By now, you've probably heard NASCAR and Goodyear are having tire problems at the newly repaved Michigan International Speedway. Here's a quick primer on what's happening:
What are the basics?
During Thursday's open test session and Friday's practice at Michigan, about one-quarter of the teams noticed the tires were "blistering," which is when the tires take so much heat that they start to break down and increase the chance for blowouts.
Following a 204 mph lap by Greg Biffle in Friday's final practice, NASCAR and Goodyear decided to ship in a new left-side tire for Sunday's race.
The cars will use the original tire for this afternoon's qualifying session, but then NASCAR will hold an additional 75-minute practice at 6 p.m. (live on SPEED) for teams to try out the new tire in advance of Sunday's race.
Why is the old tire better than the new tire?
It's not necessarily better, just more reliable. The new tire is super hard and was run at Charlotte for all races at that track in 2006 and 2007 after the surface was repaved. It produces less grip, but it is far less likely to break down.
Goodyear and NASCAR couldn't take a chance of tires blowing out with the record speeds at Michigan (drivers are approaching 220 mph on the straightaways), so a more durable tire was needed. The new tires, built in 2008, are part of a backup plan Goodyear has for every track on the circuit.
"Safety is always our No. 1 concern, and by bringing this tire here this weekend, we will accomplish that goal," Goodyear's Greg Stucker said.
Each team will have 10 sets of tires for the race, which is the same amount as originally planned. They will also have extra sets to use in tonight's practice session.
One thing to keep in mind: Weather forecasters are predicting overnight and morning rain, which will wash all the rubber off the track and make the first laps even more treacherous on Sunday.
Has this ever happened before?
Goodyear has changed tires in the middle of a race weekend as recently as March 2011 at Bristol – when the track didn't "rubber up" enough – but adding a practice session is extremely unusual for NASCAR.
In the 1995 Dover race won by Kyle Petty, Goodyear and NASCAR noticed the tires were blistering after practices and the Busch Series race. So Goodyear decided to truck in a different tire and NASCAR scheduled a 30-minute practice session on the morning of the race, according to this retrospective article.
Changing the tire at this point effectively wipes out all the data collected by teams during Thursday's full-day test and Friday's practice sessions.
Who is to blame for this?
Goodyear held an early-April tire test at Michigan, with drivers Jeff Gordon, Matt Kenseth, Brad Keselowski, Juan Pablo Montoya and Kyle Busch trying out different rubber compounds over a two-day period.
The tire manufacturer, NASCAR officials and the drivers all knew repaved Michigan track would be fast, but the top speed during the test was 198 mph. Biffle went 204 mph on Friday.
As recently as Thursday, NASCAR believed the higher temperatures this weekend would make the track slower and thus have the tires travel at speeds similar to those seen in the test session. But drivers only kept going faster, and some teams' tires couldn't handle it.
Kevin Harvick was the most outspoken about the tires, telling reporters the race had turned into one of making the car and tires survive instead of actually racing.
Responding to the concerns, Goodyear allowed every team in the garage to "scuff" all their race tires during practice on Friday, which was another rare move. "Scuffing" the tires is when teams take "sticker" tires – brand-new tires with the Goodyear labels still on them – and run them for a couple laps to get them worn in.
The idea is that by putting some laps on the tires, it would help the heat dissipate throughout the rubber instead of build up into the blisters. When new tires are combined with a smooth new racing surface, sometimes the heat has nowhere to go and causes the tire to bubble.
After letting the teams scuff their tires, Goodyear wasn't planning on making a change – even after practice. But by last night, there was a enough concern for NASCAR and Goodyear to err on the side of caution.
If there is blame to be placed in the situation, it mostly falls on Mother Nature for the higher-than-expected temperatures, though an argument could also be made that Goodyear's tire engineers should have realized teams would get faster and improve their cars in between April's tire test and the race weekend.
Will this tire make for a more entertaining race on Sunday?
No, but it will make for a safer race. And with drivers going faster than they've ever driven before, NASCAR and Goodyear should be applauded for this decision.