TOKYO (Reuters) - Replacing potentially lethal Takata Corp 7312.T air bags in a mass recall is more challenging and time-consuming than expected as rival parts suppliers struggle to make bag inflators that replicate the originals fitted by the Japanese firm.
The recalls so far cover tens of millions of cars made by more than a dozen automakers - and spanning some 170 model variants in the United States alone.
It's rare in a product recall to have alternative suppliers make the replacement parts. But the unprecedented scale of the Takata recalls, where defective air bags have been linked to 10 deaths, has prompted several automakers to source replacement inflators from Takata's rivals.
The recalls highlight the interdependence between Takata, its rivals and automakers facing delays for replacement parts.
"Automakers are very reliant on Takata to produce replacement inflators and to cooperate with ... (rival) companies making Takata-designed inflators," said Scott Upham, CEO of Valient Market Research.
For now, Takata, which the Wall Street Journal reported has hired restructuring lawyers, remains integral to the process. "In the near term, Takata will be kept afloat until all the replacement parts are produced," Upham said.
For the ongoing recall, alternative suppliers including Autoliv (ALV.N), ZF-TRW and Daicel Corp (4202.T) have to fashion replacement inflators from similar sized designs in their own product portfolios, and adapt them to Takata's original design to fit the air bag module - the casing containing the air bag.
Inflators, made of stainless steel or aluminum, are not a one-size-fits-all product. They come in basic disk or tubular shapes: 'hamburgers' for driver and front passenger seats, and 'hot dogs' for rear seats, according to an engineer at a major air bag supplier.
'Hamburger' inflators resemble burger cartons with pinched edges that can measure up to around 10 cms (3.9 inches) on each side. The size, dimensions and the amount of propellant needed to activate the inflator can vary according to vehicle model.
"We need to look at the space between the instrument panel and the steering wheel, and make sure we can fit it," said the engineer, who didn't want to be named as he is not authorized to speak to the media.
"That's complicated because we're trying to fit into an existing space that Takata designed with its (automaker) customer, and we may have to change our design to do this."
Takata said it has "dramatically increased" output of replacement inflators and is "working closely" with other inflator makers to supply replacement kits.
But it remains under pressure from automakers and regulators to speed up a recall that is now in its eighth year.
The range of recalled models means more inflator designs have to be modified, tested to calibrate their propellant force, and manufactured to fit each different model. In some cases these models date back as far as 2000, and parts makers have to re-tool to replicate obsolete designs.
"We're having to produce a similar inflator which performs the same way in the module as the original did," said an executive at a major parts supplier, who declined to be named due to the sensitivity of the issue. "We're having to take a (design and testing) process which usually takes 2-3 years and speed it up to a matter of months."
Thomas Jonsson, spokesman for Autoliv, the world's leading air bag supplier, told Reuters: "We're seeing our deliveries of up to 20 million inflators being dragged out longer than expected."
"Since we don't have products off the shelf that are identical to the original inflators, there's a design phase and a validation phase for each different product."
A spokesman for Honda Motor Co (7267.T) said its announcement last month that repairs on 2.2 million recalled air bags would begin this summer was indicative of the slow pace of procuring replacement parts.
And there may be more recalls to come, adding to the pressure for replacements.
U.S. National Highway Traffic Safety Administration (NHTSA) chief Mark Rosekind told Reuters on Thursday that more testing was ongoing to look at potential safety issues with unrecalled inflators.
"That might create a new decision point" about whether testing data supports another (recall) expansion, he said. "We can probably expect there will be an expansion - the question is going to be how large," he said.
He said NHTSA is also keeping an eye on quality assurance issues of replacement Takata inflators.
Since last year, parts suppliers have boosted replacement inflator capacity, and by mid this year should produce around 5 million replacements each month, according to Valient.
Honda said it is sourcing most replacement inflators from suppliers other than Takata, and Nissan Motor Co (7201.T) said it also is securing some replacements from rival suppliers.
Toyota Motor Corp (7203.T), which recalled 11.8 million air bags last year alone, says it switched to Daicel for around a quarter of the replacement inflators it needs, with Autoliv providing some others and Takata the remainder.
A spokesman for Daicel said production was "going as planned" and there were no delays.
Reporting by Naomi Tajitsu, with additional reporting by David Shepardson in WASHINGTON; Editing by Ian Geoghegan