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Discussion Starter · #1 ·
I just purchased a 2009 528i a day ago. Today I noticed a brake light warning. It said my brake pads were at minimal thickness and that it was time to get new brake pads. I called the person I bought the car from. He said that it might be the car hasn't gotten use to my applying brake pressure. I'm planning to go on a roundtrip of approx. 300 miles.
Should I get the pads on before my trip? Take another trip or at have a break shop or dealer look at them?

Thanks,
 

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Discussion Starter · #2 ·
(folks, sorry about the confusion)

I just purchased a 2009 528i a day ago. Today I noticed a brake light warning. It said my brake pads were at minimal thickness and that it was time to get new brake pads. I called the person I bought the car from. He said that it might be the car hasn't gotten use to my applying brake pressure. I'm planning to go on a roundtrip of approx. 300 miles.
Should I get the pads on before my trip? Take another car or have a brake shop or dealer evaluate the pads ?

Thanks
 

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I just purchased a 2009 528i a day ago. Today I noticed a brake light warning. It said my brake pads were at minimal thickness and that it was time to get new brake pads. I called the person I bought the car from. He said that it might be the car hasn't gotten use to my applying brake pressure. I'm planning to go on a roundtrip of approx. 300 miles.
Should I get the pads on before my trip? Take another trip or at have a break shop or dealer look at them?

Thanks,
The person you bought the car from is blowing smoke up your arse. The brake warning could indicate a number of things such as minimum pad thickness or low brake fluid in the reservoir which could also be caused by a leak in the line.

If you don't have the knowledge or experience to check these things, then take the car to a mechanic for advice. By the way, the brake fluid is a special low viscosity type, not just the typical DOT 4 type.
 

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Lauryn: There are three braking system indicators on the dash and idrive.

1. Brake pad: This is caused by the physical wear of a sensor on 2 of the 4 wheels. When worn, the sensor must be replaced, it cannot be reset. You have about 20-25% of pad life left, and can drive safely for quite awhile before replacing the pads. Replace them, since if they wear completely they will fail to brake well and will destroy your rotors.

2. Brake fluid: This is a level sensor on your fill cap in the fluid reservoir. It's serious, check asap. Sometimes it's just a stuck sensor, but most often fluid level is low. This can be caused by a leak, or pistons traveling to their limits in the brakes (rare, because fluid should be replaced every 3 years). Check immediately.

3. ABS: Some failure of the ABS. Very rare. There are several failure points. but most commonly the Hall effect sensors; secondly the pump and controller. Dangerous, have it looked at at once.

Confirm that yours is the brake wear indicator. You can drive it. Get it fixed in a timely manner.
 

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I just purchased a 2009 528i a day ago. Today I noticed a brake light warning. It said my brake pads were at minimal thickness and that it was time to get new brake pads. I called the person I bought the car from. He said that it might be the car hasn't gotten use to my applying brake pressure. I'm planning to go on a roundtrip of approx. 300 miles.

Should I get the pads on before my trip? Take another trip or at have a break shop or dealer look at them?

Thanks,
The person who you bought the car is full off it. Applying brake pressure will not do anything to trigger the light.

We have pad sensors and when the pad is thin enough the sensors will rub off against the rotor and trigger the alert. You are at minimum pad thickness.

My guess is you might be ok for your trip as there is a little slack built into these sensors for replacement but your there so replace them sooner than later.

Also check your rotors, they may need to be resurfaced or replaced

Sent from my iPhone using Bimmerfest mobile app
 

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Discussion Starter · #6 ·
I found the inspection sheet from the certified technician who did the pre-sale inspection for me.
outer brake pad depth;front _9_mm, rear_6_mm.
Brake rotor thickness; front_31_mm,rear_22_mm.

I called the tech this morning and told him about the brake pad warning light. He said he'd noticed it during the inspection & that they didn't take time to clear it because there wasn't enough time. He said for me to bring it in & they would clear it. He described it as a 30 minute job. He said the brakes were fine.
 

