Shimano R785 Discs - Lots of travel

I had a similar issue to this when i first set up my RS685's and R8020's.

My solution was to file down the bleed block by about 1mm which meant the pistons moved further out and reduced the pad clearance, so the brakes bit sooner.

You can also just take out the wheel and give the brakes a couple squeezes (but don't go too far!).

This is well worth a watch https://www.youtube.com/watch?v=gQ_oIAPuQR8

As for noise, my disc brakes only squeal after I've given everything a very good clean, they squeal a couple times until they bed in again, then they are maintenance free for ages. Quite a few people have had issues with leaking piston ring/seals.

In terms of power, I've had no issues with my 160mm downhill, in the rain. Two finger braking only needed for very quick stops. I switched to 140mm rotors on my summer bike as I don't need the extra power (I don't ide it in the rain and I'm 67kg).

And just to add to Part-Robots thoughts, I have run RS785s for a couple of years completely trouble free. I have found them excellent. I’m just fitting the new DA to my new project build so hoping they are just as good if not better. Hood shape certainly seems very nice although I have no complaints about the RS785 hood shape!

I would add, to those having trouble getting the lever pulls the same, the key is bleeding the rear properly. The difference between front and rear is that the rear hose has a long routing, much of it not ‘downhill’ from down tube to rear stay, to caliper.

I found that raising the front of the bike up on my stand (breeze block under two of the feet) and then bleeding it, with the occasional tap of the hose really helped in getting all the air out. Take a look for yourself, especially where the hose comes out of the chain stay and into the caliper - that will normally be ‘uphill’ for a bike sat on the ground on its two wheels, or in a bike stand which keeps the bike pretty much level. You need to tilt the front of the bike up sufficiently to get a constant ‘uphill’ slant of the whole rear brake hose from caliper all the way to shifter.

If you do this it really helps in allowing air bubbles to rise to the lever end and into your bleed bucket. Tapping the brake line helps dislodge bubbles that are clinging to the internal wall of the hose. If the hose run is not completely uphill all the way it is easy for a bubble to get trapped at a ‘high point’ in the hose. 

This technique made all the difference for me when I first set up my RS785s. Prior to trying this I just kept getting a spongy rear brake feel upon bleeding as per instructions.

It is well worth downloading the Shimano Dealer Manual If you are not familiar with the levers especially as it explains free stroke and reach adjustments which these levers have.

Once correctly bled, I quite easily adjusted both levers to have the same reach and importantly, same free stroke before pad engagement. Absolutely spot on and I have never looked back since. Best brakes I have ever had on a bike, both wet and dry conditions with sintered pads... can’t wait for my first ride on the new DA which I am hoping will be the next level...;-)

PP 

Ah, the venerable non-series hydraulic levers. I have a fair amount of experience with these so hopefully this will help

1) A well setup RS687/785 system has about about 3cm at the tip of the levers and that is good; if it were 5mm at the tip you'd not be able to move them at all at the hoods.

2) They are never spongy beyond the elasticity in the hose and the levers. If they are spongy, you have air in the system.

3) Once you've "pumped" the pistons into place, the distance between the pads and rotors are about 0.5mm. I wouldn't call that small (it's bigger than SRAM though)

4) You can't stop a bike going 100km down a steep hill with your little finger unless you're willing to wait several km to slow down. I don't know where that stupid meme came from, but it persists

5) Unless you're over 100kg, 140mm rotors are way big enough - just look at the pro peleton. I have 140mms on one bike and 160mm on the other and there is zero difference. The difference in weight between those two sizes is, surprisingly, just a couple of grams.

6) Squeal:

6a) Organic pads are much quieter than metal pads which sound like a trumpet. I prefer metal because I like to stop better in the wet.

6b) ... That said, most of the issues people experience are from not bedding them in properly.

6c) Road bikes go on the road usually and roads are covered with the combustion by-products spewed out by motorised road vehicles. Much of this is lubricious and it often ends up on your rotors and pads (have a look at them; that's not just brake dust on there). Consequently you should clean your pads and rotors often. This involves heavily cleaning them with isopropyl alcohol until they look like new and then setting them on fire.

6d) Discs are noisy in the wet. So compensate for your embarrassment by sarcastically saluting anyone with rim brakes as they come barrelling past you in the wet unable to stop so quickly.

Hope that helps.

