one time use bolts

[Konrad]

What is the technical reason for one time use bolts? How does work and why is it so important.
I installed BMR LCAs and my understanding is that some of those bolts are one time use. I didn't have bolts and didn't have time to go get them so I put the old ones back in. How big a deal is that?
I've got noises back there but everything feels tight.

 

[mbuckcoyote]

Torque charactoristics of bolts change from use. When torqued down, they stretch. When loosened the do not retract, therefore becoming weaker on second use. The use of torque angles suggest that replacement is necessary as well but, that's not something attributed to LCA's.

However, IMO, if you use the same bolts and don't overtorque, you should be fine. The only time I might discard old for new is on heads, exhaust manifolds, flywheels and rear ends, basically.

There's also the thing that manufacturers want to sell you on the idea that bolts should not be re-used. In some cases, this is true.

 

[Konrad]

Yeah I figured it was one of those things that's better to do that way but not the end of the world if you didn't.

 

[streethorse]

I recently replaced a control arm, tie rod, and ball joint on my daughters
VW Beetle. All the nuts & bolts were 1 time use style, They came seperate
from the parts. Cheap insurance so to speak. I noticed they are tighter
when putting on. You cant just spin them on by hand, it takes a wrench
all the way down. Pretty much insures they wont back off somehow.