Hey everyone (sorry if this info is in another thread- I can't seem to find it).

What is the size dia and length of the bolts that connect the exhaust to the cat? I am installing a cat back on my R53 and of course the bolts are rusted to heck and back. I was gonna pick up some replacements before I start the job-- anyone know what size these bolts should be?

Thanks!
-C

 

The nuts are M10 - the stock bolts measure about M10 x 40 mm (the shaft and threads of the bolt not including the head is 40 mm long).
The bolts are integral to the front flange of the pipe (fits up against the cat's flange).
I don't think you'll get the old ones out without destroying something so get some new
ones about that size, and use some anti-seize on the threads when assembling.

 

Where can I buy the new bolt / nut? I'm heading to Ace to ask for M10 nut and M10 x 40 mm bolt - is this an automotive only bolt? I'll try the BMW dealership but I doubt it..

 

Ace, Lowe's, etc. should probably have something appropriate -- probably doesn't need
to be exactly 40 mm long.
Could get a longer one and cut it if necessary.