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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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  • March 12, 2016 at 11:33 am #866421
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    KiwiMike
    matthewn5 wrote:
    Schadenfreude time! I’m still using rim brakes and am having none of the abovementioned problems.

     

    People who understand disc brakes wouldn’t dream of relishing in your abject terror, upon discovering that white line on the T-intersection of that A-road is just a bit too close to let your rims dry off in time to stop.

    March 12, 2016 at 11:01 am #866419
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    fukawitribe
    matthewn5 wrote:
    Schadenfreude time! I’m still using rim brakes and am having none of the abovementioned problems.

    I’m so glad you’re taking pleasure in this – what a lovely chap !

    March 12, 2016 at 10:08 am #866417
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    matthewn5

    Schadenfreude time! I’m still

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

    March 12, 2016 at 5:26 am #866415
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    wingmanrob

    To all of you with these

    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?

    February 27, 2016 at 1:02 pm #866413
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    Anonymous

    Just an update.

    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.

    February 4, 2016 at 12:17 am #866411
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    the infamous grouse

    regarding the free stroke,

    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.

    February 3, 2016 at 11:05 pm #866409
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    rnick

    I look after the family’s MTB

    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. 

    February 3, 2016 at 6:59 pm #866407
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    thobson

    Thanks for all the comments,

    Thanks for all the comments, they have been very helpful and I’m pleased to hear that I’m totally crazy! I will try to bleed the brakes myself and shorten the distance the pads have to travel. Hopefully I will have some success

    February 3, 2016 at 11:09 am #866405
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    watlina

    I’ve had an issue with the

    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.

     

    February 3, 2016 at 9:30 am #866403
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    sergius

    I guess I’m just lucky (or

    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.

    February 3, 2016 at 7:36 am #866401
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    Anonymous

    I ahve exactly the same issue

    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.

    February 2, 2016 at 11:58 pm #866399
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    kev-s

    Was the free stroke screw

    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

     

     

     

     

    February 2, 2016 at 8:08 pm #866397
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    hampstead_bandit

    seen a good number of brand

    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. 

    February 2, 2016 at 7:56 pm #866395
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    surly_by_name

    You need a proper bleed. Find

    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). 

    February 2, 2016 at 7:06 pm #866393
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    graybags

    I have the same hydraulic

    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.

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