Shimano brakes

[fatbikephil]

You shouldn't get air dissolved in brake fluid so it was coming from somewhere. Funnily enough when I did the deore brake on the ICT the air did clear eventually so maybe it was in the system. The other thought is that its being sucked in past the piston seals. But yes it was very hard to suck or push fluid through (I did it both ways) suggesting a partial blockage somewhere or oil that is too thick.

[boxelder]

This is why I'm a Geography teacher by trade and not a mechanic/engineer. Any technical advice I can offer is barely good enough for Facebook.

[ScotRoutes]

when I did the deore brake on the ICT the air did clear eventually so maybe it was in the system.

Tra la la la la la...

[jameso]

Fwiw my Shimano brakes get bled from caliper up, got a clamp-on Shimano bleed kit that directs the overflow from the lever reservoir into the bottle. Been using the same XTs on one bike or another for 10+ years, bled through every 3-4 years. There have been bleed process fails in the past but they seem to be good now and if no air goes in, no issues.

[Alpinum]

The other thought is that its being sucked in past the piston seals. But yes it was very hard to suck or push fluid through (I did it both ways) suggesting a partial blockage somewhere or oil that is too thick.

I thought I once read somewhere (IFU?) that you shouldn't pull (apply vacuum) the liquid with shimano brakes.
I can only guess it's for that reason (sucking air past the quad ring seals) you got air in the hydraulic. In my experience there's also the already mentioned risk of pulling air through the bleed nipple of the caliper. My only advice is to make sure the nipple is closed and and to flush the system only by pushing hydraulics from the caliper mounted syringe into the beaker screwed to the lever.
Changing the hydraulic I fill one beaker (standard Shimano), discard its content, refill the syringe and fill the beaker again following up on the regular bleeding procedure.

Whilst doing this, give the pistons a clean.
You can find some advice for this on youtube.
Basically this:

remove the pads, pump the lever a little for the cylinders of the caliper to move out (inward to where the rotor would be), then clean the (once) white cylinders with a cord wetted with isopropyl alcohol by slinging the cord around the cylinders and pulling on it to remove dirt. Once that's done, a drop of mineral oil (the one you use to bleed the brakes) on the cylinders, push them back in with a tyre lever or so, clean any residue inside the caliper with a cloth and alcohol, reinstall the pads and wheel and see if it's any better. This usually helps to mobilise the cylinders and can make quite a difference. When running through that procedure the only critical parts are to not move the cylinders inward too far or else they pop out which gives a nice mess and requires bleeding and to give it at good clean before re-installing the pads (to not contaminate them and the rotor).

[Cyclepeasant]

May I ask if many of you that are using Shimano hydraulic brake calipers on your bikes,how many have experienced the "micro leaking " of the calipers resulting in contaminated pads and discs with the resulting squeal and no braking?
I have three Shimano braked bikes and they all suffer from this problem.
The folding tern s8i rear brake failed within 4miles from new.

Madison,the Shimano importers do not admit it is a common problem.


I have hope mono minis that are 20? Years old and a set of Hayes that are older and they still work fine.

[Lazarus]

Madison,the Shimano importers do not admit it is a common problem.

They are lying its a well known problem - that said even if say 0.001% of every brake they ever makes fails that is thousands of failed brakes, given their volume of sales/

I wonder f they will say what is an acceptable failure rate
The lack of spares is even worse as you have to bin everything [ also got some 20 year old hopes still in use

[redefined_cycles]

I got rid ofy micro leak and squeal by getting rid of the calipers and putting on new ones. Worked for about a year but the squeal is back. From fairly pig sounding to really really pig sounding.

Just to add, that I'm beginnin to hate Shimano brakes more than I'd read about it (the hate on the older models). S H I T brakes. I might yry the putoline method!!

[whitestone]

Madison,the Shimano importers do not admit it is a common problem.

They are lying its a well known problem - that said even if say 0.001% of every brake they ever makes fails that is thousands of failed brakes, given their volume of sales/

I wonder f they will say what is an acceptable failure rate
The lack of spares is even worse as you have to bin everything [ also got some 20 year old hopes still in use

We've had three bikes with Shimano brakes (not XTR level) and all three developed the caliper micro-leak just after the 2 year warranty expired That level of occurrence is several orders of magnitude greater than any manufacturer would/should accept as a fault.

From memory the companies I worked for in consumer electronics reckoned on about 1% failure at "in production testing" in the factory and virtually nothing by the time the goods reached the end user. Again from memory, I believe that Apple work factor in a 3% return rate to their pricing but most of those returns aren't "failures" but customers being very, very fussy: there was a partial fingerprint on the edge of the screen, etc.

[Lazarus]

Six sigma is 4 per million failure iirc.
Suppose it depends how much trouble the company want to go to make a good product ( as presumably that adds costs )

[fatbikephil]

Yup, on two sets of brakes. The oil never seemed to make it onto the pads as far as I could tell - I just became aware of a mist of it on the caliper and fork leg. As I'd noted above somewhere, this was almost certainly why I had continual problems with them losing the lever and being full of air bubbles...

I tried new seals but I couldn't for the life of me get the pistons back in with the new seals fitted. Hope pistons (and suzuki pistons) have a bit of a radius on the back of the piston to help them in. The shimano pistons were quite 'square' I don't think the new seals would have worked. The pistons looked very scuffed and I suspect this was why they were leaking not due to duff seals. I think people on ebay are flogging alloy pistons but these will likely just seize if you get any salt anywhere near them.

Will see how long the latest pair last - I got them cheap as one was a front left and the other a rear right. As they come with the hoses disconnected this wasn't a problem.

[Cyclepeasant]

Personally,I think it's unacceptable.
I would be interested how Shimano USA is dealing with this problem!

Having worked on cars and motorcycles,I cannot recall one case of new brake failures or on vehicles of a few years of age.

I don't understand how this is acceptable in the cycle industry,and from the world's biggest manufacturer!

Perhaps, I should just replace them with better quality brands such as Hope etc.

Has anyone persuaded Madison to replace Thier dodgy calipers?

Sigh!

[fatbikephil]

In a way it's a bit odd as Shimano are quite good at sorting problems but they seem to be struggling with this one which is strange as it's not exactly new tech.... after years of working with horribly corroded car brakes that don't leak a drop, it's annoying. More so as they only will flog you a complete caliper rather than seals and pistons. I'm past writing snotty letters to people these days and tend to just vote with my feet so I'll give them one more chance with the latest brakes (a do like the very 'bang on' feel of shimano brakes) then probably go back to Hopes.

[Jurassic]

I'm past writing snotty letters to people these days and tend to just vote with my feet so I'll give them one more chance with the latest brakes (a do like the very 'bang on' feel of shimano brakes) then probably go back to Hopes.

I've been a defender of Shimano brakes in the past, I've had multiple sets on different bikes from cheapo Deore single pots, XT two pots, XT four pots to Saints and they've all been flawless when bled correctly. Unfortunately my newest bike has new model XT four pots on and I've had endless problems with them. I've tried all the tricks of the trade but the levers still keep gradually coming back further than I like. I'm going to try the Putoline trick with them as a last resort but if that doesn't work I'll be looking at Maguras or possibly Hopes (which I don't really like but at least they're consistent).