It's a bit past mid-season, your racing effort has been fairly successful and you need to have some decent finishes to round out the year. What you don't need are problems that come up and ruin a whole race for you. If you have been racing for any length of time, you will have experienced a problem that comes seemingly out of nowhere and bites you in the tail, usually at the worst possible moment. Most racing jinxes come from lack of maintenance or failure to recognize a potential problem.
Use a large-dial air pressure...
Use a large-dial air pressure gauge and record all pressures, both cold and hot. DO NOT EVER use a clamp-on air hose end to fill a race tire, or any tire for that matter. Unattended tires that are being filled this way can and do overinflate to the point of exploding.
Here's a list of some of the areas where things can go wrong to cost you a good run or even a race win. We will also provide some hints on how you might avoid some of these problems. The top 13 racing jinxes are:
1. Tire Preparation
A team has prepared its car exactly the way it needs to, the setup is perfect, the engine has been gone over and tuned to the day's conditions, the crew is on top of all of the many maintenance items. The only thing different is that the usual tire specialist was not able to attend this race and the crew recruits a guy who "knows all about" tires.
He is allowed to select, air up, label, and position the tires for mounting on the car. No one watches over this guy and no one checks up on him to see if he indeed knows what to do.
Everything goes well with the selection and setting the air pressures, the only problem is that he places the tires backwards from the usual procedure and the crew then proceeds to mount up the tires. The left-side tires go on the right side of the car and the right-side tires go on the left side of the car. This results in air pressures and sizes that are reversed. The tires were labeled correctly but the writing is too small to see easily. So, no one catches the mistake until after the race. Needless to say, the car ran like crap.
Plainly label each tire with...
Plainly label each tire with information about which corner it was run on, the date, the set number, and so on. You can avoid mistakes that end up with the tires being put on the wrong corners of the car. Your team should designate one or two permanent crew members to prepare and care for the tires. This job is so important to the success of the team. If you use a new person for some reason, work with him to develop the good habits that are necessary.
"Can't happen" you say? This can and did happen. I have heard similar stories around the pits, so don't think it can't happen to you. Tire selection and inflation is one of the most important parts of the chassis setup. Make sure your tire guy knows what he/she is doing. If you're not sure of their expertise, check everything they do until you are confident in their ability.
Stagger changes can also be a problem. Again, all seems perfectly fine, the driver in practice likes the setup and you are in the top three with your lap times. You bolt on a new set of race tires and go out to compete. Somewhere along about lap 20-40 the car goes tight or loose. Needless to say, you don't finish very well that night.
After the race, you measure the stagger and find out the rear stagger either closed up or grew beyond what works at your track. At some racetracks, we can get away with this better than at others. I worked with a team that won a race and the rear stagger closed up to 3/8 inch from the normal 1 3/4 inch. The driver said he couldn't feel the difference.
At another track, if the stagger changes more than 1/4 inch, the car will not handle. That's tough to deal with. The solution, as much as is possible in this situation, is to get to know the particular tire you race with. Each brand and product number of tire has its own characteristics for growth related to your car and the track you are running on. The choice in new tire sizes must be made by knowing how much the tires on each side of the car will grow.
Practice is the time to evaluate the tire growth situation. The tires on both sides will grow due to elevated temperatures and the increased pressures that go along with a hotter tire. The right sides will gain more temperature and pressure than the left sides and therefore the sizes on the right side should grow more. How much is dependent on many factors, some of which are: a) having the correct stagger to begin with, b) having a balanced setup, or not, c) using dry air or nitrogen, d) the structure of the tire as well as the particular production batch, e) and believe it or not, how hard you run the car.
This team would do well to...
This team would do well to limit the amount of suspension droop so that the spring would not drop so far below the adjustment ring on the shock. This leaves the chance that the coil spring will not properly seat on the ring once the car is lowered. Some spring companies offer special spring retainers that will help keep tension on the spring and guide the spring onto the ring.
That last one is one to watch. If your driver has practiced at a speed that is somewhat slower than race speeds, not only will the setup feel different between the different speeds, the tire sizes will change differently. To see true pressure/temperature gains, simulate race speeds-in other words, get after it in practice. If you have noticed, the top drivers never pussy-foot around the track.
2. A Hung Suspension Spring
This is very simple and straight forward. When you jack up the car, the spring has an opportunity to hang in the lower control arm, in the case of a big spring car, or hang in the shock with a coilover car. This can happen in any type of race car from a Stock class Bomber to a sophisticated Formula car and even in the Cup series.
