How worn do the front brake pads need to be for the sensor to trip?
 

Just had my car in for it's 45K service and they recommended new front pads and rotors and new rear pads. Since my front wear sensors haven't gone off yet I'm curious, how worn do your pads need to be for those to go off?

45K sounds a little early for new rotors, but it depends on your driving & conditions, ...
 

as far as new pads, 45k is not unheard of, especially depending upon how they get used.
it's easy to eyeball them, and determine how close they are to being done. the sensor will light up with a safe amount of pad left, but the work should be done right away after you get the indication, especially if you brake enthusiastically.

for the rotors, it's a simple measurement, that determines when they should be replaced. it is <i>conceivable</i> that they are near that wear limit after 45,000 miles, but it sounds like a stretch.
if the dealer is recommending replacement, they should be able to provide you with the original thickness, the wear tolerance, and the actual measured thickness, so that you can make the judgement. if they won't give you these three numbers, shine it on.
do not let any shop convince you to have the rotors 'turned'. they should be replaced, or not, ... never turned.

also, there is little to no advantage, as far as labour time charges to have the rotors changed at the same time as the pads.

Re: 45K sounds a little early for new rotors, but it depends on your driving & conditions, ...
 

Yeah, 45K seemed reasonable for the pads, I'm also a little dubious about the rotors being worn just haven't had a chance to get under there with some calipers to measure for myself. It was mostly curiosity of when the wear sensors trip.

Aren't brakes covered under the OEM..........
 

......factory warranty? I have a 2006 A3 that is going in for the 45000 service soon, car is still under factory warranty. I thought everything, even wiper blades, was covered by the warranty on 2006 and earlier cars.

No--as of 7/2005 the warranty doesn't cover "wear and tear" items
 

such as brake pads, rotors, bulbs, wipers, seats, etc.