Holy Grail: Road disc brakes that don’t rub?

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  • Holy Grail: Road disc brakes that don’t rub?
  • Digger90
    Member

    I’m fed up with my SRAM Force Hydro-R calipers rubbing on the disc rotors, it’s driving me nuts.

    I’m experienced mechanically, and have bled the systems (front & rear) several times. I’ve also stripped, cleaned, lubed and rebuilt the Master Cylinders per PSImet’s great vid on YouTube. I’ve advanced, cleaned and lubed the caliper pistons multiple times – far more often than with each pad change.

    But they still rub – the pistons just don’t retract far enough.

    And riding here in the UK in winter conditions, whenever I ride through puddles or on sh*tty roads, the brakes produce that horrible grating, gritty, rubbing noise for far too long. Dabbing the levers several times does nothing to stop this… it’s down to inadequate pad retraction.

    Next step is a full caliper and piston strip and rebuild with fresh seals.

    I’m otherwise happy with SRAM Force Hydro-R brake performance, but the inadequate pad retraction issues are ruining it for me.

    Googling around, it seems that Shimano hydraulic road brakes also suffer this problem. There aren’t many (any?) reports I can find about Campagnolo hydraulics.
    There are reports that Hope RX4’s have better pad retraction, but others have had problems with those too.

    Are there ANY road disc brake systems that don’t rub?

    stumpy_m4
    Member

    My Shimano RS-505 have been trouble free since 2016

    tjagain
    Member

    Have you lubed the seals? Are your discs straight?

    hopster
    Member

    Have Sram Rival and a set of Force Hydo-R brakes. One set is over 4 years old and other than an annual bleed they’ve been maintenance free. If they do start rubbing (which is rare), I just reset the piston by forcing them back into the caliper with the wheel removed, replace the wheel and pump the brake a few times. Then check the rotor is straight.

    Premier Icon joebristol
    Subscriber

    I can’t say I’ve noticed my shimano road discs rubbing and I haven’t touched them with any maintenance since new a couple of years ago. Commuted through all sorts of mucky weather and all good really.

    scotroutes
    Member

    Pad rubbing was a “feature” of my BB7s but that was partly due to my preference of having little lever travel. Not had any issue with my Shimano hydraulics since fitting them.

    Premier Icon vinnyeh
    Subscriber

    My Shimano RS-505 have also been trouble free since 2016.

    Premier Icon linusr
    Subscriber

    Are there ANY road disc brake systems that don’t rub?

    I doubt it. From time to time any disc brakes are gonna rub because in normal use the pads are very close to the disc. I have cheapo Shimano hydros on my MTB, and BB7 and TRP Spyres on my winter/CX road bike. These bikes rattle and tyres thrump so much I cannot hear the occasional rubbing of the discs and they work great in the wet and off-road. I have rim calipers on my lightweight (steel Pinarello) road bike. I’m not tempted to get a summer road bike with discs. Get a pair of ear plugs.

    Is this that you can’t get them to run silently at all, or that they make a noise for a while after going through mud or puddles?

    If a) -Try different rotors. Yours are probably warped. Quite difficult to get them totally straight again. Saying that I’ve had new rotors that were warped

    if b) – they all do that, sir

    With a), I once had an issue like that with a lefty hub on a Cannondale Bad Boy. Was an issue with the disk mount not being faced correctly.

    tjagain
    Member

    All my disc braked bikes ( mtb) run without rubbing – all old hopes tho

    My Shimano RS-505 have been much better since swapping out the Cube’s Fulcrum RacingSport 77DBs for Hunt Aero Light Disc wheel in summer 2018, former used to rub when out of the saddle while climbing inclines/hills.

    Don’t know if it’s wheel change in general, or whether latter are fitted with centerlock rotors while Fulcrum were 6-bolt.

    Premier Icon epicyclo
    Subscriber

    TRP Spyres.

    Premier Icon snotrag
    Subscriber

    Ultegra levels and RX4 calipers here. Faultless.

    I was almost a bit embararsssed to install them when they arrived as they really do look straight off a mountain bike but they work so well!

    Digger90
    Member

    Just to be clear – yes, my rotors are perfectly straight, and are of good quality, and yes, I have cleaned and lubed the piston seals.

    mtbtomo
    Member

    When people say their discs aren’t rubbing, do they mean they’re silent and spin freely enough or do they genuinely mean they’re really truly not rubbing? Because to my mind unless you can see daylight between pad and rotor, whether it is the lightest of contact or not, then your pads are rubbing.

