Posted by Mike H ( Missouri) [108.162.216.169] on Friday, May 18, 2018 at 08:52:59 :
In Reply to: Re: U-bolts revisited posted by Desoto61 [162.158.186.159] on Friday, May 18, 2018 at 06:01:15 :
Two things I have thought about this.
One is that the threads of all bolts will distort but they can distort without yielding and therefore they will return when loosened. Torque to yield bolts are a specific bolt and a standard bolt should never be torqued to yield. The purpose of torque to yield is to obtain consistent clamping force and therefore greater reliability for high production applications. When the bolt hits yield the torque to tighten the fastener quits climbing and you have hit the yield point, if the torque you are applying to the nut is still going up as you tighten it is not yielded yet.
Second is that there are many fasteners on trucks and cars that are equally stressed and are equally critical to the safety of the vehicle. In fact it could be argued that all bolts in the drivetrain and chassis are. A few that quickly come to mind are wheel studs and the flange bolts on driveshafts. While I have never personally heard of failed u-bolts I have had wheel studs shear off on a trailer and I have also sheared the bolts on the drive flanges. Fortunately the failed wheel studs was on a trailer and I caught it before all 8 had failed. The driveshaft failure was at the axle side and off road. Both were the result of the connection loosening up.
I would bet someone does replace the drive flange bolts every time on a driveshaft but I know of no one that changes wheel studs each time, including wheel shops and dealers. Just something to think about.