What is the definition of a tire heat cycle?

Need to make sure I understand what I am talking about.........

So, in order to better understand tire heat cycles, what is the definition of a heat cycle?

What happens if you drive the car but never get the tires to proper operating temp. What is this considered, 1/4 heat cycle if anything?

Thanks for all your help.

Kind of a "How big is a rock?" queston here, but I can provide some context hopefully.

First, try not to think in terms of "heat" cycles. It's the convenient term we use, but more accurately think of it as a 'stress" cycle. The point of a het cycle is to more precisely align the granular structure of the tire so performance and wear is optimal over its service life. Doing this requires not only heat, but physical stress as well. Heat AND massage, if you will. 

Static heating, honestly, doesn't do much. It can be a shortcut for a first heat cycle to statically heat the tires then go out and drive a few laps to massage them in without having to spend laps getting them up to temp, but the stress is as much of a part (if not more) of the process as the heat.

As for partial heat cycles, well, it depends. is something better than noting? Yeah, probably. How much better? Well, that probably depends on countless factors that are nearly impossible to test without going through hundreds of sets of tires in controlled conditions. 

It kind of feels like the real question you're asking is "How to I treat my tires if I have limited opportunities to properly precondition them?" and that's a super valid question. it's actually one I faced recently on the way to the SCCA Time Trials Nats with a new set of Bridgestones. Hurricanes stole my test day that I was going to use to heat cycle the fresh rubber. So instead I threw the tire heater on them for a couple hours and got them nice and toasty, then went for about a 50 mile drive on some nice roads with rougher asphalt to really give the tread surface as good of a conditioning as I could. At the event I just went full send from the first session and I've noticed no unusual wear or performance.

So the real answer is there are ideal practices, and there's what we have to live with in the real world. today's tires are far less sensitive to heat cycling and break in than they were a decade ago, and sometime you just have to play the hand you're dealt, and, usually, things don't turn out so bad. but given the opportunity, even if that opportunity is to prep something at a less-than-ideal level, best practices dictate that you do what you can when you can.

In reply to Stalker_LS3 :

I'm glad you asked that and thanks for the explanation J.G.

I think the other question this usually works out to is- "Will driving my tires to/from events count as a heat cycle and degrade the useful life of the tire?" I think the usual answer there is not meaningfully unless you're comparing vs stickers at TT nationals or something.

I've both had my Bridgestones heat cycled by tire rack and done it myself. According to previous discussions on the topic, both are equally effective,and that's been my experience.
 

An important factor is to remove the tires or jack up the car, and let them sit for at least 24 hours. 

"heat cycle" is used in two related-but-not-quite-the-same ways.

The more general definition is in terms of "counting heat cycles", because the rubber compound in a performance tire usually has maximum grip the very first time you run it on the track ("stickers").  Every time you take that tire out on track, heat it up, and then let it cool down again you lose a certain amount of that grip; and the tire "heat cycles out" when the performance has dropped to the point that it's not worth running it in a competitive setting any more even if there's still a ton of tread left.

The second usage comes from the fact that some tires have increased longevity if the first heat cycle is very carefully managed, with a "rest" period between that cycle and the next time it's used.  A lot of people refer to this process as "heat cycling", and it's what Tire Rack attempts to reproduce with their service.  Ideally it's something like a 4 lap run, starting off with low cornering loads and building gradually to a full speed run (albeit with no sliding) for the last one.

As for effects on the tire -- the useful life of the tire is affected by both the absolute number of heat cycles as well as the "depth" of each cycle (how long it last and how hot it gets).  A 3 lap qualifying run will take a lot less out of a tire than a 6 hour enduro, even though both are "one heat cycle".  So driving on a tire without heating it much will have some effect, but how much will really depend on the tire.  For example, driving to an event on a set of Hoosier A7s is wasting a lot of their potential performance, but doing the same on many of the 200tw compounds out there is probably not going to make a difference that you can measure.

Amplifying what Codrus said:  We are talking about two vastly different things here, though related. 

A properly performed "initial heat cycle" conditions the rubber in a positive way.  There is no downside to this operation, only potential upsides.

Every subsequent time a tire is cycled/stressed, especially when pushed hard and long, it does take something out of it.  How much depends on many things, not the least of which is the magnitude and length of that stress.  Since that stress creates heat, the process is called a heat cycle, cuz the next thing that happens is cooling.

Further, every tire is different, so there are no hard and fast rules as to how quickly a tire's performance will degrade.  Only experience with a particular model in a given application can give proper prediction.