If this happens, it will change your weight distribution dramatically. There are several ways to help prevent this from happening. First and foremost is to limit the suspension travel in droop from where the wheel is at ride height.
With a Detroit Locker rear...
With a Detroit Locker rear differential, springs are used to force the axles to lock up upon acceleration. This trick unit only unlocks the left axle while leaving the right one locked all of the time. Because only one spring is installed does not mean that it doesn't need maintenance too. Using a rearend cooler will greatly increase the life of the locker springs.
If you have installed a chain or cable between the frame and lower control arm, when you jack up the car, the spring won't have the chance to hang on the seat. Some teams use ring spacers between the spring and the seat on a coilover. These can shift and end up between the seat and the spring causing a substantial difference in ride height at that corner
With a big spring design, the spring can rotate to where the open end of the coil spring will not be at the proper place within the lower control arm spring pocket. This will affect ride height and the weight distribution causing the handling to go south on you.
3. Bad Locker Springs (And Other Rearend Maladies)
I have seen many teams chase their setups all season long when the real problem had more to do with maintenance. With a Detroit Locker-type of differential, the springs that do the job of locking both axles up upon acceleration can and do get weak as time goes on.
The pulley alignment is important...
The pulley alignment is important to being sure that the belts will track inline with the pulleys. You can use a steel straight edge to check how the pulleys line up. Put the edge on the engine pulleys and look for the alternator, power steering pump, and oil pump pulleys to be inline and offset correctly.
Excess heat in the rearend will accelerate the process of these springs going "bad." When they do lose their tension, the axle that the bad spring is supposed to lock up will not. This leaves you with a car that drives off one rear tire and exit performance will definitely suffer.
Specialty rear differentials sometimes use aluminum gearsets to help distribute the forces between the rear wheels. These need to be inspected and possibly replaced as often as necessary to insure that there will not be a failure. Consult the manufacturer to obtain a proper maintenance schedule for your product.
The solution might be to use a rearend cooler if you race for more than 35 or 40 laps. Break apart the rearend and check the tension on the springs often to prevent a failure. The manufacturer can tell you the designed rate of these springs and how often to replace them.
4.Ignition Wire Problems
The carburetor throttle linkage...
The carburetor throttle linkage stop should not be used for a pedal stop. Install a stop behind the throttle pedal inside the foot box to limit the amount of pedal travel making sure that when the pedal is fully compressed that the throttle butterfly valve is wide open and not past inline with the throat.
On initial installation, many teams will wire the ignition so that the leads from the box to the distributor will be crossed. On some models of ignition boxes and distributors, similar color wires are not intended to be mated. This is not a racing problem because you will never get the motor to fire properly anyway.
Follow the instructions on both the distributor and ignition box so that the proper wires will be joined. Additional problems may arise from the way you connect the wires. Always use heavy-duty quality connections to reduce the chance they will break from all of the vibration that race cars produce. Solder the connections and use heat shrink on all joints. A little time and effort spent here can save a loss of ignition down the track.
5. Belt Alignment Problems-Pulleys
How many times have you seen or heard of a team experiencing loss of oil pressure or cooling due to a broken or thrown engine belt. Most of these occurrences can be traced right back to a misalignment in the pulley system. The belts always seem to come off during the race and not in practice when it could be easily fixed. Why is that?
Shocks must be mounted so...
Shocks must be mounted so that there is no binding or interference with any suspension parts or the chassis. This is a common problem and causes handling problems. This is an extreme case, but again, not all that uncommon. This stocker class car had two front shocks that were bad from rubbing on the springs. The top mounting hole had to be relocated to center the shock in the spring.
It doesn't take much of a bend in a belt to cause it to de-pulley and come off. The solution is to inspect the alignment of the belts on all pulleys on the engine. Use a straight edge and lay it against one pulley to see how that one lines up to other pulleys. Don't necessarily trust your eyes because often the problem lies out of your eyesight.
6.Broken Throttle Parts
Loss of throttle is a common cause of a race car loosing power abruptly. The throttle shaft can shear off, the connecting bolt can break or loosen or the linkage can just fatigue and break somewhere between the gas pedal and the carburetor. This is another area where we seldom do proper inspection and don't discover there is a problem until we have a failure.
