Take a look at our newest tire sheets. Developed by our very own tire specialist, Robert Osaki. Tire specialist for the 2014 K&N West Series championship team. Download and print as many as you need for free!
- DOWNLOAD PDF JOES_Tire_Sheets.pdf
Tires & Temperature
You spend piles of time figuring out how to make more horsepower, optimizing shocks and building lighter cars which all come together where the rubber meets the road. Every speed secret on your car is applied at the contact patch so creating the optimal footprint is the meeting place for all of your hard work. Tires are the single most important aspect of speed as every adjustment from motors to springs relies on the grip you manufacture at the contact...read more »
To dissipate heat racing tires are very thin. Thick tire rubber holds in heat and the potential for blistering increases. Tire engineers balance the rubber thickness with tire compounds to produce a package that considers car weight, corner speed, track abrasiveness, outside temperature, intended lap use and several other variables. Since the thickness of tire rubber can vary you need a pyrometer with an adjustable tip length probe. We want consistency and measuring tire temperature down at the cord is the best way to ensure accurate and repeatable numbers. If your team is measuring tire temps at varying depths then the information on the tire sheet is going to set in motion changes that could slow your car down.
Pyrometers must be used constantly - scientifically. Rubber is a poor conductor of heat yet it is a great insulator. If you are trying to assess camber temperature curves then you want to know the inside, middle and outside temps based on your camber setting and corner performance. If you measure the inside location at the rubber surface, the middle location and mid tread depth and the outside at the cord your temp sheet is going to have more inconsistency than Michael Jackson has had cosmetic procedures. The cord heat is insulated away from the outside elements and the most heat will be found beneath the rubber and down at the cord. Scientifically – it makes sense to measure all 12 locations at cord depth where the purest temperature is located.
Adjust your pyrometer probe so that the adjuster stops the probe penetration just before the probe reaches the tire cord. Using the stop on the adjustable tip will allow your crew to quickly and consistently get down to a consistent depth near the cord each and every time. Your temp sheet will provide scientific quality information due to the repeatable and consistent probe depth.
Reading rubber temperature down at the cord is best as the friction of your tire pulls and stretches the tire rubber. The stretching effect creates heat just like when you bend a coat hanger back and forth. More friction creates more contact rubber stretch. Measuring down near the cord displays the data resulting in efficient chassis adjustments.
If you have a pyrometer with a fixed tip you can make it work but you introduce depth variables. How many times have you seen a temp sheet that showed you needed to take out RF camber and sent the car back out without an adjustment. A second temp reading shows you have too much camber – I will bet probe depth variation is the issue. With a fixed tip your crew needs to “feel” the cord to ensure the probe is at a repeatable and consistent depth.
Your probe tip is made of thin steel which heats up quickly sucking the heat out of the pin hole made in the tire rubber. Be sure to move quickly. If you leave the probe in one spot in the tire rubber and watch the display you will see the temp rise and then begin to fall as the heat is sucked out of the test location. You need to record the maximum temp in each probe location. High quality pyrometers lock in the maximum temperature automatically increasing accuracy. Utilizing a temp lock feature gets you around the car in nearly half the time.
I am often asked if Infra Red pyrometers are good for tires. You certainly can use Infra Red pyrometers for tires but it is a quick check and the information is simply less precise than using an adjustable tip probe. IR pyrometers measure the tire surface. The surface temperature is impacted by engine heat, brake heat, puddles etc. Camber in the front tires places only a few inches of the tire on the ground at the low speeds encountered when travelling back to the pit area. The track surface is cooler than tire operating temps so the tire surface area in contact with the ground pull heat from the strip in contact with the track at a different rate than the rest of the tire – this difference skews your camber curve readings. The rubber down at the cord is insulated for a longer period giving you more time to measure temps relative to on track performance and probes can reach down past the surface for a better look.
When using IR pyrometers for tire temps bear in mind that the surface recordings will be much cooler in comparison to probes and you will lose the fine detail that can be found with probe type pyrometers. IR pyrometers are great tools for measuring track, header, brake and cockpit temps. Using the right tool for the job is usually sound advice.
To ensure the best relative tire temp readings follow these steps:
- Use a properly adjusted pyrometer probe tip to measure down at the cord.
