Adjusting shimano cable disc brakes

[So]

My wife and one child have Specialized Pitch MTBs.

My wife handed me her bike this evening with about 5psi in each tyre, a chain as dry as a nun's minge and brakes that didn't brake but screeched.

I dismantled the brakes and burned off the pads with a blowtorch, the same with the discs.

Both brakes work now and don't screech.

The front is very sharp, but the rear isn't quite as good as I think it should be. The cable routing was poor, so I modified it and that helped but I'd say it's only 95% as good as it should be. My son's is noticeably better.

So discs and pads burned off.

Caliper tightened with the brake on.

Disc is true.

Any tips please?

[Justin S]

Decent stainless low friction brake cable and new outers are a start. Low range bikes come with galvanised cables and less stranded, so more friction when pulled.

[So]

Justin S said:

Decent stainless low friction brake cable and new outers are a start. Low range bikes come with galvanised cables and less stranded, so more friction when pulled.

Yes it is a slightly heavy pull. But as I say my wife's bike is the same as my son's and his is OK.

Contamination of the rear pads that has not been sorted with the blowtorch?

[Justin S]

Blowtorch isnt the greatest way to decontaminate pads as they dont get as hot as a car or motorbike. Best to replace with new and clean the disc with a cleaner which evaporates. Not had to , but I have a can of carb cleaner from Toolstation in the cupboard, which is good or a can of mtb disc cleaner, which is similar from the bike shops but you pay more for a different sticker.
Alternatively , these cable discs can be a bit hit and miss with operation . You have adjusted the inner pad screw as well ?

[So]

Justin S said:

Blowtorch isnt the greatest way to decontaminate pads as they dont get as hot as a car or motorbike. Best to replace with new and clean the disc with a cleaner which evaporates. Not had to , but I have a can of carb cleaner from Toolstation in the cupboard, which is good or a can of mtb disc cleaner, which is similar from the bike shops but you pay more for a different sticker.
Alternatively , these cable discs can be a bit hit and miss with operation . You have adjusted the inner pad screw as well ?

Yes, but it seems that only the outer pad moves, is that correct?

So the inner screw pushes the inner pad as close to the disc as possible, without touching it, so that the outer pad deflects the disc as little as possible?

[dontlookdown]

Yes that's right. Those one-sided adjustment brakes are not great because as you have spotted the disc is deflected every time you put the brakes on. It's inherent to the design however well you adjust them.

If you have cleaned up the pads and deglazed the discs (abrasive paper followed by solvent for the discs) and there is still an issue, new pads might help. Just get the ordinary resin ones for normal use, the harder formulations are noisier, more expensive and wear the disc out substantially faster.

It could also just be a sticky cable. If it's good enough prob best to live with it. Cable discs are a bit hit and miss generally IME. I do prefer them to rim brakes esp in the wet, but for night and day difference you need hydraulic ones.

[Barchettaman]

Use a ‘posh’ new brake cable and housing, and proper cable cutters to cut it to length.

Jagwire are good and offer a noticeable performance advantage.

In future, acetone on a clean microfiber cloth is best for cleaning disc brake rotors. Keep the blow torch for your crème brulée.

[So]

I've done everything suggested here and I assume that the difference between my son's bike and my wife's might just be that he brakes harder, so has kept the pads in better condition.

Thanks chaps.