Anyone know anything about disc brakes?

Why is my brake howling?

It's a single pot SLX, think it's an m7100.

It does the contaminated pad style howl and doesn't really bite but once it has some heat(?) in it it shuts up and bites fine.

Out on the trail it only takes a few hundred meteres of non-use for the howl to return.

The bleed is good, there's no leaks (tested by setting it up with the lever clamped to the bar and left for like, a fortnight and it didn't lose any oil or anything).

Currently it's setup with new, genuine Shimano (sintered I think) pads and rotor though it started howling when it was fitted with different pads/rotor and once completely shat the bed and stopped working with the lever pulling all the way to the bars but I'd been dragging the brake down a bit descent like a total noob so probably just boiled the oil.

It has to be the brake/pads rather than anything to do with the rotor right? Is it just the time of year where everything is a bit moist?

I'm going to try swapping the brake with one from another bike which curently is running quietly...coz that'll prove?

Checked the caliper alignment without the pads in? Both pistons moving equally and properly balanced? Damp air makes my brakes squeak a bit for the first few taps of them (sintered too) but quietens down with harder braking

Yeah I'd say alignment was pretty good, getting no rubbing or anything. Will have a look at how the pads are moving.

When it started howling it had performed well one day and then when I pulled the bike out a couple days later it was howling. At that point it was summer and there would have been no obvious contamination so I feared the worst and thought the piston had cracked but subsequent investigation has pretty much dispelled that.

@PhilDAS too late my order arrived this morning. First impression - the coupler looks thicker than expected. Not really an issue if you plan to keep it near the cockpit, but I did need mine to be closer to the caliper, so it might be a minor issue. Thankfully I do have some other hoses I could use if I cut it at the cockpit, just not ideal and extra work.

Took my SLX brake off today and I dunno, circled in green is some moisture which has beaded up the way I imagine it’d do on an oily surface and circled in red is some mud which hadn’t dried out like the rest, possibly due to sitting in an oily surface? Or maybe in reading too much into things?

If we say that they are signs of a leak then the joint between the calliper halves looks like the culprit, I’ve not heard of this as a common issue, anyone else?

Edit: helps if I attach the photo!

1 Attachment

Got yer circles mixed

Clerkenwell screws ;) or postage namrich in Brighton

Leaking from a failed o-ring between the caliper halves is very common with Shimano calipers

Doh!

Bum.

Guess I need a new caliper if I'ma keep on using these then.

Yeah, supposedly you can source a third party replacement but you'd have to be confident it was the right one

2 pot caliper is cheap enough to just whack a new one on rathe than pissing about with o-rings.

It'd also seem to be possible to run a 4 pot caliper with my existing lever so might do that.

It'd also seem to be possible to run a 4 pot caliper with my existing lever

Yeah, the levers ain't specific, I run 4pot deore with GRX levers.

Change to the 20 quid SRAM complete brakes and you can use dot brake fluid

I've swapped to some sram Guide 4pots that I picked up cheap on crc a while back. Not quite £20 cheap but they were pretty bargainous.

Slx brakes and now SRAM? What am I missing here? There's low level sram which runs mineral oil instead of DOT, but it's not clear what's being swapped around here.

When I said I’d try a brake that was running quietly on another bike, that was a Guide. Since it looks like the front SLX is leaking and I don’t want to have a Sram front and Shimano rear I’ve just fitted both the Guides.

I will replace the leaking SLX caliper but there’s no rush really as they’ll now go on my full sus which I’m going to hold off on building until the weather improves I think.

You're missing that he's swapping the whole brake incl lever, not just the caliper

I've read the back and forth on Dot vs mineral oil, but what's the benefit here in switching to Dot for this problem?

Mind you, I do have 4-pot mineral oil brakes on my otherwise SRAM Eagle hardtail

I have an old 90s steel Kona I was thinking of converting to disc, does anyone know who can do this in the London area and what the cost would be?

So you are sorted.

None, for this problem. Apart from cheap replacement of lever, caliper and pads.

Not sure how reusable the mineral oil is as it is quite expensive while I have lots of dot brake fluid in the garage and it is cheap.

Got you. Speaking of DOT. I have some Level brakes I picked up from here. They use one of those split pins to retain the brake pads. Before I remove them, do the calipers have threads so I can swap the pins for the right sized hex bolt + clip?

No idea haven't fitted the brakes yet.

Currently deciding what to go with on with the bike as the forks need looking at and the crank BB needs looking at too.

Sorry dude, that was an open question to our fellow disc aficionados. Should've used punctuation to split my reply to you lol.

What SRAM brakeset did you grab for 20 quid though, that's a steal? Offer still available online?