M Scotte skrev:Förklara gärna för en okunnig vad meningen med heat cycling är då?
En heat cycle är vad det heter ifrån kalla till varma till kalla igen, är en heat cycle. Vissa däckfabrikanter säger att man ska göra precis som du säger martin att man ska köra dom "varma" under en lång uppvärmning för sedan kylas av under typ 24timmar. Detta är ju just för att däcken ska hålla bättre under dess livslängd.
Det håller jag med dig om med dig om till fullo.... Men dit jag trodde tråden var påväg var hur man ska använda däcken för maximalt grepp.....
Har mycket erfarenhet av just detta igenom gokart,formelbilar,STCC och Porsche m.m
Här är en text som just detta....
This excerpt is from Chapter 8 of The Racing & High-Performance Tire.
The Real World, Using Tires
People who are actually using tires-serious road racers, circle-track racers, and autocrossers-have learned a lot about tires by trial and error. Hopefully these excerpts from The Racing & High-Performance Tire offer up some whys that will generate more knowledge among these racers and make them more confident when they're using their tires at the limit. Lower lap times forever!
Tire Give-Up
A racecar uses a set of tires a length of time, termed a tire stint, mainly determined by the number of laps required to use the fuel allowed by the rules. In most race series it takes more time to refuel the car than it does to change tires, so no time is saved by refueling only. In professional racing there is no reason for the tires to have a useful life that is any longer than a fuel stint.
For most tires the first lap or two are the fastest laps those tires will ever produce. Recently Michelin returned to Formula 1 to compete with Bridgestone in a good old-fashioned tire war. Some Michelin F1 tires appear to increase in performance after five to seven laps and reach peak grip during laps 10-20 before falling off slightly.
The Goodyear tires sold to NASCAR Winston Cup teams these days "give up" at least a second in lap time from the second through the tenth lap and continue to deteriorate until the end of the stint. In fact you can see the tires give up during the two-lap qualifying runs for the Winston [now Nextel] Cup races. The first lap is almost always the quickest and many drivers just run one lap and go back into the paddock. The amount of give-up from the first to the second lap is 0.05 to 0.1 seconds per mile of lap.
So why do tires give up? The reason is similar to that described in the section on tire scrubbing. The rubber in tires, especially tread rubber, undergoes cyclic stress at very high levels. The work done by these rubbers result in heat generation. The combination of high cyclic stress and high temperature is bound to generate mechanical and chemical changes in the rubber.
Some elastomers, and rubber falls into that category, exhibit stress softening and permanent set. Stress softening has been attributed to displacement of polymer network junctions and entanglements and/or the incomplete recovery to original positions of those junctions and entanglements after stress deformation. The presence of fillers [carbon black and silica] introduces possible additional softening mechanisms, including breakage of rubber/filler attachments, disruption of filler structure, or chain slippage at filler surfaces. When intermolecular structures are irreversibly disrupted or reform in new positions while the polymer is extended, the result is permanent deformation. The rubber is said to have "taken a set."
A rubber compound is a mix of many materials, including chemically active agents. An excess of certain kinds of active agents can provide an opportunity for a disrupted or broken bond to repair itself by rebonding at the same location or in a new location.
Another mechanism for tire give-up is more simple. The tire might wear to a tread thickness too thin to generate enough heat and the tire temperature falls out of the range for max grip. A thick tread, even a slick, deforms and the resulting hysteresis generates heat. A thin tread deforms less, generating less heat.
Heat Cycles
Rubber is a complex substance, a mixture of materials and chemicals manufactured with mechanical processes and various heat and pressure cycles. In use, tread rubber sees mechanical working and time at elevated temperatures very similar to the processes it saw as it was manufactured. It makes sense that more of the same processing would further change the rubber.
The material in a new race tire is semi-stable. If the tread rubber had been totally cured it might be too hard to do its job. So stress and heat can continue the curing process. Even small amounts of energy from ultraviolet wavelengths in sunlight, ozone in air, heat, or mechanical working can cause the rubber in a tire to continue its vulcanization process or change in some way.
The first heat cycle is called scrubbing and was described earlier. Every heat cycle changes a tire to some degree, generally in the direction of harder, less flexible, and less adhesive. Race tires can loose effectiveness before the tread wears through if they go through many heat cycles. For some tires three cycles is too many, while others show a performance drop off initially and then maintain a good level of performance until the tread is worn off. Smart race organizers are incorporating long-lasting tires into their rules so that "spec" tires can lower the cost of racing.
Men som sagt är man ute efter att sätta en så maximal tid som möjligt i t.ex. SS så är det bäst att köra på helt nya däck....
MEN det finns ju en risk att dom håller sämmre under resterande livslängd! Men vill man plocka den där extra sekunden så kostar det
