Have seen similar with extended use of neat bike cleaners

Beagleboy, I wasn’t say you’d attacked it with a dremmel but that flat areas etc like around bleed nipple and banjo entry isn’t usual for corrosion. Corrosion will normally attack one area and radiate out from there.
Let us know what Hope come back with.

still looks like road salt.

would stick good money on it.

Looks galvanic to me.

What is your frame made from?

Beagleboy wrote: I regularly clean it with a bucket of soapy water, then a nice rinse down with the garden hose.

Don’t want to get onto my ‘sopbox’, but was that washing up liquid you were using?

Only shimano use mineral oil.

and magura

And Tektro 😉

Seriously though, that’s pretty scary.

That does not look good, better go and check mine! Glad you are recovering.

What has been said about road salt in winter makes sense to me though… and it does not need much. I was shocked at the state of our kids spesh hotrocks a few years ago when they insisted we took them to holland with us in december. Just the bikes being on the roof of the car when travelling in winter on some salted roads caused bits to seemingly corrode overnight! I was quite shocked…

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

All sorted then.

Phew 😮

galvanic corrosion LOL

I’ve seen similar on some old road clipless pedals and pace fork drop outs. That was down to road salt. That was not caused by washing up liquid.

Thats AWESOME 😀

Looks galvanic to me.

What is your frame made from?

That was my first thought, Ti frame or bolts by any change?

Beagy was that on the 5 swingarm.

nikk wrote:

Looks galvanic to me.

What is your frame made from?

cynic-al wrote:

galvanic corrosion LOL

Why LOL? I could be wrong, but how about showing some respect and explaining what is up, rather than a childish ‘lol’.

thisisnotaspoon wrote:

Looks galvanic to me.

What is your frame made from?

That was my first thought, Ti frame or bolts by any change?

Would be interested if it was a possibility.

Dear God Almighty 😯
As to the corrosion being caused by hydraulic fluid-Not a chance it could cause that level of corrosion.
Im forever farting about with old C2’s and the like and regularly have the stuff all over my jumper,hands the bike or the floor and ive never seen the like.
Id also like to say i keep the old fludi in an old coke bottle before taking it to the council refuse area to get rid of it.sometoimes it can sit in the plastic container for months and its never attempted to eat its way through like im seeing here.

I hope the hope come back and tell you its a defect and if they dont id seek another opinion 😕

Sorry for not getting back earlier folks, I went for a bike ride then had a sleep. 8)

To my shame, I don’t use a dedicated bike cleaner like mucoff. I use a squirt of Ecowash washing up liquid (from Asda),in a 5 gallon bucket of water out of the garden water butt, finished off with a good rinse from the garden hose. I also tend to clean the bike with the wheels still in, and as I’ve mentioned before, the site of the corrosion is on the underside of the caliper, between the post mount adaptor and the frame (Orange 5). So yes I suppose I could be at fault for not spotting the corrosion in time.

I live in Stirlingshire, so my bike needs washed very regularly, but again to my shame, when doing so, I don’t strip the entire frame down and inspect every component for wear. 🙄

I checked the front caliper last night, which is subjected to the same maintenance regime as the rear, and it doesn’t have a mark. It’s as bright and shiny as the day I fitted it 2yrs ago.

I’m not trying to make excuses here. If my washing up liquid is so alkaline that it can eat metal then it’s a fair cop. I’m just pointing out that I had a nasty shock, and other’s might want to take a second to double check their calipers as well. Outwardly, the thing looked perfect, just a little gunked up with what I thought was a thin layer of road grime and cow poop. It wasn’t until I’d removed the caliper from the frame, then the mount adapter, that I was able to get into the gunked up bit properly and watched as it crumbled away in my hands!

Beagy

Cow poop – that stuff can destroy tarmac, I wonder what it does to ally? It might stay wet and help promote corrosion.

I have never seen anything like that before and I never clean my bikes.

Trundles off to shed to check them…

I was going to suggest an overtightend bleed nipple but I’m sure Hope would be interested to have a look at it as well.

Beagleboy, have you sent Hope the image and the parts?

I dont think the issue is any of the above, but do let them have a chance to see it.

Yep I’ve sent them pictures and am posting the caliper down to them,it would have been away today but I couldn’t print out the form they sent me at home. No ink in my printer. Me and my shoddy maintenance regimes again. 😈

Hope you didn’t go for a ride without your rear brake….you could crash you know…

Thanks for the advice Teamslug 😉 Luckily my hardtail has two working brakes (8/9 yr old Hope Mono Mini’s on a steel frame), which have managed to survive my apparent slapdash approach to bicycle maintenance. 8) As have the original Hope Mini’s fitted to my tandem. I’m a bit of a fan of Hope kit, all my bikes are kitted out with Hope headsets, hubs, brakes, bottom brackets and bling.

B. 😀

Me too. Stem/headset/brakes etc etc. Never has problem with anything and the spares list is just amazing. Be interesting to find out what Hope think.

Okay – dumb Q…
If the calipre is cnc’d from billet aluminium why would a DOT leak etch the outside – when the inside is bathed in the stuff?

So imho if it’s corrosion it must be something other than brake fluid. – but not cow poo(:ex-herdsman) 🙂

@Stuey, may be wrong by lack of oxygen inside maybe? a lot of corrosion is massively accelerated by is presents

Stuey, may be wrong by lack of oxygen inside maybe? a lot of corrosion is massively accelerated by is presents

Yes, but that looks like the metals corroded away untill it got thin enough to leak, that would have to be leaking constantly for months. And most brake systems (i.e. cars) are open to the atmosphere with no real sealing and no ill effects.

