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HT BOLTS
Andy W - 12/10/04 at 09:57 PM

I was in the workshop this evening, On the floor was a 10mm nyloc with a small amount of stud in it. Looking at the stud it was obvious the bit of stud had sheared from somewhere. It didn't take long to find where it came from (not much 10mm on the front of my Indy) One of the bolts holding the bottom ball joint was the culpret. The top of the caphead was still sat in the hole, so it didn't look to obvious.
Questions
The bolt was a 12.9ht
Should I have only used 8.8ht
Have I just had a dodgy bolt
(could have been dodgy for me)
I don't think it had being sheared long I've done 750 miles in the car, and the washer was still stuck under the wishbone. I'll be changing all four bolts as a matter of course.
I guess i'm lucky I found the bolt, I wouldn't like to find out what happens if the ball joint comes adrift.

Mix - 13/10/04 at 08:31 AM

Did you use a torque wrench to install them? If not you may have over torqued the bolt and initiated the failure on installation.

Mick

Andy W - 13/10/04 at 03:08 PM

All bolts were torqued correctly. I'm not sure how true this is, but somone mention when bolts are plated this can make them brittle; they then have to go through another process to normalise the bolt. Perhaps this one missed this.
Could a load of crap though

Hugh Jarce - 16/10/04 at 04:47 AM

quote:
Originally posted by Andy W
...somone mention when bolts are plated this can make them brittle; they then have to go through another process to normalise the bolt. Could a load of crap though

Correct. It's called hydrogen embrittlement: when the plating process entraps hydrogen in the steel fastener which weakens it within a very short period of time.
Reputable manufacturers post treat the plated fasteners (which must be done within hours of plating) by heating to a moderate temperature. This drives the hydrogen out without upsetting the integrity of the bolt.
An aweful lot of fasteners are flooding the market that are either poorly made or are not deimbrittled.
You probably would be better off with Class 10.9 fasteners in and around your suspension, but the best thing you can do is to ask for name brand fasteners and ask to see the box they come in. Any self respecting manufacturer will certify the box contents.
On a similar vein, if you're having any other fasteners (or car parts) plated, ask to have them properly deimbrittled.