Brake firmness/pedal feel

[wheelhaus]

I think I just need to do another extra thorough bleed. I might need to bleed he master cylinder, it ran dry once during a bleed and I believe we completely cured it, but I still wonder sometimes. There might be a small little something in there.

I've heard conflicting opinions on master cylinder bleeding, is it really necessary to remove it and do a bench bleed? I've cracked each of the fittings under pressure at the MC and ABS to do some point bleeding, but I wonder if I'm just paranoid.

[P86RAVES]

I think it's a characteristic Subaru's braking system. My previous car had the same pedal feel as this one.

There is this: http://www.chasebays.com/product/sci...ter-eliminator

Which might help, but I don't have any first hand experience to say that it does.

I do feel that the issue with the booster; like you said, pedal-down / off-pedal / and then back down leads to reasonable pedal feel. From that I'd guess it's something to do with vacuum.

When I built a 240SX with Z-brakes I used the booster from an Automatic S14, which was larger than the one form a manual car. The combination of parts let to a fantastic pedal feel over stock.

[Tbird232ci]

Originally Posted by P86RAVES

I think it's a characteristic Subaru's braking system. My previous car had the same pedal feel as this one.

There is this: http://www.chasebays.com/product/sci...ter-eliminator

Which might help, but I don't have any first hand experience to say that it does.

I do feel that the issue with the booster; like you said, pedal-down / off-pedal / and then back down leads to reasonable pedal feel. From that I'd guess it's something to do with vacuum.

When I built a 240SX with Z-brakes I used the booster from an Automatic S14, which was larger than the one form a manual car. The combination of parts let to a fantastic pedal feel over stock.

If there was a vacuum issue, you would lose assist. This means the pedal would get damn near solid and require more effort to press. There would be virtually no softness to the pedal if this were the case.

Bleeding the brakes wouldn't help much unless you exceeded the brake fluids boiling point, moisture got into the system, or air got into the system. While moisture getting into the system isn't uncommon, it tends to take years to happen. Most of the cars I've owned have been ~20 years old, and none of which had a measurable amount of moisture, but the fluid was heavily contaminated from rubber components breaking down. None of which we should have issues with. If you have air getting into the system, you have fluid getting out. That's typically easy to diagnose.

How worn are your rear pads? I'd hate to see someone throw an assload of money at parts when it could be a typical fault just by design.

[Tbird232ci]

Originally Posted by wheelhaus

I think I just need to do another extra thorough bleed. I might need to bleed he master cylinder, it ran dry once during a bleed and I believe we completely cured it, but I still wonder sometimes. There might be a small little something in there.

I've heard conflicting opinions on master cylinder bleeding, is it really necessary to remove it and do a bench bleed? I've cracked each of the fittings under pressure at the MC and ABS to do some point bleeding, but I wonder if I'm just paranoid.

I've changed quite a few master cylinders without bench bleeding them with no issues. Older master cylinders had cup shaped seals that would tear if they were actuated dry, and because the master cylinder couldn't pull fluid back to lubricate the seals, they would bind and tear. Most modern master cylinders don't have this issue.

[wheelhaus]

Originally Posted by Tbird232ci

I've changed quite a few master cylinders without bench bleeding them with no issues. Older master cylinders had cup shaped seals that would tear if they were actuated dry, and because the master cylinder couldn't pull fluid back to lubricate the seals, they would bind and tear. Most modern master cylinders don't have this issue.

Ok cool, I'll do a bleed this spring anyways, so maybe there's some air in there somewhere still. Maybe you'd be a good person to ask... I cant remember where I heard or read this, but someone was talking about brake bleeding and how the brake pedal should never go to the floor when you're pumping, because it will over-stroke the MC into an area where the bore isn't as clean and it can damage the seal. It sounds plausible but have you ever actually seen it?

[P86RAVES]

Originally Posted by Tbird232ci

If there was a vacuum issue, you would lose assist. This means the pedal would get damn near solid and require more effort to press. There would be virtually no softness to the pedal if this were the case.

I'm not saying that there is a lack of vacuum, just how the vacuum is handled. I don't know that there can be too much vacuum, but that is what it "seems."

With the Impreza, the brakes would engage before you could actually feel any stiffness in the pedal. Let's say at about 20% you could start slowing the car down and tell the brakes were engaged, but only at about 35% would you feel feeback from the pedal.

The FRS I'm finding is the same way. The brakes will engage, the feedback is limp until a certain point.

[Tbird232ci]

Originally Posted by wheelhaus

Ok cool, I'll do a bleed this spring anyways, so maybe there's some air in there somewhere still. Maybe you'd be a good person to ask... I cant remember where I heard or read this, but someone was talking about brake bleeding and how the brake pedal should never go to the floor when you're pumping, because it will over-stroke the MC into an area where the bore isn't as clean and it can damage the seal. It sounds plausible but have you ever actually seen it?

Sounds plausible, but unless you're fluid is heavily contaminated showing you have seals breaking down, I wouldn't be concerned with it. Most master cylinders have a hard coating in the bore so they don't tend to get damaged and crap doesn't stick to them.

It sounds like something you would hear from an old school mechanic would tell you, which isn't entirely a bad thing.

[kandiflippin]

Hate to revive an old thread but has anyone successfully fixed this and if so what was the issue? Same problem where my brakes are extremely squishy the first time i press the pedal but if I pump them they are 100%, I did a quick bleed once with no success, then I ran 32oz of fluid through the system incase there was any air trapped in the middle of the line, and finally today i swapped the OEM bleeders back on ( was using the speed bleeders) and ran another 32oz of fluid through everything. I saw the next suggestion being pads and rotors but everything still looks like it has alot of life left.

[Hyper4mance2k]

My guess is that there was just something wrong with my stock front pads. I threw the stock pads in the trash and it went away. I went with Winmax W1s, and they made a world of difference. I don't have the 2013 anymore; I bought a series.Blue and the problem wasn't nearly as bad as it was on my other car. The Winmax pads didn't make as much of a change on the new car as they did on the previous car.

However, I highly suggest adding a master cylinder brace. I got the GrimmSpeed which added more to brake feel than any set of stainless lines I have ever installed. With the car off, have someone with some leg strength step hard on the brakes while you look at the master. You will be amazed at how much deflection there is in our firewall.

[ryoma]

+1 on it being a worn pad issue. when I just put in a fresh set of W5's the brake feel was great with no mush. now that the front pads are worn down to about 30% and the rears at about 60% I get a little mush in the pedal even right after a fluid bleed. a second pump gets rid of it. however, I still get great pedal sensitivity but I just have to push the pedal down a little further before it firms up and behaves like normal. maybe about half an inch to an inch of mushiness before it firms up? somewhere around there.

[sessma]

I've had a 2017 Toyota 86 for a couple years (75k miles), and the brake pedal gets long after 10-15k miles. I found this very unusual until I noticed in the Owner's Manual that the brake fluid should be replaced every 30k miles. Replacing the brake fluid this often is not the norm for a production car, but it does correct the long pedal ... for a little while. Pumping the brakes as on the race track helps considerably ... and not a bad habit at all ... but should be unnecessary in a production car. My 2 cents.

[Pat]

Hmm...I have always heard street cars should get new fluid every two years regardless of usage. That's mostly in line with what your image shows.

[sessma]

Yes, that's a good idea to get rid of moisture and any air, but in my experience it's rarely listed in the maintenance schedule as a routine service.