Tires are the most consumable parts of a race car. Tires are the mechanical interface to the track. Tires will attribute a good bit of how the car performs on any given day. Tires, however, are still one of the most misunderstood components on the car. How do you assure that you always have the best tires on the car? This is not a complex process; it will take the development of some tire management skills and some rigor around documenting your tires. Yes, the dreaded notebook again. You do not need a bunch of fancy tools or computers and fancy (expensive) software applications. At the minimum, you will need to keep some notes and keep track of your tires race to race.
If you are running open tires and have an unlimited amount of money to spend on tires this would be a much simpler task. Just use new tires every single time the car hits the track. But such is not the case for most weekly racers. The majority of racers cannot afford new tires every race and for some classes it would wasteful. Many local racers are required to use one brand and compound of tire. This is usually done under the guise to save the racer money, not really sure this is the most logical reason, but that is just the way it is in many associations. While forcing the racer to use a specific tire brand and compound of tire may sound like a way to control costs, many racers are not always in sync with this practice. You also need to keep good track of the wheels you are using. More on that in a bit.
Let’s start with the easiest method of managing tires. Sell your old tires prior to wearing them out completely. Sell them while they are still in reasonable condition. We need to face the fact there are always racers on tight budgets. If your old tires are not completely worn out, there is usually someone who needs a lower cost option to keep on the track. It will help keep you in newer tires and not an entirely bad way to help with your cash flow. You should always try to sell your used tires; it just makes good financial sense.
First, you need a good set of eyes to inspect tires, this applies to new and used tires. Look for any obvious damage to the tire. Yes, new tires can become damaged; there are perils in the journey from the manufacturer to the final customer. Not so much at the point of manufacture but from poor handling or lack of care in transport and storage. Review the bead of the tires on the inside and outside, where the tire will be interfacing with the wheel, damage in the bead of the tire can cause a variety of problems, the least of which can be leakage between the wheel and the tire. Not a good problem. Look at the sidewalls and the treaded area for obvious issues. The first inspection should occur when you are still in the place of purchase. Once you leave the “store” with the tire, it’s all on you. Most tire retailers will not refund your tire if it is “damaged” once it leaves the shop. Buyers beware. Look at the side walls of the tire. You are looking for any obvious damage like small punctures or scuffing also look for tire repairs, like patches and plugs on used tires. If the tire has some repairs you may want to pass on the tire just to avoid any potential issues in the future. While this is not a problematic area when purchasing new, it still happens. If you are buying used tires, you need to be especially diligent in the inspection for damage.
Keep track of your tires, just from an inventory perspective. From an economic perspective, there is really no need to purchase tires in bulk even if you get a “better deal” from a cost perspective. Racing organization’s being what they are, it is possible that the brand and or compound of the tire could change and you could be stuck with a bunch of tires that are no longer legal to use in your racing organization. The deal on tires is not always as good as it seems after the sale is complete. You can tie up a good bit of money in tires that could be used elsewhere in your racing budget. Practice inventory control. Just like in the real world, inventory is dollars and letting a bunch of new tires age in your shop is just not good inventory control. Also, why should you pay for the privilege of aging tires in your shop. Let the tire guys deal with the inventory.
Most tires used on cars come with a date code that the manufacturers place on the side wall of the tires. This code usually will tell the year and the week of the year that tire was manufactured. There are other numbers on the code as well and these sometimes mean different things from different tire makers. They also may tell you the lot and batch codes as well. Contact your tires manufacturer to see how to read the codes. At the very least, you will want to purchase tires that are as “fresh” as possible if it is October, you will want tires that are from a manufacture date as close to October as possible. If the tire was made in February, it means the tire is already nine months old. It still may be new, but it has been sitting around in inventory for nine months. While it may not have compromised the tire, you just never know.
Let’s talk abought wheels a bit. Your wheels should be inspected on a weekly basis prior to hitting the track. You should be looking for obvious damage, dents, bent wheels and any cracks. If your tires lose air during the week, look for and locate the leak. A leak on track will rear its ugly head at the worst possible moment, like when you are leading. If you are running a bead lock wheels, you need to keep track of the hardware that holds the bead lock in place. Damaged bolts should be replaced and all of the bolts should be checked for proper torque. In fact, it is a good idea to completely change out the hardware on a regular basis. The threaded holes in the wheel need to be inspected and cleaned out frequently. Also, the sealing surfaces need to be inspected as well. Check with the manufacturer of the wheel for the correct Torque specification. And, make sure you any bolts you replace are the same grade as the wheel came with. If the wheel came with grade eight hardware replace it with grade eight hardware not just some bolts you have in the shop. The grade matters. Do not use lower grade bolts just because you may have some. Use the correct hardware. A point of safety, deflate the tire, prior to loosening and or removing any of the bead lock hold down hardware.
Wheels also play a large part in how well the tire works. Tires tend to heat up quicker on narrower wheels. Why? Good question. I have observed racers, where it is allowed, use a narrower wheel, for qualifying. The tire tends to reach temp sooner on the narrower wheel. Not a significantly narrower wheel but an inch to an inch and a half narrower. The narrower wheel tends cause the tire’s side wall to flex more and the tires tend to increase in temperature a bit quicker.
