What is the dimension of race car tires?

Answer 1

NASCAR© Winston Cup TRUE TIRE HISTORYWheel and Tire Characteristics:

The 15" wheel rim is made of steel, fixed to the hub by five nuts (imposed by NASCAR). Formula 1 wheels use a single nut and four tire changers (two in NASCAR), which largely explains the difference in the pit stop durations below 10 seconds in F1 (Formula One) versus 16 to 20 in NASCAR. Lightweight metal rims are also available on the market.
The dimensions of the tires are usually 28 x 12 x 15", being the diameter, width, and wheel rim diameter. In standard tire description, this corresponds to 300/54 R15, which is an ultra-low profile: height/width = 54%. They are inflated with nitrogen, which is much more stable with temperature than compressed air. This allows the pressure to remain almost constant over a large temperature range. The tires are inflated around 50 psi. and teams adjust this pressure to improve the grip of the tire or to equilibrate the inside, center and outside tire temperature.

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Details:

In the early days of NASCAR, the tire changers were using the good old cross to screw and unscrew the nuts. Today, pneumatic air guns have replaced it, but NASCAR allows only 2 air guns per team during the pit stops. However, the five nuts are still there and most teams glue them to the rim prior to the race to gain a few seconds. When the new wheel is placed, the air gun torque breaks the glue and the nut is tightened normally. Numerous tire changers keep spare nuts on a ring attached to their belt or even in their mouth!
During the pit stops, the right tires are changed first for a simple safety reason: to have the right side cleared when the car restarts.
If a wheel gets out of control of the crew and rolls into the pit road, the team gets a penalty. This happened during edition 99 of Daytona 500 when a wheel escaped its tire changer and kept rolling for more than 150 ft. on the pit road. The outgoing cars had to swivel around it to avoid a collision; some of them even went through the grass.
Being a tire changer is not an easy job: each wheel weights more than 50 pounds and the incoming tires are hot, very hot... The average temperature for a race car tire is 200°F. Nevertheless, each wheel is exchanged in about 7 seconds!!!
Tires which are new from factory are called "stickers" because they still wear the manufacturer ... sticker; after a few laps, some tires are put aside for the race so the driver does not restart with unverified tires. These tires are called "scuff".
Bias ply tires also have their advantages: they allow the team to introduce some "stagger", by under inflating the left tires and over inflating the right ones. Since bias ply tires expand in diameter with pressure, a stagger is introduced. It is the difference between the diameter of the left (smaller) and right (larger) wheels. Stagger improves the car capability to turn left, but also increases tire temperature and wear-out in the straight-aways. For this reason, this method is mostly used on short tracks, where 0.5 to 1" stagger is not uncommon.
Radial tires have somewhat perturb Ted this practice, because they expand laterally with pressure. Stagger can only be introduced by using tires of different diameters.

History:

When NASCAR is born in 1947, the race tire market is solely dominated by the Firestone Tire Company.
NASCAR's emerging popularity in 1954 gets noticed by Goodyear and they re-enter the competition by using police car tires at the now 4-year old Darlington speedway, and finally defeats Firestone five years later establishing a new speed record with Jim Reed at this same track. 1966 is a milestone year for the racing tire industry when Firestone and Goodyear started manufacturing the "Inner Liner Safety Spare", called Lifeguard for NASCAR racing.
This tire is in fact a second envelope inside the tire, which prevents instantaneous deflating and allows the driver to return to his pit after a flat. From now on, all NASCAR are be equipped with the Lifeguard.
The two tire giants will alternate victories and speed records when Firestone stops producing racing tires in 1974. Goodyear remains the sole supplier until 1987, when a company from Indiana, Hoosier, starts supplying racing tires, first in the NASCAR Busch Grand National series, then in Winston Cup racing, where Hoosier wins several races.
It is interesting to notice that all tires manufactured so far are bias-ply type, when in Europe Michelin had long ago invented and patented the radial tire. The story doesn't tell if Michelin's patent expired, was bought or turned around, but in 1990, Goodyear proposes the Eagle radial race tire which immediately proves considerably superior to the now obsolete bias-ply tire. This puts a temporary end to Hoosier's contribution in NASCAR Winston Cup. The following years see new generations of tires and improvements of the inner liner.
Hoosier tries returning to Winston Cup but succeeds to win only 3 races during the 1994 season and withdraws from Winston Cup and Busch Grand National, to concentrate on the smaller series, such as Winston West and Featherlite.

Today, Goodyear's yellow-lettered EAGLE tire is the only one used in NASCAR.

Tire History

Tire History

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