Panhard bar bolt came out on the highway! (2 Viewers)

[turbo8]

 

[TeCKis300]

Fasteners are sometimes also specced this way to get the bolt to stretch more easily and slow the progression of clamping force.

Yes. To bring this full circle, so the stretch is not localized in the threads.

 

[bloc]

Yes. To bring this full circle, so the stretch is not localized in the threads.

Or to get stretch at a much lower clamping force than would ever occur at the threads due to cross section.

Point is, when they want a large bolt but don’t want it to hold *too* tight, for whatever combination of reasons.

On the euro cars I’ve worked on this was because they usually threaded into inserts that can’t be changed, but not the case here with the separate nut.

 

[linuxgod]

View attachment 3519565

Looks like a typical Toyota suspension bolt. The front sway bar bolts are the same. The taper at the end makes it easier to get the bolt in straight without cross-threading if things aren't perfectly aligned, especially if you're going through a suspension part (i.e. if you have an arm with a bushing that sits in a cradle).

I can't exactly speak to why the whole bolt isn't threaded, but partial threads are pretty typical on longer bolts. The neck near the flange being slightly larger is probably to ensure a tighter fit where the flange head clamps into the mount. Then again I'm not an engineer, I'm just guessing. I do know flanged bolts have a lot more holding strength than regular hex bolts, even when the latter use a washer.

FWIW now that you have it I would use the Toyota part, if for no other reasons than (a) it's probably less prone to rusting than whatever you sourced and (b) it might be stronger than grade 8. Also I'd be inclined to use some loctite on it if you didn't already, so this is your chance to apply a bit. But in practical terms if the bolt you have is holding tight you could probably leave it and it would be fine for the next 500k miles.

 

[bloc]

Ah, yeah, pretty standard Toyota suspension bolt. The diameter change is also in large part because the threads are rolled, not cut.

Based on the description this is more what I was imagining..

 

[bloc]

FWIW now that you have it I would use the Toyota part, if for no other reasons than (a) it's probably less prone to rusting than whatever you sourced and (b) it might be stronger than grade 8.

Also this.