Remember, if you go too narrow, it will impact the tires contact patch with the racing surface. We need to remember that a little is a good thing. More is not always better. This is why we test and document as possible. However, excessive temperature is not always a good thing during the race. As the tire reaches operating temperature, all things are good. But, if the tire gets too hot bad things happen, the tires blister and chunk and start to degrade from a performance perspective quite quickly. The tread can get “feathered” having the appearance of using very coarse sandpaper on the tire. How hot is too hot? You need to research your particular brand and type of tire. The manufacturer is a great starting place to ask what the optimal operating temp for your particular tire. Your job is to make the tire reach that temp as quickly as possible and not over heat. Seems simple enough but in reality, is a difficult task. In longer races tires can get to hot and other things like brakes can put a good bit of temperature into the wheel and that finds its way into the tire.
After the car comes off the track you need to do a few things. Check the tire temp as soon as the car stops, check your air pressure and check the tires tread for the hot durometer number, then once the tire cools down check the cold durometer number. If you are really a numbers guy, it would be good to jack up the car as soon as possible and record the race ending tire diameters to see if the stagger has changed over the course of the race. All of these numbers need to be documented and kept as part of your notebook. Tire temp and air pressure are very common but many racers do not check durometer. Durometer is simply a measurement of how hard the rubber is on the tread or where the tires interfaces with the track. The smaller the number the softer the rubber. The more the tire hardens the more the tire’s ability to grip the track degrades. It is really simple to do and it takes just a bit of time.
Just as a special tool is required to check air pressure, temperatures and tire diameter you will also need a durometer to check the hardness of the rubber. A durometer is a simple gauge with an analog scale and a small probe sticking out of the bottom of the gauge. When you place the durometer on the tire the probe will be pressed against the tire and the needle on the gauge face will point to the number that corresponds with the rubber hardness. The hot durometer number is or should be lower when the tire is at operating temp. Again, some questions you should be asking the manufacturer.
Where do you purchase a Durometer? There are many sources even Amazon sells Durometers. They even have digital durometers. They range in price from $30 to well over $800. Longacre, the racing tool guys, have a nice unit in the $80 range. I own one of the Longacre gauges and it works great and is very durable.
Tire temps can be measured with a probe type thermometer or an infrared gun type thermometer. The gun type thermometer is quick and the prices are in the 20.00-range. The infrared gun type thermometers are quick and You probably have a good tire pressure gauge and cloth tape for measuring tire diameters. A quick word on tire pressure gauges. If your tire pressures run 10 to 15 PSIG you should get a tire pressure gauge that has a max pressure of 30 PSIG. You want to tire pressure gauge to place the range you will be measuring in the middle of the gauge. The middle of the pressure range of the gauge is the sweet spot. If your working tire pressure is 15 PSIG do not get a 100 PSIG gauge.
Tread depth, although we are talking about dirt tires, this also applies to pavement tires, we need to keep track of the tread wear as we use the tire. There are many tire gauges on the market they are simple tool. Just place the tool on the tire and measure the depth of the tread no different than measuring the depth on the tread on your street car. Tire management is not brain surgery or rocket science, it is a process that any racer can master.
- The age of each tire on the car, how long you have owned the tire. New/Used
- How many laps the tire has on it, or how many races it has been used.
- The manufacture date, year and week of the year,
- The diameter of the tire.
- The cold durometer. (The durometer will change as the tire gets heat cycles on it, the tire will be harder cold and harder hot as it ages.)
- The wheel width and the condition of the wheel.
- The circumference of the tire
- The air pressure in the tire cold.
- Tread depth
- Air pressure measured as soon as possible once the car is off the track.
- Tire temperature measures as soon as possible once the car is off the track.
- Durometer of the tire, measured as soon as possible once the car is off the track
- Diameter of the tire hot, measured as soon as possible once the car is off the track.
- Tread depth, measure prior to any further use
- General condition of the tire and wheel, you are looking for obvious damage to the wheel or the tire.
Once you have this data what do you do with it. The short answer is it depends. The longer answer is that you can start to draw a causal link between performance and tire use. Every time the tire hits the track it will go through a heat cycle. A heat cycle is simply every time the tire is heated to its operating temp or possibly beyond the optimal operating temperature. For example, if your tire is used for practice, two heats and a main event that is four heat cycles. The number of heat cycles the tire goes through the more the performance will degrade, the longer it will take to heat the tire to its optimal temperature. You will see a lap time difference between a new tire and one that has gone through multiple heat cycles. And, the difference will not be a good one. This is where you can use the data to make decisions about your tires. Each type of car will abuse tires differently. A Sprint Car will go through right rears faster than a left front tires. A street stock will not abuse tires like a higher horsepower car. The track will have a great deal to do with tire wear from a physical perspective, but a heat cycle will always degrade the optimal performance of a tire. How your driver drives the car can have a huge impact on how the tire performs and lasts.
The reason you need this data is to make decisions about the replacement intervals of the tire. A tire can look good from a physical perspective but it may have aged out or have gone through multiple heat cycles and does not generate grip like when it was new. Is it ready to be sold or is it past any further serviceable use? The more data you have the better the decisions you can make. It really is just that simple.
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