Technical How to set up and tighten axle nut

[bugsymike]

Even more so compared to days of old. Fittings generally are much more highly stressed and taken nearer to their limits than ever before. I'm thinking of stuff like head bolts and others which could be happily reused on stuff like the old "A" & "B" series Leyland stuff but now, with stretch to yield, must never be reused. When My Ibiza had it's new gearbox fitted I noticed several new nuts/bolts, in particular the front wheel hub nuts. I queried this and was told they are only allowed to be tightened once. If ever slackened they must be renewed.

As far as I know the idea is when the cylinder gasket or whatever settles rather than the bolt requiring re torqueing it retains tension. Unlike when after doing the head gasket job in the past the customer was told to come back in 500 miles to re tighten bolts etc. As we used to do.
This reduces the chances of "cheapskate" customers thinking they can save money by not going back for that necessary job and then complaining when the head gasket blew as a result.

"Stretch bolts are designed so that they can be elongated beyond their elastic limit into the plastic region without problems. When a specific tightening torque has been reached, the bolts are turned further through a defined angle, which pre-loads them into the plastic region."