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Posted

Don't put too much money on it since contaminated brake fluid is still incompressible.

yes on paper....heat it up with I don't know...hot rotors and see what happens with moisture that contaminated the brake fluid.

.....

 

 

 

demmit...just fell into the same trap as cpt

 

smile and wave.....smile and wave

Posted (edited)

I also had a lot of trouble recently getting rid of air on my Juicy 3, especially the rear brakes.

 

Found that you need to use the procedure in the manual rather than the video on the SRAM website if that helps at all.

 

Lots of tapping on the housings and I even loosened the caliper housing from the frame and held the bleed hole upright while sucking with the syringe to remove all small bubbles.

Edited by CapeLandy
Posted
Disc = non-compressable

Pads = non-compressable

Brake line = distortable depending on material but for the moment let's say non-compressable.

Brake fluid/mineral oil = non-compressable

A closed hydraulic system transmits force using a non-compressable fluid in a linear fashion.

So, lever force is transmitted along the brake line and moves the pads against the disc.

If there is air in the system it compresses and allows the lever to move without transmitting the force along the brake line.

 

Ergo there is air in your system. How it got there is another matter.

Yes all correct EXCEPT IF the disc rotor is not exactly in line (parallel) to the pad surfaces. This can result from mis-aligned caliper and/or worn out discs. Both will absorb some lever travel and give reduced braking effort.

 

And yes, to be fair this can occur with any of the popular brands..........

 

Have owned Juicy 7 and they were nice but the previous model XT brakes were better and needed less maintenance. The current XT brakes are savage with big rotors - true one finger brakes

Posted
Disc = non-compressable

Pads = non-compressable

Brake line = distortable depending on material but for the moment let's say non-compressable.

Brake fluid/mineral oil = non-compressable

A closed hydraulic system transmits force using a non-compressable fluid in a linear fashion.

So, lever force is transmitted along the brake line and moves the pads against the disc.

If there is air in the system it compresses and allows the lever to move without transmitting the force along the brake line.

 

Ergo there is air in your system. How it got there is another matter.

Yes all correct EXCEPT IF the disc rotor is not exactly in line (parallel) to the pad surfaces. This can result from mis-aligned caliper and/or worn out discs. Both will absorb some lever travel and give reduced braking effort.

 

And yes, to be fair this can occur with any of the popular brands..........

 

Have owned Juicy 7 and they were nice but the previous model XT brakes were better and needed less maintenance. The current XT brakes are savage with big rotors - true one finger brakes

Posted

Are the old pads worn exactly parallel to the backing plate? If not this is a sign the calipers and new pads are not aligned to the disc. If the brakes were working well before changing pads this could be the reason. Juicys have those cone washers on the mounting that allow you to get the pads exactly parallel to the disc. Do this alignment first. Then if the brake levers still fell spongy air is the likely cause and bleeding is needed. It wont hurt to clean and gently sand the new pads by rubbing against fine sandpaper backed by a flat surface such as wooden block.

Not sure if anyone else has commented on this... a common newbie problem on rides/races where they complain about the rotor rubbing on the brake pads.

 

Loosen the caliper mounting bolts sufficiently to move the caliper when braking. Then squeeze the brake lever to get the rotor in the centre (aligned) of the brake pads, and tighten the mounting bolts (without letting go of the brake lever).

 

This way you won't have the rotor rubbing on brake pads while riding.

Posted

Not sure if anyone else has commented on this... a common newbie problem on rides/races where they complain about the rotor rubbing on the brake pads.

 

Loosen the caliper mounting bolts sufficiently to move the caliper when braking. Then squeeze the brake lever to get the rotor in the centre (aligned) of the brake pads, and tighten the mounting bolts (without letting go of the brake lever).

 

This way you won't have the rotor rubbing on brake pads while riding.

Brake setup 101.

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