I have struggled with this a few times and last time I did it I spent a bit of time trying to understand it. I think I know what is going on now and will try to explain it here. These directions relate to a right-hand drive car, i.e. when I refer to drivers side I mean the right hand caliper.
Before I get down to the actual steps involved, it is important to understand the relationship between (i) how far the cable-end is screwed up into the car (ii) the travel of the handrake lever in the car and (iii) the effectiveness of the handbrake.
The lever on the drivers side (right) calliper seems to move through the full arc of movement almost regardless of how far the handbrake cable is screwed into the car.
The passenger side (left) calliper is a lot more affected by how far the cable is screwed up into the car. The further the cable is screwed up into the car (i.e. the more thread that is showing) the further the lever on the calliper travels when the handbrake in the car is pulled on - i.e. the lever on the calliper travels through its full arc and therefore potentially offers more pressure on the brake pad. However with the cable screwed a long way up into the car the travel on the handbrake lever in the car can become excessive (i.e. the lever points to the roof before the pads stop the disks moving). As you screw the cable adjuster into the floor this acts on the passenger side calliper and puts its some way into its arc of movement, i.e. it starts to apply the handbrake. This reduces the distance you need to lift the lever in the car but also closes the gap between the pad and the disk. To keep the all important 0.1mm gap you have to back the piston off a bit. The net result being that handbrake lever is already part way through its arc of movement before you have actually applied any pressure to the pad and this inturn means that you now have a reduced arc of movement and it may no longer be enough to put sufficient pressure on the pad to stop the disk moving. In summary it looks like you have to find a compromise between how far you pull the handbrake lever and how effective you want the handbrake to be on the passenger side calliper.
Clear as mud?
Anyway. With that in mind. Here is what I do when adjusting the handbrake:
- Jack the front of the car up until both wheels are off the ground (it makes it easier to check if the handbrake is working on both wheels later in the procedure)
- Release the handbrake (if not already released)
- Make sure there is a 0.1 mm gap (or measure by feel as advised above) between all pads and the disks.
- Engage the handbrake.
- Did the handbrake act fully on both disks, i.e. are both front wheels unable to rotate?
If yes, go to step 8.
If no, remove the passenger seat (optional but makes adjustment much easier) then go to the next step.
- Check if the handbrake lever on the calliper has travelled through its full arc (i.e. is the lever hard up against the pin that limits its travel).
If it isn’t, get back in the car and screw the cable further into the floor (this will increase the arc of movement by making the end point of travel for the lever further away from the start point)
If it is, wind the cable out from the floor a bit (this will increase the arc of movement by moving the start point of the lever back a bit)
Note: How much to screw the cable in/out is trial and error but be aware of the compromise discussed above - start small. Also, if the levers are passing through their full arc of movement already (i.e. it is hard up against the pin and the beginning and end out its travel I don't think there isn't any point making any adjustment. I could be wrong but I think the cable must have stretched and needs replacing - good luck with that!).
- Go back to step 3.
- Is the travel of the handbrake lever in the car excessive?
If yes, wind more of the adjuster into the floor and go back to step 3 (you can get into and endless loop at this step and if this starts to happens you have to find a compromise between handbrake travel and brake effectiveness that you can live with)
If no, you have won this battle (thank all that is holy to you)
- Lower the front of the car
- Refit the passenger seat.
It is complex and difficult to explain but this procedure works for me. It is still a pain in the arse but at least it takes a lot of the guess work out of it.