I’m guessing it’s road salt, my aluminium cannondale looked worse for wear after a winters commuting, as soon as it gets under the paint it wreaks havock, so the swingarm will be fine, but the brake calliper isn’t painted so unprotected from corrosion.

@Stuey. Its the presence of oxygen and moisture that starts the corrosion.IMO its the lack of moisture and hence oxygen and water that prevents the inside from corroding.

“Aluminum owes its excellent corrosion resistance and its usage as one of the primary metals of commerce to the barrier oxide film that is bonded strongly to its surface and, that if damaged, re-forms immediately in most environments.”

“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”

Some may say that this is the salt in the washing up liquid but as the rest of the bike is good then the argument holds no water with me. Glad that you are okay despite your off. Is the bike okay, bar the brake caliper?

It will be interesting to see what comes back from Hope once they have had chance to look at it. I wonder if it was a bad casting with contaminated/poor quality ally in there that made it more susceptible to the corrosion. Hopefully it is not something in after market pads else we may all have issues.

since that is a post mount calliper, just curious if there is the same damage on the brake adapter, which will also be Alu, and if Hope, probably has the same anodized coating.

Would be very odd if the calliper is damaged in that way but the post mount adaptor it is bolted to was fine.

There’s some right smug b@stards on here.

I’ve left an old hayes caliper in a bag along with a lever body that leaked all over it for over a year. The paint came off, but there didn’t appear to be structural damage. You clearly keep your bike clean, or at least clean enough to prevent stuff like that happening and there’s no way it would happen from washing up liquid.

I’d say its a manufacturing defect with a leak/brake fluid acting the the catalyst. Hope have a really good rep so I’d be surprised if they didn’t replace it for free

If, as some people are suggesting, hydrolic fluid can do that damage, then why doesn’t it routinely ‘eat’ its way out of the brake (from inside to out like)?

If, as some people are suggesting, hydrolic fluid can do that damage, then why doesn’t it routinely ‘eat’ its way out of the brake (from inside to out like)?

the brake fluid theorists have covered that 101 times up there —–^

My money’s on road salt and possibly some galvanic action betweeen the calliper and a bolt/pad/pin/backing to accelerate it. I can’t see how the brake fluid could have gotten out before the corrosion started as it apears to have corroded form the outside untill it made the holes. And to lose a continuous trickle of fluid for ride after ride and not have the brakes fail sooner? there’s only about 10ml of fluid in the resevoir.

Looking into galvanic corrosion more, I think this is the most likely action to create so much damage.

I suspect that the cow s**t stuck to the underside of the brake and, possibly with the addition of salty washing up liquid, acted as an electrolyte. Would I be right in saying the bike was kept in a shed? That would allow the wet to remain for an extended period. My feeling is the brake disc itself was the cathode, and that there was a bridge of electrolyte (for example, the brake disc was close enough to allow the surface tension of the water to bridge the gap, or there was enough muck left on that helped such an effect).

Look up “lasagna cell” to see what can happen overnight to aluminium foil in contact with a steel tray and an electrolyte (salty lasagna).

wow – so If I covered an uncooked lasagna with say magnesium foil it may produce enough current to cook itself – but leave the dish tasting of sodium-hydroxide – soapy yuk 😀

Interesting stuff. The bike is kept in a dry garage, and usually gets a nice wee rubdown with a dry cloth after it’s shower. There’s no sign of any corrosion around the fixing bolts, or on the post mount adaptor. Likewise, the topside of the caliper is in perfect condition.

Dunno if this will be any clearer.

Remember that the caliper is flipped over and the post mount removed for the pic.

I do ride on the road a fair bit. It’s the better part of a 8-10 mile road bash out to the trails that I regularly ride, so roadsalt could be a likely culprit, but I’ve never seen the likes on any of my other bikes, nor on the front brake of this one. I find it hard to believe it’s brake fluid corrosion as the brake was set up two years ago, and hasn’t been fettled with since. Likewise, I’m a bit skeptical about the corrosive effects of fairy liquid. Why haven’t my other bikes melted?

B.

Got it:

wee rubdown

STWer shouldn’t really p155 on their brakes. 🙂

(Edit still very impressive corrosion pic. If it was galvanic shirley only happen between different metal interface – not sideways across the calipre ?)

I wonder if its a manufacturing defect. Could the billet of Aluminium the brake was machined from have been faulty. We get aluminium extrusions at work that sometimes have faults caused by the material been so easy to recycle and impurities entering during recycling.

I do ride on the road a fair bit. It’s the better part of a 8-10 mile road bash out to the trails that I regularly ride, so roadsalt could be a likely culprit, but I’ve never seen the likes on any of my other bikes, nor on the front brake of this one.

I’m a bit skeptical about the corrosive effects of fairy liquid. Why haven’t my other bikes melted?

If it was galvanic shirley only happen between different metal interface – not sideways across the calipre ?)

Any salt solution is an electrolyte. This could be road salt + water, cow muck, or fairly liquid (that contains salt).

Electrolyte doesn’t directly affect aluminum, but of there is a dissimilar metal in contact plus the electrolyte, there could be a problem.

My hypothesis is that cow muck and other general dirt was left on the underside of the brake caliper. This, by itself or combined with road salt and / or washing liquid, created a semi-permanent wet electrolyte that, through one method or another, contacted the stainless steel brake disc, causing extensive galvanic corrosion.

Wouldn’t there be corrosion on the disc rotor, or on the contact points between the rotor and it’s alloy spider as well then?

IS MY WHOLE BIKE GOING TO CRUMBLE INTO DUST????? 😯

I rest my case

Well problem is shimano brakes don’t work as well as hope and you need to refill them on a regular basis 😉