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Shimano R785 Discs – Lots of travel

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  • February 2, 2016 at 5:56 pm #25329
    thobson

    My bike is fitted with Shimano’s BR-R785 disc brakes which seem to get good reviews but so far I’ve been disappointed and I wanted to get others opinions about my issue. I’ve previously had discs on mountain bikes and i’ve been very impressed (even with cheap setups) but the road discs seem to be worse than standard calipers.

    The first problem seems to be a lot of travel between the pads and the rotor. When I squeeze the brakes most of the ‘squeeze’ is just moving the pad in the air before it makes contact with the rotor, so there’e a lot of travel. Can this be corrected/changed? The bike shop have already bled the discs following Shimano’s instructions.

    The second problem is the (lack of) stopping power. I’ve read that you can control the brakes using ‘just your finger’ but to brake downhill I need to squeeze really hard from the drops to get any sort of power. Could this be due to the travel in the brakes? Or are 140mm rotors just not big enough?

    My final complaint is about the noise – I know that all discs are prone to making some noise but I get a terrible squeal when the discs are wet. In town people stop and look at me, thinking I’ve just run over a cat! Can anything be done to improve this? 

    If anyone else has experience of road disc brakes I’d love to hear your opinions about my ‘issues’ with them. At the moment I’m thiking to sell the bike and go back to regular calipers 🙁

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  • February 4, 2018 at 2:35 pm #866451
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    Canyon48

    I had a similar issue to this

    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).

    February 3, 2018 at 10:53 am #866449
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    Pilot Pete

    And just to add to Part

    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 

    February 3, 2018 at 10:09 am #866447
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    part_robot

    Ah, the venerable non-series

    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]

     

    February 3, 2018 at 1:51 am #866445
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    TelemarkTumalo

    I was noticing a difference

    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!

     

    August 6, 2017 at 6:50 pm #866443
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    CXR94Di2

    I’ve thought about the bleed
    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.

    August 6, 2017 at 5:24 pm #866441
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    StraelGuy

    I’ve just fitted a set off

    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. 

    February 18, 2017 at 7:37 pm #866439
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    Johnnyvee

    You could also remove the

    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. 

    February 18, 2017 at 10:36 am #866437
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    tincaman

    Thanks for the advice on

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

    January 25, 2017 at 5:18 pm #866435
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    CXR94Di2

    . . wrote:

    . . wrote:

    CXR94Di2 wrote:
    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

    Does this not result in overfilling so you won’t be able to push the pistons back all the way next time you change pads?

    It would be prudent to do this procedure at the time you fit new pads, maybe once a year or two depending on bike usage. It also serves a good measure that when lever travel gets too long then it probably is time to change pads.

    January 25, 2017 at 5:09 pm #866433
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    . .

    CXR94Di2 wrote:

    CXR94Di2 wrote:
    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

    Does this not result in overfilling so you won’t be able to push the pistons back all the way next time you change pads?

    January 25, 2017 at 3:59 pm #866431
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    CXR94Di2

    Reviving this thread. Having
    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.

    March 17, 2016 at 7:42 am #866429
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    chrislee99777

    Shimano R785 Discs is a good

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

    March 14, 2016 at 10:45 pm #866427
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    Deveron53
    matthewn5 wrote:
    Schadenfreude time! I’m still using rim brakes and am having none of the abovementioned problems.

     

    YAWN…

    It seems that on EVERY disc brake discussion thread on a road-based forum there is a resident of postcode eh16 5ta blabbing on about how good he thinks his rim brakes are and how he’s never going to give them up and how they perform faultlessly. No one cares. Why did you bother to post that useless comment in this thread? Really, why?

    I too come from mountain bike background and expected more power from hydraulic road brakes. I’m waiting until a good, cheap, affordable hydraulic disc system comes out. It’s early days yet. I’m using the low-end Avid mechanical disc (proper road-pull not V-brake pull) and getting excellent braking performance from the hoods and I’ve got 160mm front and 140mm rear with 105 5700 levers. The Avid mechanical discs have always been excellent even on mountain bikes.

    I reckon the thinking behind having a large pad travel is to help eliminate pad drag. It doesn’t really matter to mountain bikers but the sound of a disc ringing off a pad when riding will probably cause some roadies to have heart palpitations.

    March 12, 2016 at 11:29 pm #866425
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    Anonymous
    wingmanrob wrote:
    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?

    Is the lever reach adjustment all the way out?

    Try winding it in at least 1/2 turn.

    March 12, 2016 at 10:13 pm #866423
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    matthewn5

    KiwiMike I ride all year in

    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.

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