Shimano R785 issues

[anonymous-user]

Recently built up a new bike and used these off my previous bike. From the start they were pretty dire, took a lot to bleed them and they just rubbed, no power. I changed the pads, cleaned the discs and this appeared to cure the problems. Took the bike to Italy, first ride the front brake is howling, rear seems ok. Return two weeks later and both are unusable. No stopping power, howling. Upon inspection the discs are greasy to the touch, I would say the calipers are leaking, loads on the web about it and it would make sense as they were working at the outset.

Looking to replace them, and not with the same R785, which is obviously a heap of st. Hope look good but I will have to swap lines as it appears that the hose connection is different? Are Ultegra/DA calipers compatible or do I just junk the hoses and use Hope?

Really disappointed with the low quality of these compared to the XTR on the MTB, they just work.

[Your Dad]

yonex said:

Recently built up a new bike and used these off my previous bike. From the start they were pretty dire, took a lot to bleed them and they just rubbed, no power. I changed the pads, cleaned the discs and this appeared to cure the problems. Took the bike to Italy, first ride the front brake is howling, rear seems ok. Return two weeks later and both are unusable. No stopping power, howling. Upon inspection the discs are greasy to the touch, I would say the calipers are leaking, loads on the web about it and it would make sense as they were working at the outset.

Looking to replace them, and not with the same R785, which is obviously a heap of st. Hope look good but I will have to swap lines as it appears that the hose connection is different? Are Ultegra/DA calipers compatible or do I just junk the hoses and use Hope?

Really disappointed with the low quality of these compared to the XTR on the MTB, they just work.

Following as I've just ordered 785 calipers.

[anonymous-user]

So, I had a long conversation with a dealer who has had a few of these issues with Shimano. He said it's either a leaking seal, broken piston or the o ring inside. The problem is the 785's are out of stock and on back order. So...



One interesting snippet though. As the bike is stored at the top of the house, which is around 35 deg this week he said with the road hydraulic there is no breather, so if there is expansion then the oil can get forced past the seals when the bike is laid up for a while. This makes perfect sense, and is utterly st.

Anyway. The Hope calipers should mean I have reliable and rebuildable brakes for the future. Also going to have to upgrade to 160mm rotors, not a bad thing as the stock 785 set up I felt was never as good as my only SRAM red, or DA9000 set up in the dry.

I'll update this when they arrive...

[Steamer]

Interesting - all my bikes have Shimano, as you say SLX - no problem (although they make a racket in the rain!)

However - my winter / beater bike has 7(something) Shimano Deores and they really don't like sitting for more than a few weeks without use.

[frisbee]

Mine did that and they were pretty corroded from winter commuting as well. Some rumours that it was the early ones that had problems, so I just replaced like with like.

They were about £30 each on Amazon a few months ago.

[anonymous-user]

I managed to improve things no end tonight, after spending £200 on new callipers

Removed the pads...




It was the same both ends. The fluid had leaked past the seals and contaminated the pads. Started with brake cleaner with pads removed, blasted the caliper clean. Then sprayed onto the pads to try and flush as much crap off as possible. Next sanded them back with 60 grit until fresh material was revealed.

Then...

This is brilliant stuff, tastes just like grappa wiped the rotors clean then used the 60 grit to take the shine off the surface.

Refitted and went for a spin. They were loads better, after 10km things were pretty good, as good as they’ve been so at least I can ride for the moment.

New callipers are due in at the weekend so can pick them up before heading back out. They might screw up again but at least I have a 10 min fix for the moment.

[Crippo]

Have you used the bike in the wet?
There is a debate about the suitability of discs for road bikes because if you use the bike in th wet the water mixes with oil that is on some roads, and it can contaminate the discs and pads. It depends upon the road you use and how lucky, u lucky you are. Your issue may not be relevant to this but I know some shops are dubious about some disc contamination issues because of this potential....just a thought

[anonymous-user]

Crippo said:

Have you used the bike in the wet?
There is a debate about the suitability of discs for road bikes because if you use the bike in th wet the water mixes with oil that is on some roads, and it can contaminate the discs and pads. It depends upon the road you use and how lucky, u lucky you are. Your issue may not be relevant to this but I know some shops are dubious about some disc contamination issues because of this potential....just a thought

In Italy it's mostly dry where I am here, but I did use them over a winter before and was not overly impressed. The XTR's are awesome, wet, dry, leave it hanging up for a month no drama at all. Same with the old X3 Hope's. This failure was totally the seals leaking, likely because there is no vent.

[shouldbworking]

Crippo said:

Have you used the bike in the wet?
There is a debate about the suitability of discs for road bikes because if you use the bike in th wet the water mixes with oil that is on some roads, and it can contaminate the discs and pads. It depends upon the road you use and how lucky, u lucky you are. Your issue may not be relevant to this but I know some shops are dubious about some disc contamination issues because of this potential....just a thought

That sounds like absolute fiction from the kind of people who are still angry about the invention of the derailleur and any technology since.

If there were an issue you'd think car manufacturers or mountain bikers would have noticed. Even if there were, how would it be different from rim brakes becoming less effective when covered in road grime?

Horrible feeling I've fallen for a troll post here

[numtumfutunch]

My winter/commuter bike has R785 and they are fine

Completely stress free with great power and modulation

I use sintered pads, possibly this is the difference?

In terms of bleed I needed a new caliper after a frustrating Shimano bolt of cheese shear probably due to a factory over-torqing of a pad retaining bolt leading to pain and misery and the new caliper was completely fine after a minimal bit of faff

Cheers

PS I think he calipers are rebranded XT

[anonymous-user]

numtumfutunch said:

My winter/commuter bike has R785 and they are fine

Completely stress free with great power and modulation

I use sintered pads, possibly this is the difference?

In terms of bleed I needed a new caliper after a frustrating Shimano bolt of cheese shear probably due to a factory over-torqing of a pad retaining bolt leading to pain and misery and the new caliper was completely fine after a minimal bit of faff

Cheers

PS I think he calipers are rebranded XT

Sintered pads isn’t going to cure the leaks.

Picked up the Hope callipers today, really nice bits of kit, shame to get them dirty!

[Usget]

Just cos you had one leaky set doesn't mean 785s are junk... I had a set which didn't leak, so I think they're great.

Hope calipers do look cool though, I might be tempted with a set just for the bling value.

[anonymous-user]

Usget said:

Just cos you had one leaky set doesn't mean 785s are junk... I had a set which didn't leak, so I think they're great.

Hope calipers do look cool though, I might be tempted with a set just for the bling value.

Meh. One winter and all the paint fell off. Leaking seals, total bh to bleed. Cheap, but...

I’ll get the Hope callipers on soon and see how they match up.