[/quote]Agreed some people seem to be lucky but this does seem to be an extremely common problem not related to any particular level either (lx,deore,slx,xt etc)… Mind you I have not heard of the xtr’s going very often… Perhaps that has to do with the slightly tighter tolerances on the magnesium cast and machined caliper body. Either way madison should warranty without question and the lbs should not be arguing.

. The reason XTR calipers don’t suffer so much is that the lever seals give up the ghost so quickly that the caliper seals don’t have a chance to fail first .

freeagent – where did you get the O-rings from?

I need to pull mine apart and find out what size the RS505s take.

Sorry for the delayed response – O-rings came from Ebay – there is a link on P1 of this thread.
So, 2 weeks in, I’ve done a total of about 100 miles over 4 different rides, and the brakes are both silent and powerful.

Bookmarking this thread, just in case. Good work.

Nitrile also goes by the most commonly used trade name Buna-N, which should help those trying to source them from alternatives.

As a side note Nitrile/Buna-N is also the O-ring material for the vast majority of suspension components. As it is resistant to mineral oils/greases, hydraulic fluids (HFA, HFB, HFC), solvents and relatively flexible at low temperatures 😉

Finally gave up with the front caliper. Despite putting a new o ring it has continued to leak. The rear one is still fine though.

Bought a Hope RX4, bleed was a bit more of a faff compared to the original but having done it once I could make it a bit easier next time round. You will need a threaded syringe for the caliper.

Riding it is good, braking is more powerful than the shimano one. There is less lever travel which given the original has a long lever throw is not a bad thing.

Will replace the back one if it fails too but happy to keep it on into then.

Really useful post, I’ve got the same problems with leaking 785 calipers and will try replacing the o-rings before splashing out on some RX4s.

Would someone mind confirming the replacement o-ring size, is it 3mm x 1.5mm?

cheers

Just fitted a new 105 hydraulic groupset with 785 calipers tonight. Front brake working nicely, squeezed the rear lever and…drip, drip, drip on the garage floor. Oil freely leaking around the ceramic piston. The bike hadn’t even got off the workstand!

From a quick search, there seem to be a number of people reporting leak problems with these brakes.

Yep, the problem still exists, only yesterday afternoon I had a brand-new bike, straight out of the box with a caliper that had shat itself pretty badly. All nuts and bolts tight, no trace of fluid on the outside, but the pads and pistons were swimming. We keep a stock of calipers for replacing these, as if we didn’t, somebody would end up having to wait for their new bike, which never looks good for anyone involved.

Yip, same here. Mine were leaking from the centre o-rings as mentioned above. Fixed that but now they leak via the piston. Can’t find any reference to fixing that issue so it’s a warranty return. PITA.

Just sorted my 785s with new o rings.

Initial problem sorted so thanks OP :0)

To revive this thread did anyone post a link to the correct sized O ring? I found lots at 1 mm but nothing as close as the found. Any suggestions, and yes, I have googled for it.

did anyone post a link to the correct sized O ring?

It was on the first page – to eBay 😀

My rear RS505 did this. Very slow warranty through Canyon. 6 weeks later got the replacement, put it on, new pads, bled up nicely, freewheeled down the road, back working nicely. Used the front to come to a stop, GOBBLEGOBBLEGOBBLESHREEEEEEEEEIIIIIIIIIKKKK. Oh look, the front has failed after 6 weeks of hard sitting around doing nothing.
Never had a Shimano brake, was going to buy some for another bike. Not a chance now. Total crap.

Anyone got any more pics of what these leaks look like or is it always seen like this? Image is from earlier in the thread

Had endless joy with Shimano brakes and now think this is happening on my cx bike. Oily rear disc.

The Hope looks soooooooooo nice.

The o-rings linked to on the first page are the original 70shore not 90 as recommended in the guide. How are the ones in the link holding up for everyone?

Interesting, I have this problem, I guess a simpler fix might be to seal around join between the two halves with something, might work for my commuter anyway.

Loctite anerobic flange sealant. I’ve used this on crankcase mating surfaces several times and never had a problem with leaks. It goes on as a liquid, the surplus stays liquid and can be wiped away. The remainder between the sealing faces goes off and forms a seal. Whether or not this would effect a seal in a hydraulic circuit remains to be seen. Might be worth a try.

I have just ordered M7000 complete replacement for my old M785s. If I can’t flog them I will strip and try the suggestion above with the seals from ebay at the back (I think the front leak is from the piston rather than the caliper halves).

My son Harry is frantically searching for a new set of brakes at a good price (he is 12). His Old Shimanos were squealing so badly it was getting painful to be near him so I replaced them with an old set of Avid Juicy 5’s. He hates the look of the Avids (apparently this is important to a 12yr old) so he is now all over the internet showing me good deals on new shimano brakes. Is there a model where the leaking seal issue vanished and was never spoken of again? I am guessing that any good deals we find will be a potential squeal issue again?