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I found the inspection sheet from the certified technician who did the pre-sale inspection for me.
outer brake pad depth;front _9_mm, rear_6_mm.
Brake rotor thickness; front_31_mm,rear_22_mm.

I called the tech this morning and told him about the brake pad warning light. He said he'd noticed it during the inspection & that they didn't take time to clear it because there wasn't enough time. He said for me to bring it in & they would clear it. He described it as a 30 minute job. He said the brakes were fine.
Visit You Tube and find a video on how to reset brake light on an e60. Lots of videos there. It's a 1 minute procedure if you know which buttons to push.
 

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front _9_mm, rear_6_mm -- plenty of meat left...BMW specifies as minimum 3 mm
front_31_mm, rear_22_mm -- plenty of meat left...BMW specifies as minimum 28.4 mm front and 18.4 mm rear
 

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I found the inspection sheet from the certified technician who did the pre-sale inspection for me.
outer brake pad depth;front _9_mm, rear_6_mm.
Brake rotor thickness; front_31_mm,rear_22_mm.

I called the tech this morning and told him about the brake pad warning light. He said he'd noticed it during the inspection & that they didn't take time to clear it because there wasn't enough time. He said for me to bring it in & they would clear it. He described it as a 30 minute job. He said the brakes were fine.
What he described is a 4th indicator, which is supposedly a "condition based sensor (CBS)" that detects brake usage. The wheel sensor has two circuits at different sensor depths.

Until the first is worn off and opens, the CBS simply estimates wear arbitrarily. When the first does wear off, the CBS warns yellow and iterates at a different rate, until the second circuit is worn off. Then the CBS warns red that pad replacement is needed (even if it still has 10K or so).

Realistically, the only one that matters is the red warning. When triggered by wearing through by rubbing the rotor, you'll have about 10K miles left on the pads. The rest isn't very accurate.

The maintenance indicator he described is not a 30 min job to reset; it can be done in about 5 minutes. If you have Carly for BMW, it can be reset in a few seconds. Don't let them charge you for it.

Apologies for not including in the above list, but I've always felt the CBS's mileage estimates were useless so never considered them.

As twh says, you have plenty of mileage on your brakes and rotors.
 

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Well, the brake pad warning light isn't completely useless. The brake pad sensor is two stage. You first get a yellow warning and later it wears though to another level and you get a red warning. So, even if you ignored the yellow warning, the red one should get your attention.
 

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Pulled from some BMW doc...

Brake Pad Wear Sensors

Dual Stage

The outer side of the brake pad on the left front and right rear brake is equipped with a two-stage brake pad wear sensor. The housing is inserted in the brake pad. It is therefore worn down in the same way as the brake pad by the friction together with the brake disc. Consequently, the two conductor loops are also worn down one after the other. As a result, the electrical resistance at the connections of the sensor changes with the degree of wear:

• < 5 Ohms for new brake pads
• 470 Ohms on reaching wear stage 1
• >100 k Ohms on reaching wear stage 2

The resistance is measured by the relevant control unit and communicated to the corresponding driving dynamics system via the bus system. Here the wear stage is evaluated for the purpose of activating warning indicators and for the "condition based service" function.

Single Stage

The single stage brake pad wear sensor is also installed on the left front and right rear brake. It is mounted the same as the two stage sensor. The major difference is that the single stage contains a single conductor loop instead of two. Once the loop is broken the control module recognizes an open circuit and turns on the brake pad warning light.

Wear sensors should always be replaced when the brake pads are replaced along with resetting the CBS data for pad replacement.
 

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So, does the resistance level increase linearly as the pad wears, or is it a three-stage step?
 

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The way I read this is it only has three states: not worn, worn stage 1, worn stage 2. That is, it does not read intermediate values that correspond to continuous wear. But, once the first step is reached, the car's computer has some idea of how many miles are left in the pads and display that. The car has the date and mileage the pads were lats reset and can use that data to come up with something reasonable for what's left.
 

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Thanks. That makes sense. So the "mileage remaining" is arbitrary until stage 1 triggers --
 
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