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Disc brakes on road bikes...

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Re: Disc brakes on road bikes...

25 Nov 2017 03:13

winkybiker wrote:https://www.flickr.com/photos/winkyintheuk/albums/72157665522087839

I've now got a month-or-so and over 1000km on my new Dura-ace disc-braked all-road bike (see link above). Here's my experience:

1) They work great in the dry. A bit better than my SR on Exalith-treated rims, but not much in it from a practical perspective, really.

2) They work OK in the wet, but once saturated, the initial bite is much worse than when they are dry. In the wet, once the water is cleared, they are better than my SR rim brakes, but I actually expected less performance drop-off in the wet from discs than what I am experiencing. This has been quite disappointing as wet-weather performance was what I was really after.

3) Clearances appear to be too tight in the calipers. Small bits of debris from wet roads seem to very commonly get lodged somewhere in the calipers, causing a scraping and pinging noise from the rotor. It's not the pads rubbing, as it never happens on dry roads, and is not related to braking. If I ride through a puddle, the noise is almost certain to start, and lasts for a few hundred metres before whatever was stuck eventually clears itself. Next puddle, it starts all over.

4) The deafening squealing of the pads in the wet is absolutely infuriating. But for the performance of the brakes, this would perhaps be a deal breaker for me. I've tried both sintered metal and resin pads. Hard braking, light braking, everything in between. No difference. They squeal like banshees until they are well and truly hot and dried out (which only happens on the most severe downhill stops).

5) Some have advised that there is a mystical "bedding in" process that must be followed. I have had much conflicting advice on this, but don't really see how it is much different to just using the brakes. I also have absolutely no time for this level of stuffing about. Kind like the reason I won't use tubeless road tyres.

6) I replaced the front OEM resin pads after about 600km. They were more than 1/2 worn. I expect longer life from the new sintered pads. The sintered pads also seem to have better "bite", but both are compromised in the wet.

7) The return springs on the pistons and pads don't really seem strong enough. It sometimes takes a few seconds for the pads to clear the rotor after I release the brakes. Yes, my pistons might be dirty (after just 1000km!), but really, who needs this issue? I'd gladly put up with some more lever force for a more positive return.

All in all, I'm glad I went to discs for my all-road/winter bike due to better (but worse than expected) wet-weather performance and the fact I'm not wearing the rims, but on the basis of my experience, I would never contemplate discs for a "summer" carbon race bike that was going to see mainly fairweather riding. I just don't see that the upside is worth the compromises.


Chalk it up to user error. After about 200 DA disc bikes since the beginning of the year I have yet to hear back from anyone experiencing anything what you have. Squealing? You don't know how to clean your pads and rotors? Your wet weather performance is lacking because you think bedding in is something "mystical" and you "have absolutely no time for this level of stuffing about." What that tells me is that you should either learn how to do this properly, or bring it to somebody who does. Nice bike, btw.
User avatar Giuseppe Magnetico
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25 Nov 2017 10:51

Yeah, nice bike winky!!
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Re: Disc brakes on road bikes...

25 Nov 2017 15:52

Giuseppe Magnetico wrote:
winkybiker wrote:https://www.flickr.com/photos/winkyintheuk/albums/72157665522087839

I've now got a month-or-so and over 1000km on my new Dura-ace disc-braked all-road bike (see link above). Here's my experience:

1) They work great in the dry. A bit better than my SR on Exalith-treated rims, but not much in it from a practical perspective, really.

2) They work OK in the wet, but once saturated, the initial bite is much worse than when they are dry. In the wet, once the water is cleared, they are better than my SR rim brakes, but I actually expected less performance drop-off in the wet from discs than what I am experiencing. This has been quite disappointing as wet-weather performance was what I was really after.

3) Clearances appear to be too tight in the calipers. Small bits of debris from wet roads seem to very commonly get lodged somewhere in the calipers, causing a scraping and pinging noise from the rotor. It's not the pads rubbing, as it never happens on dry roads, and is not related to braking. If I ride through a puddle, the noise is almost certain to start, and lasts for a few hundred metres before whatever was stuck eventually clears itself. Next puddle, it starts all over.

