Thruxton Sheered rear shock bolt

What you got torque wrench set to? Are you using Newton Meters? Not lbs/feet

 

28 Nm is correct Kev.
This is when using new bolts which you were.
I can only think the tight/damaged female thread has caused the head to shear off.
Were you gradually working up to 28Nm i.e. 24, 26, 28. ?
It does seem like you have had some bad luck.
Once you have got the broken stud out, I would definitely run a tap through all the fixing holes.
I would Forget about using the torque setting, tighten the bolts until the rubber bush starts to compress, the threadlock adhesive will hold it in place.
Overtightening could strip the thread out of the female fixing which would not be good.
Fresh start tomorrow!

 

The tapping drill size for M8 is 6.8mm
Ideally you should not have to go to this size as you do stand a very good chance of taking some good thread out of the fixing hole.
Drill a 5.0mm hole as central as you possibly can and use your stud extractor.
If that doesn't get it step up to 5.5mm, then 6.0mm if needed.
You will find the bolt thread collapsing and then run your plug tap all the way through the hole.
The threads may have been tight from previous threadlock still in the thread which is why it is always best practice to run a tap through them.
Good luck and take your time.

Use coolant and a sharp drill when drilling, you will be surprised how hot the bolt will get which will make it expand

 

Bloody hell Kev!
Those shockers certainly didn't like being changed
Is there any of the extractor stuck out ?
If there is you could carefully angle grind flats on it to fit a spanner or socket and then very gently turn.

 

Kev,
One last option to try at home if all else fails.
The extractor if not long enough to make flats on it will have to be machined out.
To do this you will have to use a solid carbide twist drill (not a masonry bit) as they cut properly.
You will need a drill guide which needs to fit onto your shock absorber mounting with a hole the same size as your carbide twist drill through the middle to guide the drill.
This will make sure that your drill is exactly central to the mounting so you could actually drill up to 6.0mm diameter without damaging the thread.
Carbide will drill the extractor, nice and steady allowing it to cut.
If you know a local engineering shop they should easily knock up a drill guide for you (£10ish)

 

Hi Kev, if you can get the broken extractor out then you could do the following:

1. Using a left hand thread drill bit of a size slightly bigger than the existing hole and using your drill in reverse, you will be able to gently drill and unwind the broken bit of bolt out of the shock spigot.

2. Looking at the picture you posted earlier I'm convinced that what you have on your bike is the top shock bush. If you've got some decent mole grips you should be able to grip the metal outer collar of the bush to pull it off; then you will be able to remove the rubber bush. This will give you much better access to the snapped bolt end.

 

Kev,
I believe the shock absorber bush is virtually the same length as the fixing spigot.
Removing it will not give you any improvement in gripping the broken bolt, but I repeat what I said in my last post that I would make a drill jig that locates on the fixing spigot and use it to accurately drill the extractor and stud out.
So for this operation the shock absorber and bushes do need removing from the spigot

 

I cant understand how a bolt can snap below its torque? Mind you, I have got things back from professional mechanics, overtightened and fu*k"d.

 

This is like a suspense thriller. C'mon Kev, you can do it...

Sorry I can't be of any assistance, but I recognise the situation.

 

Whats that, is it another extracter? Keep going dude

 

Hay Kev whats happening ?