiling and an even softer compound.
An important parameter is the temperature. This must be in a suitable range at about 80 ° C - and thus higher than in a normal car tires - are. Below is a race tire only low adhesion. It is important for the correct air pressure and chassis geometry, often with a lot of negative camber to increase the contact area ( the percentage of the tire tread, the contact with the asphalt ) during cornering. Since heating of slick tires is significantly larger than in conventional tires, they must be approached with far less cold air pressure (often 1.5 to 1.8 bar ). The air pressure at the operating temperature increases by about then. 0.7 to 1 bar and then still lower than the road tires in the rule. This, however, a larger contact surface is achieved. Ideally, the measured temperature should be the same on hot tires driven over the entire width; a sign of the uniform load on the road contact.
There are small holes are located at several places in the tread for wear measurement, which can be known by using a profile depth gauge as well as of road tires. The holes are distributed uniformly over the circumference of the tire and are located right and left, close to the edges of the tread, in order to determine and uneven wear of the inner and outer sides can.
A higher mileage of slicks is achieved by a so-called heat cycling. The tires are made by machine or by one or two short Einfahrrunden to operating temperature and then stored for at least 24 hours. Chemical processes in the rubber mixture then make these more stable; no loss of adhesion.
Slicks on bicycles
There are various coat manufacturers who have slick tires on offer. Mention may be made Schwalbe, Continental and Michelin. They are mainly used in cycling, but also increasingly common to find town wheels on the asphalt because they provide the best traction when driving and allow through a lower rolling resistance, a more rapid and less energy -requiring driving.
The use of slicks has its origin in the U.S. motorsports scene of the 1950s and 1960s. At the time, tires were " shaved " for drag racing, so reduced tread depth. Especially popular this were products from Dunlop and Goodyear Blue Streak. From 1971 to 1997, specially produced slick tires in Formula 1 were used, with which the lap times achieved to date could be greatly improved. Also in touring car and motorcycle sport therefore sat down the faster slicks through in the 1970s. In 1998 they were banned in Formula 1 again to reduce the maximum cornering speeds for safety reasons. Instead, so were called " grooved tires " prescribed ( first forward with three longitudinal grooves, rear, each with four, and from 1999 front and rear four per grooves). In the following years, however, showed that these tires were becoming more powerful and thus hardly brought a gain in safety. Since the 2009 season, slicks are allowed in Formula 1 again.
With slicks a larger contact area between the road and tires is achieved. This results in a higher static friction (grip), so with the added gearing effect a stronger driving force ( traction ) and can be transmitted mainly cornering force. In addition, a profile would deteriorate the smooth running of the tire on asphalt and the power transmission due to additional rubber deformation or flexing. Also, the noise is reduced by the absence of profiling, tires squealing hardly occurs. By eliminating negative profile a tire has more rubber and thus more wear - reserves. He can still work well at high loads and temperatures up to about 100 ° C.
Lap times on race tracks dry can be greatly improved for these reasons by slicks. According to road tests of the magazine sport auto with production sports car on the old, short variant of the Hockenheim ring ( without the new chicane at the end of the cross bar ) is the gain of time in comparison to street-legal production tires for about four seconds, compared to street-legal sports tires still about 2 seconds; starting from a driven with slicks lap time of approximately 1:14 minutes.
Slick tires are used in dry and slightly damp racing conditions. The main problem is the drop in temperature below the optimal range, whereby the adhesion strongly decreases depending on rubber compound used in the damp track. If there is moisture on the asphalt, forms between the tire and road, a water film, it comes to hydroplaning, where the vehicle is no longer controllable.
The border area between adhesion and adhesion loss is narrower than slicks in profiled tires; skidding thus occurs while at higher speeds, but much faster. Since the maximum traction during acceleration and braking, and cornering force is achieved but ( in curves) only at a slip of about seven to ten percent, requires taking advantage of the possibilities of slicks considerable skill and experience.
The rubber compounds used in slicks and the stress on circuits limit the mileage of the tire to a fraction of those of road tires. So can already be worn down to the carcass after less than 200 kilometers, the tread.
The large contact area and the lack of negative profile can slicks are very sensitive to road bumps and ruts. The directional stability can be greatly impaired, so that constant steering corrections may be required.
Usually slicks are sold only by the racing tire departments of the tire manufacturer and only to holders of racing licenses.
- The independence of the friction surface is only valid for rigid bodies, which do not include motor vehicle tires.
- This tire is forbidden for motor vehicles on public roads due to the provision of at least 17% negative profile share.
- This tire has for motor vehicles on public roads because of there not achievable operating temperature no advantages.