Bottom front strut bolts

[Seppi72]

As those of you who subscribe to the listserver might know, I had a scary time last Saturday in my 240Z. The bolts holding the right front strut to the transverse link and steering knuckle backed out and the strut came free. Fortunately, this happened at low speed and I only destroyed the right fender and tore a brake line.

However, the last third of the two bolt holes in the bottom of the strut assembly got stripped when the bolts pulled free. I thoiught about having 12 x 1.25 helicoils inserted, but a mechanic suggested another route that I'd like to run past you guys.

He suggested that I drill out the threads entirely and go with a longer bolt and nut setup instead. He figures it would be a cheaper repair and I like the idea that I could use a grade 6-8 bolt and safety wire the nut so nothing like what happened will happen again.

This is a modified 240Z, so I'm not worried about a concours look and I figure any future owner will see what I did and know why I did it.

Comments are welcomed.

[Arne]

Bob, when I read your story in the e-mail, I wondered about the Heli-coil route. Personally, I'd feel better with it drilled for a separate bolt and nut. That's assuming that both surfaces that the nut and bolt-head seat against are machined and parallel. I can't recall off-hand if the other surface of the threaded part is machined or not.

Just out of curiousity - were/are you running bump-steer spacers?

[a7dz]

I agree with Arne only other thing is if you can not find a nut with safety holes in it you may Want to use a lock nut set up like the thrust rods use. If the surfaces are not parallel then build a spacer or shim to make the bolt and nuts mating surfaces parallel.

[jmortensen]

Sounds like bump steer spacers with stock bolts. The bolts I'm running go all the way out the top of the holes. This is a very stressed area in the suspension, and correct length bolts are even more important here than other areas.

[John Coffey]

I don't think the top side of the strut casting presents a square surface for a nut or bolt to bear against. In addition to boring the hole you would have to machine the top of the casting flange to be square to the bottom. Sounds like a lot more work then is necessary. I would:

1. Source a replacement strut and throw the damaged one away.

2. Bore the hole slightly oversize and tap for the next larger metric or SAE bolt. I think those bolts are M12s so you could bore to .475 or .4844 and tap for a 1/2 bolt. If they are M10s you could bore to .4062 and tap for a 7/16bolt.

[Seppi72]

The car uses Eibach progressive springs and Tokiko shocks. There are no bump steer spacers. From the bottom up it's transverse link, ball joint, steering knuckle and strut.

The more I think about it, the more I like the bolt concept. I'm even thinking I'd install it pointing down so that if the nut worked loose, at least the bolt would stay in place and not fall out. Yeah, it might shake, but this time I'd know enough to stop RIGHT THERE.

The "top side" of the strut is not flat, but since the bottom part is, it should be fairly easy to machine flat spots for the washers. Heck, they could be cut using a flat file and some elbow grease.

John, you're the racer here. What's a good source for the bolts that I should use?