Stripped seat bolt threads

[rwtags]

So I was installing sport seats into my car, and the bolt that holds my seatbelt to seat frame stripped out. Not sure if it was me or previous owners, but it wasn't that hard to strip. A long piece of metal was sprawed up under seat.
What's the next biggest size up that is a common thread size I can get grade 8.8 on? Preferably that I can get at home Depot.

[rwtags]

luckly, a longer bolt was able to get the seat on there perfectly, with a few washers

[ForcedFirebird]

You may have used the wrong bolt (or a PO of your car). All cars that were imported to the USA were mandated to have 7/16" by 20 thread for all seat belts (so all MFGR's used 7/16-20 on all seat belts since the 80's). Being a German car, they put 17mm hex heads on them, and are easily confused with 17mmx1.5 bolts.

[rwtags]

Now I don't know if I got the right bolt, all the bolts in the can for the seats are m10x1.5, even studs in the front are, I brought everything to home Depot and tested everything, even looking up on parts site says m10x1.5. I must be missing something

[ForcedFirebird]

https://www.google.com/search?safe=off&client=firefox-b-1-d&q=seat+belt++7/16%22+20+thread+in+%22bmw%22&sa=X&ved=2ahUKEwisgZjY3ZThAhUoq1kKHYdCBDYQ5t4CMAp6BAgAEAc&biw=1333&bih=638

All seat belt bolts are 7/16"-20, no matter make if car is/was ever going to be sold in the United States. Imported cars will have a 17mm hex head on them so there's no odd tooling in building the cars.

Your seat mount bolts are metric, anything related to the seat belt will be domestic threads. Hold all the seat bolts thread to thread, look at the light through them, and you will have some odd ones. One of the e30 seat belt bolts has a very thick shoulder, and small threads with a plastic washer, gold color galvanized. The threads are not metric on it - very close to 10mmx1.0 (7/16"-20 is 11mmx1.2) - so the major diameter of the threads will be larger on the seat belt bolt, and after about 5 threads, they won't line up.

[rwtags]

Could explain some stuff.. I'll go see if I didn't mess it up too much, looking back there was a 8.8 bolt in there.. metric not grade 8.. so previous owner didn't know as well.. how deep are those threads? I got various sizes m10x1.5 and the longer ones bottomed out pretty good, I think I have a 35mm in there now with like two washers.

If anything I can just get a longer bolt? And slap a nut on the underside of the car? As long as I move the fuel line a bit out of the way? Pretty sure the seats I have in now I don't ever want to take out, just want to be as safe as I can be in this car.