Why Change All The Hardware?

[ACiancio]

I know this is kind of a pointless question but everything I have read about changing your struts says to replace all the hardware as well. being an engineering tech I need to know why. is it a stress issue or the fact that the locking property's of the bolts/nuts is compromised. like i said a pointless question but I want to know.

[mojojo]

Well, as you can imagine, installing a nylock nut cuts grooves in to a nylon insert in the nut. During initial installation these grooves are formed, and obviously have the most conformation to the individual bolt's threads at this point. Removing the nut and reinstalling, the nylon is arguably compromised over a new nut. A metal locking nut (like on the strut tower mount) provides resistance by varying the degree of the final thread. This is then compromised when removed and reinstalled.

Being a mechanic, I would quote all of these parts in a job estimate-for a potential customer (liability issue). However, on my personal car, I would use my own discretion whether the part should be replaced. In my own cars, whenever I'm dealing with these types of hardware, I generally do not replace them, instead would use a thread locking compound where appropriate.

[ACiancio]

thank you, that was my plan, if the nut/bolt looked in good shape I was just going to use some locktite 242 on them. but I thought I would ask around a little in case there was something I was over looking.

[64pvolvo1800]

thank you, that was my plan, if the nut/bolt looked in good shape I was just going to use some locktite 242 on them. but I thought I would ask around a little in case there was something I was over looking.

Another concern is the strettttttcccchhhh of the bolt. The torque + degrees of additional rotation on most of our hardware does in fact stretch the bolt and the second time around it may or may not afford proper security. Most of our suppliers either offer or furnish the necessary hardware for the front end stuff anyway. Not worth the hassle of losing one on the highway in my book. Look up the elastic properties of steel and alloys and such in your metals engineering classes.