- Get to the car quickly – speed matters!
- Record the highest temp at each location with an automatic max temp feature or by manually witnessing the highest temperature. Move around the car quickly.
- Start at the same tire each and every time and record the individual Inside, Middle and Outside for all 4 tires. Consistency is the goal.
- Record track temp and outside air temperature on your tire sheet to monitor the difference that these variables have on your tire temps – over time you will be able to forecast better compensating adjustments.
- Keep in mind that tire temps are of more value on a car that is handling well and with tires that are in good shape. Tire temps on cars that are in left field are about as valuable as politicians’ promises.
Using your scientific tire temps you can evolve my rule of thumb tips shown below. My tips are based on a car that is set up properly and just needs fine tuning. Your team should adjust the suggestions below based on your real world testing and document your own pre-determined adjustment to form your own game plan. Creating a game plan in advance will allow you to quickly asses your adjustment options improving your decision making when things get hectic at the track.
Your tire sheet temperatures suggest a camber adjustment is needed but knowing the adjustment amount is an educated guess. My rule of thumb for adjusting camber is a 1/8” shim for 12 degrees of temp difference between the inside and the outside. A 1/16th shim is a good start for 6 degrees difference. Trial and error starts somewhere and your team can modify my rule of thumb based on your actual conditions. Strive to find and document a pre-determined shim thickness associated with the degree difference across the tires on your car.
Starting Cold Air Pressure.
Air pressure and tire temperature work hand in hand. If you take precision tire temp measurements you can gain an advantage over the competition by adjusting your cold air pressures before the race based on data you have collected over time. You can adjust your pre-race air pressures to a finer degree if you record outside and track surface temps in conjunction with your tire temperatures. If it is really hot out and you have tire temps that are 20 degrees higher than your last trip to a given track you can adjust the cold temps for better race performance. The rule of thumb that I used on a 2900 pound touring late model with bias ply tires was 1 degree of pressure gain for every 10 degrees of additional tire heat. You can visualize that there would be more pressure gain in the heat of summer verses a cool spring. Testing dictates your actual heat induced air pressure compensations. Adjusting your pressures based on recorded results will help you to optimize pressures for more speed on a long green flag run. Understanding the correlation between pressure and temperature will help you to optimize pre-race pressures during those times when your race set has residual temperature from practice and the race is going to start before the tires cool completely. Strive to know the actual temperature induced pressure gain based on your driver, track and conditions.
Air Pressure Adjustments
Inflating each individual tire properly means better grip, more wear and more speed. With accurate tire temps my rule of thumb is to adjust individual pressures 1 pound for every 5 degrees of over or under inflation shown as hot or cold center temps on my temp sheet. Your team can tailor the starting point of this rule of thumb to your actual situation. Your team may decide on 1 pound per 4 degrees or something different but the goal is to find the pressure needs for your car and tires. Establishing a baseline for inflation pressure adjustments will help you to dial in the winning set up and add consistency to your set up process.
Measure and record your tire temps with a quality pyrometer. Use the scientific data to form a pre-race game plan. Use your game plan to make the right call when it matters most. By using science you can take the black magic mystery out of your tires by building consistency in your adjustment process.
Emotional pressure to find speed will be reduced if you manage your tire pressure with a plan. Every set up out there relies on the contact patch and getting the desired pressure at the point the rubber meets the road. Several important factors need to be considered for optimal tire pressure.
To achieve precise tire pressure readings you must have an accurate tire pressure gauge. Starting with the right gauge is paramount. Nearly all gauges are more accurate in the center of the...read more »
- Digital Tire Pressure Gauges JOES Digital gauges are available in 0-60 PSI at .1 resolution or 1-150 PSI at .5 resolution.
- Analog Tire Presssure Gauges JOES Tire Pressure Gauges come in three pressure ranges: 0-15 PSI, 3-30 PSI & 5-60 PSI. They are available with a air bleed valve and hold valve models are available.
Proper Tire Prep & Purge
If you are into skinning cats, you will find that there are more ways to get racecars around corners than there are cats to skin. On the other hand, skins on racecars are what connect your secret set up to the ground. More adhesion at the contact patch creates long lasting speed. Balancing the grip at all 4 corners produces a fast car and any talk of skins can be limited to tires – you can leave the cat lady alone. Maintaining desired tire size is...
