Di2 Failure mode

[Phil W]

BTW hydro brakes will of course (sooner or later) fail to a leak. There is no maintenance regime (other than routine replacement of seal parts, and even then it isn't guaranteed) that helps to stave off this outcome.

True, but I am running xtr 2004 hydro and it is still on original hose and fitment etc.  So 14 years and still going strong and the mileage is not inconsiderable.  As for not noticing pads wearing down, only if you are mechanically inept and probably would not notice a flat on a fast downhill either.

It is a bit like household plumbing which as we know regularly lasts a couple of decades before leaks start, and the leaks start small.

[Brucey]

needless to say they don't all last that long....   and nor do the leaks always 'start small'.

You can probably quantify the amount of work that a brake has done by how many pad sets it has got through. Count about four organic/semi-metallic pad sets equivalent to one sintered pad set, maybe?

cheers

[sg37409]

IME with low end shimano hyd brakes, the callipers weep oil inside. Virtually invisible to the eye, but the effect is very evident to the ear and in terms of performance. Replacing the pads works for a while, but only replacing the calliper works longer term. Ive got about 2 years of very regular (town) use out of a calliper. The performance is so good, I put up with this pita.

[Brucey]

there is a known (and quite common) issue with some shimano calipers; it seems that the 'O' ring that seals the joint between the caliper body halves doesn't always fit/seal well.  Folk have experimented with going a size up on that O ring and sometimes it has worked OK for them.

I have a couple of failed calipers to investigate at some point but the culprit will likely be

- poor tolerancing on the depth/width of the O ring groove
- porosity in the caliper body castings
- poor surface finish quality on the O ring sealing faces.

To test for this issue , clean the caliper body thoroughly, install some old pads, wrapped in tissue paper, and leave the bike pvernight with an elastic band pulling the  lever towards the handlebar, so that there is a modest pressure in the system. If the system is leak-tight, the tissue will stay dry. If there is a leak, the tissue will have oil on it. If the leak is slow enough, the oil will be localised and you will be able to identify whether it is coming from one of the piston seals or the caliper body joint.

Shimano parts like these have a two-year warranty on them and you shouldn't have any trouble claiming if there is a leaky caliper joint; virtually nothing you can do to a system will make that joint leak if it is good to start with.

cheers

[mzjo]

I assume the mechanical disks are because you want to be able to take it apart with the S&S couplers? If not, seriously consider hydro. They probably fall (even further than mechanical disks!) foul of Brucey's ideals, but they work very well indeed, and need less faffing about with than mechanical disks...

Not really, it's more that on a the side of a mountain in Scandinavia, I can bodge working brakes with a spare cable, where as with Hydrolics, whilst they look to have a very high MTBF, I am concerned that the failure would be somewhat terminal.

I've been using cable disc brakes for 10 years, I understand them, and know their quirks. I know that Hydrolics are better in every measurable way, but if I lose the liquid due to collission, accident etc... I'm screwed. I can carry a spare brake cable.

J

Apart from the fact that screwed is not the word I would use in front of a lady, I am inclined to say that any collision or accident that leaves you with inoperable hydraulic brakes may well also leave you with much bigger complications of the type "inoperable body". The subset that includes hydro brakes us and excludes corporal damage may very well be infinitely small.

I would however accept the other failure modes and inconveniences that the more experienced riders have mentioned. I did think of "push-pull" couplers as a way of disconnecting pipes for an S&S coupled frame but I think probably the tiny amount of air admitted at each reconnection would pose a problem on a bike brake system, fully sealed should work better.

[Brucey]

the manufacturers of such 'dry break' couplings claim that they are suitable for hydraulic brakes.  However blurb is one thing (they may have omitted that some kind of bleed is required; a small bubble in the line might make its own way out of the MC without trouble I suppose...?) and reality is quite  another; I have not felt the urge to splash the cash on such couplings so I have not yet tried them for myself.

BTW my solution to a travelling bike is to take an old Rudge Bi-Frame and to convert that to dropped handlebars.  I daresay the frame weighs a pound or two more than it might otherwise but then the bike isn't larded up with stuff like disc brakes or fragile gear shifters and so forth.  It looks slightly odd, but goes about as well as most touring bikes and rides like a normal bike. There are no couplings required in the controls; the only complications are that

a) the cable runs are positioned so that they can fill up with crud a bit too easily for my liking and
b) if full mudguards are fitted they need to be QD to get a the smallest package.

 Overall, for the amount that I use the bike I can put up with its few shortcomings.

