We also covered last month that there are two fundamental forms of tire shake: driving over the tire, or“ sticking the tire,” and aggressive shake, or“ taking the tire off,” where you spin the tires but don’ t have enough power to smoke the tires. As I did with the weak shake, I’ ll break down aggressive shake into several subsets.

Let me also reiterate another point that was made last month – how early and how long your car stays in the“ shake zone” is a function of how much power you make. Lower-powered cars will tend to shake very early. The more power, the further out the shake zone moves, and the longer it is.

The basic cause of“ taking the tire off” is, at some point, the rate of acceleration of the tire exceeding what the track could take. Sometimes sticking the tire early or having a very flexible wheelie bar will send the tire into a spin-hook cycle that eventually has a rate of acceleration so great that it takes the tire off. Sometimes it just comes from being too aggressive. Other times it comes from being too conservative, then too aggressive.

Early aggressive shake – I have seen this misdiagnosed many times as“ weak” shake. The car basically has too much wheelspeed but doesn’ t have enough power to smoke the tires, so the tire starts spinning and grabbing. This is not to be confused with bouncing off the wheelie bar too hard.

Slow shake – This form of shake comes from not having enough wheelspeed early, then either the power ramps in too quickly, the clutch comes in too early, etc. It then tries to accelerate the tire too much,

too quick. In today’ s power management, this often comes from being too conservative early, not having good wheelspeed, and then trying to ramp in too much power too quickly. If the cause is too much timing out, more timing will give you more wheelspeed and you have less of a gap to bridge from full timing to getting the power back in.

Under the curve – This could easily be filed under weak shake, but I think it’ s pretty close to slow shake described above. In the above slow shake example, the tire is not really all that pissed off, it’ s just not all that fast.“ Under the curve” shake happens when you get what I call

the signature of death – when your driveshaft graph looks more like a jagged straight line than a curve. In this case, the tire is pissed off, and at some point, it will let you know about it by taking the tire off. You see this a lot on cool tracks. It’ s easy to miss the tune-up on a cool track. You didn’ t miss the tune-up enough to just totally stick the tire, but when the converter / clutch start coming together with the power curve, many times the tire says“ enough of this” and goes into shake.

This type of shake can be a real bitch if it backs you into a corner trying to get qualified. The bad part is when the track is cool and

the air is good – it’ s easy to get over center on the aggressive side. And you know that going into the last qualifier. I have probably lost jobs because of this, but I would rather go down swinging than looking.

Aggressive shake( late) – This form of taking the tire off is just from getting too aggressive. Too much of something. It could be from ramping the power too soon, too quickly, too much clutch, too much ratio, turning on a leanout too early, too big of a leanout, etc. All of this is too much relative to what the track can hold. You typically fix it by turning down whatever caused it to be too aggressive. Just remember if the track gets better for the next run, it may hold what you just threw at it.

Outta control shake – This type of shake basically happens when you did a bad job of smoking the tires early. The wheelspeed is just out of control. Many times this will not flare the motor as much early because the tires are not creating enough resistance to keep the motor and driveshaft separated. As a result, the two are much closer together when the converter or clutch tries to lock up. When that happens, it takes the tire off and goes into shake. You just narrowly missed a hero run.

As these types of shake are caused by an excessive rate of acceleration, they often can be fixed by removing power from the problem area. This is true even in the cases of slow shake and under-the-curve shake.

It’ s very important to remember the more“ perfect” you can make your driveshaft curve look, the more you can throw at it. While some small spin-hook cycles may not be enough on their own to cause tire shake, they limit what you can get away with. With any spin-hook cycles, the tire often“ takes a set” lower than what it would have with a perfect curve. The same is true when the tire comes out of an early spin – it often hooks and takes a set lower than what it could have.

Next month we will take a look at trying to make that perfect curve by setting targets. DI