Confused about differing torque values

capers1962

capers1962

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Hi folks,

I've been reading (too much, it seems).

In a document i found within this collective and in the Haynes manual, they both mention the sump drain plug should be refitted and tightened to 42nm - that ifs tight (I've refitted front caplier bolts with a lower torque value than that (not to a GS though)).

I have also read elsewhere, that it's a 2 stage process - 23nm and then 32nm.

I am concerened that 42nm is very tight and the last thing I want to do is crack the sump or strip the threads, cuz that would be a very (very) expensive repair. :blast

TIA
 
There are a few differences between the 1200 WetHead and the 1250 ShiftHead torque values.

R1200%20Wethead%20Torque%20Sheet-L.jpg
R1250%20ShiftHead%20Torque%20Sheet-L.jpg
Blank%20R1200%3A1250%20WetHead%3AShiftHead%20Cam%20Timing%20and%20Valve%20Clearance%20Worksheet-L.jpg


Here are a couple of diagrams that also help explain variations in using a torque wrench with an adaptor...which is required when torquing the bolts that hold the cams to the cam gear wheels.

Screen%20Shot%202017-10-18%20at%208.33.01%20AM-M.jpg
Screen%20Shot%202017-10-18%20at%208.34.39%20AM-M.jpg
 
Thanks to everyone for the very useful info.

I'm still scratching my head as to why the caliper mounting bolts only need 38nm and the sump plug is 42nm.
There must be a hell of a lot of pressure in there or the brakes on a GS are optional use only ....:eyebrow

As I say, very useful info.
 
capers1962 said:
Thanks to everyone for the very useful info.

I'm still scratching my head as to why the caliper mounting bolts only need 38nm and the sump plug is 42nm.
Click to expand...

'cos one is M8 and the other is M20?
 
I can honestly say in my 46 years of spannering bikes (or cars) I have never torqued up a sump plug, I have never stripped one either.
 
Paul G (BHT) said:
I can honestly say in my 46 years of spannering bikes (or cars) I have never torqued up a sump plug, I have never stripped one either.
Click to expand...

That's why dealers can charge such high rates, it takes a lot of time to torque every nut and bolt or fastening loosened and tightened during a service.
 
42nm is correct. It's a big bolt. You're crushing an aluminium washer to create a oil-tight seal. Not attaching load bearing component. There be science involved.
 
As an amateur spannerer (?) and therefore occasionally coming a cropper when 'a little knowledge is dangerous', I learned the hard way that torque values are usually for dry threads. I added copper grease, used the specified torque setting and was disappointed when I stripped a thread...

It's highly unlikely a sump plug thread will ever be free of lubrication - I'd be even more nervous of this high torque settings on a lubricated thread.
 
As per Paul G (BHT) above, I have never ever tortured a drain plug, I haven't even reused the crush washer each time (I might have turned it over to change the contact areas). And in all these years I've never ever had a loyal or stripped a thread - in fact I haven't strip a thread since my teenage years.

I would just do it by feel, as also mentioned above.

Sent from my SM-G975F using Tapatalk
 
The Other PaulG said:
As an amateur spannerer (?) and therefore occasionally coming a cropper when 'a little knowledge is dangerous', I learned the hard way that torque values are usually for dry threads. I added copper grease, used the specified torque setting and was disappointed when I stripped a thread...

It's highly unlikely a sump plug thread will ever be free of lubrication - I'd be even more nervous of this high torque settings on a lubricated thread.
Click to expand...

42nm is NOT high torque. I can't remember off the top of my head but it's a much bigger bolt than most sump plugs. . And I'm sure it's a fine pitch too which has even more threads to spread the load. Your wheel bolts are a smaller diameter and have a higher torque (60nm), Go figure !!

I'm guessing that you stripping a thread was probably because the thread was previously damaged or cross threaded. Or you REALLY gave it some beans.
 
Slipperyeel said:
As per Paul G (BHT) above, I have never ever tortured a drain plug, I haven't even reused the crush washer each time (I might have turned it over to change the contact areas). And in all these years I've never ever had a loyal or stripped a thread - in fact I haven't strip a thread since my teenage years.

I would just do it by feel, as also mentioned above.

Sent from my SM-G975F using Tapatalk
Click to expand...

It's just as well you don't use a torque wrench if you don't replace the crush washer. (I don't understand why you wouldn't though). The torque is calculated with the assumption you will. The higher torque is to crush the washer. Which is sacrificial to the load applied.
 
cookie said:
I figure they are steel bolts into steel threads.
Click to expand...

Only recently were the flanges changed to steel. Traditionally they were aluminium. They were changed due to hack-handed tyre fitters with 300nm rattle guns making them crack.

But anyway. 42nm is not a lot of torque at all.
 
I guess the 42 Nm ( correct for 1250) “seems high” comment is in relation to other sump nuts folks may have worked on, say a Hexhead at 32 Nm or my 3.0 six cylinder car at 25 Nm.

Of course the torque value is dependent on bolt size, thread pitch, application, material etc etc.

Just worth mentioning before folk start wellying into a magnesium crankcase on a KTM or some such as there is no doubt that a stripped thread can bring a sinking feeling almost every time ;-)
 
The developed into something quite interesting and informative.

I have fallen foul if the cracked sump casting, not from over tightening, but from loosening a sump plug on a 'new to me bike' that had been tightening way to tight and the shock of coming free cracked the sump (on a Jap bike) - oh how I laughed.
I suppose it is from this bitter pill, I asked the question.

Anyway, thank you all for your thoughts and science.
 
Last edited:
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