Brake levers go to the bar after sitting

[AbnormalWrench]

I don't know if anyone else has noticed this, but it is weird. I didn't have this problem until the rainy season started. I get done riding. I park the bike and everything is working fine. 5 days later I go to load the bike to head out to the ORV park, and my brakes act like they have air in the system. The levers go to the bar when trying to stop. I eventually figured out that if I grab the calipers and push against the sliders so the pistons get pushed most of the way in, then pump up the brakes, the problem either mostly goes away, or completely goes away. But then the next time I let the bike sit, it does it again.

I have been lazy about pressure washing the bike lately, which might be related. Never had a bike that would do that though

 

[Lost]

Eh?
That's a new one.
Only thing I can think of is possibly that air contracts under cold temperatures. The reservoir has a little air sealed in there. Maybe it's creating a small vacuum?

Id pump the brakes like you have previously, then open the reservoir caps and reseal. See if it happens again?

 

[Theo]

I eventually figured out that if I grab the calipers and push against the sliders so the pistons get pushed most of the way in, then pump up the brakes, the problem either mostly goes away, or completely goes away. But then the next time I let the bike sit, it does it again.

What do you mean by the "sliders"? Do you mean that you make the calipers float?
Have you checked that the brake fluid levels aren't getting too low because of worn brake pads? Maybe if they get too low the brakes start sucking air into the reservoirs and when the pistons are pushed in the levels rise again. Then you use the bike, the fluid expands a little because of heat and you don't have the problem until the bike cools down.

I didn't have this problem until the rainy season started.
[...]
I have been lazy about pressure washing the bike lately, which might be related. Never had a bike that would do that though

AFAIK, the problem with moisture is that, when the brakes get hot, the water will start boiling and becoming vapor, which is compressible. When the brakes are cool, though, water shouldn't cause this.

 

[AbnormalWrench]

I don't think there is air in the system, because if that were the case, pushing the caliper pistons in wouldn't do anything - that wouldn't get rid of the air in the system. I think the problem has to do with the brake pads. Something like mud is getting behind the pads, causing them to not fully seat. So you have to pump the lever to take up the slack.

It didn't do it this last weekend, so I didn't dig any further into it.

 

[AbnormalWrench]

Haven't been riding the bike much lately because of a weird computer problem, which I'll probably post about soon. But either way, went to move the bike this morning and had no rear brake at all and my usual trick to get it working again wasn't working. I was needing to do brake pads anyway, so since I was going to be taking it apart, it was a good time to figure out what the heck was going on. Brake fluid level was fine. Installed the new brake pads, but it made no difference, still had no lever. Tried to do manual bleeding but, it wouldn't build enough pressure to do anything. So did the reverse bleed procedure and that fixed it. I think I was somehow getting air into the master, but not sure how. Might have something to do with the brake pads being very low, but that doesn't really make sense either. But it is nice to have functioning brakes again.

 

[jcozine]

FWIW @AbnormalWrench, mine is doing the same thing after 1.5yrs, no change in weather and pads are barely worn, so I don't think those are factors. Stark is saying the seals are consumables but doesn't make them available separately, really irritating. Haven't had any luck searching. Anybody else know of a master rebuild kit for the Formulas?

I've had other brakes do this when the rubber starts to go off in them, sometimes you can fix it with fresh fluid but it always gets worse with time. Never had it happen so quickly though.

 

[AbnormalWrench]

My rear brake was a little soft for the first pull when I went to go riding Sunday - I've ridden it maybe 6 times since I replaced the brake pads and bled the master. So it seems to be a continuing problem for me also.

 

[AbnormalWrench]

Went riding yesterday and had no front brakes at all. The brakes were fine when I loaded the bike the night before. I almost crashed thanks to it, when I was going down a steep hill and another rider came around the corner. I started a ticket with Stark and sent them a video. I guess we'll see if they give me the same BS answer. If they do, I'm going to replace both master cylinders with something else.

 

[jcozine]

Dang the front ones too?? Thought those would be solid for being from a mainstream brand.

It’s crazy they take such a hard stance on replacing these, with them being safety-related parts and all, when Anton himself was publicly saying the formula brakes weren’t up the the task right after they debuted. Irritates me that early adopters just get stuck with stuff like this and the short kickstand. My enthusiasm for this brand is at an all time low.. might sell before the warranty is up