clutch torque setting - shimming

[nicolas]

I am still trying to understand this topic and practice. and someone needs to explain it to me.
I know how to do it. but why and how do you come to the numbers and what does the clutch and disc do differently?
I am trying to make sense of it and the reasoning (or benefits and disadvantages) behind it.

[richie]

Bolt it all on like stock no shims, lock flywheel with lock tool, check break away torque[you need to bed disc in slightly if its all new so try to turn it against cover and flywheel at least one revolution] then shim cover out say 1mm, repeat checking break away torque, it should measure higher, then increase shim to 1.5mm, test again, repeat this in 0.5mm increments until break away torque no longer increases and even starts to drop.
Now you know maximum you can get with that cover and disc combo[you will find after it has done some miles usually it increases a little more] now you have to decide how much you actually need, [this is really down to experience & testing]. Usually you want the smallest amount you can use without it slipping in 3rd and 4th gears.

cheers Richie

[nicolas]

OK. that is what I have done.  as we added shims to decrease the grip. but is this the right way? say for instance I want 180Nm. I am well over 250 Nm without shims. so it increases as I shim it out. that is indeed what I noticed so we shimmed it ou further. and I shim it out even more to achieve 180Nm. it adds up to 2.5mm of shims to achieve this.

but now I ask my self if this setup is right? is shimming it out this far common practice or is the group or disc, or both too much for achieving 180Nm?
and one other question. if I find the maximum torque of my engine to be 180Nm, what percentage of safety do I need? if any, as it will more likely grip better when bedded in.

it still feels a bit backwards to lessen the tension, but I think it is to manage the slip and forces better.

[richie]

OK. that is what I have done.  as we added shims to decrease the grip. but is this the right way? say for instance I want 180Nm. I am well over 250 Nm without shims. so it increases as I shim it out. that is indeed what I noticed so we shimmed it ou further. and I shim it out even more to achieve 180Nm. it adds up to 2.5mm of shims to achieve this.

but now I ask my self if this setup is right? is shimming it out this far common practice or is the group or disc, or both too much for achieving 180Nm?
and one other question. if I find the maximum torque of my engine to be 180Nm, what percentage of safety do I need? if any, as it will more likely grip better when bedded in.

it still feels a bit backwards to lessen the tension, but I think it is to manage the slip and forces better.

yes that is correct, you are actually moving the springs in the cover to the correct place, with no shims you will notice the fingers on the cover are already inwards similar to they would be with the  release bearing pushing on them, as you shim it out the fingers move out to nearer where they should be. This is because the parts aren't a good match, you could surface the flywheel or the clutch cover to create the same thing[or use a thinner disc] but thats much more permanent than using shims.

Trial and error is the only way to find exactly what you need for grip as heat will change how it grips as well

[nicolas]

thanks. I did all the machine work on flywheels to achieve the vw specs... seems to be a non issue since you need to shim it out anyway... but that is a different topic. I am glad to be educated on this. and it is always good to know what and why I am doing something. thank you.