Originally Posted by Sid Squid (Post 2464053)

Don't even try to undo them, get a hacksaw blade and wrap a few turns of tape around one end, then cut one side off of the nut - cut parallel to the axis of the stud. Try to cut along the surface of the thread, as close as you can so as to remove as much of the nut as you can, it won't matter if you nick the threads a bit but try to keep it to a minimum.
When you've cut right through and removed a section of the nut, using a suitable rod as a drift tap the nut - and I mean tap, don't lean on it any harder than you need to - in the direction required to undo it, it won't be gripping the stud very hard anymore, and a little tap should see it start to move.

I really mean this - don't try to undo exhaust nuts that are even stiff to turn, cut them off. The various threads on here detailing how trying to undo the nuts attest to how easy it is to break the studs, and what a pain it is if you do.
I've never broken an exhaust stud and I've been required to remove some really rusty crud in the past - this works.

Originally Posted by andrewsmith (Post 2464099)

Geo that looks like fun.

I'd to what Sid specced, I'm able to get mine off with a 6 side socket (and penetrating oil) and they're siezed.
4 stainless steel nuts are £8 on Westgate Rd, the studs are a few quid each

Originally Posted by Geodude (Post 2464202)

Just checking size of studs/nut are M8 x 1.25mm thread on a curvy and would brass nuts be better choice than stainless?

Originally Posted by yorkie_chris (Post 2464204)

£8 are you f***ing kidding?

Yeah normal metric coarse. I prefer stainless stud and nut.