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Near emergency braking and brake pedal pressure

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Old 02-16-2017, 10:44 AM   #1
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Default Near emergency braking and brake pedal pressure

In near emergency braking situations, like when front traffic is slowing down a lot faster than you initially thought, I always need to apply a lot more pressure to the brake pedal than I thought I would need. So much more that I'm wondering if I would have not needed both of my foot if it would have been a real emergency braking.

I don't know if this "normal" of if there could be something wrong with my brake.

By the way, it's a SQ5.
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Old 02-16-2017, 04:07 PM   #2
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Warranty? Stock brakes, no mods? Take it to the dealership. And if they've got another SQ5 there, ask the shop if you can test drive that, along with yours, so both you and the tech can compare yours to what is normal.

No SQ5? Compare it to a plain Q5, the SQ certainly should stop as well or better.

If you do a 200' emergency stop and stop 6" short of a concrete barrier...you're safe. But if it took just one more foot, 201' instead of 200'...you'd be in the concrete.

Get a pro on it, get it in the shop.
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Old 02-16-2017, 04:08 PM   #3
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I'm not sure how to answer your statement because you didn't ask a question. There are too many circumstantial questions that could impact my answer

Do you know what ABS feels like in your SQ5?
Do you know what threshhold braking feels like in your SQ5?
Are you running OEM brake fluid?
Are you running OEM brake pads?
Are you running OEM brake rotors?
What tires are you running, and what road conditions were present when you experienced this?

Audis are known for great brake pedal feel, in my experience.

You don't *appear* to know a lot about your vehicle or its braking characteristics and I certainly do not want to come across in any negative way... so please help us help you by being more clear.

This isn't meant to be negative in any way, but your statement can't be answered from the way it has been stated, in my opinion.
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Old 02-16-2017, 04:19 PM   #4
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I see the question, which is if you get in over your head, will you need both feet on brake pedal?

The answer is no if your brakes are in order. There is actually an obscure new vehicle federal spec on this IIRC. AKA the little old lady lowest common denominator brake pressure test. It is actually among the reasons a lot of the high dust pads came to be for OE fitments IIRC, since semimetallic was a classic way to get there. Or at least that's what Audi said back in late 80's when a lot of owners brought it up.

And if BTW you are using aftermarket ceramics, some ceramics are known as "slippery." Knock on some of the Hawks for example on the Mini S enthusiast board I used to frequent, though others liked them. Net, if you are on any type of ceramics, you may want to try a different compound or get back to OE.

Last edited by MP4.2+6.0; 02-16-2017 at 04:23 PM.
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Old 02-16-2017, 04:23 PM   #5
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Yeah, not much specifics to go on here. I don't know what your point of reference is. A lot more than you thought could mean anything. But to put your mind at ease, these cars have emergency brake assist. In a real emergency situation the car will help you bring it to a stop. They have software that can detect an emergency braking situation and when detected it provides brake boost assist to bring the car to a stop in the shortest possible distance. If you step on the brakes and then suddenly you need to apply more brakes that's not an emergency situation. It may be perfectly normal. All depends on how linear the brakes are. I don't have any experience with the SQ5 brakes, but I'm personally a fan of linear brakes. Audis OEM brakes sometimes have a bit of a hockey stick response, which I don't particularly like.

Knowing what tires you have and what the weather is when this happens is very important. Your tires ultimately dictate how quickly you can slow down.

Last edited by superswiss; 02-16-2017 at 04:25 PM.
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Old 02-16-2017, 04:50 PM   #6
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My SQ5 is all stock regarding the braking system. Tires are DWS06 but since I didn't even reach maximum tire adherence, this is probably not the relevant. Brake have been inspected recently and are in good shape.

This bad feeling I have with the brake happens when I'm already on the brake (normal braking) and then need a lot more braking. I apply more pressure but braking force doesn't really increase. I then need to apply a lot more pressure. So much more pressure that I'm always taken by surprise.

Being 48 years old, I'm used to threshold braking and thus never jump on the brakes. Beside on very slipery surfaces, I never triggered a ABS system. Because of this, I suspect brake boost is also never trigerred

I will check with my dealer. Thanks for the comments!

Last edited by Yoshimura; 02-16-2017 at 04:57 PM.
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Old 02-17-2017, 02:18 AM   #7
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The brake fluid housing in your engine compartment has a filter. If you dont change the brake fluid as recommended it gets clogged (I dont remember the service change interval). That could cause maybe the problem you are experiencing?? I read this in a TSB some weeks ago. If that is the case you have to change brake fluid housing and brake fluid.

Last edited by apoelistas; 02-17-2017 at 04:52 AM.
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Old 02-17-2017, 09:54 AM   #8
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OEM brake fluid change interval is every 2 years. With a 2015 SQ5 he'll probably be due soon. The main reason brake fluid needs to be changed is because it absorbs moisture. Water has a much lower boiling point and is more compressible, so that results in either the brakes giving out sooner or soft break feel.

Good point, though. OP, you should probably go for a brake flush. You'll be due soon anyway and then see if that improves things.
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Old 02-17-2017, 10:19 AM   #9
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Quote:
Originally Posted by Yoshimura View Post
My SQ5 is all stock regarding the braking system. Tires are DWS06 but since I didn't even reach maximum tire adherence, this is probably not the relevant. Brake have been inspected recently and are in good shape.

This bad feeling I have with the brake happens when I'm already on the brake (normal braking) and then need a lot more braking. I apply more pressure but braking force doesn't really increase. I then need to apply a lot more pressure. So much more pressure that I'm always taken by surprise.

Being 48 years old, I'm used to threshold braking and thus never jump on the brakes. Beside on very slipery surfaces, I never triggered a ABS system. Because of this, I suspect brake boost is also never trigerred

I will check with my dealer. Thanks for the comments!
You could have a defective brake vacuum assist unit. With the engine not running, does the brake pedal go from easy to push to harder as you press it a few times? If the pedal pressure feels the same in this test then the vacuum assist doesn't seem to be working correctly. You can also have glazed rotors. On a country road brake very hard from about 50-55 mph, to almost zero, a few times, allow a minute or two while still driving between stops to cool the rotors.
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Old 02-17-2017, 10:33 AM   #10
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Quote:
Originally Posted by superswiss View Post
OEM brake fluid change interval is every 2 years. With a 2015 SQ5 he'll probably be due soon. The main reason brake fluid needs to be changed is because it absorbs moisture. Water has a much lower boiling point and is more compressible, so that results in either the brakes giving out sooner or soft break feel.

Good point, though. OP, you should probably go for a brake flush. You'll be due soon anyway and then see if that improves things.
This is my 3rd Audi and I have never changed brake fluid in the past and never had any brake performance issues. My last Audi A4 was 12 years old, sat outside all its life, had the same initial pads on it for 12 years that I replaced the OEM with Hawk ceramics in the first month of ownership. Great brake performance was the same over the 12 years.

My father has a 1988 Buick Park Avenue that he only drives on nice weekend days, 90K miles, same factory brake fluid in for 30 years. I measured the brake fluid water content a few months ago and it was less than 2%. Car brakes just fine.

Of all the well braking cars on earth, how many do you think change their brake fluid every 2 years?

Don't get me wrong, I respect changing brake fluid with high moisture content, but I use a fluid moisture gauge and when it hits 3% I would probably change the fluid.

If moisture content is such an issue why doesn't all manufacturers just use silicone brake fluid that won't absorb moisture and has a very high boiling point.
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