Ever seen this before?

I crashed very heavily on Saturday morning whem my rear brake failed at a very critical moment. There was a ‘click’ from the lever, then nothing except for my girly screams as I made a beeline for the wall at the other side of the trail exit. When I got home, I saw that the brake was empty of fluid, so I cleaned it with a rag to see where the leak was. As I cleaned away all the gunk that had accumulated on the underside of the caliper (between the caliper and post mount adaptor), the metal appeared ‘rotten’ and flaky.

What also appeared was the chuffing great hole, just to the left of where the hose enters the caliper body.! 😯

A mate reckons that this could be caused by the pad material mixing with water and forming a corrosive paste that’s eaten through the caliper body. I reckon it’s seriously scary and that everyone should have a good look at their brake calipers.

Is this just another case of my blighted luck? Or is it something more common that I just wasn’t aware of until it was too late?

Beagy

Wow 😯

Was it slightly loose on the mount and somethings got underneath and worn it away?

blimey!

looks really even for corrosion but can’t imagine it’s caused by abrasion.

Never seen that happen! Might be worth dropping an email to Hope (that looks like an X2 caliper?) to see if they’ve seen anything similar?

Crikey indeed. It looks like corrosion, but I can’t imagine what’s caused that. How old is it?

(Be prepared for comments along the lines of you shouldn’t be using your rear brake…..)

X2 or an much much older Mini/M4?

Bizarre issue though

I reckon you’ve had a tiny leak from either the bleed nipple or the hose union. Brake fluid is very corrosive and eats painted surfaces and bare ali too. No way that was caused by pad material.

It’s not through abrasion, the caliper was firmly clamped to a mount adaptor and the frame. I’ve contacted the chaps at Hope (it is an X2 caliper )and they’ve replied very promptly, asking me to send it down to them so it’ll be in the post tomorrow.

The accident I had wasn’t serious, I’m battered and bruised, but I’ve had worse. However, if it had failed at countless other points on the day the consequenses could have been life threatening, which kinda scares me and is why I’m posting this up.

If it’s a manufacturing defect, then fair enough I think I’d actually be happier with that, but if there’s some insidious corrosion going on underneath a layer of used brake pad material then I want as many folk as possible to flip their bikes over, wipe the grime off and check their brakes are Ok.

B. 😯

wow, not pretty, you riding in acid mud? 😉

Mineral oil wouldn’t have done that….

but hope brakes use dot 5. Only shimano use mineral oil.

You can see the bleed nipple threads in the casing, and the o ring grove has popped out! Looks like alot of material has been lost 😯

I rest my case 😉

have you been cleaning with caustic soda ? 😯

Did you buy these brakes new or are they 2nd hand?

Only shimano use mineral oil.

and magura

so you havent cleaned you bike in that long its got holes underneith the crap. lol unlcky about the brake fail tho 😐

Point is Hope use Dot 5 and this IS corrosive. I dont really want a list of which brakes use what…Dont reckon Beagle does either as he plummets headlong into a wall. Druidh has a point…mineral oil wouldn’t cause this but hope haven’t gone this route..be interesting to see what hope say. I’ve run a set of X2’s for a year and they show no signs at all of any corrosion or pad material build up.

I’d be tempted to check the front one as well. Have you got a clean pic of the 2 side by side – as it does look like it’s load of metal

They were bought new, about 24 months ago. Surely I would have lost power over time if there was fluid leaking from the system? Over the last week there was a couple of instances where the brake felt spongy, and I though maybe it was time to bleed them (never been done since fitted), but the power always came back after a couple of squeezes.

When I used the rag to clean away the gunk, it honestly felt like I was removing flaky, rotted rust from the body. Something’s eaten my brake. 🙁

caustic soda has that effect on aluminium.

Just found this. Maybe your fluid had some water in it?

“Another problem with moisture in brake fluid is that it causes corrosion. Moisture laden brake fluid begins to attack the metal in the brake system. Experts disagree on precisely how long this takes. Most agree between 2 and 3.5% moisture per year may be absorbed.