Bias Ply Tires
Managing tires can be a daunting task. Keeping good notes and having the proper tools for measuring and purging saves valuable time and is often the difference that gets your team the big win.
Bias Ply tires (radials are a different animal) require constant care to minimize variables. Maintaining the desired size and air pressure is an art. With a little care and a repeatable routine, tire sizes can be managed preventing erratic growth changes. Prevention and a dedicated tire specialist is often the team component that keeps your car in the front. Maintaining a consistent approach to tire preparation is what allows you to land on all fours regardless of track conditions.
The goal is to keep the tires the tires sized properly avoiding unpredictable growth. Variables can be controlled or at least reduced. Starting with tires that are manufactured to the desired size is a best practice. Attempting to change a tire size by artificially stretching it with added air pressure is a sure way to produce false sizing numbers that change at the first heat cycle. A good racecar goes to junk if stagger changes in an unpredictable fashion.
Using a tire roller helps to measure stagger (roll out) quickly making quick work out of your tire stack adjustments.
For bias ply tires my general rule of thumb is to use a maximum of 2 pounds of pressure to increase or decrease the size of the right size tires from my optimal pressure. Any pressure beyond 2 pounds, above or below, the ideal right side tire pressure changes the spring rate, camber temps, and tire foot print potentially reducing speed. For left side pressures, I might allow a 3 pound variance but since we tend to run such low pressures on the left side use caution to avoid crossing over the minimum pressure line. Buy the tires at the right size. Spend the time to remount tires that are the correct size.
Tire Tape Measure
A 1/4" Stagger tape, used with a tire roller, gives you price readings. Be sure that your tape remains exactly straight andÂ true on the tire.
There is debate on how much bias ply pressure variance you can utilize to get to your optimal stagger. For this article we are focusing on bias ply – it is well known the radial tires are extremely sensitive to pressure changes and even quarter pound pressure adjustments can be dramatic with radials.
Dave Juarez, the tire specialist at Gene Price Motorsports for the #26 Greg Pursley driven K&N Pro Series West team says, “with bias ply I can get away with 3 to 5 pounds of added pressure without adverse affect. For qualifying, 5 added pounds frees up the car and helps to build heat quickly”.
Growing tires is a bit of a myth. Sure, you can change the size with more pressure but making a tire bigger by stretching it only gains a small amount and that growth is often inconsistent. Dave Juarez says, “filling a tire to 50 PSI and letting it sit in the hot sun can make it stretch. Generally, a heat cycle is needed to keep the tire at the desired size”.
A common mistake I have seen with bias ply tires is that teams over fill tires to “stretch” them in an effort to grow the tires to get more stagger. These teams overfill the tires and then quickly drain the air down to race or practice pressure and take a measurement. This method always ends up with false size readings. As soon as the tire heats up, the artificial “stretched” reading disappears and the tire shrinks back to near its original size. You might grow the tire a fractional amount but if you were counting on the extra stagger to get through the center you can be assured that the tire size will change at race temperature.
Championship driver and JOES Racing Products owner Joe Constance says, “2 pounds of variance is ok to get stagger, 2 more PSI in the rights and 2 less PSI in the works fine but any more pressure change than that and you are fighting evil with evil.
I have seen all kinds of tricks to change tire sizes. Over filling tires and bouncing them like a basketball to gain size. I have seen teams run too much air pressure in practice to help grow tires with a heat cycle – go too far and you risk cooking cooks the tire center. I have seen teams try to shrink left side draining them of air after a heat cycle and then dousing them with cold water. This method can harden the tire and rarely has much sizing benefit. It is tough to change once a tire is manufactured. Adding pressure or dropping pressure will get you a size change but really the size is determined at the time of manufacture.
Juarez says, “I have bounced tires also but it is a desperate last resort. You might be stretching the center of the tire but I wonder what is happening to the contact patch? It is hard to stretch a tire at the side walls. I still think you get what you get and after one or two heat cycles just count on tires being about that you originally measured. I have had tires stretch or even shrink during a race but it is out of your control. Just be very consistent with the way you prep your tires and you get a pretty good feel for what they are going to do”.
