Re: Disc brake tuning

On Sat, 27 Apr 2024 07:06:36 -0500, AMuzi <am@yellowjersey.org> wrote:

On 4/26/2024 9:11 PM, James wrote:

This might have been mentioned, but I'm not about to wade
through the endless oceans of shit being posted here to find
out.
 
Just like with rim brakes, it's important to ensure that
disc brake pads are aligned with the braking surface.
 
Disc brake pads I've encountered come with a leaf spring
that pushes the pads against the pistons to retract the pads
when the brake is released.
 
The leaf springs don't seem to be well formed from the
manufacturer, such that the pads can be resting not squarely
on the piston face while the brake is released.
 
I've found that by carefully bending the leaf spring it's
not difficult to make sure the pads are pushed square
against the piston faces, and parallel with the disc.
 
Without having done this the brakes can feel spongy, as it
takes excessive brake lever movement before the pad has
aligned with the disc and the pad is really doing some braking.
 

>
With new pads, look closely at the pad-rotor space
(flashlight, maybe magnifier) from as many angles as
possible. Is everything parallel? A pad touching at one end
or corner would give that symptom.
>
If so, slack the caliper mounting bolts, apply the brake and
hold it firm to the rotor while tightening the mounting
bolts. Check again to ensure that everything is parallel.
Some removal of crud may be necessary before aligning the
caliper to its mount.

+1. On my Shimano Hydrolic it's two bolts with Allen heads.
Loosen, hold the brake tight so the pads will align with the disk, and
tighten the bolts while holding the brakes. When you release the
brakes the wheel should spin freely, nothing "touching". If there is
any drag, repeat the process.
To OP:
"Spongy" could mean you've leaked brake fluid. Either by
pulling the brakes without the wheel in place(never do that), or maybe
you allowed the pads to wear down so much the "pistons" came out too
far and when you pressed them back to fit new pads you damaged them.
[]'s
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