Breakage is not an acceptable way to schedule maintenance. Each moving part in the car needs to be inspected often. Put this item on your maintenance sheet and make sure someone goes over every part of the throttle linkage system.
This dirt modified uses a...
This dirt modified uses a coilover eliminator device for mounting the spring on the trailing arm. Care should be taken to maintain this unit. If it's allowed to corrode, it will seize and ruin your setup. Even a restricted movement can alter the handling a great deal.
Properly attached and adjusted pedal stops can help prevent stress on the throttle linkage and carburetor shaft. It's not a good idea to use the carb throttle stop as a pedal stop. An overzealous driver can apply way too much pedal pressure and twist the shaft off. Take time to adjust the linkage so that you will be applying full throttle (butterflies wide open with maximum pedal throw), but not stretching and stressing the linkage.
7. Shocks Bottoming Out Or Over Extended
A radically errant setup can often be traced to a mechanical binding problem. Often, we find that a shock is either bottoming out from excess travel or hanging in rebound from too short a useable travel due to improper mounting.
Once you have finished building your car and have established the ride heights, measure how far each shock's shaft extends into the shock body. If you know the length of travel of the shock, you can subtract and know how much rebound, or compression, travel you will have available.
There are a multitude of Heim...
There are a multitude of Heim joints and similar components that need to work freely in order for the car to handle the way we predict. One tight joint can significantly alter the way the car reacts to the dynamic forces and can make the job of driving it a nightmare. For dirt cars, this maintenance might need to be conducted on a weekly basis.
Problem areas are with the left rear in rebound, the right rear in compression, and the right and left front in compression. On entry, the right front compresses which then causes the LR to go into rebound. If the LR shock becomes fully extended, then a lot of load will be transferred off the LR corner and you will loose grip in that tire making the car loose in.
If the RF shock becomes fully compressed, that corner will be effectively locked up stiff and the RF tire will lose grip. Coming off the corner, the RR corner will experience a lot of travel and the shock will compress up to four inches depending on the setup. Make sure you have enough shock travel available so that there is no chance that the shock will bottom out.
8. Suspension Binding
Another source of mechanical binding lies in the use of sliders in some cars. The various designs of coilover eliminators and big spring sliders need constant maintenance. Follow the manufacturer's recommendations and inspect these units often. They will bind up and stick if not properly maintained, especially on dirt cars.
The shock mounts are under...
The shock mounts are under a lot of stress and loads on a circle track car. We need to be sure that the design is adequate to withstand these loads. The welds must be inspected often and we need to make sure the shock is not contacting the chassis. This car has a support brace that is mounted very near to the spring mount and will provide rigidity to prevent stressing the chassis tubing.
With all race cars, and especially the dirt cars, we need to break down and inspect all moving parts in the chassis on a schedule that makes sense. When we wash the car after a race, the water tends to collect in the various parts that handle chassis movement. A good car can slowly go to bad without proper maintenance.
The parts we are talking about include the upper and lower control arm pivots and ball joints, the wheel bearings, the rear trailing arm connecting links, steering components, throttle linkages, sway bar links, and all other connecting points that may corrode or seize from lack of lubrication.
Most race teams that ignore this important task will experience a car that slowly fails to respond to chassis setup changes. This is a clue that maybe you need to look at beginning a maintenance schedule ASAP.
9. Broken Shock Mounts
The bolts that connect the...
The bolts that connect the control arms and other suspension components should be checked often for tightness. Should a front lower mount become loose, the moment center location will change, the bumpsteer will change and the bolt will be stressed to the point of failure. It's a good idea to tack weld washers over the slotted holes in the position where you want your control arm to be mounted. If the bolt loosens, at least the arm angle will remain the same. Check these and other bolts for tightness often.
The mounts that hold your shocks on the car take a lot of abuse in all forms of circle track racing, especially with the coilover types of suspension designs. One of the worst failures you will encounter is a broken shock mount. This can't be fixed during a race.
The way the shock mount is attached to the car can be an indication of trouble. Each mount should be strong enough and supported adequately so that the loads the mount will experience will be distributed without stressing the joints.
Regular inspection of the metal around the mounts can often show the start of a crack or stressed area so that we can re-weld or replace the mount. This exercise can greatly reduce the chance that you will lose a shock mount during a race.
10. Loose Bolts
The suspension parts endure a lot of force from braking to acceleration. The control arms at the front and the ends of the rear links can become loose as the bolts are pushed and stretched lap after lap. If these loosen during a race, the car will become un-driveable.
