The heads of pins that are 1/32nd of an inch too wide are the latest setback in SEPTA's efforts to return 120 of its rail fleet to service, rail officials said Monday.

Replacement parts should start being installed by Thursday, SEPTA authorities said, but it’s another manufacturing problem that’s hit SEPTA’s Silverliner V cars. These cars were pulled from service at the beginning of July after SEPTA officials found that almost all of them had cracks in their equalizer beams, a key component of their undercarriage. The loss of the 120 cars has caused overcrowded trains and scheduling chaos that Jeff Knueppel, SEPTA’s general manager, estimated cost SEPTA 20 percent of its ridership.

"I feel for every person that's upset on these platforms," Knueppel said, adding that the latest issue wouldn't prevent the authority from meeting its goal of returning Regional Rail to a regular schedule by mid-October.

The pins that caused the problem are thick cylinders of metal that hold a foot in place on each end of new equalizer beams being installed in the Silverliner V's. The feet rest on the cars' wheel bearings, allowing the 9-foot steel beams to transfer weight from the car to the axles. Each car has four beams, and each beam has four pins. Because the pin's heads were slightly too wide,  in some cases they were scraping against the metal of the train cars' trucks as the cars shifted and bounced during trips, Knueppel said. The issue didn't present an immediate safety concern, Knueppel said, but that kind of friction could eventually create areas of uneven stress distribution on the car trucks.

SEPTA found the contact between the pins and the truck when it disassembled one of the repaired cars for a check on the new parts' performance this weekend, he said.

The new equalizer beams have been installed in 18 of the 120 Silverliner V cars so far. Those cars, eight of which were being used, were pulled from service again on Saturday to have the feet on the equalizer beams replaced. The sides of the feet themselves will be thinned, and new pins with narrower heads will be installed, officials said. Hyundai Rotem, the cars' manufacturer, was responsible for creating the feet and is covering the cost of repairs.

Hyundai Rotem engineers designed the pinned feet based on drawings and measurements of tolerances, but were not able to measure the cars directly prior to installing them, spokesman Andrew Hyer said Monday.

"As you're getting ramped up in production of anything sometimes you have to have some tweaks," Hyer said.

SEPTA has been seeking to get the Silverliner V cars back on the rails as quickly as possible, but Hyer said the accelerated schedule has not led them to compromise safety. The issue with the pins is a minor one, SEPTA officials said, and the kind of problem that can crop up in manufacturing.

This is the second issue found with the pinned feet, officials said. The holes for the pins were initially drilled too small and the pins were rubbing off the zinc plating on the feet, a problem that's been resolved. The fatigue cracks that originally caused the cars to be taken off the rails also were related to the feet at the ends of the beams, officials said. The original feet were welded incorrectly, with a poor design, leading to an uneven weight distribution. Feet that are forged directly into the beam, rather than being attached with either a weld or pin, would be the surest way to prevent problems in this area, officials have said. SEPTA said no options are being ruled out long term, but said the pins are a safe solution and will get cars back on the rails as soon as possible.

"The forged would have taken longer," Knueppel said. "I've got to try to get back to the weekday schedule."