Robin Pemberton, NASCAR's vice president for competition, announced following practice for the Nationwide and Sprint Cup series that a different specification of right-side tyres will be used in Saturday practice and Sunday's race, after cords became visible - especially on right rears - after only 30 laps in some cases, when they should last a full fuel run which amounts to nearly four times that distance.
The issue has affected both Nationwide and Cup teams and it will be handled differently for each series.
"Tonight we will be making a tyre compound change for the right side tyres for both [Sprint Cup and Nationwide] series. The Nationwide series will qualify in the tyres they are today, and will change those tyres during a competition yellow at roughly lap 25 during the race [on Saturday] afternoon," said Pemberton.
"In the Cup Series they will also be making a compound change. [Saturday] morning the Cup teams will receive one set of the right side tyres in which they can practice on during both sessions, and they will have an adequate amount, roughly the same number of tyres for the Cup race on Sunday afternoon."
Goodyear had introduced a new right-side tyre specification that featured slight construction and compound changes relative to what teams ran last August at the same venue. According to Pemberton and Goodyear officials the track did not rubber in as they expected with the new compound, creating a situation similar to what they experienced at Indianapolis in 2008, when excessive wear forced a stop-and-go race with the caution waving every 10 to 12 laps to prevent multiple tyre failures.
Cup teams will now race compound 4386, which they ran on the right side at Kansas and Fontana last autumn. According to Goodyear's NASCAR project manager Rick Campbell, the new tyre features an identical tread compound, although with a slight difference in construction, including a 16th of an inch less diameter than the 4408 specification that teams raced last August at Bristol. He claims that despite the marginal stagger change, the new tyre is almost identical to what was last raced at the half-mile track.
"Working with the teams, crew chiefs have treated that construction change as inconsequential," Campbell told AUTOSPORT. "They have experience with the new compound and for set-up purposes they treat the new tyre in the same way as the 4408 used last August. They expect the same performance.
"We've run this compound here in March conditions, in cooler weather with good wear. So it's a known quantity at Bristol and it's provided good racing, rubbered the track in, managed good wear rates effectively and with a good performance."
Cup drivers will qualify on the compound they used in practice, but they will be able to try a set of the new spec during Saturday's practice sessions and will then get a complete 10-set tyre allocation for Sunday's race. A competition caution to check wear rates early into Sunday's 500-lap event is also expected.
Goodyear expects the 1,200 tyres of the new compounds for Nationwide and Sprint Cup teams to arrive at Bristol from the Charlotte area on Friday night.