Many circle track cars use...
Many circle track cars use aluminum axle housing tubes because they are lighter. They also have a greater chance of bending and so the rear wheels need to be checked more often for unwanted toe. You can do a very accurate alignment check on your rearend with strings. Once the rear has been aligned, measure from the front of the axle tubes to specified chassis points so that rechecking the rearend square is quick and easy at the track. A simple rear wheel toe and camber check will tell you if the rear axle housing is bent.
If your car is doing strange things, one of the first and easiest things to check is for a loose bolt in the suspension system. Even if the joint is fairly tight, but not real tight, it can slip and result in a rearend that is out of alignment, a serious problem nonetheless.
If you find a loose, or "not-so-tight" bolt in your suspension system, think about realigning the car as soon as possible and definitely before the next outing. Educate your team members to this so that they can make the team aware when they are "nut and bolting" the car. Merely tightening the bolt does not necessarily fix the problem
11. Bent Axle Tubes
Rear wheel alignment is so important to how the car will perform that we should be aware when things might go south in that department. Incidents happen in the course of racing and testing that could cause the rearend axle tubes to become bent.
The bend could be in any direction to affect toe, camber, or both. A set of rear wheels that are toed either in or out excessively can cause the rearend to lose grip all of the way around the track. Sometimes the cause can go unnoticed.
Common causes are a brush with the wall or contact with another car. When either of these happens, make sure to check the toe and camber at the rear wheels. We often concentrate on front wheel toe and camber settings and forget that rear wheel geometry is just as important.
12. Plumbing Problems
How you plumb your car for cooling the water or oil can be a problem. There are some common misconceptions about these two that can cause overheating and/or engine failure. Here are a couple of common mistakes teams make.
When plumbing your water lines, remember to install a proper sized pulley on the water pump so that the speed will not be too slow or fast. It is a general rule of thumb to match the pump pulley size to the crank pulley size.
You might also need to install a restrictor in the radiator at the point where the water enters the motor at the nipple. There are several sizes available to regulate the flow rate to more efficiently allow the water to cool.
In plumbing a dry sump system, always place the filter where it will be the last thing the oil passes through before entering the motor. If not, lots of unpleasant things can happen. New oil coolers often have slag and other pieces left inside that come loose and flow into the motor if not filtered out. Placing the filter before the cooler could be a problem.
Flow the oil through the radiator oil cooler into the bottom and out the top. This pushes any air that may be trapped in the unit out to prevent cavitations. Use hose ends that are the free-flow design, where the bend is made with tubing and not an abrupt 90-degree turn drilled into a solid aluminum block.
13. Poor Geometry
A laser alignment system can...
A laser alignment system can help you check alignment of the wheels as well as bumpsteer and Ackermann effect. This is quicker and more accurate than using strings, bumpsteer plates, or turn plates. The beam can be projected well beyond the car and even small errors are multiplied and easily seen.
Last and definitely not the least of our racing jinxes is poor geometry in the chassis. This can be anything from improper moment center location to camber, caster, anti-dive or pro-dive, alignment, and steering system geometry problems. I can't tell you how many times a team has chased its otherwise great setup only to discover that the culprit was a geometry problem.
The most significant geometry problems are: a) excess toe-in or toe-out of the front or rear wheels, b) rearend misalignment, c) excess bumpsteer at the front end, d) roll steer at the rear end, e) excess Ackermann or reverse Ackermann steering effect, f) wrong caster and/or camber settings, and g) improperly designed moment center location that affects the front dynamics as well as the camber change characteristics.
In today's racing, a team must be aware of the geometry issues in its car. Gone are the days when we left it up to the car builder to decide what is right. While it's true that many top car builders are up to speed with all of the technological advances we have experienced over the past 10 years, it's imperative that we absolutely know where our car stands on geometry issues
I can tell you with few exceptions that the winning teams in this day and age know their car inside and out. They apply the technology and develop their own car aside from what everyone else is doing. Above all, they do not follow the leader.
If any of these examples spur you and your team to action and helps you to avoid a costly jinx, then we have done our job. We can always learn from the experiences of others and that is exactly where these stories and examples come from. All of these mistakes have happened in the past and will happen again. Jinxes don't come out of thin air, but rather from our lack of knowledge and attention to detail. That makes them avoidable.