Upper wishbone through bolt - how tight? - Alfa Romeo Forum
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(Post Link) post #1 of 5 Old 16-04-13 Thread Starter
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Help Upper wishbone through bolt - how tight?

Recently replaced the upper wishbone on my 147. It has lasted a couple of weeks and is now "sqeaking". When I bolted the new wishbone to the upper mount I tightened up the through bolt to what I would say was reasonably tight (not scientific I know). THis seemed to have the effect of locking the wishbone to the mounting bracket. I checked on the forum and found a torque setting of 40 -49 nM so used that and put everything back together. I have to say that this seemed a pretty low figure. I also gave everything a good coating of sillicone spray before assembling everything - looks like I should have given everything a good coating of silicone grease.

Can anyone confirm the torque figure or shall I take it off grease it up and put it back tight (90nM ish)- it could be that with the wishbone being new it was going to take a good amount of force to make it move around the bush. I presume that is how it works - the wishbone clamped to the tope bracket rotates around the bush held by the through bolt.

Checked everything else (drop links, ARB and lower wishbone) so I am sure it is the top wishbone.

Thanks for any help
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To save you doing then job again. Take then out and grease. Spray doesn't last
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To save any further confusion.... Lets look at what kind of bolt and nut it is.

The bolt offers little in tightness to it's operation, it's a stabilizing bar in its self that's why they use a Nylock nut on the end.
It doesn't surprise me that the torque figure you have mentioned is so low. Nylock nuts are generally about 45-55% of the specified torque settings that you would apply to a full steel nut. Nylock nuts will over torque and strip its threads if you take it too far beyond it's design.

Nylock will reduce its holding ability the more you remove it... a factor of around 60% of it's original tightness after its first strip down...
If you are contemplating removing it to take the bushes out and greasing them up properly (which should have been done prior to fitting)... Then no matter if you tried to double the torque, it won't make a shadow of difference to the Nylock nut and will end up stripping.

On another loosely based but handy bit of info... Ever wonder why all your spanners are longer the bigger the the jaws are?
They are designed so that an 8 stone person and a 16 stone person can apply a similar tolerated torque factor due to fulcrum length of the shaft and not the strength of the individual...
So naturally due to the tensile strength and torque of a nut/bolt depending on its thickness and size, that's why a 10mm spanner is thinner, and a lot shorter than a 17mm spanner to prevent too much torque applied.
Most manufactures factor these values into their specified torque requirements with this in mind so using a 17mm spanner on a 17mm nut will be roughly around the torque required anyway until you can't tighten up anymore regardless of how big or small you are... You only end up with only so much leverage.
Cylinder heads and stretch bolts are a different matter though and should always have a torque wrench designed for the job...

In other words, remove the arms, pop out the bushes and grease them up with red rubber grease and fit it all back together, nip up the nut with a spanner as tight as it is comfortable with a spanner and don't worry.
(Post Link) post #4 of 5 Old 17-04-13 Thread Starter
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Many thanks for the responses. I have obtained some proper silicone grease so will remove the wishbone and grease up the bushes. I experimented on the wishbone that I took off and was surprised at how easy it was to remove the bushes from the wishbone - simply drifted them out and then put them back in with a pair of oversized sockets in a vice. As expected they were dry. The new wishbone bushes will probably be a little harder to remove, but I think well worth it. I might try to get some photos take to post on here - as if I can do it then so can everyone else
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What's the thread size on the bolts? Need some new nylocs on mine I think
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