4) The deafening squealing of the pads in the wet is absolutely infuriating. But for the performance of the brakes, this would perhaps be a deal breaker for me. I've tried both sintered metal and resin pads. Hard braking, light braking, everything in between. No difference. They squeal like banshees until they are well and truly hot and dried out (which only happens on the most severe downhill stops).

5) Some have advised that there is a mystical "bedding in" process that must be followed. I have had much conflicting advice on this, but don't really see how it is much different to just using the brakes. I also have absolutely no time for this level of stuffing about. Kind like the reason I won't use tubeless road tyres.

6) I replaced the front OEM resin pads after about 600km. They were more than 1/2 worn. I expect longer life from the new sintered pads. The sintered pads also seem to have better "bite", but both are compromised in the wet.

7) The return springs on the pistons and pads don't really seem strong enough. It sometimes takes a few seconds for the pads to clear the rotor after I release the brakes. Yes, my pistons might be dirty (after just 1000km!), but really, who needs this issue? I'd gladly put up with some more lever force for a more positive return.

All in all, I'm glad I went to discs for my all-road/winter bike due to better (but worse than expected) wet-weather performance and the fact I'm not wearing the rims, but on the basis of my experience, I would never contemplate discs for a "summer" carbon race bike that was going to see mainly fairweather riding. I just don't see that the upside is worth the compromises.


Chalk it up to user error. After about 200 DA disc bikes since the beginning of the year I have yet to hear back from anyone experiencing anything what you have. Squealing? You don't know how to clean your pads and rotors? Your wet weather performance is lacking because you think bedding in is something "mystical" and you "have absolutely no time for this level of stuffing about." What that tells me is that you should either learn how to do this properly, or bring it to somebody who does. Nice bike, btw.


How often would you think I have to clean my pads and rotors? They instantly get covered in road gunk. It's been raining pretty much non-stop for the 4 weeks I've had the bike, and I'm out in it every day.
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Re: Disc brakes on road bikes...

25 Nov 2017 17:34

If grime is building up that fast did you bother to check if there's a hydro leak? Judging by your essay I wouldn't be surprised. But If not then dirt isn't your problem. You should be able to pack a ball of mud around the caliper and not lose any performance. What you did reveal point after point is that whoever set your bike up shouldn't anymore. All those compounding problems you listed are a result of a poor set up. If you set it up bring it somewhere and have them fix what you messed up. If a shop did it ask they get the brakes working properly or demand your money back and never go there again.
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Re: Disc brakes on road bikes...

25 Nov 2017 18:19

Giuseppe Magnetico wrote:If grime is building up that fast did you bother to check if there's a hydro leak? Judging by your essay I wouldn't be surprised. But If not then dirt isn't your problem. You should be able to pack a ball of mud around the caliper and not lose any performance. What you did reveal point after point is that whoever set your bike up shouldn't anymore. All those compounding problems you listed are a result of a poor set up. If you set it up bring it somewhere and have them fix what you messed up. If a shop did it ask they get the brakes working properly or demand your money back and never go there again.


No, the grunge is from the road. Grit, leaves, water, oil, diesel etc. The usual crap that is on the road and sprayed around by tyres when it is wet. The rotors look perfectly clean (as they get scrubbed by the pads, of course). The resin pads I removed were also clean and looked good. Just worn. There's no hydro leak. The brakes are absolutely perfect in the dry, and once the water has been cleared in the wet. On a decent downhill stop, they dry out, grab better and shut up. It's the more minor slowing-down where they can't heat up and dry out that the noise is most bothersome.

I've googled about and still see conflicting advice on "bedding in". Hard stops, gentle stops, douse them with water and such. It really seems all over the place. Most of the advice seems to be focussed on that fact that when pads are new, the braking is poor until it is done. Yes, I experienced that. The first few applications took more lever force, but that reduced over time. That's not my issue. The braking is great in the dry. Examples I found of how to eliminate squealing seem to show dry brakes squealing. Mine don't do that.

