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Tires and why they work…

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Lets look at tires on a race car.

There are many things that affect the tires on a race car, many of them are not really understood by the average fan. I want to try and help explain some of then here.

The more important points to think about are:

  1. Size The size of each tire is different, right sides are not the same as the left side, for example if you take a Styrofoam coffee cup and lay it on it’s side you will see that it will roll in a circle, this is the same way teams help to improve the cornering of the car, but running different size tires on each side. The bigger the track the smaller the difference in tire sizes from side to side. Bristol will take more “stagger”(the difference in size from side to side is called stagger) than say Daytona or Talladega will.

  2. Compound the compound of the tire is set by Goodyear based on its own test at a given track. The tire companies conduct a lot of test at different tracks to try and come up with the best tire for that track, sometimes they hit it and sometimes they don’t. Goodyear give the teams a suggested tire pressure for the best wear and performance, but the teams often venture away from this suggested pressure and often pay the price in the form of poor wear or performance. A hard compound tire will last longer but won’t give the grip that a soft compound tire will so teams have to deal with the tire that Goodyear brings. A softer compound tire will give better grip but will give up in durability over the run.

  3. Air pressure Air pressure in the tires is very important, first it changes the size of the tire more pressure equals a bigger tire, less pressure equals a slightly smaller tire. And pressure affects the temperature, the air in the tire will have moisture as the heat in the tire increases the moisture will turn to steam thus increasing the pressure, so teams have to know how much the tire pressure will gain from it’s temperature sitting on pit road to the temp it will get up to on the track. It varies from tire to tire but it is usually 2 to 3 pounds. So it is here that very detailed record keeping is vital. Tire temp’s are checked at 3 points across the tire outside middle and inside, tires that have a high inside temp will show that the car may have to much camber, a tire with a high middle reading will show that the tire pressure is too high, and to low temp on the middle will show the tire is to low on pressure. So when the cars come off the track you will see the guys running to check the temp’s of the tires, now you know why…

Factors other than the tire itself which affect tires are:

1)Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it’s tilted forward, then the caster is negative. This helps the car to turn into the corner and will really help getting a car to turn

2)Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the top of the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber This is used to help control the tire contact patch, or the area of the tire that that is actually in contact with the track.

3) Weight the more weight that is placed on a tire the more friction, thus the more wear that the tire will undergo. Teams will try to get the car balanced by looking at the 4 tires temp’s, trying to get all 4 tires pretty close in temperatures. This will signal the tires are all gripping equally and give the driver a better feel. A car with a “push” or where the car don’t want to turn, it “pushes” toward the wall, this car will have higher front tire temp’s due to the car sliding the front tires, and car that is “loose” or one where the rear end tries to pass the front will have higher rear tire temp’s , so this is one of the tools teams use to find out how the car is performing. Just by looking at the tire temp’s.

Each of these factors will be a consideration of the crew chief during testing and the race. They use the results of testing to determine what they will do during the race. Different chassis set ups give different results on tire wear for each car. It is the crew chief’s job to balance all of this input and try to give the driver the best handling car he can during the race.

I hope this hasn’t confused you too much…. if it has shoot me a question and I will try to give you a better explanation of how things work….

Now lets go RACIN!!!!!!

the dr.

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4 Comments

  1. SLY 1 says:

    Well it is a bit more than I can understand but it is
    very informative to say the least,thanks dr for the
    information,,good job once again.

  2. Jack says:

    dr. I did pretty good in algebra and even geometry but it’s a good thing I don’t have to pick the tires for Kyle Busch. LOL I am slightly confused to say the least but I guess this could be called something that I don’t need to know. If I ever have a tire question I know who to ask. YOU DA MAN

  3. jbcom says:

    Good stuff…DR……….Coffee Cup analogy puts it into perspective.How much does banking play into tire size from left to right. Typically greater banking pitch at smaller tracks…correct? That is the reason for larger stagger at say Bristol. People call Nascar “turning left” if they only understood the complexity of setup,adjustments and crew. All this after the car is built. John

  4. drflavio309 says:

    jbcom You are right about the banking bigger banking means more stagger generally speaking, of couese there are exceptions to the rule… thanks for your commnents.
    the dr.

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