hawke94

The brake pad picture came on in the center display and the red brake light came on in the speedometer. This was a few days after getting the 35k maintenance done. The SA said they did a brake flush and my front pads has about 50% left. I took the car back last night to ask about the brake pad message, they checked the brakes, and said the inner passenger front pad is low, about 3mm. During the 35k service, they checked only the driver's side, which was 50% left, so the issue never came up. They didn't know why only that inner pad was so low. They also did this quick diagnosis in the parking lot. I thought the wheel had to be removed to check the inner pads. They apparently checked the front pads and brake fluid on the parking lot in 10 minutes. Is that possible? Or are they feeding me a story? Is it possible that they messed something up during the brake flush?

Thanks!

Parsec

Why don't you take the wheels off and check the thickness yourself? Shouldn't take more than an hour to do both wheels and you will confirm whether they are feeding you BS or not. You can confront them and take your business elsewhere if you find something fishy with their story.

hookooehoo

Normally if the inner pad is thinner that means you have a piston in the caliper that is not operating correctly. I have had this a few times on other vehicles I have owned. you can either buy a rebuild kit and replace all the seals and what not or just purchase new calipers.

depending on how open our wheels are you can just turn the wheel and normally see both pads with out taking the wheels off if you have an open wheel design.

hawke94

Thanks for the reply. That's what I was looking for. I'm not the most mechanically inclined so I made an appointment with my local mechanic to do the front brakes. I'm fairly happy with getting 36k miles out of the front brakes. Is this a common issue with Audi? My wife's B6 A4 had the same problem.

Highpark

I sold my A3 with 1400000 KMs and still 50% of the original brakes left. Its all how you drive.

spijun

True, but depends on where you drive, if you have a lot of driving downhill much faster wears out brakes with automatic gearbox
I'm with A4 (manual transmission) replaced brakes 135,000 km, with the Q5(S-tronic) I replaced brake pads at 47,000 km

MP4.2+6.0

I just had the front brakes apart on my 2013 with the larger size rotors used on most of the Q5's. As in, the same for Hybrids, TDI's and 3.0T's at 345mms. 2.OT's are smaller but probably similar design, and SQ's use bigger rotors and one more piston. When I have time, a later post will explain the "why" I was tinkering (modding), but for this reply there was nothing "wrong" with them.

I found a more basic design than I expected. Basically high volume basic production vehicle, just sized up for the weight. The design will be similar to most of what is sold volume wise, though the sizing is more robust for Autobahn standards than the typical US or Asian designs. The net of it was it was only a single piston on one side (I expected two given the rotor and caliper size, but that two piston layout is only SQ I think). The piston is pretty oversize, presumably to spread the force across the pad more evenly plus give more fluid volume to absorb brake heat. But, what it's not are either at least two pistons on one side (the SQ, my prior A6 4.2 and current A8), nor is it remotely close to true dual or more likely quad or greater pistons on opposing sides (RS type stuff in Audis; aka high performance Brembos, BBK's, etc.).

Back to plainer English for the OP question/issue, these kinds of set ups with a single piston applying the force are floating caliper designs, so the other pad side (the outer side) has to move with the outer caliper mass on some positioning pins or slides as the pressure is applied. The rear design on all the Q's and most any Audi I have ever seen is the same too, just smaller and even more prone to the potential issues seen with the design.

The common issues come down to even pad pressure and wear. Two scenarios most often seen, with the caveat that 95%+ they work fine for most vehicles and drivers: One is that the sliding mechanism hangs up slightly, which can either result in slightly uneven force across the pads or simply one side sticking a bit more and not retracting as fully when the brakes are off. That means more pad wear on one side. The other more common issue is a pad wears at somewhat of an angle on at least one side. That variously can be because of a physical piece of debris cocking them off angle, poor assembly, worn parts, or simply a design issue where the piston is fairly small in size compared to the pad dimensions. For the last one, that can manifest itself more with the rear set up in my experience; the front pistons and pad mounting all looked robust and designed to minimize this.

Assuming parts (other than pads and rotors) aren't worn, the "fixes" are really just good cleaning of the relevant mechanical contact surfaces and lubrication of the siding pin elements where called for by the design (usually inside of rubber boots like in the back). Over time and assuming no bad/worn mechanical parts or assembly goofs, it's usually just road grit and other crap that can enter the sliding part area or a bit of corrosion that hang things up a bit. Beyond that, it comes down to the design quality. For the front I would say it's current quality design basic but solid and generously sized; for the rear it's pretty basic but standard Audi across all the models from low to high for 20+ years now. Across Audis in the back, the range of variants are mostly just vented rotor or not (only the base 2.0T is unvented IIRC) and the diameter of the rotor (pretty generous for the Q's regardless of motor).

hawke94

Thanks for the explanation. I have a much better understanding of how the brakes work now. Good to know that the design is more robust than the average car on the road.