Brakes were installed and set up by the guy that built the bike. He's very experienced and has been doing this for a living for years. Not some random shop guy with minimal training.
winkybiker
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25 Nov 2017 18:38

The combination of squealing and lack of wet weather performance is the result of your pads and rotors not being properly bedded in when set up. You need to start over. Take your rotors off and use fine sandpaper in a circular motion on both sides where the pads make contact. 250-300 grit. Remove the pads and sand them too, I'm sure they're glazed over as well as the rotors. You want to start with fresh pads and rotors, this is critical. After sanding clean with alcohol or automotive brake cleaner. When it's all ready to go again bed them in properly. Ride around doing about a dozen hard stops. Hard, don't drag. Our method has always been short sprints then hard enough braking to where you're almost locking both wheels.

By the way; credentialism means nothing. I know 18 year old rookie shop mechanics that can run circles around the old guys claiming a life of experience. So pardon, but tenure doesn't do anything for me.
Last edited by Giuseppe Magnetico on 25 Nov 2017 19:08, edited 1 time in total.
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Re:

25 Nov 2017 19:04

Giuseppe Magnetico wrote:The combination of squealing and lack of wet weather performance is the result of your pad and rotors not being properly bedded in when set up. You need to start over. Take your rotors off and use fine sandpaper in a circular motion on both sides where the pads make contact. 250-300 grit. Sandpaper the pads too, I'm sure they're glazed over as well as the rotors. Clean with alcohol or automotive brake cleaner. When it's all ready to go again bed them in properly. Ride around doing about a dozen hard stops. Hard, don't drag. Our method has always been short sprints then hard enough braking to where you're almost locking both wheels.

By the way; credentialism means nothing. I know 18 year old rookie shop mechanics that can run circles around the old guys claiming a life of experience. So pardon, but tenure doesn't do anything for me.


The guy who built the bike definitely knows what he's doing. But I'll take your advice and start over. I'll use your bedding in method of hard stops, (which is more or less how I "bedded in" the current pads) rather than the others that have been suggested. I've got a little loop that has a short downhill that I'll use for the hard stops. I'll let you know how I get on. Thanks.
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25 Nov 2017 19:21

I don't think he does. Otherwise you wouldn't be having these problems and revealing these set up inconsistencies on a forum with your review.

... and stop quoting everything, we're the only two people here right now. My scroll wheel needs new bearings.
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25 Nov 2017 19:35

Also, you don't need to incorporate hills into initial bedding in. Short sprints from a stop, and short hard braking. No need to get into descending speeds to do this. You'll just end up right back where you're at now.
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25 Nov 2017 23:11

OK, I'll do it exactly as you have suggested.

The overall set-up is fine, and Sam knows what he's doing. I'm going to assume it was ham-fisted bedding in on my part for now.

But apart from the bedding-in, what other aspects of the set-up would you be suspicious of? The calipers are bolted square and secure to the frame and fork. The hydraulics are fine. The discs are properly secured to the wheels and lined up correctly. It's all good quality stuff, and brand new. I've given the whole thing a hell of a work-out over the past month. Commuting in mostly very wet weather along a steep, hilly route (covered in fall debris) with hard downhill stops in quite a few places.
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Re: Disc brakes on road bikes...

26 Nov 2017 00:14

Just a reminder; I'm only 500 or so miles south of you so we're pretty much riding in the same weather. Consider different rotors. These new RT-900 by design are going to louder in the wet than most. But they shouldn't be as bad as you describe if broken in right. Even the RT-99 are much quieter. I've been using Sram/Avid Centerline X since they were released a few years ago. I can make them squak, but only in the wet on technical singletrack under very hard breaking. Otherwise completely silent in all-weather on the road, probably the quietest rotors I've ever used. In the Summer months I actually switch to Ashima ARO-8 rotors.
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26 Nov 2017 01:57

Excellent point about the rotors. Any noise is likely exacerbated by the big resonating heat-sink fins in the Shimano rotors. I have some others on the spare wheels I might try.

