Disc brakes suddenly stopped working

[KneesUp]

I’ve recently acquired my first bike with disc brakes of any sort - they are hydraulic Tektro brakes, but I am not sure on the exact model; there doesnt’ seem to be any marking on them.

The bike was pretty badly maintained when I bought it (the chain and cassette were both very badly worn and smothered in oil and crud) so I’ve replaced the chain and cassette and cleaned everything up. All was going well until on a ride to town yesterday (all of 3 miles) I noticed with some degree of concern that the front brake had stopped working altogether. It had previously worked fine. Given that the bike was obviously not looked after I assumed the pads had had just enough life to work, but because I live at the top of a hill, I’d worn off what I was assuming was the remaining nanometre of meat from the pads.

However, I’ve just taken them out and they look to have loads of life left, albeit it the backing plates are rusty.



.

Any idea why my brakes have suddenly got literally no braking properties at all? The lever pulls all the way to the bar and the bike doesn’t slow at all - you can’t even perceive any extra effort needed when you are a pushing the bike. I’ve put penetrating oil on a stuck bolt on the mudguard bridge at the back but I was careful not to get any on the discs. However, if a tiny amount of mist has got on the disc (and it would be a tiny amount - I was careful!) would that go from ‘brakes are fine’ to ‘brakes do literally nothing’?

I’ve ordered a bleed kit as that was my other thought - I’ve no idea when the oil was changed, if ever, but again I’m unsure what the mechanism would be to go from ‘brakes work’ to ‘you have no brake’ in the space of 3 miles. I’ve also got new pads, and I’ll fit them anyway (and clean the disc first)

Basically I’m after some diagnosis of what could have gone wrong because the sudden fall off in braking effectiveness has spooked me a little given that I’ve ridden a bike with disc brakes no more than 10 miles on road and the front brake is now totally useless! Thanks in advance.

EDIT - just measured the disc thickness - it’s 1.7mm, which I think means it’s not excessively worn (google suggests a new disc is 1.8mm and they should be replaced at 1.5mm?) The pads have roughly 2mm of meat.

 

[All uphill]

Hydraulic fluid gone missing?

 

[Dadam]

Sounds like you have no, or not enough, fluid pressure in the system. Do the pads move at all when you press the lever?
Evidence of a fresh leak at the caliper? I assume it would be fairly obvious if leaking from the lever end.

 

[KneesUp]

Hydraulic fluid gone missing?

Sounds like you have no, or not enough, fluid pressure in the system. Do the pads move at all when you press the lever?
Evidence of a fresh leak at the caliper? I assume it would be fairly obvious if leaking from the lever end.

There is no evidence of a leak and they were working. The pads do move - I noticed one side was sticking a little but I gave it is poke and both sides do now move.

The bike has been upside down briefly (because my bike stand has been stolen … ) I’m not sure if that could be an issue - but they worked after that. The brakes take mineral oil not DOT so the fluid can’t have absorbed loads of water (one of my initial thoughts was maybe the fluid is mainly water by now and I’d boiled it off)

 

[si_c]

Those pads are glazed so I'd replace them anyway - which bike did you get, that should help identify the brakes and so the pads you need.

If the lever pulls all the way to the bars with no noticeable action then the hydraulic system has failed, most likely because air has entered the system and is causing the problem. This can be fixed by bleeding the brakes.

You can get a kit online for a reasonable price if you are confident doing it yourself and the process is quite straight forward, particularly for hybrids or mountain bikes - check youtube for guides. It's something you'll need to do semi-regularly so learning to do it is always a good shout, same as with changing tyres or inner tubes and chain maintenance.

 

[fossyant]

Will need a bleed. Easy enough to do, just need a bleed kit, correct fluid, and you tube.

 

[si_c]

There is no evidence of a leak and they were working. The pads do move - I noticed one side was sticking a little but I gave it is poke and both sides do now move.

The bike has been upside down briefly (because my bike stand has been stolen … ) I’m not sure if that could be an issue - but they worked after that. The brakes take mineral oil not DOT so the fluid can’t have absorbed loads of water (one of my initial thoughts was maybe the fluid is mainly water by now and I’d boiled it off)

Get some WD40 silicon spray and spread the pads out so they are flush with the caliper, then extend them out a few mm, spray on the WD40 (must be the silicon spray as regular could damage the seals) and then push them back in. Repeat a few times and this will help loosen up the pads.

I'd still do a bleed though.

 

[KneesUp]

Those pads are glazed so I'd replace them anyway - which bike did you get, that should help identify the brakes and so the pads you need.

It’s a Hoy Shizuoka (a hybrid) for commuting duties - I picked up some pads yesterday that fit ( I bought the ones that listed the most Tektro brakes on the packet and kept the receipt :-) ) so I still don’t know what model the brakes are, but I do know it’s the pad that Clarks call VX811 and it’s the same pad as in TRP Spyre amongst others.

 

[raleighnut]

Hydraulic master cylinders can fail even on cars (seals go)

 

[KneesUp]

Right - my bleed kit has arrived. I've never done this before so I asked ChatGPT for advice given I've no bike stand at the moment.

This will be fine, right? As long as the missing instructions aren't important, and I look out for bubbies?

 

[Dadam]

I wouldn't rely on GPT! Did the kit not come with instructions?
Here are Tektro's instructions

And these are the ones that come with the kit from Epic Bleed Solutions (I've still to get round to bleeding the Tektro brakes on my hybrid)

 

[si_c]

Don't flip the bike upside down, that will cause any air to rise to the caliper rather than the master cyclinder where it needs to be - this will make bleeding much harder as you'll struggle to get air out of the caliper as it has a tendency to get trapped.

If you're only doing the front wheel, you can take the wheel out, rest the forks on a towel (helps with spillage anyway) and put the bleed block in. Lift the handle bars so that the bleed port is parallel to the ground (it may be easier to rotate the handlebars to do this). Then bleed the brakes.

Do you have a bleed cup or is it a pair of syringes?

 

[Dogtrousers]

I wouldn't rely on GPT! Did the kit not come with instructions?
Here are Tektro's instructions

And these are the ones that come with the kit from Epic Bleed Solutions (I've still to get round to bleeding the Tektro brakes on my hybrid)

Or, in fact, why not ask Cyclechat? We'd give you a load of conflicting information and then have a huge argument about whether disc brakes are any good.

Maybe not as useful as a set of instructions, but more entertaining.

 

[roubaixtuesday]

huge argument about whether disc brakes are any good.

Well, at least they're maintenance free (ducks for cover)

 

[cyberknight]

Those pads are glazed so I'd replace them anyway - which bike did you get, that should help identify the brakes and so the pads you need.

If the lever pulls all the way to the bars with no noticeable action then the hydraulic system has failed, most likely because air has entered the system and is causing the problem. This can be fixed by bleeding the brakes.

You can get a kit online for a reasonable price if you are confident doing it yourself and the process is quite straight forward, particularly for hybrids or mountain bikes - check youtube for guides. It's something you'll need to do semi-regularly so learning to do it is always a good shout, same as with changing tyres or inner tubes and chain maintenance.

indeed they are dire, try sanding off the film back to the pad with a bit of sandpaper 1st though as you can sometimes rejuvenate pads if they are not to far gone