Here is a 'how to' on replacing front brake discs and pads.
I did this on my Laguna 1 phase 2,but the basic principles are the same no matter what car your carrying this out on.
The first thing to do is remove the cap from the brake fluid reservoir.This will save you spraying brake fluid everywhere or damaging the master cylinder.Also,make sure the keys are in the ignition,but with the ignition off.If your car has ABS the pump could be damaged if you have the ignition switched on.
Next,remove the front wheels and put the car on axle stands.Work on one side of the car at a time,and turn the steering to gain easy access to the caliper.
Next,remove the lower caliper bolt.
To do this you will need a 13mm spanner on the bolt and thin headed 17mm open ended spanner to stop the inner slider from spinning.If you haven't got a thin 17mm spanner,then it is possible to use long nose pliers or molegrips.
Once this bolt is removed,pull the caliper up and then slide it off of the top slider.
It's a good idea to support the weight of the caliper by either tying it up to the suspension leg or resting it on top of something so as not to damage the flexible brake hose.
Next,remove the two brake pads......
Next,remove the two 18mm caliper carrier bolts.They will be reasonably tight.....
Once the carrier has been removed,the two disc holding bolts will need to be removed.It is best to hit the heads of them with a hammer before trying to remove them as they are T40 torx bit headed bolts and they have a tendency to round off.Hitting them with a hammer loosens the treads and makes them easier to remove.
Tap the disc away from the hub,and this is what your left with.....
Next,the hub face must be cleaned with emery cloth to make sure that it is flat and smooth.If this isn't done,then the new disc will warp causing brake vibration.Once cleaned it should be nice and shiny.
It is now time to fit the new disc.They are covered with an anti-corrosion coating and this needs to be removed before the disc is fitted.A special product is available for this job,but any solvent based product that evaporates will do just as well.Bolt the disc onto the hub using the two bolts removed earlier(recommended tightening torque,15Nm)....
Next,clean the faces of the caliper carrier which the pads touch.This will stop the pads sticking in the carrier.
Next,bolt the carrier back on and tighten the bolts to 100Nm.The pads can then be placed into the carrier.It is a good idea to grease the contact patches between the pad and the carrier,and between the pad and the caliper.This helps prevent the pads sticking in the carrier and also helps to prevent brake squeal.There are special products available to grease the pads,and copper grease should NOT be used!.Also,becareful not to get any of the grease on the disc face or the pad friction face......obviously,the pad friction face goes towards the disc.
Next you have to squeeze the caliper piston back into the caliper.This can be done a number of ways,but I tend to use a large pair of water pump pliers.You have to be gentle when pushing the piston back as it is possible to damage the seals in the master cylinder or the caliper if you try and push it back too fast.This is also why you remove the reservoir cap as the fluid you displace goes back to the reservoir and needs somewhere to overflow if nesseccary.
Once the piston is fully back,you are ready to re-fit the caliper.It's a good idea to grease the sliders before re-fitting the caliper,and make sure they are both free and easy to move.Slide the caliper over the top slider and push the caliper down making sure that the 'see-saw' springs on the pads are against the inner face of the caliper.
Tighten the caliper slider bolt to 35Nm and you are 50% of the way there...
You must now gently pump the brake pedal to bring the piston into contact with the new pads.Push up and down on the pedal slowly,not going beyond half the pedal travel,until the pedal goes solid.
Once you have replaced the other side,do the same and check the fluid level in the reservoir.Adjust the level to get it to the maximum level by removing some of the fluid by either soaking it up with some absorbant paper or using a syringe if you have one.Re-fit the cap,and if any fluid has leaked out,wash off with water.
This is only a guide,and if you are not confident with a set of spanners please don't attempt this job.Your brakes can save your life,so please becareful.If you do have a go at changing your own discs and pads,take your time and double check everything.
After fitting the new discs and pads,avoid heavy braking for at least 200 miles to allow the pads and discs to bed in.
I hope someone finds this usefull,and I will update it again tomorrow as I'm sure I've forgotten a few things........