I cleaned the pads on a flat whetstone. They were certainly black and grungy, but a couple of seconds of light rubbing brought back the sparkle. But the dirt didn't seem ingrained at all. I also noticed on one pad a noticeable scoring line, as if maybe a small rock had been lodged in the discs in one of the slots (ironically designed to assist with self cleaning). No sign of the rock now, but maybe it kind of clogged everything up somehow.
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28 Nov 2017 18:07

So, here's an update.

Cleaned pads, and replaced the rotor with a different model. Still a Shimano with an alloy carrier, but without the fins and laminated structure of the Dura-ace version. I cleaned the rotor with isopropyl alcohol. I bedded in the brakes as suggested, with a dozen short sharp stops at the start of my ride. The performance increased noticeably over the first 4 or 5 stops, and by the end of 12 stops it was excellent and seemingly as good as it was going to get.

The ride in to work was fairly dry and no issues at all. A bit of rain on the way home and wet roads meant a bit of noise returned on initial application of the wet brakes, but nothing that would really be bothersome.

The ride in this morning was properly wet, with water running across the road in many spots, and at times heavy rain. Observations:

1) The new rotors collect MUCH less muck from the roads, and the issue of debris snagging and rubbing on the rotors is essentially eliminated. It's gone from near-constant to only-occasional. This is a huge win. It was driving me nuts. I think the big fins on the DA rotors were collecting muck and flinging it onto the braking surface or direct into the calipers. The brakes had no chance of self clearing. It's now much better. Note to self: Save the finned rotors for the summer.

2) The squealing in the wet has been reduced, but not eliminated. Eventually, by the time I was in town, the stops were getting pretty noisy. Earlier in the ride the noise was less prevalent and would stop after a second or two as the brakes presumably warmed up and dried out. But by the end, they were fully saturated and consistently noisy (I don't have any "hard" stops in the second half of my commute to get them warm).

3) The brakes continue to work well, but the initial bite in the wet is still a bit lacking compared to my expectations. Don't get me wrong, they do stop well.
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Re: Disc brakes on road bikes...

28 Nov 2017 18:57

If you only cleaned the rotors with alcohol and didn't use the sandpaper first like I instructed then you didn't pull off a true bedding in process. The whole point of this is to start with fresh pads and rotors to 'bed in' pad material into the surface of the rotors before you start wet riding. Glad you see a difference with the rotor swap, but you're always going to squck in the wet if you don't bed in properly from the beginning. Meanwhile, I rode this weekend in the wet, not a single chirp from my brakes. ...How that be, winky?
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28 Nov 2017 19:12

The rotors were new. They supply them out of the box unsuitable for use? (They do with motorcycle tyres, so I'd not be surprised).

I'd also be interested in why my very first few rides, a month ago, which were with brand new pads and rotors, and were in the dry, didn't result in the transfer of the necessary material to the rotors.
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Re: Disc brakes on road bikes...

28 Nov 2017 19:17

Giuseppe Magnetico wrote:How that be, winky?


That, my friend, is the million-dollar question.
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28 Nov 2017 19:18

Yeah, new is good. Well, I'm gonna throw my hands up about your incessant squealing in the wet. It's more apt to happen in wet riding but not that much. Maybe try Sram Centerline X like what I ride. The silence is deafening!
Last edited by Giuseppe Magnetico on 02 Dec 2017 01:45, edited 1 time in total.
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28 Nov 2017 19:55

Yep, I'll try different rotors, for sure. That 1/2 my annoyance is gone is a good start. Thanks for all the advice.
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08 Apr 2018 06:16

Try backing off the tension on your through axles. Over tightening can create some interesting and unexpected results. They can generate a lot more force than a QR, so play with that. They are not going fall out. Nice pics though... gotta love a quality Ti setup. BTW, Is that the Nanaimo ferry?
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05 Jun 2018 15:33

I just skimmed through the issues here so I'm sure I missed plenty, but noisy disc brakes are usually from vibration, and wet makes it worse so its a balance of alignment.

EDIT: I took a few things off of my post after reading a bit more.

Thisthread is from last fall so hopefully winky got it figured out!
Last edited by jmdirt on 05 Jun 2018 19:37, edited 1 time in total.
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