Brake conundrum-tech advice/opinions

Evening all,

Just bled my shimano xt (785) rear brake three times. Using various methods.

1) back bleed using syringe at caliper and funnel at lever.

2) forward bleed with two syringes

3) traditional open close bleed port as you press and depress the lever.

All three times I’ve got a great feel at the lever, no sponge and a full on loud thump as the pads contact the rim. This is telling me I’m pretty sure there is no air in the system

Yet… there seems to be very little power compared to before changing the hose.

What the hell is going on? I’ve removed wheel and pads each time so there is definitely no fluid on the pads and rotor.

Just done another bleed on this. Solid lever feel, full on thump as the pads hit the rotor but no power, really hard to even lock a wheel up.

Anyone got any idea? Fault in the lever/caliper maybe?

Did you put in fresh pads at the same time?

Not got something oily have you?
With good feel and initial contact that might be first check.
Or fluid leaking so as you apply pressure the pads don’t squeeze harder but the fluid is getting out instead.

If it feels solid at the lever, then almost certainly a lack of friction between pads and rotor – most likely oil contamination.

Take pads out and stick them under the grill/use heat torch on them until smoke stops (all oil burnt out).

Clean the rotor with isopropyl alcohol and or give very light sanding with wet and dry paper.

Stick pads back in and bed pads back in again. Should all be good.

Cheers guys, I’ll try torching the pads and rotor

dont torch the rotor. de-grease the rotor.

Yeh that’s what I meant. Is isopropyl alcohol just white spirit?

No no no no no no! White spirit is not!