Dave Juarez states, “if you get a heat cycle on a tire and quickly drain the hot air and replace it with cold nitrogen the second the car comes off the track you can make the tire a little smaller or at least keep it from growing more”. Dave continues, “Adding nitrogen to a hot tire can help it to grow but not all that much”.
Joe Constance says, “I never had any luck stretching tires on my Saturday night racing. I like to put 30 psi in the lefts and 50 in the rights and leave them for 30 minutes to let them get a set when they are new. After you put a heat cycle in them you get what you get. You can make them bigger or smaller with air pressure but you need the right size tire with the right pressure to be fast”.
Using nitrogen instead of compressed air helps with consistency. Nitrogen is nearly moisture free and air from a compressor contains moisture. You get moisture in the actual air but you can also get a lot of vapor from the compressor tank and lines. Moisture inside the tires creates added heat expansion and if any tire contains more moisture than the others in the set then stagger changes unpredictably.
Purging air out of your tires and replacing it with nitrogen will remove moisture resulting in consistent stagger throughout the race. This purge tool has a slide collar to "dump" air quickly through fast flow ports that can be used when your tire specialist is attending to the tire. The collar slides to the closed position and a bleed valve prevents air and unwanted atmospheric moisture filled air from re-entering the tire during the purging process allowing your specialist to work on many tires at once. Top teams use multiple purge tools. The purge tool clips on the Schrader valve and automatically adjusts your tire to nearly any pressure allowing your crew to multitask with confidence.
Nitrogen works well. Top teams have used Argon in their tires to further reduce moisture content. Argon and medical grade nitrogen produce such a small moisture reduction benefit that it is not worth the added cost. Dave Juarez states, “I have tried Argon and some other types of Nitrogen. Medical Grade Nitrogen was believed to be the preferred type but I did some research and found out that the only reason it is classified as “Medical” is the way in which the tanks are cleaned and filled. The chemical make-up is the same so there is no advantage within the tire”. Basically, Dave thinks standard nitrogen is a good economical choice.
Clipping on a purge tool to several tires allows tire specialists to replace moisture filled air with clean and moisture free nitrogen in record time. This purge tool clips on and can be set to very low PSI, preventing atmospheric pressure from re-entering the tire. The clip-on feature allows the tire specialist to set race pressures by adjusting the bleed valve, from very low, to maximum race pressures. Top teams have several purge tools clipped onto multiple sets of tires. On hot days, the clip on feature, allows teams to automatically bleed off pressure created by heat build up from the sun.
Joe Constance takes a practical approach and takes care to keep water out of the tire during the mounting process, Joe explains, “Keeping water out of the tire during the mounting process is a big deal. If you are not careful you can get a bunch of mounting soap and water in one tire and half as much in another. I like to use WD 40 for mounting tires. WD stands for water displacement. The WD 40 lube is slippery enough to mount the tire and you can keep the tire sized right by avoiding using water all together”.
I have seen all kinds of devices that claim to eliminate moisture in tires. The goal is to maintain consistent growth. The practical goal is to have the tires grow in concert with each other so that set size is predictable. I once had a guy that wanted me to build and market a $60,000.00 dollar vacuum chamber to pull the moisture from each tire. The reality is that there is moisture in the tire rubber. The moisture inside the rubber is part of the manufacturing process and is a needed element for tire performance. Taking care of your tires is good but a $60,000.00 vacuum chamber gains you about zero in performance yet costs you a ton. I wish I was joking but there are folks that think a $60,000.00 dollar machine would be a good deal for short track racers. I am embarrassed to even admit I know about such a machine.
Using a top quality pressure gauge fine tunes your stagger with optimal pressure. This gauge comes complete with an angled chrome chuck and a ball chuck ensuring it works in every application. You always have the right gauge and can avoid worrying about being committed to one style of chuck. Racers can change out the chuck in thirty seconds as, for this gauge, the chuck threads on so teams can change as needed.
