Hydraulic disc brake woes

[stevie_b]

Until a couple of days ago my bike had cable disc brakes. At the weekend I changed them to hydraulic disc brakes: I kept the existing rotors and fitted some 2nd hand levers and calipers (Shimano BR445). Before fitting them I checked that both pistons in both calipers moved OK, which they did. No sign of oil leaks either, but more on that in a bit...

My problem is that the brakes squeal like mad when I apply them, I mean *really* squeal. It sounds like the Four Horsemen of the Apocolyse running their fingernails down the devil's blackboard, whilst a group of typical One Direction fans clap eyes on Harry Styles. It's enough to make small children cry as I cycle past them whilst braking.

My rotors are resin-only, so I wondered if the pads that came with the hydro brakes are non-resin. With no easy way of telling by inspection alone, I removed the pads that came with the hydro brakes, cleaned the rotor with brake cleaner, and inserted the pads that I used with my cable brakes (a combination of pad and disc which I know was squeal-free). The squeal is much reduced (not gone though), but now the brake lever moves quite a lot before the brakes start biting. The old cable-brake pads have much less meat on them than the ones that came with the hydro brakes, but even so I thought that hydro brakes were self-adjusting such that the pistons stay close to the disc, instead of retracting all the way back into the caliper (which seems to be what's happening).

When I took the hydro pads off, I thought I felt some oil on the back of the pads (i.e. where the piston pushes it against the disc). It had been raining but it felt like oil to the touch.

Any thoughts/ideas about eliminating the squeal completely, the excessive lever travel and other symptoms of oil loss at the caliper to watch out for?

 

[Pale Rider]

As a general point, disc brakes do squeal from time to time.

Try rubbing the surface of the pad with a fine file or emery paper.

You could do the same with the rotor.

An old mountain biker's trick is to deliberately get the brakes muddy and let the grit in the mud do the job for you.

 

[stevie_b]

I might try rubbing down the newer pads. How can I tell if they're non-resin (hence unsuitable for my disc)? I couldn't see any identifying part numbers on them.

Something I've read is that the brakes not self-adjusting (i.e. lots of lever travel before bite) might indicate air in the system, hopefully not a seal leak.

 

[Al T]

When squealing became more of a problem on car disc brakes back in the early 90's after the changeover from asbestos to non asbestos materials it was quite common to sell pads with an anti squeal shim attached to the back of the pad where it makes contact with the piston, normally made of a slightly softer non metallic material than that of the backplate of the pad which would handle the heat transfer & also kind of soak up the squeal noise / resonance. Do cycle pad manufacturers offer similar options now on their range of pads for problems like this?

 

[Tom B]

Could this just be bedding in and the newness of the friction surfaces mating?

My new brakes took a good few rides to come in nicely even after doing a couple of laps of the estate with the brakes rubbing.

 

[stevie_b]

It could be, I'll try "riding the brakes" on the way home tonight.

I know exactly what you mean about the anti-squeal shim on cars as I've stripped car brakes down, but I've never seen an anti-squeal shim for sale for bicycle brakes (not looked that hard for it either!). I suspect something's intrinsically wrong though with either my kit or the way I've put it together, partly because the pistons seem to retract fully once I let go of the brake lever. My wife actually grabbed the lever when I had it on the bench and gave it a squeeze. I thought "oops", but to my relief the pistons didn't stay pushed together. I thought that was a bit strange at the time, perhaps I should have paid more attention to that.

 

[I like Skol]

So, you bought second hand hydraulic brake components.........

These are the exact problems that lead to me buying new on critical components as these. By the time you have bought some fluid and bled them a few times and then add in the cost of a set of new pads plus the time involved it becomes more financially justifiable to get a set of something like THESE new. The Shimano M615 Deore set-up is almost identical to the XT version in looks and performance and if you get the euro-spec Fr/LH & Rr RH (You will want to shorten the hoses anyway so this is when you swap the handing) you can have these fantastic brakes delivered for a shade under £65 (and they come with resin pads as standard).

Sorry this doesn't help your situation but it's a valuable point to consider in future. In the meantime I think you probably know that a new set of pads are going to be required one way or another. You may have discovered the reason the original seller was selling?