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Numsa members at Goodyear in Uitenhage have embarked on a protected strike.
The trade union's regional secretary, Phumzile Nodongwe, says the workers downed tools on Tuesday morning.
He says they are demanding a relief allowance when placed on staggered breaks, which has always been a standard practice in the company.
Nodongwe says the company plans to place a sizeable number of workers on a staggered break without the usual payment of the relief allowance.
Comment from Goodyear was not immediately available.