Juarez says, “I have used air dryers, desiccant moisture removers, clean nitrogen and so on but the most benefit is gained by having a consistent plan”. Depending on conditions, I purge the tires with nitrogen a minimum of 2 times but generally would prefer to use a humidity gauge and purge the tires as dry as possible. Usually it is 4-5 purges that are needed to purge down to a “zero” state – well near zero”. Dave continues, “If I am mounting the tire, I use the least amount of tire “soap” or mounting medium. When I seat the bead I use compressed air that goes through a dryer first”. Dave goes on, “you can create some stagger starting your right side air pressures slightly higher than “recommended” during your initial practice run on stickers but only if scuffs are allowed by your series on pit stops. When you run slightly higher right side pressures, the heat cycle in the tire will “hold” a bit more stagger.
Personally (Jeff Butcher), my goal in managing tires is to work with the tires and not against them. For short track cars and sticker tires I always put 20 PSI in the lefts and 30 PSI in the rights – I made sure the guys at the tire truck didn’t over inflate them from my numbers as I wanted the tires to be in their natural state every week without crazy air pressures that produced variables. In my experience, consistency allowed for predictability. Artificially growing tires was a sure way to have the stagger change during race conditions. I did make sure water was kept out of the tires and I used standard nitrogen, medical grade simply was a cost item that didn’t equal the value. I purged the tires 2 times as that seemed to be the point where the most benefit was gained. Purging more than 2 times gained a little but it takes time and our hauler had a limit on how many heavy nitrogen bottles it could carry. We had a nitrogen sponsor but 2 times seemed to remove most of the moisture. Consistently purging 2 times each week was a “routine”.
I think the mistake that is made by many teams is that cold measurements, taken after stretching “tricks”, create dramatic size changes that disappear during/after a heat cycle. The tires are what they are based on how they were manufactured and to think you can stretch the sidewall seems like a “mental stretch” to me. Really, you would have to break down the side wall cords to grow a tire so in my view, high using high air pressures with the goal of making a tire bigger simply ballooned out the center of the tire for a short while and any stretch is a mirage.
Joe Constance says, “I have only used nitrogen but if you are going to slop a bunch of tire mounting goo with moisture in it on the bead before you mount it you might as well save some money and just use air from your compressor. It is very important to keep the inside of your tires as dry as possible”. Constance continues, “I am around a lot of teams that are on a budget and they may only have one nitrogen bottle - it would be nice to purge tires two or three times but they don’t usually have the time or money. Since many teams only carry one nitrogen bottle to the track, one purge becomes the max. As long as they are consistent they can usually calculate how much the pressure will grow”.
Matching sets, especially when you have multiple new sets, is part of the art performed a tire specialist. Dave Juarez states, “In a perfect world, the left sides would all be the same and the “average” would come from the right side tires”. Dave continues, “I try to match sets so you could switch left sides to add or deduct stagger on pit stops. I tend to lean toward using my Right Side tires to add or subtract stagger since the Right Side Tires take most of the load during a race. Most often, the 2-tire stop is right sides so having the option to switch tires around coupled with adding/removing air pressure is critical to handling and performance after a stop”.
Dave thinks, “Most of the pressures and tire sizing depends on your application or set-up. Most drivers can’t tell the difference in 1/8” of static stagger. During a run when the air pressure builds, the associated stagger change and air increase will have the greatest effect on handling. Pay closest attention to your “set” choices based on the set-up and handling of the car. If the Crew Chief and Driver are on the same page, it is far easier to “follow” and “manage” your available set options which is a big help in selecting sets for the race and qualifying. Nowadays, it is more important to keep your “brand” or serial numbers as close together as possible so your tire inventory comes out of the same batch creating added consistency.
Joe Constance says, “I love Saturday night racing and pit stop races are rare for the cars I have driven. The few pit stop races I have done were under budgeted with a limited crew and we made the best out of our hard working Bad News Bears volunteers. I had some knowledgeable long term faithful help but we often didn’t have enough manpower. Often, we had the track mascot or trophy girl changing the right rear tire on pit stops. I do know that you can feel a Â¼” of stagger difference and even that small amount has a major effect on handling so know your tires is critical.
Joe continues, “Communication between the driver and crew is important and using different tire sizes to dial in the car can get you to the front. A well chosen stagger change can be huge. Making sure you know what tire sizes are on the car at all times helps you select the best set of rights or lefts and keeps the monkey in its mascot suit preventing your team from doing inappropriate things to a football.” (Joe said that quote a bit differently so I edited his words for the article – I am all sure you all can figure out what it looks like when teams do inappropriate things to a football after a Keystone Cops pit stop).