FWIW if you must have disc brakes on a bike that packs down small, there is something to be said for centrelock discs; they can be removed fairly quickly and this greatly lessens the chances of them being bent whilst the bike is being transported.

cheers

[LittleWheelsandBig]

A tired rider crashed during a long brevet I was riding in France a couple of years ago. His damage involved some lost skin and torn lycra. A Shimano hydraulic brake was toast and hydraulic fluid leaked onto his hand for the last day. He finished the fairly flat route to get to the finish.

[mzjo]

A tired rider crashed during a long brevet I was riding in France a couple of years ago. His damage involved some lost skin and torn lycra. A Shimano hydraulic brake was toast and hydraulic fluid leaked onto his hand for the last day. He finished the fairly flat route to get to the finish.

Oops; I really didn't think master cylinders were that fragile! Was that on drop bars? I am more used to the idea that in a crash the units can turn and most of the time the tips of the levers will break (aided by a suitably placed file cut to prevent the whole lever going but most would not want to do that on very expensive top end bike kit).

[Kim]

Apart from the fact that screwed is not the word I would use in front of a lady, I am inclined to say that any collision or accident that leaves you with inoperable hydraulic brakes may well also leave you with much bigger complications of the type "inoperable body". The subset that includes hydro brakes us and excludes corporal damage may very well be infinitely small.

Depends on the bike.  My tourer has a habit of landing on the handlebar controls when it falls over (I have a sacrificial bell to protect the left side, but the right has a mirror in that position so is still vulnerable).  Normally it's the bar-end shifters that are the problem (I have a parking brake on a friction thumb-shifter that can be re-purposed as a backup), but I've had mostly-cosmetic damage to cable brake levers in crashes I've cycled away from that could well have been terminal for hydraulics.

[LittleWheelsandBig]

A tired rider crashed during a long brevet I was riding in France a couple of years ago. His damage involved some lost skin and torn lycra. A Shimano hydraulic brake was toast and hydraulic fluid leaked onto his hand for the last day. He finished the fairly flat route to get to the finish.

Oops; I really didn't think master cylinders were that fragile! Was that on drop bars? I am more used to the idea that in a crash the units can turn and most of the time the tips of the levers will break (aided by a suitably placed file cut to prevent the whole lever going but most would not want to do that on very expensive top end bike kit).

Yes, Dura-Ace hydraulics and (from vague memory) Di2. I think the hose pulled out of the lever when the lever rotated on the bar during the crash but didn't have time to thoroughly diagnose things by the side of the road.

[Brucey]

IME with low end shimano hyd brakes, the callipers weep oil inside. Virtually invisible to the eye, but the effect is very evident to the ear and in terms of performance. Replacing the pads works for a while, but only replacing the calliper works longer term. Ive got about 2 years of very regular (town) use out of a calliper. The performance is so good, I put up with this pita.

further to the above, I have stripped one of the failed shimano calipers I have.  The leak was evidently massive; the pads were absolutely gopping wet with oil.

I can report that there was very clear evidence of corrosion in the grooves that retain the main piston seals. The piston bore and the grooves are bare, unprotected aluminium. There was also a little filiform corrosion on the caliper body, of a sort that is commonly seen if a little road salt gets under the caliper body paint in the winter.

A side effect of the corrosion was that the pistons became sticker than normal, because the groove with the seal in it was only just large enough to contain the seal to start with, and the seal became pushed more tightly against the piston. This meant uneven piston movement and a lack of piston retraction, as well as a worsening leak.

  The corrosion in the seal grooves is relatively thick and flakey; oil would have had no trouble in seeping through it and out of the hydraulic circuit.  I have seen similar corrosion in caliper bodies that use DOT4 fluid, too. The shimano mineral oil appeared not to provide much corrosion resistance; the corrosion was almost as bad (where it mattered) as with the DOT4 calipers, even though the DOT4 fluid absorbs water and is known to stimulate corrosion.

For commuting/winter training use, especially on roads with road salt, I would describe such failures as 'entirely predictable, and almost inevitable'; there is literally nothing to prevent salty water from penetrating and corroding the vital working parts of the caliper.

The caliper in question was a basic shimano hydro caliper, but the materials and construction used are not dissimilar to more expensive models.  As I commented elsewhere in this thread, it is the fate of all hydraulic systems to fail to a leak. If you use them in the winter weather, this counts double, and on the road, more again. I would (without hesitation) describe the design as 'completely unsuitable for UK road conditions'.

