- Disc brakes problem (road bike Shimano BR785/505)
I’ve got a problem that I cant solve on my 2017 CAAD 12 disc.
There is a little bit of braking, followed by an amazing screaching noise, followed by reverberations that you can feel through the bike – all with very minimal braking performance.
Bike has Shimano BR785/505 calipers and 105 levers.
The brakes were originally amazing, endoing or locking up the rear wheel at will.
They’ve deteriorated. First the rear stopped working well so i relied on the front, now the front have gone the same way.
I’ve tried: new pads (uber pads), new rotors (swapped from other bike), bled the brakes, both pistons are moving, levers feel reasonably firm, calipers appear well aligned to the disc.
Any advice before I take it to the LBS appreciated.
Thanks.Posted 1 month ago
The standard answer to this is that some older Shimano callipers leaked, causing the pads to get contaminated.
New pads would obviously work initially but then get contaminated again. Similarly your rotors might end up contaminated unless you clean them constantly.
The brakes on my dad’s bike were quite obviously leaking, there was a ring of fluid that had accumulated on the back of the pad, but apparently others can be quite subtle, enough to contaminate the pads, but not enough to see.
Hopefully your LBS will be big enough to just warranty them without fuss, I had a massive battle with my shop to get them warrantied, thankfully Madison eventually stepped up to the plate and sent me new brakes.Posted 1 month agoJonEdwardsMember
Yup, leaky caliper seals. I’ve got the same calipers on my winter bike. Back lasted just under 2 years and I got replaced under warranty, the front (now 3 yrs old) is also now leaking.
You can fudge the issue by dragging the relevant brake down a decent hill to get the pads and rotor b*st*rd hot, but its far from ideal and that moment when you try and stop for the lights at the bottom of the road, straight out the front door, and realise the front brake does dick all isn’t too pleasant.
Shimano kit is a 2 year warranty period except XTR/DA which is 3.
I’m very tempted to get Hope RX4 calipers, except they’re each twice the price of a Shimano one and I’d have to buy 2, not 1 because matchy-matchy.Posted 1 month agosubmarinedMember
My rear 505 did exactly the same. A warranty replacement calliper fixed it (you could see evidence of fluid seepage on the caliper and pad backing)Posted 1 month ago
Fitted the new one, took it out for a very short test ride, and then submitted the warranty claim for the front that had failed in exactly the same manner whilst the bike was parked up.philjuniorMember
It does sound like contamination, quite possibly from leaky calipers.
I find the wrong sort of weather with gritted roads doesn’t help too, could it be that? Particularly if you never get heat into them or only use the bike occasionally.
If there’s no sign of oil on the pad, I wouldn’t assume it was a leaky caliper, but would look for other sources of contamination, or just put new pads in and clean the disc/replace it if it’s nearly done in anyway.Posted 1 month agopdwMember
As above, lots of noise and no power is a pretty is almost certainly contamination due to brake fluid. On mine (505 calipers) it was the piston seals. I was quite surprised that a leak sufficiently small to not cause a noticeable drop in the fluid level in the lever could repeatedly soak the pads to the point that they basically didn’t work. A paper towel wrapped around a bleed block and the brake pulled on overnight with an elastic band confirmed that they were leaking, and a warranty replacement fixed it.Posted 1 month agophiljuniorMember
I’m very tempted to get Hope RX4 calipers, except they’re each twice the price of a Shimano one and I’d have to buy 2, not 1 because matchy-matchy.
Haha, please don’t say this, I’m just about to go from hy-rds to full hydraulic as the hy-rds are old and pretty much done in with seized bolts here and there, plus my rear cable routing lets water pool which isn’t pleasant when it freezes and you have no rear brake in icy conditions.
I needed post mount, but didn’t go for the Hope calipers!Posted 1 month agoescrsMember
As everyone has said its leaky calipers, known shimano issue and why i no longer run their brakes after having the following leaky calipers
M8000 XT caliper
Sometimes you cant even see the leak, Chain reaction couldnt find the leak on my Zee caliper so they sent it back to shimano who pressure tested it and told CRC to replace it under warranty
Will only run Hope brakes now on my Mtb and Road bikesPosted 1 month ago
Thanks for replies.