Constance believes, “I always try to get all the same size lefts, I vary the rights about a Â¼” going off of the sizes marked on the tires when new because they are never exactly what they say they are and this gives me some adjustment during the race. I always try to keep the rear stagger the same and compensate for the wrong front stagger with other chassis adjustments. The goal is to have the best set for the end of the race. Only the last lap counts!
Dave Juarez, “I like to use a tire roller and I trust a tape measure more for precision. I will measure along the tire shoulder when the tire is on the ground when needed and easily get accurate and repeatable results. I also need a stagger tool as in our series we are not allowed to jack up the car post qualifying”.
A billet CNC machined tire caliper gets you an accurate tire size readings quicklyÂ without the need to jack up the car. Many race series impound the car after qualifying making a precision tire caliper invaluable.Constance agrees, “I like a tape measure because it is a little more accurate. Adding a tire roller just makes the measuring process so much easier. Being consistent and using a quality tire pressure gauge improves speed. Take tons of notes on your tire sets, and keep the inside of every tire as dry as possible. Experience is invaluable and the more knowledge you can gain the faster your team will run. Tires are everything so have a tire specialist on your team that is detailed and thorough”.
A quality tire specialist helps any team win. Tire experts are the hardest working people in the pits and need to react precisely to split-second decisions made by demanding crew chiefs. Top Cup Crew Chief, Shane Wilson, relies on JOES Racing employee Robert Osaki, flying him around the country for special events. Robert is well known for being the nicest person on the planet and is regarded as one of the best tire specialists in the business. Here, he is shown helping Gene Price Motorsports get their rubber to the road at Infineon Raceway in California.
Tires are a big investment for any team and a good tire guy is invaluable. Just think about the last pit stop on a big TV race and how the tire guy can mess up the fastest car on the track by handing the tire changer the wrong size tire or one with incorrect air pressure? Managing and massaging tires is an art. JOES Racing Products employee, Robert Osaki, is known as one of the best tire guys in the business. Top teams such as Gene Price Motorsports and Kevin Harvick Industries fly Rob around the country, at great expense, because they can trust that he knows his tire stack inside and out. Rob’s knowledge, care and experience make him an asset to any team. To win races, your team needs a tire specialist that treats each tire like family. Find a cat like Robert Osaki and your car will always go on all fours.
Grip in the corners creates speed that will get you to the front. Fresh tires are the equivalent of bolt on speed. In order to maximize grip, selecting the best tires will help you to get the corner speed you need to win more races. Since tires are a major investment it pays to spend some time ensuring that the tires you purchase are fresh – equally important is that your tires are consistent. Striving to find a “matched” set will increase overall speed. How...read more »
Dial Type Durometer
A Dial Type Durometer can be purchased in a combo kit that includes a Dial Type Tread Depth Gauge. Using a Durometer is more effective if you use a Tread Depth Gauge and a Pyrometer to ensure consistency in your testing procedure.
Digital sensors are designed for accuracy and display giant numbers with resolution that gives you the extra edge. Digital displays provide an actual number taking the guess work out of reading a needle – the resolution is improved through both sophistication and viewing angle. Digital versions provide “relative hardness” that are easy to read even at night. The prominent display gives your team a modern advantage for only a few dollars more. The digital world that makes iPhones and computers available at reasonable prices has created mass produced sensors and chip components that indirectly improve the quality of all digital devices. Digital Durometers are benefactors of the digital world.
Quality analog versions work fine, but noticeable gains are made with new digital technology. The counter debate for the dial type is that they never need batteries and can sit in the tool box for long periods and always be ready to go.
Digital Durometers should include a back light helping you to see the accuracy even at night. Digital sensors benefit from the same mass production philosophies that make your smartphone and tablet cost effective.
Measuring tire rubber hardness is less exacting as compared to using dial indicators to measure the thickness of steel. Since you use hand pressure to push your durometer into the tire, it is common that 2 people can come up with different readings. As long as a dedicated crew member performs the task the same way each time then repeatable relative numbers will give you reliable information. The variance in actual accuracy will be limited how different crew members apply pressure. Eliminating variables will provide the best results with both Analog and Digital Durometers. Experience and feel will be enhanced by utilizing a measuring process that eliminates as many variables as possible. With training, all of your crew members should be able to produce the same readings.
