Ok all, so we replaced the stock exhaust last night but ended up braking 3 out of the 4 bolts on the cross member holding the exhaust in the middle of the car.
Anyone know what size they are? I want to get the broken ones out and replace them with stainless.

 

https://www.realoem.com/bmw/enUS/par...-Mini-Cooper+S

 

If your bolts broke the last thing you want to use is stainless bolts. I bet your captive nuts were very rusty from road salt and that's why the bolts broke. With stainless bolt you will promote the corrosion of the captive nuts that seized in the first place. Thus is galvanic reaction. It is a chemical reaction of dissimilar metals. The metal that more readily give up electrons loses.

 

Thank you both!

 

Don't forget to use Anti-Seize on the threads of the new bolts.

 

+1 There are different anti seize compounds if you really want to get picky, copper, zinc, nickel.... Being in the rust belt area, definitely use some sort off protection!

 

Ok, So they are 5/16th bolts and I used Permatex anti-seize. We got all but one of those darn broken bolts out and there are no more rattles! The Milltek sounds great!

 

They cannot be 5/16. They are matric as just about every fastener on the car except the oil pressure switch.

 

Not sure. I took one of the bolts to Home Depot and tried it on their size finder and they fit 5/16. The new ones went right in nice. I figured they were metric too but it would not fit in any of the metric sizes.

 

Probably more like a M8, but with damaged threads in the captive nuts the 5/16 "worked"