    Companies spend who knows how much marketing the saving of watts through all these aero gains, but I bet you can lose that saving just by the rotor skimming the pad the slightest amount. But Google it and you won’t find anyone admitting how much power is being drained from rubbing rotors and pads.

    Even if you run thinner rotors they will self adjust with use so you’re back to square one.

    I think there is perhaps an iteration or two more to go for road discs before they iron out the negatives for road use.

    That said, the Rival hydraulics on my cross bike seem to rub or not every time I undo the quick release to remove the wheel. The thru-axles on my winter bike seem to make wheel changes have less of an effect but it’s not perfect.

    coatesy
    Member

    Cleaning and lubing the pistons will make your problem worse, the pistons will slide through the seals and run closer to the disc. Leave them covered in shite like most people do, and the pistons will stick to the seals, the seals will flex and then return, and thus retract the pistons (The downside is more lever travel before anything happens, something I detest in a brake, so am happy to keep them clean & free running.)

    Digger90
    Member

    coatesy – I get the logic of that, and in fact I tried it, but that simply made matters worse. The pistons didn’t retract as much – and therefore rubbed even more – than when I cleaned them.

    mtbtomo – yes, I mean they are noisy when simply riding along, seated, i.e. not mashing the pedals/standing, no massive lateral frame/wheel twist etc.

    The rubbing, grating, gritty noises occur quite often when just riding along, but are far worse when riding through puddles, wet roads, or roads with debris/sh*te all over them (as they are during Dec/Jan/Feb for example).

    Premier Icon linusr
    Subscriber

    Just to be clear – yes, my rotors are perfectly straight, and are of good quality, and yes, I have cleaned and lubed the piston seals.

    And you have thru-axles front and rear?

    AdamT
    Member

    I wasn’t going to post, but felt like I had to since my RS505’s have also been trouble free since about 2016. I have two pairs of wheels too and neither of them rub when swapping between them.

    Premier Icon linusr
    Subscriber

    @Coatesy

    Cleaning and lubing the pistons will make your problem worse, the pistons will slide through the seals and run closer to the disc. Leave them covered in shite like most people do, and the pistons will stick to the seals, the seals will flex and then return, and thus retract the pistons (The downside is more lever travel before anything happens, something I detest in a brake, so am happy to keep them clean & free running.)

    That’s a good observation. I was tempted to clean and lube my at the last pad change and bleed. Glad I didn’t now.

    scotroutes
    Member

    The pistons are only supposed to slide through the seals to make up for pad wear, not every time you brake. It’s flexing of the seal that pulls the piston off the disk. I guess that the seals can go hard, preventing this from happening. One of the reasons I stick to genuine Shimano mineral oil.

    tjagain
    Member

    MY guess is the [pistons need to be reset then. Wheel out and push the pads back and then wheel in and pump the lever. Try the hope method for centralising as well?

    Is the calliper centred correctly over the disc ? Or did you do the old loosen the bolts and squeeze the lever to centre the pads ?

    Premier Icon davosaurusrex
    Subscriber

    Shimanos on my Defy and they do rub but it’s negligible so doesn’t bother me. QR as well so getting them back in the same spot when putting a wheel back in is a bit faff compared to thru axle but not too bad. Would go thru axles next time though

    Main reason for posting though is to highjack the thread (soz OP) to ask if anyone has a managed to get the rear lever on shimano road hydros to feel as good as the front? I’ve just reverse bled the crap out of mine, bike up on end doing the rear and whilst it’s better it’s still not as solid as they the front. Is it just the length of hose or a bubble trapped somewhere?

    scotroutes
    Member

    I can’t say there’s any difference in mine front to rear – on road or MTB. Most likely to be a bubble somewhere.

    Premier Icon solarider
    Subscriber

    I have SRAM on all of my bikes – road, MTB and winter road bike which gets the worst of the weather and road grime. Non of them rub.

    I am fastidious with bleeding and find that tapping the caliper and hose from the caliper to the lever during the final stage when the caliper end is closed is essential. Usually a solitary bubble pops out and that is the trick to even and maximum pad retraction.

    SRAM do run closer than Shimano or Hope and that does make them more prone to rub and makes them more sensitive to bleeding and rotor alignment.

    Digger90
    Member

    In answer to some of the questions:

    Yes, I run thru-axles front & rear

    Yes, the calipers are centred perfectly to the rotors

    And yes, I have advanced the pistons and cleaned them on many occasions.

