Suspension bolt question

[br4nd0n]

I have a need to replace the bolt (part [HASH]90105-10212-00) that connects the top half of the rear shock to the frame. I have a class 12.9 steel black oil finished socket cap bolt and wanted to know if using it would be a problem. I've read that 12.9 is really strong, but it can be brittle and don't want the bolt to snap on me. I also wanted to know if the type of metal and finish would cause any weird corrosion problems. I have no knowledge in this area (most automotive things) and was hoping someone who is experienced with this could chime in.

[bmwpowere36m3]

You mean to the engine? Either way 12.9 grade fastener will be fine, 10.9 would be sufficient as well. The "problem" with black-oxide fasteners is they'll rust very quickly… especially when exposed to the elements. It wont affect their strength (purely surface), it'll just look bad and possibly cause rusty stains nearby. I avoid black-oxide fasteners for almost everything… expect where I didn't really care looks-wise or "indoor" use.
 
I would get another bolt from the dealer (can't be to expensive) or from a good fastener supplier (like Grainer, Fastenal and McMaster are big ones, NAPA might even have them). Get the appropriate length, pitch and zinc coated (either silver or yellow/gold).
 
*EDIT* I also wouldn't used a socket head, if by that you mean the one with an internal allen/hex.  Use a regular hex head bolt.

[br4nd0n]

Yeah, I guess it does connect to the engine now that I look at it. Anyways, I need the bolt to have an allen/hex cap because I have a cylindrical piece that goes around it and it is too narrow to get a normal socket inside. Without an allen/hex cap I won't be able to tighten the bolt down.

[bmwpowere36m3]

What cylindrical piece? Well, finding socket head/allen bolts that are zinc plated will be more difficult (especially metric and that length). Likely will need to look online… sucks, but I would over installing a black-oxide one. I've looked locally when in need of a metric zinc plated allen for my cars and had a tough-time finding them.

[bmwpowere36m3]

https://www.fastenal.com/products?r=~|categoryl1:%22600000%20Fasteners%22|~%20~|categoryl2:%22600039%20Sockets%22|~%20~|categoryl3:%22600040%20Socket%20Cap%20Screws%22|~%20~|sattr01:^Metric$|~%20~|sattr03:^%22Alloy%20Steel%22$|~%20~|sattr09:^Zinc$|~
 
search by size, pitch and length

[br4nd0n]

Have you seen a Bursig Side Stand? The receiver for the top half of that gets attached to the top half of the rear shock. That cylindrical receiver is too narrow for a normal socket head. Originally, I was without the bolt needed to mount it. I ended up purchasing the bolt I mentioned in my earlier post a while back and thought I should ask before trying to use it. If this bolt doesn't work out, I may have to find someone who can sell me the bolt that Bursig supplies for their side stand.

[pattonme]

http://www.svracingparts.com/ sells a clone. I expect the attachments are similar.

[br4nd0n]

pattonme, I actually got mine from svracingparts a while ago and it didn't come with the bolt. I have yet to put this thing together and was hoping to finally do it.

[bmwpowere36m3]

I would contact the seller... I'd imagine the part should come with any hardware required to mount it.

[br4nd0n]

This was a while ago and I did contact them without much luck.