I recently purchased a Thule roof rack for my 328i off craigslist, it came with everything but the bolta to mount it to the car. I read on here that the bolt size is m6x16, so I picked some up at Lowe's yesterday. The problem is that the bolts barely thread in, maybe a quarter of a turn or so. I don't want to strip out the roof rack mounting holes on the car. So my question is are these the correct size bolts and I just need to use a little force to get them in, or is there a smaller size I'm supposed to use?