Checking the thickness of the brake pads can be done through the hole in the shield of the brake mechanism. To do this, shine a flashlight into this hole. To accurately measure the thickness of the brake pads, the brake drum must be removed as described in section «Removing the brake drum». The new primary brake pad should be slightly thicker than the secondary brake pad. Since the lining of the primary brake pad wears more, both pads are ground almost simultaneously. If the thickness of the pad together with the lining is 2.5 mm or less, the brake pads must be replaced.