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Question about bladder in SRAM ROAD brakes

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Question about bladder in SRAM ROAD brakes

Old 11-23-23, 06:16 PM
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Question about bladder in SRAM ROAD brakes

I have replaced hoses and bleed mountain bike brakes several times before but this is my first time with SRAM Road levers (hydro APEX1 cable shifting version). Front install went smooth I only needed to shorten the hose from the caliper side, run it though the fork.. then new barb, olive, attach and bleed. The rear was a bit more involved, I had to replace the hose and while it was apart I noticed the bladder or rubber reservoir was "sucked" not standing up but I got it back in place and did not give it much thought. I have bleed and re bleed the rear 4 times now, but the lever gets really close to the bar, it feels great, nice hard stop no sponginess just comes close to the bar. after I bleed I remove the syringe I notice a fair amount of fluid spilling out, and feel like its the bladder collapsing. Leaks during the final step of the bleed when you push DOT in as you slowly let the lever return, but no leaks using it once it all buttoned up, feels great but the lever is close to the bar.

Any idea what I should look at? would a deformed badder cause this? I feel like (total guess) a leaky fitting would get worse and fluid would would leak more as I squeeze the lever but thats not whats happening here.



Last edited by RayLee; 11-23-23 at 06:19 PM. Reason: add image
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Old 11-25-23, 02:57 PM
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sounds like you need the caliper piston to "self adjust".. i call the technique "Flicking the lever"... also required at times with Magura and other hyd, brakes...
the only thing that retracts the caliper piston is the tiny SQUARE Seal around the piston... it is not releasing from the surface of the piston well... it may have been assembled dry or the seal may have been made sticky with a solvent/cleaner... the trick is to outrun the retraction a bit...
i "Flick the lever" by pulling it in fairly rapidly while simultaneously sliding my finger off the end of the lever, thereby letting the lever SNAP back outward as fast as it can...

hey, it works.
kinda like "pumping up the brakes" after a brake rebuild on a car/truck, just in miniature.

the way to reduce the problem after rebuiding is to Coat The Piston and Seal with a light smear of Hyd. fluid. BEFORE assembly... or not over-clean the brakes in the first place...

you still might need to "Flick the Levers" some anyway

PS.. the "bladder" seal is a gasket and a way of helping reduce the chance of any air in the reservoir from entering the hose/caliper while a bike is bouncing along or gets inverted for a flat repair... the fact that it was extended when you opened the res. says that it was doing it's job as the pads wore down. There's a small chance that an improper fluid was introduced to the system making the Gasket get soft and expanded some.... This can be checked as you re-install the gasket/"bladder"... do the holes and/or edge line up correctyly to the seating surface? yes? it's fine.. no. they are outside their seating surface? Then you need a new gasket and a complete flush/drying of the system with isopropyl alcohol... allow one day for evaporation to guarantee complete drying... do NOT blow your breath or compressed air through the system.. your breath carries a LOT of Moisture... and the moisture content of air is hopefully stated in a comprehensive weather report.

Last edited by maddog34; 11-25-23 at 03:26 PM.
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Old 11-25-23, 06:00 PM
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thank you very much, these were "new" no retail box Apex1's (pretty old) and I feel they sat around dry for a long time. I will check the piston / do the flick. I am getting some leakage as well, the bladder was deformed and I did not clean it at all, just slapped it back in best I could. think I have enough info now to give it another go.

thank you again
Ray


Originally Posted by maddog34
sounds like you need the caliper piston to "self adjust".. i call the technique "Flicking the lever"... also required at times with Magura and other hyd, brakes...
the only thing that retracts the caliper piston is the tiny SQUARE Seal around the piston... it is not releasing from the surface of the piston well... it may have been assembled dry or the seal may have been made sticky with a solvent/cleaner... the trick is to outrun the retraction a bit...
i "Flick the lever" by pulling it in fairly rapidly while simultaneously sliding my finger off the end of the lever, thereby letting the lever SNAP back outward as fast as it can...

hey, it works.
kinda like "pumping up the brakes" after a brake rebuild on a car/truck, just in miniature.

the way to reduce the problem after rebuiding is to Coat The Piston and Seal with a light smear of Hyd. fluid. BEFORE assembly... or not over-clean the brakes in the first place...

you still might need to "Flick the Levers" some anyway

PS.. the "bladder" seal is a gasket and a way of helping reduce the chance of any air in the reservoir from entering the hose/caliper while a bike is bouncing along or gets inverted for a flat repair... the fact that it was extended when you opened the res. says that it was doing it's job as the pads wore down. There's a small chance that an improper fluid was introduced to the system making the Gasket get soft and expanded some.... This can be checked as you re-install the gasket/"bladder"... do the holes and/or edge line up correctyly to the seating surface? yes? it's fine.. no. they are outside their seating surface? Then you need a new gasket and a complete flush/drying of the system with isopropyl alcohol... allow one day for evaporation to guarantee complete drying... do NOT blow your breath or compressed air through the system.. your breath carries a LOT of Moisture... and the moisture content of air is hopefully stated in a comprehensive weather report.
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