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 Flywheel bolt torque inquiry. 
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Joined: Thu Dec 08, 2016 6:49 am
Posts: 3
Post Flywheel bolt torque inquiry.
I need to understand how the torque setting for flywheel bolts on the forum is generally around 240-250 ft.lb. I was looking just to find and compare numbers to what I'm seeing given the manual is stating a stepped torque pattern of 20Nm of pretighten then a 60° +/- 5° turn I have through determined this final turn to finish in the 130-140 ft.lb. range. What am I missing here? I have a quality torque wrench that has a Max of 250ft.lb. it's fairly new and we'll taken care of, no chance it's that far off calibration. Is this a question of using new bolts or used bolts? I'm just not seeing this 240-250.

Thanks,
Matt


Wed Jun 07, 2017 1:26 pm
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Joined: Wed Apr 14, 2004 9:58 pm
Posts: 1436
Location: Idyllwild, CA
Post Re: Flywheel bolt torque inquiry.
I would interpret "a stepped torque pattern of 20Nm of pretighten" to mean tighten to 20Nm in the tightening pattern, then increase by 20Nm (to 40Nm) and repeat, then increase by 20Nm (to 60Nm) and repeat, etc. until you get up to the full torque. THEN tighten an additional 60 degrees.

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Wed Jun 07, 2017 2:41 pm
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Joined: Sun Sep 25, 2011 11:19 am
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Location: Woodside, CA
Post Re: Flywheel bolt torque inquiry.
What is being called for here is an applied angular displacement to achieve a given elongation and
resultant force on the flywheel. There is no torque per se, By pre-torquing to 20nM you are just
taking the slack out of the interfaces, that is then followed by a 60 degree turn which will move all members
in by ~0.25mm -- elongating the bolt. This is a special bolt designed for this purpose and is 12.9 hardness.
I'd go around at 20nM twice just to make sure it's snug, THEN you give it the stretch ala a 60 degree turn.
Mark the flywheel bolts carefully or socket. I don't know what torque that may translate into, might go
beyond 250nM, A breaker bar would do. Don't forget the loctite and on the inner surface of the bolt head.
That's needed to reduce friction otherwise it will take a lot of muscle.

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Wed Jun 07, 2017 7:41 pm
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Joined: Thu Dec 08, 2016 6:49 am
Posts: 3
Post Re: Flywheel bolt torque inquiry.
I agree with the above. I have done countless installs of flywheels on the pinz fleet I work on and I just reached a point of curiosity to see what people were actually thinking here.
New bolts should be used every time, unfortunately new bolts hit you for around $18 bucks a pop, which may sway some, but oh well. I'm just baffled by how some are so persistent​ about the high torque value that as the manual shows does not actually exist.


Thu Jun 08, 2017 9:47 am
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