Originally Posted by Chowbow
I say go all out and get a flex joint in there like OEM pipes do and do a high flow cat version as well.
I agree with Chowbow about the flex joint. It's still early days to comment but long term use and reliability of any aftermarket DP's is very, very questionable. Only one aftermarket DP manufacturer, called Supersprint Exhausts, have provided a flex joint at this stage.
Since DP's carry the hottest exhaust stream in all the system, it's natural that there will be a lot of metal expansion and contraction going on in there! Welded joints to flanges and pipe joints will need to stand up to long term heat induced movement in this part of the exhaust system.
Having flex joints in each DP is a no brainer and could help alleviate any undue metal stress inflicted cracks or weld failures to the downpipes.
If you think downpipes don't move at all, you are fooling yourself. BMW's engineers knew better and thats why factory DP's have flex joints.
Something to think about.