My bike came from Evans in July 2017 so not much chance of a warranty replacement now, shame the it would have been in warranty if I’d not ignored it for so long and just ridden my summer bike.
The bike is my training bike and generally filthy so very likely that I wouldnt spot a fairly minor leak.
So, what are the direct replacement caliper options? Its sounding like you cant replace the seals.Posted 1 month agoescrsMember
Seals are and pistons are non replaceable if i remember correctly
You can replace the caliper with pretty much any other Shimano caliper
Personally if you can afford it id go buy some Hope RX4 calipers, Shimano warranty is pretty good but you will always wonder if they are going to leak again
Hope warranty is one of the best out there, calipers can be completely rebuilt at home or by them and they carry stock of spares for years (they have spares for 15 year old calipers)Posted 1 month agofathomerSubscriber
My winter road bike is on calipers 6 & 7 from memory, this is it’s 4th winter! All from leaky calipers! Fortunately there cheap and easy to replace.
Strangely, never had one go the same way on the mtb’s, though run Hope’s now, more modulation and no wondering bite points.Posted 1 month ago
At ~£40 a caliper they are hardly a consumable! I bought a disc braked training bike to avoid replacing rims, not to replace calipers every winter!!
I’ve got a 4 spare pairs of 785 pads and 1 pair of the 505s, so it might be worth persevering with the shimano’s, especially having seen the price of the hopes.
Am I best going for another 785 up front and a 105 BR-R7070 for the back? Around £37 each.Posted 1 month ago
I have squealing Shimano 505 variant brakes too but power is OK. Can’t quite believe its leaking seals as it squeals within moments of fresh pads being put in, but I stand to be corrected.
There’s a school of thought that says rotors can be contaminated too as contaminated material gets deposited onto braking surface. I’ve never quite believed it myself but perhaps you could try and sand down your rotors to remove the current surface material and bed them in again with clesn pads?
Otherwise squeeling could be down to alignment or install (rotors rotating the right way?)Posted 1 month agokcrMember
I had problems with my 785s this summer; minimal bite unless the brakes are jammed on really hard, at which point they squeal and grab the disk. I’m not convinced it’s a leak issue, because I’ve not experienced any degradation in the lever action, over the best part of a year, and as mentioned above, on some occasions I could see pads glazing up almost immediately when I replaced them. It seemed as if the discs were developing a very polished surface in good conditions and glazing the pads instead of biting. Most of my riding has been a short commute with fairly minimal braking, so the brakes don’t get heavy use. Sanding the discs helped a bit, but the problem reoccurred.Posted 1 month ago
I’ve just replaced the pads again and they’ve been performing OK, so I wonder if a bit of dirty weather is helping to keep things working?
I’m not convinced it’s a leak issue, because I’ve not experienced any degradation in the lever action, over the best part of a year
I had concluded that the leaks are so minor that they are accommodated by the volume of the reservoir in tbe lever.
Most of my riding has been a short commute with fairly minimal braking
I honestly think, and have had shop mechanics agree with me, that disc brakes just don’t suit light or gentle use. I think this is where my dislike of discs on road bikes stems from, I ride in such a manner that I rarely brake hard, which just seems to lead to glazing and screeching in wet conditions. There’s a reason both my commuters are now back to rim brakes!Posted 1 month agoTurnerfan1Member
Usually an o ring issue in the rs 785.Posted 1 month ago
Made of the wrong material apparently.
Just take caliper half apart and replace o ring.
There was a big thread on here some years ago including the link to the appropriate o ring on Ebay!
Sorted out all my leaking issues anyhow!
Just for balance, I have one of the earliest sets of R785s and they’ve not leaked and have been in almost daily use. I did replace one of the calipers a year or so ago, but that wasn’t due to leaking.Posted 1 month ago
Have had mtb calipers leak though. Worst was a brand new Deore twinpot. Could almost see it dripping!
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