Rubber deforms and the best readings are obtained when you take readings quickly – if you allow the Durometer to sit in one spot, the specially sized Shore A measuring probe will sink into the tire surface. The tire rubber deforms around the Durometer measuring probe. If you leave the Durometer in place for 30 seconds on one tire and 3 seconds on the next, your readings will suffer and accuracy is lost.
The best way is to ensure the tire is free of debris - a scraper should be used to remove loose rubber unless you are measuring the hardness of sticker tires.
Place even pressure and take care to hold the durometer flat on the tire. Flat positioning on the tire creates the best results. It is a myth that rolling the measuring pad on your Durometer over the tire provides better readings, in fact “rolling” introduces un-needed variables. Simply holding your digital Durometer flat, with consistent and light pressure for a consistent time period provides the best results. Just set it on the tire with consistent finger pressure and measure it – simple replaces complicated every time. Doesn’t it make sense that holding a measuring tool flat on an even surface will provide better accuracy than rolling the Durometer over the surface? Why introduce a moving target by rolling a flat surface over the face of the tire?
Using a Durometer is simple – consistency is key to producing repeatable results. Simply place the Durometer flat on the tire surface with moderate finger pressure. Rolling adds a variable so just set the thing on there and take your reading within a second or two – easy.
Really, measuring tire hardness with a Durometer is a simple process. Marketing hype is replaced by utilizing a simple repeatable process each and every time. Use the finger guide located at the top of the Durometer, provide light and consistent pressure, and verify that the durometer is flat on the clean tire. Then, take readings quickly and take 1 second +/- for the Shore A probe on your Durometer to stabilize – for the best results, be sure to time the measurement so that each measurement is taken with the Durometer foot pad on the tire for the exact same amount of time. Consistency is what will produce “Relative Hardness” that can be recorded to produce real results for future use.
If you set the Durometer into the tire and hold it in one place you will see the hardness number will rise - then as it is held in one spot the reading will start to drop. Hold the Durometer in one place too long and you can be assured that the Durometer measuring probe is sinking into the tire providing you with erratic results. Experiment by holding the Durometer in one spot on the tire for several seconds and you will visually see how the Shore A probe deforms into the tire – the longer you hold the Durometer in one spot – the more you can watch the reading drop as the probe is simply sinking deeper into the rubber. The process is simple – make sure the Durometer is flat on a clean tire surface and with even pressure simply record the reading. You can save rolling around for other more exciting endeavors.
Creating a repeatable process will give you the best relative hardness numbers and give your team the best chance at recording accurate readings. You must start with a clean tire. In the case of testing new tires, you can avoid worrying about debris or rubber build up. New tires are easier to test than used ones. When testing used tires, ample time must be spent cleaning the area to be tested. A flat scrapper easily removes debris off of hot tires that just finished making a few laps. Used cold tires have debris build up that has solidified on the surface. The rough texture will give you erratic results. Be sure to put some muscle on a scrapper on cold used tires. With a little effort you can witness the embedded loose rubber falling to the ground revealing the actual rubber surface that connects your chassis to the contact patch.
Several spots should be checked on the tire as tire rubber is not perfectlyÂ homogeneousÂ (some areas of every tire are harder or softer than others). Small areas in the tire can be harder than others and the variation in the rubber surface must be averaged out. The rubber surface can be uneven creating variances. I check an area on the tire in 3 to 5 places. I always throw out the high and the low and then look for a hardness number that comes up to the same reading in several locations. If the tire is hot after a run it will pick up loose bits of rubber on the way into the pits – use a scraper to get down to the “real” tire rubber surface. The same theory applies to checking tread depth – you want to measure the real tire surface and avoid all the loose debris that can skew the readings.
Since rubber becomes softer as it is heated it is critical to measure the temperature of each tire before taking the Durometer reading. If you have two tires with the same compound and one is 100 degrees and the other is at 50 degrees the cooler tire will read significantly harder. You could warm up the same 50 degree tire to 100 degrees and find that the durometer readings would equalize. To check Durometer readings you must have tires that are equal in temperature. Even one tire measured on the shady side will read harder than the side facing the sun.