If you must use disc brakes for commuting, it probably makes more sense to use mechanical discs.  BB5 or BB7 may have their issues, but provided you keep the FPA from seizing, strip and lube the ramps/balls every year or two, and keep the cables in good shape, they ought to last a very long time indeed. Replacing hydro brakes every eighteen months would soon get old, as would the possibility that at any moment they could puke oil over the discs and pads and leave you with basically no brakes...

cheers

[jiberjaber]

IME with low end shimano hyd brakes, the callipers weep oil inside. Virtually invisible to the eye, but the effect is very evident to the ear and in terms of performance. Replacing the pads works for a while, but only replacing the calliper works longer term. Ive got about 2 years of very regular (town) use out of a calliper. The performance is so good, I put up with this pita.

further to the above, I have stripped one of the failed shimano calipers I have.  The leak was evidently massive; the pads were absolutely gopping wet with oil.

I can report that there was very clear evidence of corrosion in the grooves that retain the main piston seals. The piston bore and the grooves are bare, unprotected aluminium. There was also a little filiform corrosion on the caliper body, of a sort that is commonly seen if a little road salt gets under the caliper body paint in the winter.

A side effect of the corrosion was that the pistons became sticker than normal, because the groove with the seal in it was only just large enough to contain the seal to start with, and the seal became pushed more tightly against the piston. This meant uneven piston movement and a lack of piston retraction, as well as a worsening leak.

  The corrosion in the seal grooves is relatively thick and flakey; oil would have had no trouble in seeping through it and out of the hydraulic circuit.  I have seen similar corrosion in caliper bodies that use DOT4 fluid, too. The shimano mineral oil appeared not to provide much corrosion resistance; the corrosion was almost as bad (where it mattered) as with the DOT4 calipers, even though the DOT4 fluid absorbs water and is known to stimulate corrosion.

For commuting/winter training use, especially on roads with road salt, I would describe such failures as 'entirely predictable, and almost inevitable'; there is literally nothing to prevent salty water from penetrating and corroding the vital working parts of the caliper.

The caliper in question was a basic shimano hydro caliper, but the materials and construction used are not dissimilar to more expensive models.  As I commented elsewhere in this thread, it is the fate of all hydraulic systems to fail to a leak. If you use them in the winter weather, this counts double, and on the road, more again. I would (without hesitation) describe the design as 'completely unsuitable for UK road conditions'.

If you must use disc brakes for commuting, it probably makes more sense to use mechanical discs.  BB5 or BB7 may have their issues, but provided you keep the FPA from seizing, strip and lube the ramps/balls every year or two, and keep the cables in good shape, they ought to last a very long time indeed. Replacing hydro brakes every eighteen months would soon get old, as would the possibility that at any moment they could puke oil over the discs and pads and leave you with basically no brakes...

cheers

So the same as ceramic pistons?

[Brucey]

by itself, I don't think the piston material would make a big difference in this case; the corrosion did its evil work in a crevice between the groove in the aluminium caliper body and the piston seal ring.  The quality of the sealing between the piston seal ring and the piston itself was not compromised, i.e. the oil leaked around the outside of the seal.   There was some corrosion of the caliper body in the piston bore, but that didn't seem to have done any real damage.

 Thus I don't think it would make much difference if the piston were made from a resin (as per the less expensive brakes) or ceramic; if the caliper body is made the same way then the same kind of corrosion will be likely to  occur.

FWIW the only way I can think of staving off corrosion is to

a) make quite sure that you don't get road salt in the workings (so offroad use is less likely to be harmful, unless the soil pH is abnormal, and even then washing the bike should help)
b) to routinely put a drop of brake fluid (mineral oil) on the outside of the piston and hope that it does some good (NB this is often required anyway  to retain any semblance of balanced piston retraction)
c) to strip the caliper and to use an inert non-melting grease (such as Silicon grease) where the seal fits into the caliper body, and between the piston and bore on the air side of the seal.

The Si grease should provide some kind of barrier but it will be pushed out the crevice; every time the brake is used, the seal is pushed hard against the faces of the crevice and anything like a grease will be squodged out and in use may be lost altogether.

I suppose it is possible that the piston bore and groove are somehow treated (eg anodised) in other calipers. However I'm not sure this provides a really good sealing face and probably wouldn't be 100% proof against salt water corrosion anyway.

BTW the other leak path in these calipers is where the two caliper halves join and seal against one another. The joint is made flat on one side and a groove to accept an 'O' ring is machined in the other. In the caliper I looked at, the flat face had been polished to provide a good sealing face. The joint interface had additionally been protected (from corrosion) using some kind of mastic sealant. However the O-ring groove wasn't so well finished (so may have leaked) and the O-ring itself seemingly hadn't been made from the same material as the piston seal; the O-ring had become permanently flattened and had hardened too. You would not want to try and re-use this O-ring.

cheers


cheers

[citoyen]

As I commented elsewhere in this thread, it is the fate of all hydraulic systems to fail to a leak. If you use them in the winter weather, this counts double, and on the road, more again. I would (without hesitation) describe the design as 'completely unsuitable for UK road conditions'.

