NASCAR to use bias ply tyres for Bristol dirt race

NASCAR’s first Cup dirt race in more than 50 years will also feature a return to the use of bias ply tyres which will present a new challenge for the drivers to adjust to.

NASCAR to use bias ply tyres for Bristol dirt race

In a radical shake-up for the 2021 campaign, Bristol Motor Speedway will stage the first NASCAR Cup dirt race since 1970, as part of a wider overhaul which saw a record seven road course events on the 36-round Cup calendar, including visits to circuits such as Austin, Road America and the Indianapolis road course for the first time.

With NASCAR heading to Bristol this weekend, it marks the first return to dirt track racing for the Cup series since the 1970 race at the North Carolina State Fairgrounds in Raleigh that was won by Richard Petty. Since then only the third-tier Truck series has competed on dirt in its annual visit to Eldora.

As preparations for the dirt race are finalised, this weekend will be the first chance all Cup drivers will experience the different tyre construction in racing conditions, with the tyres designed to race on dirt surfaces known as bias ply tyres. All competitors will run two new Goodyear tyre codes for the event.

While the tyres feature the same block-style tread pattern that the Truck series ran at Eldora as recently as 2019, both the left-side and right-side tyres feature construction changes compared to those tyre codes.

Bias ply tire for Cup Series dirt race at Bristol

Bias ply tire for Cup Series dirt race at Bristol

Photo by: NASCAR Media

“Bias ply tyres are much more compliant than radials because they don’t have a belt package under the tread, making it more able to conform to an uneven dirt surface,” said Greg Stucker, Goodyear’s director of racing.

“The other obvious difference between these tyres and the ones teams run on Bristol’s concrete surface is the presence of a tread pattern. All of our tyres have a tread, but the concrete and asphalt tyres do not have a tread pattern.

“These dirt tyres have a block-shaped pattern, both to bite into the dirt and evacuate it so the cars have grip.”

The size of the left-side tyre also has some differences. The left-side tyre is significantly shorter than usual to build in more stagger between the left and right tyres.

The new tyre is based on a dirt modified tyre in Goodyear Racing’s range, though it has been widened out to 11 inches (from 10 inches on the dirt modified tyre) to give the NASCAR cars and trucks more grip.

Cup teams will receive three sets of tyres for practice, one set for their qualifying heat race and five sets for the race, with the race allocation combined from four race sets plus one set from qualifying.

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Series NASCAR Cup
Author Jim Utter