So go for the hardened 12.9 in the knowledge that if it goes it'll go with a bang, but it's unlikely to meet a force it can't handle.

Hi Saurus,
I don't quite follow what you're driving at in your first sentence.
Are you suggesting that more of the damper load is applied at the ends of the bush than at the centre, instead of being uniformly distributed along the length of the bush?
If so, I'd tend to think that the latter is more probable.

But that's probably a side issue if the following statements are taken into account...

The first point of interest in this diagram is the location of the point of contra-flexure,
which is coincident with the shear plane in the bolt.
This forms a large part of the explanation as to why bolts are designed for shear, not bending:
The two forces are not coincident, where shear is applied, bending is zero.


Conclusion
Although simple design methods may be used in checking the capacity of bolted
joints, it is important to bear in mind the full range of forces employed. In particular
the presence of tension in the fastener, clamping the joint together is an essential
aspect of bolt performance

Full article here.
http://www.alexanderscott.co.uk/Lightho ... er%201.pdf

Granted that the length of the damper mounting/bolt is likely to make bending stresses of greater significance than in a typical bolted connection, but isn't that why Citroen opted for damper mounting studs in the first instance?
Of course, there are other details of the original design which lessen the chances of failure, but that's another subject...


Damper washer, which way round? by slcchassis, on Flickr

I'm going to completely ignore any technical aspect, and say you've had the 8.8 fail, can the 12.9 do any worse?
If you're worried about a bolt shearing and the shock dropping onto the road, can you tie some wire or a cable tie loosely around the damper and tie rod to stop it going that far?

Yes been there, it's just the hassle of getting the sheared stud out.

We all know what the long term answer is

I think there are two problems, the bolt isn't very strong and a lot of shock absorber bushes are of crappy quality, as a result you can't torque the bolts up properly.
I'm going to try to replace the bushes with seamless 16 mm diameter 2 mm thick pipe and i'll use 10.9 hex bolts because of practicality, and i hope they'll be strong enough. Maybe i'll also connect them with a metal strip to reduce movement of the bolt to a minimum.

12.9s if you can torque them up will be better, wheter the POS fitment can take the torque is another matter. If the bolt shears then the 12,9 will be (more of) a bitch to remove the remnants grease them before fitting itll help to torque them and make the sheard bolt easier to remove.

its the rears isnt it? and may have some connection to the " my bump stops have fallen off is it ok to...." post elswhere

suspension may bottom out the shocks as Ive seen you filling the car with people and driving over bumpy fields....so that should answer your question about the need for bump stops too ( again usually neglected by the originator of the chassis)

Just changing the subject slightly (to your AK350 instead of your D*lly) Sam. Am I remembering correctly that your van has it's original chassis, with an earlier version of these studs, using an M9 nut to hold the shock-absorber on, rather than the normal M12? If so, could you check something for me next time you're under there, (no hurry): Does it have also have M9 nuts for the rear end of the rear shock, (to the rear suspension arm) and do all/some/none of the studs have holes for a split pin? Thanks.

It is M9 for the shocks yes, the rest I'll check when next i'm underneath her. Ironically, this will be valentines day.

Well as long as you're both happy.

Quote of the year!

Reading this thread had this pic come to mind.

It makes sense to me that a stud will 'distribute the load' better than a bolt.
Taken from the book Supercharged! by Corky Bell.

Harley