Busy replacing the clutch, tightening up the bolts and at the last turn the bolt head has come off never had this happen before.
Needed to use the bus tomorrow, will have to remove the clutch now and get new bolts tomorrow,
will make sure they are 8.8 strength these were the original bolts so l should have replaced them
already one step forward 2 steps back
Getting the thread out of the flywheel
Dont make the same mistake
90 caravelle
82 combi pickup............................you are either on the bus or off the bus
Thats my problem I over tighten just to make sure, need to invest in a torque wrench learnt my lesson the hard way
Whats your take on stainless steel bolts for the clutch, Aidan
My bus has 2L ady motor in it
90 caravelle
82 combi pickup............................you are either on the bus or off the bus
Stainless bolts shouldn't generally be used where corrosion resistance isn't required - it's physical properties are less favourable than mild steel, and it can be prone to galling, too. IMO using them to hold a pressure plate onto a flywheel would not be a good application at all.
further wrote: ↑03 Mar 2025, 20:13
Thats my problem I over tighten just to make sure, need to invest in a torque wrench learnt my lesson the hard way
Whats your take on stainless steel bolts for the clutch, Aidan
My bus has 2L ady motor in it
I wouldn’t use stainless steel in a clutch personally
I don't think it matters, DIN 933 applies to all finishes, plain, passivated, zinc flake etc...and they are being used well within their maximum limit in this case. Any observed changes in lab conditions show more variation due to storage time after production, thus once stored they pretty much behave in the predicted manner, I reckon how clean the threads in the flywheel and what residues are present from old clutch residues and any cleaning residues probably has more effect on torque than the coating
Maybe, maybe not, but, adding the coating adds another variable when torquing.
Torque settings are often quoted for clean and dry threads; dirty, oily tapped holes and plated screws are all going to add up to bolts being possibly over torqued/stressed. I'd use self coloured, non plated bolts. Depends on how much attention to detail you want to go to, or research?
Last time I changed a clutch, I cleaned the bolts, checked the threads and assembled and torqued without oil.
I'm not sure how DIN 933 or storage is relevant to the coating or not.
I went down the rabbit hole and found some articles where they found a 13% reduction in effective torque on freshly coated bolts, but also found after 14 days they actually improved torque and depending on storage conditions found that there was variation as the material was aged/effected by conditions (damp/temp etc.), we don't live in a perfect world where everything is stored in perfect conditions
So yes originally back in the day VW used plain set screws for this particular application, but VW also supplied a coated version more recently as their stock changed and they became less anal about older fittings an just supplied the best equivalent. DIN933 should mean that the precise size of the bolt/threads etc... is pretty consistent allowing for coatings, at least that's my reading of it.
I'd rather use a DIN933 zinc flake 10.9 of the correct size from Brickie than a miscellaneous 8.8 from any old supplier as had been used on the OPs previously and which sheared easily upon reuse, most garages just buy mixed packs of bolts, not always even 8.8 and rarely the highest quality, in a mix of sizes but will cut to length if necessary just so they can replace fittings when they are damaged/lost, they don't go, oh these are 10.9s, VW part number is , 16mm length, we'd best order some of these in from VW for £1 each, as they just want to quickly complete the job, they rarely look up the torque settings, they use their experience or in many cases just use an powered tool or impact driver for speed
and as I said hygiene and residues probably more important than material coating
I am not an engineer so just using common sense and lived experience, I have done this particular job many times and never had a clutch cover come loose or sheared a set screw reused or new, and I've had to remove ones that have been oiled, loctited, overtightened or swapped for something else many times
never had this happen before.
one step forward 2 steps back
