Parking Brake Service Lock - what is it ?

[portculisz4]

Having just failed the MOT with ineffective handbrake (less than 50%) I have just removed both rear discs and found severe corrosion on brake pads and inner disc surface, so just about to fit new parking brake pads and new discs. I have a question relating to the item referred to as the Parking Brake Cable Service Lock', what exactly is this and what is its function in setting up the parking brake adjustment ? I have read the Pelican Guide on enabling/disabling the lock but it gives no explanation as to why this needs to be done.

My parking brake adjustment with the old disc and pads appeared to be OK (3 clicks to enable the brake) but the brake was just inefficient for obvious reasons, I was hoping just to replace the necessary components and then adjust through the wheel as per normal procedure, do I really need to do any adjustment at the handbrake end ??

 

[colb]

The service lock takes the tension off the cables at the lever end of the handbrake to enable correct adjustment of the shoes using the adjusters inside the drums through one of the wheel bolt holes with a flat blade screwdriver to flick the adjusters up and down to lock the wheel then back them off for free rotation. Follow the Pelican Parts guide and you should be ok and achieve a decent handbrake operation. Probably worth taking the disc/drum off and clean them and the shoes before starting the adjustment process.

 

[portculisz4]

Many thanks for the response. Due to the crappy condition of the drum surface and the shoes (the handbrake has always been lousy since I bought the car) I have decided to renew both. I did not touch the handbrake end but have adjusted the new shoes (through the drum hole) and seemed to have achieved full brake pressure within 3 to 4 clicks of the handbrake so hopefully this will clear my MOT failure this time around.

 

[Rockhopper]

The risk of not releasing the service lock is that they will be over adjusted and will drag when the handbrake is off.

 

[enuff_zed]

I had one where no matter what I tried I could not get that service lock to engage. All I did was revert to the old '70s Ford drum brake method.
Pull the lever up to the first click and then adjust the shoes until there is a slightly audible rub.
Check the lever and it should go tight after two or three more clicks.
When you let it off it is going past that first click you adjusted it at and therefore should not cause any binding.

 

[portculisz4]

Thanks for all your replies and suggestions. Must admit, in my ignorance on this feature and in a hurry to get the car ready for its MOT I have just gone ahead and adjusted for locked drums and then backed off about 10 clicks without touching the handbrake lever itself. Have driven the car for about 20 miles now and checked each wheel which appears to be totally free with handbrake off and fully on after pulling handbrake up by about 4-5 notches. I still think the Z4 handbrake is inefficient compared to many other cars I have driven, but there we are, we're stuck with it (at least no problem with my MOT this time around)

 

[Rockhopper]

I said the same to my MOT man but he said mine was actually quite good. Handbrake efficiency pass for the MOT is woefully low though.

 

[colb]

Mine is adjusted to three clicks, it's not the best mechanical system to work on and get right. Always engage that cable lock to take the tension off before adjusting the shoe's end. Well worth taking the Disk/drum off the car and clean the drum surface and shoes with brake cleaner. I take the adjusters put and clean and copper slip them so they work freely when turned. Also check the cables for any damage splits in the outer covering that will have allowed water ingress to the inner cable and set up corrosion inside. Replace any suspect cables you find. Clean and copperslip the mechanical linkage that the cable operates at the bottom of the shoes to endure free movement. Only then turn attention to adjusting. Note Pelican Parts how to advises back off the adjusters 6 or 7 clicks after you get the drum locked up that should give you about 4 Or 5 clicks at the lever, in practice I found that was to many and readjusted till I got three clicks and a holding handbrake.