Brake upgrades for hill descending - Subaru Outback - Subaru Outback Forums
 
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post #1 of 6 (permalink) Old 01-06-2017, 04:21 PM Thread Starter
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Brake upgrades for hill descending

So I am approaching the brake fluid replacement interval and I've been wondering about getting DOT 4 (under the assumption that DOT 3 is probably what the factory puts in). I know this is usually a thing recommended for racing but it seems like it would also help for those long slow descents when you're too slow to get much engine braking. Am I totally off-base in thinking that?

Also any thoughts on brake pad upgrades for similar use cases (descending steeply for a long time)?I know @MiddleAgedSubie; started using HPS. What benefits are derived from using better pads off pavement?

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post #2 of 6 (permalink) Old 01-06-2017, 04:51 PM
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DOT 4 has higher boiling points, so it would make sense if you've been experiencing vapor lock with DOT 3 and you haven't been able to cure it by bleeding out the water.

High performance pads require more pedal effort when they are cold. If your trip allows you to heat them up with a few stops before you crawl down the hill they'll do great. If you're camped out at the top of the hill overnight and the way back down is a slow steep grade you may be in for a lot of footwork until the temps come up. It wouldn't take long, but it would somewhat increase the chances of a runaway in that warm-up window.



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post #3 of 6 (permalink) Old 01-06-2017, 05:19 PM
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Operating temp is a big performance factor with brake pads. Performance pads can actually really suck till they get hot. I typically have a fairly heavy car and we tow doing camping trips in the mountains etc. After nearly 300,000 miles in two Subarus, I found I do better with OEM. I get 60k out of the pads and it looks like my rotors will easily go over 100k. On the flip side my moms car identical brakes and rarely loaded with more than one person easily does 85k on the oem pads.

As for fluid keep in mind there are lots of membrains and gaskets in the brake system. A fluid thats not rated the same may contain stuff that could degrade certain parts causing issues. Even with my hard use and trailering I stick with the spec stuff. Zero issues related to that for lots of miles.
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post #4 of 6 (permalink) Old 01-06-2017, 06:45 PM Thread Starter
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Thanks guys! Good info there.
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post #5 of 6 (permalink) Old 01-06-2017, 06:52 PM
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Quote:
Originally Posted by teni View Post
So I am approaching the brake fluid replacement interval and I've been wondering about getting DOT 4 (under the assumption that DOT 3 is probably what the factory puts in). I know this is usually a thing recommended for racing but it seems like it would also help for those long slow descents when you're too slow to get much engine braking. Am I totally off-base in thinking that?

Also any thoughts on brake pad upgrades for similar use cases (descending steeply for a long time)?I know MiddleAgedSubie started using HPS. What benefits are derived from using better pads off pavement?
Brake fluid does not suddenly get water in it. Instead, the boiling point goes down starting the moment you open the can of DOT fluid and the water is pulled from the atmosphere.

Because of this, brake fluid should be changed AT LEAST every 3 years. (miles has little effect on brake fluid)

-----------

As for pads...

The Subaru factory pad material is Ceramic based. Ceramic is KNOWN to need warming-up before full braking power is realized. Also, ceramic is poor at dissipating heat. (instead, they hold heat against the rotors) Ceramic does not leave black dust all over your wheels.

Conversely, semi-metallic pads are much better at dissipating heat. They are considered more ' heavy duty'. They are more aggressive on the rotors and they leave black dust all over your wheels.
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post #6 of 6 (permalink) Old 01-06-2017, 08:05 PM
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Same thought here but I doubt that upgrading fluid alone will make a big difference.

My first San Juans trip got me thinking about a pad/fluid upgrade though I had no issues (but lots of noise, which happened only there, nowhere else). I have had a couple of occasions elsewhere where the brakes would go south after miles of non-stop braking off-road (though, again, no big issues, the stock brakes never gave up on me on an actual hill). On my second trip to the San Juans I had my current brakes and I felt much better.

On road, the combo of stock brakes and 225 65 17 GeoL ATS was not as good as I wanted it to be. My new brakes handle the heavy 225 65 17 KO2s with ease and they make the ATS look okay (the KO2 stops much better than the ATS in my opinion).

What I put on is Hawk HPS 5.0 pads. I am no expert but I have found them outstanding on and off-road.

I am using them with ATE typ200 fluid.

My HPS 5.0 were installed very diligently and make practically no noise (a tiny little bit at very low speeds, totally negligible and no noise at all in the San Juans, no matter what).

As mentioned above, performance brakes are not great when cold even though the HPS 5.0 seem better than older models. Gotta pay attention to this at really cold outside temps to avoid surprises. But all things considered, I would not want to look back to the stock pads (though they do last an eternity).

EDIT: as far as Subiesailor's comment, I am not sure if the ATE fluid helps. In principle it should if the car is taken to its limits, but the difference maker seems to be the Hawk HPS 5.0 which can handle pretty crazy temps. There is a temp chart published by Hawk.

EDIT 2: the HPS 5.0 dusting is not at all awful.

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