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initial torgue, final rorgue


moto_mixon

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I was looking at spec's to tighten the oil drain plug, and found this:

Initial torque, 23 Nm (17 ft-lbs)

Final torque, 32 Nm (24 ft-lbs)

 

Can anyone explain what initial torgue, final torque refers to?

 

TIA

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Basically it is a torqueing process that tightens up part way then to the end value in the second sequence. Typical rational is more equal stress on part being torqued (reduces possibility of warping - especially V8 heads). On oil pans it tends to keep the gasket from slipping out on one side, or getting cut on one side, expecially with the red silicone aftermarket gaskets (more used on airhead valve covers). If using the silicone gaskets make sure all surfaces and gasket are oil free/dry. Other tribal knowledge may apply...

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Ok, that makes sense for a piece that has multiple fasteners to attach it. But with a drain plug, one single screw-in plug, what else can one do except tighten it in action all the way to the final value?

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The first torque establishes the sealing pattern, the second torque partially crushes the washer. It is a poor setup compared to most Japanese bikes.

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My question is- how do they want you to implement this? Do you go to initial torque, back it off, and then go to final torque, or go to initial, followed by final torque? Seems like I end up pausing in between there to reorient the torque wrench most times anyway. Either way I don't see where it would make much difference if you don't have a leak.

 

Frank

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That's what I do.......Torque to initial torque, then back it off, go back to the same torque, then final torque. The contact area of the washer is really small, so the crush factor is critical. The first time I changed oil, I just did a torque-torque. It leaked. I now make sure that the washer is centered on the plug before and after I go to the first torque. No problems since.

Another example of BMW's unnecessary over-engineering.

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No, no. Do not "back it off". That defeats the purpose of the intitial torque value.

 

1. Tighten to the first value.

2. Tighten to the second value.

3. Go ride.

 

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