Much of the modern brake system is comprised of aluminum, a highly reactive metal. Oxygen in the absorbed moisture combines with aluminum to form aluminum oxide. This damages the metal components. Once the surface finish of hydraulic cylinders are corroded, they begin to leak and must be replaced”

Obviously this is refering to a car system but basics and materials are same.
Have you ever bled the system with old brake fluid…over time it absorbs moisture from the atmosphere.

Thanks Klunk, pretty sure that I regularly clean it with a bucket of soapy water, then a nice rinse down with the garden hose. No Caustic Soda as far as I’m aware. 🙄

from my untrained eye, it wouldn’t leak it would suddenly go pop when under pressure (braking)

but that caliper has been corroded from the outside, with no effect to the steel and brass.

It’s coz ure riding is is awsum that you has created heat like on the sun when you does braking. I has seen it, beagle you is a legend

Thanks Klunk, pretty sure that I regularly clean it with a bucket of soapy water, then a nice rinse down with the garden hose. No Caustic Soda as far as I’m aware.

ridden through an industrial sites, done any patio cleaning ?

You might find caustic soda in Fairy liquid mate, probably not enough to do that though!

I agree with Klunk. I reckon a tiny leak has run onto outside surface, fluid has absorbed water and began to corrode. Pretty drastic if the bike is cleaned regularly though.

Overtightened banjo maybe? Looks like a small crack heading from that direction

Hmm, had similar with the head of a syncros seatpost that I used to have. Ally goes a bit “flaky” and crumbly when it corrodes. I put it down to daily commutting use and salt from the roads. Plus I also had to take the bike on the ferry twice daily, so inevitably got salt spray on it too.
How often do you clean / inspect your brake calipers?? Clearly not often if they’re only 2 years old…..
Glad you didnt seriously mangle yourself though.

i’ve done that flaky bit to a calliper before. road salt did it.

dh bike hanging on rack and getting sprayed by wheel, then not a sufficient clean before storing, and the calliper looked like that.

never made a hole in the body mind, but pistons jammed up and it ultimately got binned.

that a possibility OP?

Glad your not to badly injured, goes to show regular bike inspections cleans and services of parts are vital to prevent things like this from happening.

Glad you’re not badly hurt.

Make sure you update this post with Hope’s reason why it failed so catastrophically..

I really don’t think this is any fault of Hope but a maintenance/cleaning/contaminate issue. I’ve had brake fluid in contact with metal parts before with no reaction like that. The caliper has had rounded bits flattened off not typical of corrosion, it almost looks like it’s been attacked with Dremmel.

Hey tracknicko,

Road salt might do it I suppose, although I don’t ride my full susser that much in the winter. In my defense, the area where the corrosion appears worst sits facing the ground, with a post mount adapter between it and the frame, so its well hidden and not easy to access. The bike is also kept very well and looked after lovingly.

I simply wasn’t aware that this part could be subject to corrosion, so I’m actually glad to hear that someone else has suffered with a similar problem.

Like I said earlier. I’m going to post the caliper to Hope and see what their verdict is. I’ll let folks know as soon as I do.

B. 😉

That’s some bad ass corrosion that appears to have let go in spectacular fashion, bravo!
I’ve had leaky brakes before. The fluid always ate the paint first though, so issues were picked up and sorted. I’ve never seen a hole before, that’s a new one on me.

Expect Hope to sort it, they’re good like that.

Hey Craigxxl

If you look at the bottom half of the pic I posted, do you see how the caliper has black marks on it? Those black marks got darker and deeper towards the rear of the caliper that was hidden away between the frame and the caliper mount. When I started cleaning off the black marks with a rag dipped in a wee skoosh of WD40, whole chunks of the black stuff crumbled away leaving what you see in the pic. No Dremmels, and a fairly regular cleaning schedule, albeit possibly one that wasn’t good enough in that very inaccessible area.

have you been cleaning with caustic soda ?

Dosn’t look like its had much cleaning/maintenance at all to me,otherwise you’d have probably seen it earlier.. 😉

has your wife just taken out an insurance policy on you? i’d be tempted to check the rest of the bike, and the brakes on the car, too. just saying.