torquing u-bolts

scottonthefen · Jan 1, 2020

My new springs have been on for months now (no road use yet but wheeling in and out the garage loaded up) so I torqued the shackle pins up today and went to do the u-bolts.. should I torque these up under load? when I laid down and went to make a start I was a bit concerned the weight of the vehicle would strip the thread off the u-bolt as I torqued the nuts up from beneath?

steve2286w · Jan 1, 2020

The manual has them torqued up when jacked up, don’t know how much difference it would make

Blackburn · Jan 2, 2020

Where does the manual state a torque value?

nathanglasgow · Jan 2, 2020

Blackburn said:
Where does the manual state a torque value?

75ft lbs. Its in the text of the above attached file

steve2286w · Jan 2, 2020

Slightly different in table

Blackburn · Jan 2, 2020

Got to admit never used a torque wrench on them just tightened , the standard spring U bolts strip their threads very easily.
What size nuts are the standard ones?
I have parabolic springs and my U bolts have 12mm threads with 19mm nuts so not .
Torque chart for different threads / sizes here
https://www.almabolt.com/pages/catalog/bolts/tighteningtorque.htm

rob1miles · Jan 2, 2020

They have to take the wieght of the vehicle plus the dynamic loads - axle twists, bumps etc so there's masses of safety margin. They need to be tight and all the same. The spring pack will be thinnest when its relaxed so that makes sense of tightening while jacked up.

scottonthefen · Jan 2, 2020

I've got new parabolics on the rear and refurb'd leaf springs with new u-bolts on the front.
I take from some of the posts above that jacking the chassis up near each spring to take some load off while I tighten up would be a good idea to avoid stripping any threads.

As for torquing them up.. there's an inch of visible thread above the base plates on the front, and more already below the nuts there, so I'd have to cut the bottom of the u-bolts off with an angle grinder to get a socket over the nuts as I work them up the threads. On the back, I've already got enough u-bolt beneath the nuts to have to cut them off to get a socket over the nuts there. Is cutting like this usual or are people just locating the axle on the base plate's pin, tigthening the u-bolt nuts evenly and setting the locking tabs and calling it done?

rob1miles · Jan 3, 2020

Before you go cutting can you get a deep socket to fit? If you have an old ring spanner that fits you can weld a socket to the other end so its at 90 deg then use the torque wrench on that as the reading will be correct. A very handy trick for hard to reach head bolts.

Blackburn · Jan 3, 2020

Rob how does the torque stay the same if you add extra leverage?

rob1miles · Jan 3, 2020

You add it at 90 deg, the the torque at one end is the same as the other. If you add it in line you have to do a calculation. Correcting for other angles is too much trouble!

torquing u-bolts

scottonthefen

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