[EDIT: just saw the date! Funny how these things get resurrected]

I was noticing a difference between the two brakes in terms of travel.  Neither lever touched the bar under full pressure, but the rear brake required more travel before actuation, and resulted in the lever closer to the bar.  I liked the travel of the front lever better.  So, I tried the trick of removing the rear wheel, doubled a business card, and stuck it between the pads and fully pumped the lever several times with the wheel out.  Presto-chango!  That did the trick.  Now the two levers feel almost identical.  No bleeding needed!

I've thought about the bleed/pad clearance. Using a piston spacer is all well and good but using the pads with a slip of paper on the pad surface and wrapping in cling film to protect from contamination whilst bleeding the system will give you near perfect clearance first time. Remove pads clean up any brake guild contamination from rotor and caliper. Refit pads job done.

I've just fitted a set off these this weekend and they are a swine to bleed. I filled the front one the conventional way - pushing fluid in through the caliper to collect in the pot on the lever - and had literally no brake, even after a few atempts. I tried filling the pot on the shifter and using the syringe to exert a lot of suction at the caliper and then cracking the bleed valve. This seemed to work and a huge pocket of air seemed to suck out. I've taken the bike into the village and back and although there's probably more lever pull than ideal the brakes are still insanely good. My previous bike had TRP Spyres (with bigger rotas, 160 mm rather than 140 mm) and they aren't even close to how good the hydraulic brakes are. 

You could also remove the wheel and slightly pull the brake lever a couple of times.  This sets the distance between the pads.  With the spacer you're setting them to hit that thickness which is to much.  Then the pistons retract and when the wheel is back in its still a little off. Try it and see how you get on if you over cook it you can push the pads back with a flat bladed screw driver. 

This is a usual MTB fix on shamans hydraulic discs. 

You could also bleed them but this is a quick fix. 

Thanks for the advice on pushing a bit more fluid in from the caliper end, this worked perfectly for me.

Reviving this thread. Having just built a new bike with hydro brakes as mentioned. I had to bleed once I shortened the hoses. I found that yellow spacer block which is 10mm thick is just too wide and leaves the pads too far away from rotor. I made a block at 9.5mm wide. Bled again. The final few steps are vital to give a hard lever with very little stroke before the bite.

Once you're satisfied all air is out. Refit the screw cap on the lever, inject fluid with a syringe at the calliper end so that the pistons move out and nip the 9.5mm spacer block. Lock off bleed screw. Clean up all excess brake oil. Refit pads which will now be quite tight against the rotor. Lightly fit calliper into place.

Final step, if there is a little gap align caliper and you're good to go. If they pads are binding, undo the cap on the brake lever and let a tiny amount of oil weep out. This will give you enough clearance but keeps pads close to rotor. You should now have a hard lever that bites almost immediately the brakes are pulled. I've done it to both my bike with Shimano R785 hydro, the method has worked perfectly.

Shimano R785 Discs is a good thing i have the same one~

KiwiMike I ride all year in all weather. Don't have a problem stopping in the wet. Everyone should learn how to dry the rims in the wet by trailing the brakes a little now and then.

Schadenfreude time! I'm still using rim brakes and am having none of the abovementioned problems.

To all of you with these brakes, do yours rattle? I went out today for the first time with my new 685's and unless your hands are on the hoods, they rattle like crazy.

Any solutions?

Just an update.

I bought the bleed kit and yellow shimano spacer (10mm thick) plus made up my own spacer (9mm).

Bleeding with  the yellow spacer gives an acceptable lever pull distance for the front brake, but the rear was still pulling to the bars.

Trying the 9mm spacer, the front brake is very grabby with almost no travel and the disc rubs on the pads slightly. Sneeze and you'll be over the bars.

The rear is definately better using the 9mm spacer, but still has more travel than I desire, plus the disc is rubbing slightly.

 I'll probably use the Shimnao spacer for the front and the DIY 9mm spacer for the rear.

I'm now thinking that the rear is faulty, as if the line is bulging before it gives adequate braking.

I tried some SRAM hyraulic brakes in a local shop and they had a much more positive feel on the rear with the lever only moving about 1 inch.

regarding the free stroke, check that the gaps are the same either side of the disc. sometimes if there's a bigger gap on one side compared to the other, the lever will have an exaggerated spongy feel until both pads are engaged.

