Idrive is telling me I need new brakes at 25k miles

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padders
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Idrive is telling me I need new brakes at 25k miles

Post by padders » Mon Jan 22, 2018 10:45 pm

I know everyone's driving patterns and habits are different but my CBS on the idrive is telling me I need new front and rear brakes in the next 4k miles which will be at around 25-26K miles (my car is less than 3 years old). This sounds awfully soon to me, I believe that the CBS uses an estimation algorithm to warn of things like this but I have to assume it is being pessimistic. I believe from past experience that if I were to blindly agree to brake work then a dealer would likely insist on both pads and disks leading to a huge bill, or perhaps they would check and recalibrate but I would still like to check myself. Are the min wear measurements stamped on the disks like they are on some vehicles or can someone tell me what I should check to see if indeed I do need new pads and disks. I presume there is a min pad thickness which is still safe. I accept that I may need pads sooner than some drivers since I have active cruise which is heavy on brakes vs human driving.
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BFleming
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Re: Idrive is telling me I need new brakes at 25k miles

Post by BFleming » Tue Jan 23, 2018 8:33 am

There are 2 triggers for our brakes - the 'algorithm' one (controlled by one of the onboard computers) & the wear sensor on the pads. As far as I remember you get a yellow warning if you get the mileage trigger, and the red one if you trigger the pad wear sensor. Depending on how precious your service history is to you, you can use a Carly to reset the warning message, but this is only possible if the pad wear sensor hasn't been triggered. If it has, you obviously need new pads!
It is highly unlikely you will need new discs at your mileage, but pads are a distinct possibility. But as long as you know what you're looking at, a torch should help you establish pretty quickly what you need.
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Uncle Tupelo
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Re: Idrive is telling me I need new brakes at 25k miles

Post by Uncle Tupelo » Tue Jan 23, 2018 8:41 am

BFleming wrote:
Tue Jan 23, 2018 8:33 am
There are 2 triggers for our brakes - the 'algorithm' one (controlled by one of the onboard computers) & the wear sensor on the pads. As far as I remember you get a yellow warning if you get the mileage trigger, and the red one if you trigger the pad wear sensor. Depending on how precious your service history is to you, you can use a Carly to reset the warning message, but this is only possible if the pad wear sensor hasn't been triggered. If it has, you obviously need new pads!
It is highly unlikely you will need new discs at your mileage, but pads are a distinct possibility. But as long as you know what you're looking at, a torch should help you establish pretty quickly what you need.
FWIW, my wife's Mini Cooper needed new back pads and discs at 18k and new front pads (but not discs) at 26k. Appreciate that's not comparing apples with oranges, but there are similarities as the Mini warning systems are based on BMW's. We didn't believe the amber warnings for the rears and I reset the warning code a couple of times (using the secret menu as I didn't have Carly or Bimmercode) but it always reappeared very quickly.

Also not trusting the dealer, we had a local trusted independent we've used for years check and they confirmed that the pads and disks were nearing the end of their life. He said it wasn't unusual and they'd seen a few newish Minis require unusually early brake replacements. Their theory was that the stabilisation and ABS systems overused the brakes and wore them out. My alternative theory is that some BMW pads and discs are made of chocolate.
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padders
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Re: Idrive is telling me I need new brakes at 25k miles

Post by padders » Tue Jan 23, 2018 11:21 am

Both these responses are interesting. I am sure that the modern systems such as TC, ESP and active cruise/cruise with brake do punish the brakes much more so than on older more basic cars but I am reluctant to accept that brakes should be toast after 25K. As noted by BFleming I will check the pad thickness myself and try to see if I can find a min safe value on the net, unless anyone can suggest what this figure is? I will visit the dealer but want to be pre armed in case there is 20k life left in them but they are having a slow day in the workshop. Going on past experience, many dealers and even some independents will routinely recommend disks are changed with pads to prevent any issues bedding the pads in. Personally I don't think this is necessary unless there is a pronounced ridge on the disks or they are significantly worn or warped. If they need changing then so be it but I would like to to avoid this if they really don't. This is no track car, its a run about. I have something else for the silly stuff.

Cheers for the help.
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padders
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Re: Idrive is telling me I need new brakes at 25k miles

Post by padders » Tue Jan 23, 2018 12:05 pm

A bit of research suggests that the min pad thickness is either 3mm or 4mm (depending on who you believe, will use the 4mm) so that gives me something to work with. I believe the disk thickness tolerance is stamped on the disk at the hub so will check for that unless anyone knows off hand? Obv if there is only ~5mm of pad left I will get the work done but if it is more like 8mm I am less inclined and will ask for a iDrive adjustment.
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BFleming
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Re: Idrive is telling me I need new brakes at 25k miles

Post by BFleming » Tue Jan 23, 2018 1:53 pm

Do you have the 'normal' brakes or M-Performance ones (312mm diameter discs versus 340mm & blue calipers)? Either way...

Standard Front:
312mm disc has factory thickness of 24.0mm
Minimum disc thickness is 22.4mm
Factory pad thickness is 19.2mm

Standard Rear:
300mm disc has factory thickness of 19.9mm
Minimum disc thickness is 18.4mm
Factory pad thickness is 17.2mm

M-Performance Front:
340mm disc has factory thickness of 30.0mm
Minimum disc thickness is 28.4mm
Factory pad thickness 17.7mm

M-Performance Rear:
345mm disc has factory thickness of 24mm
Minimum disc thickness is 22.4mm
Factory pad thickness 17.0mm

I would assume those pad thicknesses to include the metal backing plate.
My last note is that if you let pads get too low, the adhesive bonding the friction material to the metal plate won't last long at all. I found this out on a track day in a previous car.
Last edited by BFleming on Tue Jan 23, 2018 5:17 pm, edited 1 time in total.
2013 BMW F20 114i SE
2013 BMW F11 525d SE
1983 Porsche 944

padders
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Re: Idrive is telling me I need new brakes at 25k miles

Post by padders » Tue Jan 23, 2018 4:46 pm

Very helpful, many thanks. I have std brakes but I see you have given options for both. As you say those pad thickness figures look like they include the back plate, the min figures I quote above obviously exclude that.
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