CONCORD, N.C. -- NASCAR's bid to develop a larger cockpit-area for drivers was slowed Tuesday when the cars with the bigger "greenhouses" didn't perform well on the track during a test at Lowe's Motor Speedway.
"The bigger greenhouse dramatically affected the aerodynamics and that's not something we predicted," said Gary Nelson, NASCAR's managing director of competition. "It's a dramatically less stable of a car, and the driver comfort seems to be down."
The larger greenhouse area increases the cockpit area anywhere from one to three inches in the roof area and up to four inches in the length measured from the front windshield to the rear.
Drivers and crews have called for larger greenhouses as a safety measure to keep the driver's head away from the roll bars. And the larger design assists bigger drivers in exiting the cars because it provides increased window space and more freedom of movement in the driver compartment.
Jimmy Spencer, Johnny Benson and Todd Bodine all brought greenhouse cars to the test - giving NASCAR representation of the 2003 versions of a Dodge, Pontiac and Ford - and ran them against three standard Winston Cup cars that were participating in a tire test for Goodyear.
The greenhouse cars failed to post on-track results similar to recent wind tunnel tests done with the same cars, and they struggled to run in traffic with the three standard Winston Cup cars.
It was a setback for NASCAR after two fairly successful tests.
"We thought everything was working out really well, but now we have three cars and we get on the race track and we are actually worse than we thought we were," said Jimmy Spencer, whose Chip Ganassi Racing team has been involved in the project since the start.
"Our push is actually worse now than the current aero push we now have. Plus, the cars were unstable. So is it the tire? Is it taking away too much downforce? We don't know, but we're not going to stop working."
The issue received more attention two weeks ago after Steve Park was trapped inside his car after a wreck at Pocono Raceway.
Park's car flipped several times before landing on its roof, and because of all the safety equipment and the small cockpit area - coupled with being upside down - Park couldn't get out.
But NASCAR is finding that by enlarging the cars, the downforce and aero push are severely altered.
Andy Graves, a team manager at Ganassi, said the on-track struggles weren't an equal tradeoff to giving the driver more space. Plus, increases in standard safety gear could eat up most of the extra room.
"Sure, the driver is getting more room, but with all the head supports and other things we're using, I don't really see where this particular effort helps," Graves said.
Because of the way the cars were reacting with the larger greenhouses, both Graves and Spencer said they support adding an escape hatch in the roof until this effort can be perfected.
NASCAR plans to keep working on the project, but Tuesday's test results made it impossible for Nelson to speculate when the larger greenhouses will go into effect.
"There's a couple of hurdles we still have to cross," Nelson said. "I don't want to sound negative because I'm optimistic we can cross them, I just don't know when."