Re: Disc brake tuning

On 5/2/2024 7:24 AM, Roger Merriman wrote:

James <james.e.steward@gmail.com> wrote:

On 1/5/24 03:15, Shadow wrote:

On Tue, 30 Apr 2024 14:05:32 +1000, James <james.e.steward@gmail.com>
wrote:
>

On 28/4/24 11:01, Shadow wrote:
>

To OP:
"Spongy" could mean you've leaked brake fluid.

>
No.  Cable actuated calipers.  Not hydraulic.
>

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

>
Again, no.  Irrelevant for cable calipers.

>
To be fair, you forgot to mention that. Most disk brakes are
hydraulic now.
Sorry my reply was useless.
[]'s

>
>
Hydraulic calipers I've seen use the same leaf spring to press the
backing plate of the pad to the piston face while the brakes are not
applied.
>
There is no reason to expect the problem that I have described to be
exclusive to cable actuated calipers, and so there was no reason to
mention the actuation mechanism.
>
No need to be sorry.
>

 Can’t say I’ve noticed it being a problem with the pads being mis aligned
to the pistons with either cable or hydraulic in some 20 odd years, the
leaf springs I reuse on both the Gravel and MTB which the pads are sold
without the springs.
 The older MTB I buy cheap pads and does come with the springs I do often
replace the spring but dispose of the old springs as well only so many
(just in case) spares that are needed.
 I have once worn the pads enough to snap off a bit of the spring (still
worked if poorly and noisy) but beyond that.
 It isn’t impossible clearly though with hydraulic callipers clearances
being so tight i would expect the rotor to push the pad flat to the piston.
 Cable as they don’t self adjust will get wider gaps between pad and rotor
so more plausible for the pad to move a bit.
 Though again it’s a narrow channel so not much room for the pad to move in
any direction but intended.
 Roger Merriman

For a cable disc, I'd double check wire/casing and, with the cable disconnected, ensure the lever/cam returns smartly. The pad return spring is just not significant to pad return force.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971