Just bumping this in an effort to placate my son and also not raise yet another thread on the subject 🙂

They don’t appear to have solved it yet, judging by the brand new Tiagra caliper in our workshop that’s dribbled it’s internals away before it’s even made it out of the shop. I’d be taking a look at a Clarks M2 set(probably less than £50 a pair inc rotors & mount on the internet), we’ve sold a lot to replace worn out brakes, rather than repair them, and had no issues other than a damaged olive in one set. They’re very reasonably priced, work well, look nice (to me, obviously subjective), and even have “go fast” red anodized bits.Edit- £42.99 on Amazon.

And this isn’t just about infrequent use and the o-ring on the transfer port.

My 9020 callipers (single piece, no transfer port) which have been on my commuter for 4.5years, in almost daily use have finally developed the same symptoms as my Trail brakes did on the MTBs. Time for some RX4s…again.

I was going to suggest the Clarks brakes as they look ok in black with the red anodised bits on them. Go 180mm discs and when the pads wear out something in a bit more grabby.

Otherwise I’d be looking to find a deal on Sram Levels or some
Maguras – maybe mt2’s or mt4’s.

There are still loads of posts about leaking shimano brakes – the only ones that don’t have loads of leaks reported seem to be the 4 pot caliper ones.

I got some of the Clarks ones for £20 and end for my daughter’s bike. Theybwork well, but clearly not as much bite as an expensive set. Doesn’t matter so much when you weigh 28kg but it might when you’re 82kg. Fine for commuting tho too I’d imagine.

Thanks everyone, will take a look at the Clarks. He needs something decent as he is moving on to red trails now so I want him to be able to manage his speed effectively, that said, to the point made by @molgrips, he weighs half my weight so a lot less to stop 🙂

He’ll prob be ok with the Clarks if he’s quite light – especially with 180mm rotors. The sram or Maguras I suggested will likely be more powerful (you could add Sram guide R’s to the list as they seem to come up cheap from time to time) and better overall.

I’m nearly 13 Stone and my Clark’s m3 on 180 rotors are more powerful than my mini monos

Use shimano mtb calipers instead the road calipers.

I’ve had this issue with Rs505 (x2) and (Road) 785s, annoyingly even though I’m on here a lot I’ve just been buying new calipers.

Paul’s cycles weren’t great with the RS505 caliper the first time so I just replaced it myself and the other bike was way out of warranty so I didn’t bother. It was getting expensive in terms of pads initially as I thought it was just Road oil contaminating the pads and discs.

Just came on here to post on this same issue and this thread appeared. God bless STW!

As someone with a few sets of Guide RS that need repairs, I wouldn’t recommend these to someone looking for troublefree but otoh, the fixes are easy to install and cheap and easy to source (piston seals under £5 a calliper and lever piston in Alu plus seals around £7 a go both on eBay).

I’ve moved to Magura. The power is there, reliability hasn’t been an issue yet but lever feel is quite different than Shimano which will put many off I think (no ‘instant power’, there’s a noticeable progression through the pull).

Bump

Clarks brakes which use mineral oil like Shimanos do spare piston seals for their clout and M3 brakes. The pics look like the shimano square cut seals. i wonder if they’d fit any shimano pistons ? http://clarkscyclesystems.com/

I’m not really up on my model numbers but would the O ring listed on page 1 fit an XT calliper?

A more general suggestion for the wider topic is to try using an MTB caliper. I’ve been using a old 2 pot XT on the front of my roadie for over 6 months and it’s been so much better – not only in terms of no leaks or contamination of pad, but it doesn’t chirp or rub the disc and feels much smoother.

I’ve got a Hope RX4 ready to fit and some new Galfer rotors, but am scare it might be a backwards step!

My 785 calipers were not very good . Replaced the o ring and whilst it stopped them from making too much noise , their performance was a bit rubbish . Replaced with some XT and it is brilliant .
Wish I did it sooner .

Has anyone seen O-Rings that fit Saint calipers?

Hey thanks for the o-ring info. Useful.

I work as a shop wrench, and have had plenty of leaking Shimano calipers over the years – and had one of my own brakes too. Never tried to fix them myself, as Shimano Nordic has always warrantied the calipers with minimum fuss and fast too (give em a call or email and couple days later its sorted), but nice to know it may be possible to fix the calipers as well.

Nevertheless, I have been riding exclusively Shimano brakes for 17 years now (after some Hayes back in the early 2000s), and have had one faulty caliper. Though my own brakes are always aligned right, unlike many of the customers brakes. And at the moment my oldest in-use Shimanos are XT 765s that I got when they first came out…

Most of the leaking ones from customers have been the low end ones (sets priced around 50-80 euros), but several SLX / XT ones as well.