Brake pads

[dh58]

The brake pad light came on today saying that they are worn. Does anyone know how long I have to replace them?

[vtl]

Have you had a look at the pads through the spokes of the wheels? No pad meat left and down to the wear sensors?

If you wait too long you'll probably start scratching up the disc and ruin the wear sensor as well.

[yawn]

I was always under the impression the wear sensor needed replacing the same time as the brake pads because they get worn down too. Or am I totally wrong?

Mine has a countdown of kms prior to them needing replacement.

[froop]

Once the wear sensor goes, you have maybe another 20,000kms to go on those pads with normal street driving. If you're going to be tracking or driving them hard through the mountains or something then I would change them much sooner than that.

[dh58]

Thanks guys. Gives me time to get an order from schmeidmann

[RadiuM]

Originally Posted by sharkatron

I was always under the impression the wear sensor needed replacing the same time as the brake pads because they get worn down too. Or am I totally wrong?

Correct.

[froop]

Originally Posted by sharkatron

I was always under the impression the wear sensor needed replacing the same time as the brake pads because they get worn down too. Or am I totally wrong?

Mine has a countdown of kms prior to them needing replacement.

From my understanding, the wear sensor is a simple open circuit enclosed in plastic. What happens is as the brake pads wear down, so does the plastic, until eventually the open wires touch the rotor itself and complete the circuit. At that point it triggers a km countdown in the service computer of the car to tell you how many kms left on the pads.

To be honest, the amount of kms you can drive after the countdown is completed is probably another further 20,000kms. I've done this on my E88 and I still have about 2mm of material left. Definitely not enough to confidently do any hard driving on but I only daily this car so for me it's fine. I've got a new set of pads and rotors waiting to be installed anyway.

[flinchy]

the wear sensor only NEEDS replacing if it's triggered. It's just cheap to do it just in case anyway.

the normal km countdown is just an educated guess, until the sensor is triggered and it knows they're actually low. I think after a little while the sensor totally gets worn through and breaks anyway. haven't experienced that though.

i was told i had 5000 to go on my pads at one service, mechanic guaranteed it.. got another .... 25?kkm out before changing, and they still had over 1cm left, and hadn't triggered the sensors.

[froop]

Originally Posted by flinchy

the wear sensor only NEEDS replacing if it's triggered. It's just cheap to do it just in case anyway.

the normal km countdown is just an educated guess, until the sensor is triggered and it knows they're actually low. I think after a little while the sensor totally gets worn through and breaks anyway. haven't experienced that though.

i was told i had 5000 to go on my pads at one service, mechanic guaranteed it.. got another .... 25?kkm out before changing, and they still had over 1cm left, and hadn't triggered the sensors.

You changed your pads with more than 10mm left on the pad?!? If that's the case they were hardly worn at all. Did you mean 1mm?

[flinchy]

nah. well maybe not 10mm, but it wasn't so close to dead you'd be worried. probably more like 5mm now i think of it, you're right, 10mm is a lot. it was a while ago

had the parts to do the brake job so just did it.

[yawn]

Don't want to go too OT but should rotors also be replaced at the same time? If not what is the minimum thickness? I've heard every second brake pad change to change rotors...

[froop]

Originally Posted by sharkatron

Don't want to go too OT but should rotors also be replaced at the same time? If not what is the minimum thickness? I've heard every second brake pad change to change rotors...

The general rule is every second brake pad change. That is what they do at BMW. I'm sure there is a minimum thickness as well but I don't know it. I think DR-JEKL knows though.

[Chandon]

Originally Posted by froop

The general rule is every second brake pad change. That is what they do at BMW. I'm sure there is a minimum thickness as well but I don't know it. I think DR-JEKL knows though.

They're not changed every second time - the minimum rotor thickness is engraved on the hub and you can usually see what it is, you do need a tool to measure it though.

[froop]

Originally Posted by viciousgook

They're not changed every second time - the minimum rotor thickness is engraved on the hub and you can usually see what it is, you do need a tool to measure it though.

Ah that makes it easy if you got a tool then. Generally how many pad changes does it take to reach minimum thickness though?

From my experience, when I was going through the dealer I was getting the rotors replaced every second pad change.

[flinchy]

every second pad change with reasonable driving is still a LOT of kilometers.

[yawn]

Originally Posted by flinchy

every second pad change with reasonable driving is still a LOT of kilometers.

I think this is key here. I'm about to change my rears for the first time and I'm at 95000km. I wouldn't say I drive like a granny either lol...

[A'PEXi]

If you check the part on realoem etc, it will tell you max/min thickness for the rotor of the OEM part.