This is interesting, given that one of the supposed benefits of disc brakes is better performance in all weather conditions, hence they are often marketed as ideal for winter bikes. Must admit that calliper corrosion is not something that would ever have occurred to me as a potential cause for concern.

[rafletcher]

As I commented elsewhere in this thread, it is the fate of all hydraulic systems to fail to a leak. If you use them in the winter weather, this counts double, and on the road, more again. I would (without hesitation) describe the design as 'completely unsuitable for UK road conditions'.

This is interesting, given that one of the supposed benefits of disc brakes is better performance in all weather conditions, hence they are often marketed as ideal for winter bikes. Must admit that calliper corrosion is not something that would ever have occurred to me as a potential cause for concern.

Indeed. Motorcycles have been managing British winter weather fine for many years with disc brakes. Brucey doesn’t like them (disc brakes, to be clear) ETA - on bicycles that have “drop bars” to be crystal clear,  and will research any potential failure mode in order to support that view. Of course there will be failures, but as has been pointed out elsewhere (and refuted by Brucey, who can apparently cycle thousands of winter miles with rim brakes and never need to replace a rim) many of us view the replacement of a calliper after several years service as an acceptable price to pay versus the costs of new wheels, or rebuilt wheels with new rims and spokes, given the superior overall braking performance of discs, in particular hydraulic ones (which are ok for MTB but no good for “drop bar” - read “road”? - bikes).

[Hot Flatus]

Indeed. Well put.

Here's some balance...

Enve rim (worn through winter use with rim brakes). Inevitable. £1000.

Dura-ace disc caliper (replaced through failure, although I've yet to hear of one) £108

Taking it down to the bottom of the road range, 105, and a new caliper is £30.  Can you get an equivalent level rim purchased and rebuilt for £30?  Think not.

Rim wear is inevitable in the relative short-term. Caliper failure, not so much.



 

[Brucey]

I'm getting sick to death of others putting words into my mouth that I never said.  For example I said that rims need not wear out very quickly. That is not to say that they cannot do so. But when I see folk (following advice) reject rim brakes as suitable for (say) summer touring 'because their rims will wear out and this is a problem' I would say that they are being very badly misinformed on several counts.

If I "didn't like disc brakes" I wouldn't have them on any car, motorcycle, or bicycle. As it is I have all these, in multiples. My objection to the headlong adoption of disc brakes on (all) bicycles is mainly the current received wisdom that 'they are the best' for various jobs. In many cases they are certainly not 'the best' and those who are keen on them appear  not to be cognisant of the true facts of the matter and/or are also prepared to ignore any knock-ons and consequences that arise from their adoption. They are ably assisted in this by a basically 100% sycophantic/deluded cycling media, who are prepared to say 'everything new is lovely' without much testing or analysis to back this view up.  It is pretty clear that (say) riding on UK roads in the wintertime is very far away from the brief of most cycle designers; what works OK on a sunny weekend can rapidly turn into a complete PITA if subjected to the daily grind....

  Note that car disc brake calipers usually have an additional dust boot that prevents water from getting down the piston bore. So do many motorcycle brakes. Both regularly run higher caliper temperatures and airspeeds (which help drive moisture out) than most bicycle disc brakes do, certainly in typical winter training/commuting use.

Car brakes and motorcycle brakes without dust boots on their calipers regularly suffer seized pistons (due to corrosion),  and ones with aluminium caliper bodies of course suffer worst of all.

So, (leaving aside that motorcycles these days are also more likely to be fair-weather toys than anything else) that bicycle disc brakes can suffer similarly should be absolutely no surprise to anyone.

cheers

[grams]

I don't know how you can control for the number of bikes out there that don't need repair and therefore don't get seen by the Bruceys of the world.

There's an awful lot of MTBs sold in the last decade with hydraulic discs, many of them used as commuter and utility bikes and if they failed at the rate Brucey infers I think we would know about it.

[Brucey]

Here's some balance...

hmm not the word I'd have chosen....

....a new caliper is £30.  Can you get an equivalent level rim purchased and rebuilt for £30? 

does this caliper magically fit and bleed itself then? Does it clean up or replace the contaminated/worn disc too?....

