MeetTheRobinsons

2009 Q7 4.2 Prestige fully loaded. I have hit 20,740 miles. Bought pre certified used with 16,493 miles. I already have to replace breaks. Do i need to replace rotors yet? Previous owner is claimed to have lived in teh city and teh majority of his driving was city driving. the majority of my driving is long roads, not highway and not city driving.

Stealership tells me that my Q7 will need brakes every 20k miles and rotors replaced with every brake change. Is this true? I tried to get them to replace the brakes and rotor for free but they insisted that the Q7 passed with their pre-certified inspection and its not their problem that teh brakes and rotors need to be changed now because they dont knwo my driving habits. I found this a bit odd but i am nto sure.

any thoughts?

LOP

I'm at 25k miles and on original rotors but expect in the next 5k-10k or so to replace pads/rotors.

Now note: I do not activiate the automatic braking system as I feel it is too sensitive MAINLY and it burns the pads/rotors quicker.

I would expect if you have auto braking on full time to get about 20k out of pads. My volvo xc90 went through pads every 20k...but it would stop on a dime! consistently.

24wheeler

Pads and rotors only need to be changed when they are worn out. In the case of rotors, when they are thin or scored or warped.
Just replaced my pads after 40,000 miles of use. These were the second set and had plenty of meat left even though one of the sensors had been activated. The first set were changed at 20,000 on the front, probably only in order to inflate the dealer's profits.
The rotors are original and show little wear. They have a slight lip but nothing abnormal. Unless something goes seriously wrong, like warping due to water crossing with hot brakes or corrosion due to lack of use, they should certainly last for 100,000 miles and probably nearer 150,000 miles before they need to be changed.

Dealers do really like to change stuff that is perfectly good. The service intervals here in the UK are about every 15,000 to 18,000 miles so they really aren't going to get fat unless they can find expensive [and mostly unnecessary] extras to charge for.

Just like pads, the rotors do wear somewhat. If they don't last four or five sets of pads you should ask serious questions. Dealers rely on the ignorance and gullibility of their customers and some have a real laugh at their expense.

Jusforfun

the average pad life is 30500 miles. Ranging from 9k to 45k, figures taken from 29 reports on the forum.
The official rotor wear is 2mm.
The average rotor wear is about 1mm in 30k
That is not an official statistic, its just experience. Every case must be checked individually.
You may find they are grooved or smooth on observation. Look also for hair line cracks caused by rapid heat/cool cycles.
Generally rotors have been smooth enough for a second set of pads.
It is wise to replace teh sensors each time. They become brittle due to their constant exposure to heat and dust.
Experienced DIYers have succesfully re-used them but my own experience was not great. Next time I will just replace them as routine.
As rotors are made soft to balance wear with pads and improve braking performance it is unusual to get a third run of pads out of one set.
The front wear is way heavier than the rear.

24wheeler

As you can tell, I don't agree that only two sets of pads will see discs worn to the point of needing to be changed. I have 60,000 miles on and they will be good for 60,000 more.
If I were to have taken the car to a dealer or expressed any concern to any service centre, there is no doubt they would have tut-tutted, rubbed their chin and gravely advised a change of rotors last time, for no good reason other than to double their income.

A fool and his money are easily parted.

Jusforfun

Yes but when you take the amount of depth wear at each change you need to calculate the expected depth at the end of life of teh replacement pads.
With only 2mm wear as the given max most dealers will not go out on a limb to say they will still have less wear than that at 90k miles (expected end of 3rd set of pads).
Like you, mine looked very good so I left them... I am sure they have a good margin of safety but I will be cautious next time around and will probably also push the limit.
I suppose the simple answer to the OP is most people replace rotors at about 60k while they are still in great shape.

MeetTheRobinsons

So then I ask this,

At 20,000 miles and with my brake light on I shoudl be ok for at least another 5,000 to 10,000 miles for brakes and another 20,000 miles for rotors?

24wheeler

If your brake pad warning light is on, you should prepare to change your pads. Inspect them for any pads that are wearing faster than others and take remedial action as needed. Since you will probably need to take the wheels off to inspect the pad thickness anyhow, you might as well change all pads on the axle concerned while you are at it.
The other axle might be fine for a long time yet. Look and see.


The discs are unlikely to have adverse run-out or wear or scoring or corrosion unless there are visual or other symptoms. If they are anything but worn out, which they are unlikely to be at under 80,000 miles unless you are a beast driving, they can actually be skimmed/turned to restore the surface to as-new. But balance the labour cost of doing this in relation to the cost of new discs/rotors.

I have seen plenty of rotors last up to 150,000 miles sensibly driven. I have also seen them ruined within 20,000 miles, not due to normal wear but mainly due to deep scarring because pads were used when completely worn out.
I ruined a set of rotors once when the vehicle was left near unused for a year. The resulting deep rust pits reduced the braking efficiency to less than half of normal.

Jusforfun

I wouldnt go another 10 if the warning triggered after 20. But yes there is plenty of meat left on them. You also increase the chances of scoring or damaging the rotors te longer you leave to old pads. Pads are cheap and easy DIY.
The warning light is triggered by cutting through the loop in the sensor. Once replaced teh light will go off. No need for VAG-Com.
Chances are the rears are fine.

MeetTheRobinsons

[QUOTE=LOP;24262568]
Now note: I do not activiate the automatic braking system as I feel it is too sensitive MAINLY and it burns the pads/rotors quicker.
QUOTE]

For Automatic Braking System, how do you disable/enable it? I thought that was always on to help prevent lock ups and skidding.