Flywheel screws

[newbuild100]

GS100/94 model.

Re the above screws.


I can source "similar" screws locally (same thread/length etc)

Can I presume the O/E screws are high tensile (If so, what grade ?)

And, what makes a bolt a "stretch bolt" ?

Thanks all.

 

[cookie]

I would expect the tensile rating to be on the bolt heads, but would buy the genuine article from Motorworks etc.

 

[newbuild100]

Mm, the bolt heads are very thin, probably half the depth of a bolt that size !!!

 

[Voyager]

And, what makes a bolt a "stretch bolt" ?

They are high-tensile bolts (or Set Screws) that are designed to be installed in such a way that they are 'stretched' by a set amount to retain their tension.

This usually entails torquing them up in sequence to a (fairly low) level, then turning each in sequence by a set no. of degrees.

On my Toyota Landcruiser (for instance) the 18 head bolts are torqued in sequence to 29 lbs/ft, then turned (in sequence) a further 90 degrees, then turned (in sequence) a further 90 degrees.

Its the amount of 'stretch' applied that's important, not the torque. I have no idea what the final torque settings are - but I need a 24" power bar to complete the job .

Important point . . You only 'stretch' them once, when they are undone they are discarded as scrap .

BMW must have their reasons for not using simple set screws with thread locker .

Bob.

 

[cookie]

Mm, the bolt heads are very thin, probably half the depth of a bolt that size !!!

They're likely unique to BMW then.