Originally Posted by planenut
Most but not all, M3W's have a plate on the inner skin, where the exhaust brackets bolt through. If there is no load spreading aluminium plate on the inside of the car it's a good idea to fit one as the G56 system is heavier than the standard system. Check the rivets along the lower edge of the skin occasionally as the heads are prone to shearing off. This can happen with any exhaust system fitted but is maybe slightly more of a problem with the G56 fitted. The rivets can be easily replaced.

My 2012 car fitted with G56 exhausts had separate (quite small) reinforcing plates behind each exhaust bracket and I had noticed significant 'panel-wobble' when the engine was running.

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These plates were 18cm wide and 13cm high.
Therefore, one of my lockdown projects was to reinforce the side panels. I used 2mm aluminium, 25cm x 70cm bonded on with PU adhesive.

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Photo shows temporary wooden batons used to hold it in place while the adhesive cured. I just stuck the new panel over the existing plates.
It has certainly stiffened up the panels no end and the bodywork no longer flexes with the exhaust bracket movement.

Andy