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