Reusing Nyloc Fasteners

Ferrari 308 suspension bolts
The subject of whether nyloc fasteners should be re-used recently came up for discussion.  I had never really consided whether one should or not, I just always replaced them. I decided to do a little research…

The FAA (Federal Aviation Administration) in section 4 of “AC 43.13-1 – ACCEPTABLE METHODS, TECHNIQUES, AND PRACTICES AIRCRAFT INSPECTION AND REPAIR ” says “DO NOT reuse a fiber or nylon locknut, if the nut cannot meet the minimum prevailing torque values. ” Now… the prevailing torque is the force required to turn the nut (before clamping force occurs) compared to a free turning nut. So basically the FAA are saying that if the nylon insert is still fully functional (because the minimum prevailing torque is still required) then the fastener can be re-used. The prevailing torque for ISO metric nuts can be found here.

The US Air Force says almost the same thing in TO 1-1A-8 “STRUCTURAL HARDWARE”: “If these nuts are reused, they shall be checked to see if the locking insert has lost its locking friction or become brittle.”

So there it is, two recognised standards say it’s ok to reuse nylocs but their prevailing torque should be measured first. Given the importance of the fasteners holding the suspension components together, I think it is simpler and safer to just replace all the fasteners regardless. So here is the list of what’s needed for the front and rear suspension:

Front, both sides, all Nyloc
4 x M14x1.5 class 10
12 x M12x1.25 class 10
10 x M10x1.25 class 10 (inc anti-roll bar D-brackets)
2 x 3/8×24 (track rod ends)

Rear, both sides, all Nyloc
4 x M14x1.5 class 10
10 x M12x1.25 class 10
4 x M10x1.25 class 10 (anti-roll bar D-brackets)
2 x M8x1.0 class 10 (anti-roll bar)

And the mail man has just delivered the replacements:

Ferrari 308 suspension bolts

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