740 Front brake pads
 

Hello,

I had noticed that one front wheel was always coated in brake dust a lot more than the other, so I ordered new brake pads and a new tub of copper grease, after changing the pads the front calipers needed bleeding, just a thought if any one has this before, at least both front wheels rotate freely now anyway.
I used the YouTube video that was previously posted, and luckily they were the same calipers as mine and very helpful.


Andrew

A good job well done! :thumbs_up:

Also worth checking your guide pins to make sure they're not sticking and are well lubed - two schools of though, after the intial cleaning with a wire brush in a drill or similar, either use copper grease or silicone grease/red rubber grease.

One school of thought says copper grease can make the rubber bellows on the guide pins go soft and manky, the other says it doesn't. I've never had a problem with copper grease doing that so i wouldn't mind which i used out of the three.

Also worth noting that if you have ABS, you should open the bleed nipple about 1/4-1/2 turn while pushing the piston back to prevent dirt being forced backwards up the brake lines to the ABS modulator and/or the master cylinder then bleed afterwards.

It's good practice to do it whether you have ABS or not but almost essential with ABS - either way it make pushing the piston back into the caliper much easier! ;) :D

740 Front Brake Pads
 

It was surprising just how much resistance was on the wheel in question. Also how much the pads had worn down compared to the other side. Hopefully will see a bit of a drop in fuel consumption now.:teeth_smile:

I use copper grease on all the metal to metal contacts, edges of the pads, shims and the inside of the pistons but silicone grease on anything rubbery like the guide pin dust covers.

If you consider that across the two front wheels, they have to do the job of stopping most of the momentum of 1500kg traveling at any given speed, with the rear brakes just there for stability really, there will be a lot of resistance on the front brakes even if they're only slightly on.

It will of course wear the pads pretty quickly as well.

I'm surprised you didn't feel the steering pulling to whichever side was stuck?

Also worth checking whether the pistons themselves are sticking. I found one of them was on my 740, the dust seal had been damaged in the past at some point and despite a number of attempts to clean it up and lubricate it, the calliper was still dragging and causing the brake to run hot. There was obviously dirt or debris that was stopping the piston fully releasing.

In the end I had to fit a new calliper.

740 Front Brake Pads
 

I know what you mean, it is strange, even before changing the pads, I tested under harsh braking, it pulled slightly to one side, but I certainly didnt have to grab the steering wheel. Even whilst towing a caravan it performed as usual. Going on a 800 mile run in the next few days, so will see how it performs, will take a note of the MPG figures as well for the post about that, see if I can beat the 38 MPG think it was.

If the pads are dragging the disc because they are for example sticking in the caliper but can be forced onto the disc by the piston, let's say when they're dragging they give 10% of the available braking force but when the brakes are applied, they give 100% of the braking force. The other caliper that is free to move goes from 0 to 100% of the available braking force.

As such, under harsh braking, the constant drag is overcome by the full force of the brakes on both calipers so unlikely to pull under braking - just while driving.

Quite often with new pads, there is a burr on the edges of the back-plate - this needs taking off with a file before fitting and also it's good practice to wire brush the mating surfaces of the inside of the calipers where the pads sit to remove any corrosion.

Highly possible whoever fitted the previous pads did niether of these two simple tasks which can lead to the pads sticking in the calipers.

Another useful little task is to wedge a file in the caliper so the file is resting on the edge of the disc, where the lip builds up from where the disc is worn. Put some pressure on the handle of the file and then using a screwdriver, spanner or similar long, flat tool between the wheel studs, turn the hub/disc so the file rubs off the lip on the dege where the pads don't contact.
Don't forget to do the inboard edge of the disc as well.

A few "silly" jobs there, on their own, each job doesn't contribute much to a "nice" braking system but together, they make a big difference, improving long term reliability as well. :thumbs_up: ;) :D

Concur to all of the above. Silly little extras but they all add up. I try to clean/service the brakes once a year. If they are done regularly they don’t take long and there aren’t any surprises.

940 tdi auto 1995
 

hi all
one of my dust seals on the front wheel is slowly coming out of the caliper over the years . all original parts i clean all the bits i can yearly remove guide pins and clean and regrease but ive never had the callipers of the car ive done discs on front twice now in 19 years but the clapper dust seals look a bit daunting as it woud mean new hoses too . i have been thinking of getting new/reconditioned callipers from some where like BIG RED or BRAKE PARTS UK
all comments welcome