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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Disc brake tuning
Date: Sat, 27 Apr 2024 07:06:36 -0500
Organization: Yellow Jersey, Ltd.
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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.
-- 
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971