Pyrometers are a must when measuring Tire Hardness. You can use an IR Pyrometer to check the surface. A probe type with an adjustable probe is really the best tool for checking tire temperatures (see the JOES Knowledge Center on the JOES website for Pyrometer Tech).
Tracking tread depth in conjunction with the tire hardness will allow you to predict when a new set is in order. By measuring the remaining thickness of the rubber on a new tire you will gain insight as to when a tire will lose adhesion. By diligently tracking tread depth and recording durometer hardness through wear, you will be able to identify when it is time to hit the tire truck and step up for a new set. Over time you will learn the wear patterns and the Durometer will visually show you at what depth your specific tires give up.
Heat cycles need to be factored into the Durometer measurement process as well. Racing tires come out of the factory with a magic mix of chemicals that produce grip. Tire engineers work tirelessly to ensure your tires maintain maximum grip for the maximum time. Chemical engineers mix their recipe of friction producing materials and chemicals into the tire to give long lasting and repeatable grip. Each heat cycle “evaporates” valuable chemicals out of the base rubber. With each run, the tire becomes harder and the chemicals that keep the rubber soft and pliable are lost. Your Durometer can help you find the point in time when performance drops off. Variables such as tread depth wear, heat cycles, number of laps, age, ambient temperature all factor into the tire replacement schedule.
Â If you know you have a loose car and have been buzzing the RR all day then you must consider that the RR will have faced more abuse than the other tires. Understanding why tires get hard is a compilation of several variables.
Top teams keep notes on their tire sheets so they can save money by running tires longer (Download Free Tire & Chassis Sheets at http://tinyurl.com/8gu92hj). Detailed tracking of variables provides valuable warning allowing for a purchase of a new set before they quit mid-race. Your rules dictate specific variables and if you run the same set for more than one week you can save some money, without sacrificing performance, by utilizing the results of your Durometer tracking. If you buy a new set each week you can learn which tire serial numbers perform best and cull out any old or bad tires hiding in the at your tire supplier.
Durometers can be used to predict the end of life on tires that are run multiple times. If you run a weekly series and your tires are run for more than one week it can be very valuable to track the tire hardness. Finding a good used matched hardness set from your inventory will help you to have good practice tires.
By understanding the wear characteristics, racers can use science to determine when to purchase a new race set or practice set. Tracking the tire hardness of used tires will give you data that can be used to graph when they are too hard to achieve the best lap times. Often, race tires perform to a lesser degree even when the wear indicators show there is substantial rubber left. While there may be rubber left on the tire the chemical compounds have evaporated due to multiple heat cycles leaving the remaining rubber too hard to create need temperature and friction.
Friction creates heat. More friction – more heat. Using a Pyrometer alongside your Durometer is mandatory. If you have apples to apples wear and you go on a 5 lap run - then all things being equal you should have Pyrometer readings that are reasonably close from the two sessions. If your set suddenly looses temperature as compared to the prior run you can be assured the friction is being lost. The tire is getting harder and the chemicals that create grip have evaporated out of the tire. Tracking tires goes beyond hardness. Paying attention to all of the variables that affect your tires creates the best performance.
Hardness measurements are most valuable when used systematically with pyrometers and tread depth gauges. Lap counting and heat cycles all come into play. Maybe heat cycles are the critical factor for your brand of tires, but maybe simply checking wear depth with let you know when a new set is needed. Durometer readings will back up your concerns and the Durometer will show the relative hardness if readings are taken at equal temperatures.
Careful and consistent measuring utilizing several tools will help you to create a system that produces repeatable results. Shopping is a good idea here.
Digital Durometers are the new revolution and are only a bit more in cost. Soft tires at the end of a race could give you the added grip off of turn 4 taking you to victory lane. You can still type a letter with a typewriter, but with computers the results and time savings are vastly improved. The digital revolution is here to stay. Dial Durometers work fine when used properly and never need batteries. A Digital Durometer used properly will create an easy to read number and the backlight allows you to see your winning resolution even at night.
Tracking tire hardness with a repeatable system will give you the resolution to gain an advantage. Utilizing a Dial or Digital Durometer in conjunction with a Tread Depth Gauge and a Pyrometer will give you all the tools needed to produce consistent and recordable results that will give you the winning advantage as it relates to the theory of relativity.