Rear pedal goes soft when not used for a time

I thought I remember reading on of the brake threads where this was mentioned, but of course I can't find it.

Problem:
Rear pedal will lose resistance and be soft when I press it after many miles of non-use. 1 full press and then the pedal firms up for the second press, rear brakes work as expected. After awhile (20 minutes?) the pedal will be soft again. After an overnight sit, the rear pedal is really soft, but on full cycle and it's good.

Tried:
Full bleed, but I may not have got the SMC tilited up as far as it should be.
Not losing fluid, pads are still plenty thick.

Front brakes are fine, not losing feel there. Back brakes are good too, once they get pumped up. Is there a valve in there somewhere leaking?

TIA,
T

What is that I hear - It must be alarm bells sounding in Igofar's garage!!!!

Sounds like air may be in the system...

It sounds like nothing more than air in a rear brake circuit. A good bleed by the numbers should firm up the brake pedal.

Happened to mine after they were bled at dealership. Took it back and they got more air out of system then it firmed up.

Did a full bleed by the numbers, just not necessarily the 20 deg. up tilt on the SMC. Guess I can do another, cheapest and easiest things to start with. But in the knowledge of understanding...

Well thinking that air and fluid don't mix, wouldn't the pedal stay mushy the whole time?

Or does the air get broken up. So the air bubble gets 'compressed' into the fluid when I pumped the pedal once. After 20 minutes or so it slowly comes out of suspension?

The air gets compressed when you work the pedal. Then the fluid slowly leaks back as you ride untill you press the pedal again.

Pump the front brake lever, hold it in and put a ty-wrap on it overnight. Pump the rear brake lever and hang a weight on it or tie it down somehow also overnight. See if that works.

Yep, I think... I think it does it if left in the garage for the night. Will need to double check. Stand on the pedal when I get home tonight.

Don't feel any pulsation in the rear, but I guess if it was a very small but even warp on the rear rotor I may not. Did check the bearings when I took it darkside, about 1,000 miles ago, they seemed fine at the time.

bdalameda said:

It must be alarm bells sounding in Igofar's garage!!!!

Click to expand...

LOL!!

I would guess it's air in the system too. Mine did the same thing until I did the first flush and bleed on the entire brake system. The rear pedal is solid now. I don't know what you used to bleed system with, I used a hand pump mity-vac. Definitely going to try Motion-pro bleeder next time. I would try bleeding again, like you said.
Good luck.

ST Gui said:

LOL!!

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Hello, you've reached Igofar's white courtesy phone, I'm out on a call right now helping a stranded person with a flat tire, but if you PM me a contact number, I'll call you upon my return and help you with your brake bleeding issue...and yes, it sounds like air in the system
IGF

Thanks Larry, will contact ya shortly.

Checked the pedal this morning while rolling down the driveway. The bike had sat for 2 full days and a half (don't like this time of year) and the pedal was soft, but not completely sinking before activating the rear brake.

So if the rear pedal sits for 20 minute it gets a little soft.
Sits for a few days, pretty soft.
Sits for a week, will go completely depressed.

But every time, the second push on the pedal and it feels just firm as she should be.

I would make sure you do the tilt of that front caliper. There is no way to get the air out of it unless you do this and could account for the issue.

T_C said:

Thanks Larry, will contact ya shortly.

Checked the pedal this morning while rolling down the driveway. The bike had sat for 2 full days and a half (don't like this time of year) and the pedal was soft, but not completely sinking before activating the rear brake.

So if the rear pedal sits for 20 minute it gets a little soft.
Sits for a few days, pretty soft.
Sits for a week, will go completely depressed.

But every time, the second push on the pedal and it feels just firm as she should be.

Click to expand...

As others have said, it's air in the system. I'll call you later tonight so we can chat.
The reason it changes is because your simply pushing air from one circut or area to another.
IGF

A great big huge word of [SIZE=]THANKS[/SIZE] to Larry (aka IGOFAR). :bow1:

He called me, not once, not twice but three times baby.

If he does half the work effort on bikes as that he puts into following up with the folks on ST-Owners that ask for assistance, that he never even met before, then the folks that get to make a trip through the garage must have some extremely well maintained bikes.

Thanks again Larry. When I make the trip down the coast I'll be sure to bring a beer and dinner with me to show some appreciation, or maybe just take ya to your favorite spot.
T

T_C said:

A great big huge word of [SIZE=]THANKS[/SIZE] to Larry (aka IGOFAR). :bow1:

He called me, not once, not twice but three times baby.

If he does half the work effort on bikes as that he puts into following up with the folks on ST-Owners that ask for assistance, that he never even met before, then the folks that get to make a trip through the garage must have some extremely well maintained bikes.

Thanks again Larry. When I make the trip down the coast I'll be sure to bring a beer and dinner with me to show some appreciation, or maybe just take ya to your favorite spot.
T

Click to expand...

The white courtesy phone has no limits...ok, so I was a pest calling you so much
Thanks for the kind words, did you get the brakes bled yet?
Larry

Nope.. not bled yet.
Between the new gal, charity ride meetings and that annoying thing called working for the goberment (to paymore taxes)... no time to do the fun stuff.

Tomorrow is my day off, but I haven;t finished my homemade bleeding tool and no helper around to open/close the valves.... wonder if I put some tuna on the wrench I could get my cat too?

Now that I say it I'mthinking I could tie a rope around the brake lever and a pulley.. hmmm...
Soon, very soon.

T_C said:

Nope.. not bled yet.
Between the new gal, charity ride meetings and that annoying thing called working for the goberment (to paymore taxes)... no time to do the fun stuff.

Tomorrow is my day off, but I haven;t finished my homemade bleeding tool and no helper around to open/close the valves.... wonder if I put some tuna on the wrench I could get my cat too?

Now that I say it I'mthinking I could tie a rope around the brake lever and a pulley.. hmmm...
Soon, very soon.

Click to expand...

Shameless Plug for Motion Pro Brake Bleeding Tool...Makes it a one person job, your cat could relax and just watch you work.

Igofar said:

Shameless Plug for Motion Pro Brake Bleeding Tool...Makes it a one person job, your cat could relax and just watch you work.

Click to expand...

I just picked one up. Haven't used it but will as I start to get things buttoned up for the riding season. Got another 6" snow this morning though and more on the way through the weekend. I also have a mighty vac so I will have to see which I like better.