I look after the family's MTB's so fettling disc brakes is a common chore and I've experienced just the same problems described.  A few thoughts:

• Bleeding the brakes -  tap the cabling to help loosen air bubbles.  If you can leave over night do so - all the tiny bubbles can work their way out.  Be patient.
• Gap setting - try a thin plastic credit card or similar.
• Contaminated pads - bin them.  Boiling, burning, cleaning with special fluids (which cost nearly the same as the pads!) will not fix them.   Accept you may need new rotors.
• Dry off the brakes after cleaning - just a spot of heavy braking to get some heat in them

Oh..and they will in all likelihood squeek when damp. 

I've had an issue with the pads getting contaminated on mine, possibly when cleaning with a bike cleaning solution. The front went very soft with little stopping power even if pulled right in. My LBS re-bled, cleaned the disc and also changed the standard resin F01A pads to the metallic F03C version. It's been fine since.

I've still got the resin pads in the rear and haven't noticed an imbalance in braking power.

They do make a lot of noise in the wet but still stop well. It's frightened a few riders near me as we've all braked at the bottom of fast descents. It really is a very loud squeal. It does disappear once they dry out and have been used a bit.

I guess I'm just lucky (or mine was setup better to begin with).  The brakes start biting on mine after around 1cm of movement on the brake levers, I've 2500km on that bike so far and have not had any appreciable change in the brakes functioning in that time - I can quite happily 1-finger brake most of the time - thought I'll generally use 2-3 fingers when descending at speed.

I've not experienced any squealing from the brakes, and I've not performed any maintenance on the brakes/pads at all in the time I've had it.  It might be worth noting that this is my "best" bike, I've an older one that I've used this winter in the crappy weather.

I have exactly the same issue on my rear brake on a Di2/R785 set-up.

The LBS who I bought the bike from has had several goes but cannot solve it, so I've acquired a bleed kit and will try to remedy it myself.

I think Shimano are making a big allowance for a bent disc in giving too much gap on the piston clearance, so this needs to be taken up. Why this differs from front to back is a mystery unless my LBS haven't doen a decent job.

I've found various thickness of cardboard and plastic to try out when the brakes get bled, to find out the best  gap without rubbing on the disc.

I get squealing when grit gets caught on the pad surface, so after every wet ride the pads get popped out and cleaned and the discs will get wiped off.

Was the free stroke screw (found on the lever body under the hood) wound all the way out when the brakes were bled?

The free stroke screw only gives minimal adjustment, the best way to reduce the free stroke is to remove the wheel, pump the lever 1 or 2 times to move the pads a little more closer to the disc

Its a little trial and error to get it right, best bet is to do one pump, refit the wheel and see how it feels, if its still too much, then repeat, if you go too far and the pads rub the disc then push the pistons back in a little bit, dont pump the lever too much without the wheel fitted as you may risk popping the piston out of the caliper

Once your happy with the clearance the piston will stay in that postion only returning to the original postion once the pads start wearing down

I generally adjust mine like this every 2 months on a bike that does 100 miles every week

As for the lack of braking power were the pads bedded in properly? have they or the disc become contaiminated?

Mine work great using 1 finger braking from the hoods and im no longer using the shimano pads (using superstar components pads for 1/4th of the price of shimanos)

the wet brake squeal is quite common, the pads will stop squealing once the disc and pad have cleared/dried of water, mine usually stop after a few seconds of braking

seen a good number of brand new bikes fitted with those brakes, with leaking caliper piston seals from brand new, and contaminated brake pads. 

if its a new bike its under warranty, so take it back to your dealer and get them to have a good look

if not you will need to replace the caliper (you cannot buy seals/pistons for Shimano in the UK), replace the brake pads (should come with new caliper), degrease the rotor with Isopropyl Alcohol and refill / rebleed the brakes. 

You need a proper bleed. Find a better bike shop or try it yourself, Shimano brakes are the easiest in the industry to bleed. If that doesn't fix it you may have a hole in the system somewhere - usual culprit is around the barb when hose has been shortened and barb not inserted properly. Look for fluid leak. Squealing - ensure rotor bolts are tight, clean pads with solvent, if it continues may be because pads are contaminated with mineral oil (potentially as a result of leak/when hoses shortened, which would be convenient). 

I have the same hydraulic disc set up on my road bike and initially also had quite a bit of free travel, with the levers almost coming back to the bars before they brought me a to a halt. It took three bike shops before I found one that could bleed them correctly and now they are fine, with lever travel about half way to the bars. The feel is a lot different from calipers, but I have to say I'm very pleased with it and its more a case of not squeezing them too hard and going over the bars !

I also had the squeeling problem, but cured this by simply removing the pads and rubbing each pair together with some neat fairy liquid  between. Just rinse it off afterwards.