    I think Solarider’s point is correct – maybe SRAM calipers position the pads closer to the rotor than other manufacturer’s. That would account for the constant noisiness. I was thinking it’s insufficient piston retraction, but maybe they just run very, very close under normal circumstances.

    coatesy
    Member

    Bleeding them can be a convoluted process involving trying to eliminate “high spots” in the system where air can accumulate(take a look at your caliper, for instance. Are the pistons/cylinder bores higher than the fluid inlet and bleed port? If so, there’s potential for air to be trapped, and things will need rotating to release it.) I usually spend a while with the bleed pot on the lever too, tilting the bike forward and back, left and right repeatedly whilst flicking the lever, this regularly releases a few bubbles that would have gone un-noticed (if possible, after the bike has sat with the lever strapped to the bars).

    jonnyboi
    Member

    I’ve run shimano BR-505 & BR-785 with zero issues. Maybe it’s a SRAM thing as I have friends who have experienced issue with theirs.

    Pads and rotors don’t rub on any of the bikes I’ve ever had. there is clearance between pads and disks but even if there was a very light touch the coefficient of friction between pad and disk is very low…its not like rubber brake blocks on a rim so the amount of wattage consumed would be infinitesimally small…but it wouldn’t be quiet so you would know. My disks run quiet and smooth – SRAM, Shimano and Hope amongst my steeds. Be sure your disk is not buckled and pads centred. That is about all you can do. Oh and stop washing your bike. Water sitting on the pistons can make them stick.I tend to wipe down my bikes whenever I give it a wash rather than bucket and sponge or jet wash. If I do throw a bucket over it I’ll make sure brakes are completely dry after. I also do this when I wash the car. Nothing worse for brake disks wether it be on bike, motorbike or car than washing and letting them sit there wet.

    It’s a set up thing. Shimano brakes can rub so not a manufacturer thing…rented a couple of disk braked bikes on holiday once – Shimano ultegra equipped bikes, mine ran fine, the bike my brother used the rear brake rubbed a bit. Annoyed him at first as it was making a noise but after a few miles it didn’t bother him. He certainly didn’t notice any drag from it and the disk was running cool in normal riding so no real friction being generated. He still got up Mt Teide 45 minutes quicker than me despite the rubbing disk brake.

    shedbrewed
    Member

    When it’s wet, or dirty ie during a cross race then every pair I’ve had have done it. Rival hydro, Shimano rs505, hope v-twin. All do it as they pick up the wet gritty crap. That’s never the main think losing me power on a race. That comes from the mud that builds up in all the gaps.

    Premier Icon roverpig
    Subscriber

    Riding my bike with 105s on some soaking wet sandy trails today and they certainly did it a few times. Never lasted that long though.

    Premier Icon rOcKeTdOg
    Subscriber

    Sram brakes,a road or MTB always rub, Shimano almost always don’t

    trail_rat
    Member

    What rocket dog said. They are famed for it regardless of condition

    Shimano usually better but still happens when the pistons go sticky(road salt eats pistons and Ali housings )

    Hope better still. But also sti happens when the road grime attacks…

    Road grimes worse than the worst winter mud.

    hopster
    Member

    Super interesting podcast on disc brakes. Here

    globalti
    Member

    …and yes, I have cleaned and lubed the piston seals.

    Waste of time. The pistons don’t slide back and forth through the seals as most people think; they are an extremely tight fit so all that happens when you apply hydraulic pressure is that the seals deform, then bounce back so as to retract the pads. Yes the pistons do creep slowly through the seals but that’s a slow process as the pads wear. Grab a huge handful of brake and you can sometimes force the pistons to move and hold the pad on the disc, which is annoying. Best thing you can do is live with it until the pads wear a little.

    oreetmon
    Member

    My RIVALS do the same, muddy puddle/grinding, it very annoying.

    Also have had problems with rear Shimano brakes after bleeding. I now take the brake off the bike and hang it from the lever overnight to allow any micro air bubbles to rise, I run an old electric toothbrush over it to help ‘vibrate’ any air out of the nooks, seem to work well.

    pdw
    Member

    I’ve definitely found sram to be more sensitive than shimano. I have had a specific problem with sram brakes ratcheting on leaving very short lever throw and significant drag from the brake. Replacing caliper seals seems to have fixed this.

    Whilst it is true that you don’t want the pistons to slide through the seals in normal use I think a single sticky piston can be a problem as it may result in all the wear compensation happening on the other side leading to brake rub. I think clean but not lubed is what you want.

    globalti
    Member

    As I wrote above, the pistons don’t slide through the seals except to creep very slowly as the pads wear. Piston movement is thanks to the seals deforming.

    If you get uneven pistons or a stuck-on brake it’s because the seals on one or both sides have allowed the piston to slip through and there’s nothing to push it back, certainly not that tiny anti-rattle spring.

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