Member Since: 11 Nov 2012
Location: yorkshire
Posts: 70
EPB - (P) red light flashing - changed rear discs.
Low mileage D4 on 35kmiles.
I had an intermittent park brake (P) red light flashing after putting on or taking off the EPB. The actuator on handbrake sounds good. When releasing footbrake there seemed quite a bit of 'lurch' forward when parked on slope, nothing excessive, but more than I remember. I then put car in park gear.
The rear discs probably have 5k miles left on them but as I need to get to the park brake shoes I thought I would replace.
The rear left disc came off, following procedure to mount EPB and release tension on shoes using ratchet (needs winding downwards, top to bottom using flat screwdriver).
There was a lot of brake dust at the bottom of the brake disc (inside it). Only when I moved onto other side (rear right) it seemed an excessive amount of dust, a matchbox volume of brake dust.The brake dust seemed to get between the park brake shoe(s) and the inside surface of the brake disc.
I measured the thickness of the park brake shoes, some parts are thicker than others by intention, but other parts of the shoe are uniform. I measured 5.6mm to 6.2mm for rear left.
Rear right park shoes were over 6mm to 6.6mm
So, more wear on rear left park shoes than rear right park brake shoes. No unusual noises during driving etc.
I read there is 2mm of usable friction material on the park brake shoes. I can't find any info on the thickness of new park brake shoes. I suspect they might be 7mm when new.
Anyone know thickness of new shoes?
I have put one side back together (ratchet tightened and backed off 8 clicks and 4mm Allen key slackened half turn and disc rotated X2 whilst tapping with mallet to even tension of shoes around brake disc.
4mm nut tightened to 6nm after.
I need to bed in old shoes to new discs tomorrow after latching EPB using OBD tool.
Condition of shoes, springs (rust free) look good. When do most D4 users change their park brake shoes?
Any advice appreciated.
12th Nov 2022 11:04 pm
Moleshome
Member Since: 15 Oct 2020
Location: Wokingham
Posts: 412
I may have misunderstood the operation of the parking brake completely so this could be totally wrong.
The parking brake is an entirely separate mechanism to the main vehicle braking albeit one that makes use of a combined drum/disc. the only time that the parking brake comes into play is when the vehicle is stationary and therefore there should be minimal, if not zero, wear to the pads. If you're getting large amounts of brake dust in the parking brake assembly it can surely only be because the parking brake was not adjusted correctly and the shoes have been dragging on the drum.
12th Nov 2022 11:30 pm
popsdosh
Member Since: 09 Nov 2009
Location: cambs
Posts: 442
I think you will find that 2mm refers to the minimum friction material thickness before they need replacing . Just replaced my rear disc for the first time at 85k and the handbrake shoes were hardly worn. to be honest with new disc and old shoes I didnt need to go through the bedding in procedure and they held perfectly straight off. The bedding in is more likely to be needed with new shoes. The different amounts of dust may be because more dirt had got in one side than the other and you obviously had an adjustment issue as you were getting red lighted. mine get adjusted maybe every six months . Its the best preventive thing you can do to stop EPB issues. You can blow out dust and check lining thickness without having to remove the disc.
12th Nov 2022 11:45 pm
bmbmdmb
Member Since: 11 Nov 2012
Location: yorkshire
Posts: 70
The park brake shoes need bedding in if the park brake shoes or the brake disc are replaced. They a mating surface and there surface needs to complement to allow max surface area contact.
It did indeed need adjusting, the EPB shoes!
I think 85k miles is really good. My dad doesn't hammer the brakes yet I don't think he would see 40k miles. The inner surface of the rear left disc was showing scoring I've seen a few thousand miles before the disc friction material is worn. The pads had 2 or 3mm left before the wear sensor got wrecked. The LR technician told me the rear 350mm discs are thinner and the vehicle will apply brakes to the rear first on light braking.
I put everything back together today and need the adjustment of the EPB shoes like in Bodsys Brake Bible. The Powerful YouTube videos are useful too.
After getting the EPB bedding in mode (footbrake pressed and released X2 and on 3rd press hold, within 10s EPB button pulled up X3 and pressed down X3)
I found the rear left brake was doing a lot of the stopping using EPB switch, based on noise. By time I got to the 5th EPB pull the handbraking was keen on both sides of rear. It is essential to leave time to allow rear brakes and the EPB actuator (above centre of rear axle) to cool. By time I got to 8th handbrake pull from 20 plus mph the vehicle was stopping very well (enough to throw me forward at a near stop). On the last pull the vehicle locked both rear wheels (in a straight line). I think there were pine needles on road but you get the point, the brakes were only getting better ,(and I was going uphill).
I thought this vehicle's handbrake was great, point is, until you do the bedding in you don't know what you are missing!
I took vehicle for a 5 mile around trip to cool down the brakes after the 10th pull on EPB switch. The rear discs were as hot as front discs get in summer after a good use.
The EPB bedding in mode didn't cancel until I exceeded 30 something mph.
Yes, 2mm of usable friction material. Without knowing how thick the park brake shoes are to start with I can't work out whether the shoes were nearly worn out.
I think you are correct, adjusting park brake shoes is important. The vehicle hasn't seen offroading yet it needed some TLC. The adjustment alone wouldn't have got rid of the brake dust floating around so consider removing the rear brake disc. Despite ,'mounting' the EPB I still needed to use flat screwdriver to remove the rear disc by finding the adjuster ratchet and moving it up or down which I think works opposite way of rotation depending on which side of rear axle. So rear left was top to bottom on ratchet and rear right was bottom to up. But don't quote me.
I think the park brake shoes (kit) will need replacing either before or when next rear disc is replaced.
I scanned obd tool and no errors. Success. EPB seems to come quicker and shorter time.
Anyone confirm park brake shoes thickness when new that would be great.
Thanks
Photo showing park shoes without rear brake disc, caliper, carrier, pads etc
Ps the faces on people's faces when they see the same vehicle for the 10th time driving around estate and coming to a stop for no foreseeable reason is memorable...lol!
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