 Most LBSs consider it most cost-effective to sling any faulty flat bar disc brake in the bin rather than mess about with it.  One reason dropped bar hydro discs are not the same proposition is that you are in for a lot of DIY or a fairly substantial labour charge to get the things fitted and maintained. Many LBS are presently absorbing some of this because their customers don't expect an hour's labour charge for replacing a caliper. In point of fact it can take longer than that, depending on the hose condition, routing, and whether the bleeding goes well or not.

Busy workshops are increasingly making more realistic labour charges for certain jobs on modern bikes, as they realise they are going to go bust if they carry on subsidising them. For example I recently saw an 'aero' road bike in an LBS for recabling and all the cables (and indeed the brake calipers themselves) were hidden behind covers/within the frame/stem/forks etc.  The customer chose not to go ahead with the job when he was quoted 'about £250, but it might be more because of the unknowns in this cable routing' for parts and labour on this job.  I thought their estimate was quite realistic.

Rim wear is inevitable in the relative short-term. Caliper failure, not so much.

I own rims that have seen tens of thousands of miles of all weather use and are old enough to vote.  I have also destroyed a rim (through wear) in a single alpine descent, under very exceptional circumstances.  I don't think rim wear is quite as inevitable as some folk think.

 I also think that by contrast spraying salty water onto certain materials combinations is going to have an effect for sure.

cheers

[mrcharly-YHT]

It very much depends on the riding conditions, surely?

When I used to pile up a lot of commuting miles I was getting sick of wearing out rims. I washed off my bikes regularly, replaced brake pads with monotonous regularity, but still was replacing a rim about once a year. Brake pads lasted, in winter, about a month.

Disc brakes have been a revelation. Rims just didn't wear. I had an early pad failure with the oem pads and no problems since then. Pads, when I was still doing lots of miles, lasted about a year. Wheels were so much cleaner.

Sure, there are downsides, but for some types of riding, disc brakes are superior. More reliable, more durable, less maintenance required. More reliable braking.

[Hot Flatus]

Here's some balance...

hmm not the word I'd have chosen....

....a new caliper is £30.  Can you get an equivalent level rim purchased and rebuilt for £30? 

does this caliper magically fit and bleed itself then? Does it clean up or replace the contaminated/worn disc too?....

 Most LBSs consider it most cost-effective to sling any faulty flat bar disc brake in the bin rather than mess about with it.  One reason dropped bar hydro discs are not the same proposition is that you are in for a lot of DIY or a fairly substantial labour charge to get the things fitted and maintained. Many LBS are presently absorbing some of this because their customers don't expect an hour's labour charge for replacing a caliper. In point of fact it can take longer than that, depending on the hose condition, routing, and whether the bleeding goes well or not.

Busy workshops are increasingly making more realistic labour charges for certain jobs on modern bikes, as they realise they are going to go bust if they carry on subsidising them. For example I recently saw an 'aero' road bike in an LBS for recabling and all the cables (and indeed the brake calipers themselves) were hidden behind covers/within the frame/stem/forks etc.  The customer chose not to go ahead with the job when he was quoted 'about £250, but it might be more because of the unknowns in this cable routing' for parts and labour on this job.  I thought their estimate was quite realistic.

Rim wear is inevitable in the relative short-term. Caliper failure, not so much.

I own rims that have seen tens of thousands of miles of all weather use and are old enough to vote.  I have also destroyed a rim (through wear) in a single alpine descent, under very exceptional circumstances.  I don't think rim wear is quite as inevitable as some folk think.

 I also think that by contrast spraying salty water onto certain materials combinations is going to have an effect for sure.

cheers

Does that worn rim magically unbuild itself, and the spokes then build themselves into a new rim. Does it magically remove tyre and tube and the refit and inflate?

It takes me about 5 minutes to bleed a disc brake. I reckon I could remove, replace, and bleed a new one quicker than a rim could be removed replaced, rebuilt and true, tyre removed, replaced and inflated.

[simonp]

I rebuilt the brakes on my old motorbike cleaned out with new seals. I think at the costs quoted above I’d be binning and replacing as well.

[Brucey]

....It takes me about 5 minutes to bleed a disc brake....

that might be the funniest thing I have ever read....

cheers

[Hot Flatus]

Laugh it up

[simonp]

It's probably a lot easier to bleed the brakes on Shimano Ultegra than it was on the motorbike. Because of the ABS control unit, the brakes must be bled by drawing fluid from the caliper. You unscrew the bleed screw a little and use a suction pump to pull fluid through. However my experience was that the bleed screw threads became leaky at this stage, so I was drawing air as well as fluid. This made it very hard to know if there was any real air in the system. I left it overnight and found the brakes really spongy in the morning so had to do it again, with an MOT booked the same day.