Thorn Cycles Forum
Technical => Wheels, Tyres and Brakes => Topic started by: Matt2matt2002 on January 27, 2022, 04:22:46 pm
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Using pink salmon blocks.
Over half tread on blocks left
Toe'd in.
Rim dirty with pink 'dust'.
Cleaned x2 with break disc spray cleaner. Pink smears still left on rim
Very loud squealing.
All break parts cleaned and adjusted.
Stops very well and no drag due to pads touching rims.
But the squealing is driving me nuts
Only good point is that I no longer have to ding my bell as a warning!
Rear pads on CSS rim are blue and no issues.
Any experience of a pink squealing?
Rims are 10+ years old and 15,000+ miles. Don't appear concaved yet
Another good clean? With what?
A bike mechanic said that in cold weather the blocks can harden, so trim them with a sharp blade. Not sure I like the sound of that. Maybe roughen them up with sandpaper?
Photos taken after a short ride following the rim cleaning.
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I have answered similar questions from other parties off-Forum in the past, so this is not an isolated case and I will reproduce my answer here in case it helps others...
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Prior thread with Andy Blance's advice recounted...
http://thorncyclesforum.co.uk/index.php?topic=9845.0
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I wrote...It may not be the rim, but the brakes. IF XT/R, they have a tendency to develop slop in the linkage that leads to eventual squeal in some cases regardless of rim sidewall treatment. Similar experiences and things tried listed here...
https://www.mtbr.com/threads/xtr-v-brakes-squealing-help.303964/
https://www.mtbr.com/threads/xt-v-brake-squeel-problem.99018/
https://www.mtbr.com/threads/xtr-v-brake-squeal.216381/
The purpose of the linkage was to keep the pads parallel to the rim rather than swinging in an arc with the arm; this extended pad life and was useful when wide tires were mounted to narrow rims, to prevent the pads from striking the tire sidewalls near the rim.
At one time, Shimano made a rebuild kit available, part no. BR-M951/BR-M950/XTR. This included new spacing washers and pad mount/linkage arm/keyed mount assemblies. Cost was about USD$35. No longer easily available but some German firms still carry them, one at a cost of EUR 24.95:
https://www-onlinefahrradshop-de.translate.goog/xtcommerce/304SP2.1_package_full/304SP2.1_release/xtcommerce/product_info.php/info/p882_XTR-Rebuild-Kit-BR-M951---BR-M950.html?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc
I would try swapping the front and rear brakes and then realign the pads to their new locations and see if that quietens things. Alternatively, I'd try fitting a new v-brake without linkage to the front to see if that helped reduce or eliminate the noise. Typically, brake squeal is harmonic resonance caused by the rear of the pad cyclically digging into the rim, then releasing. Besides toeing-in the pads, making sure they are tight in their holders and the holders tight in the brakes can help. Flexible forks can exacerbate the problem, not the case here.
I would also check to see how the spherical washers are set and matched on each side of the mounting brackets and to see if they are spaced the same and mirror-imaged side-to-side. Shimano have detailed instructions at Figure 2 in the brakes manual here: https://si.shimano.com/pdfs/si/SI-B660A-000-00-ENG.pdf
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Performing some combination of the above seemed to permanently reduce or eliminate squeal for the other parties, so perhaps it would help here as well.
As for the pinkish dust, I think that is the softer Kool-Stop pad material collecting in the rougher surface of the CSS rim which may not yet be polished enough to prevent grinding the softer pads to dust.
Best,
Dan.
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The reason that the extra hard pads were specified for CSS rims was that softer pads could abrade too fast and some of that pad material could become imbedded on the rims.
I would try a harder pad than the Salmon pads.
I am running the Koolstop pads that SJS sold for CSS rims. They are quite worn, but I am on the original pads. But soon, my rears will have to be replaced, I have one pair of CSS pads left.
I occasionally have squealing brakes on my CSS rims, but that usually is in damp weather, not sure why but the squealing is much less prevalent in dry weather.
If I brake harder, the squeal is muted, so I am inclined to alternate hard braking with no braking.
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Many thanks folks.
I now have a weekend project.😉
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I use Salmon pads on my CSS rims, as do two others I ride with, none of us get that pink dust. I suspect Dan is correct and that the rims haven't worn smooth enough for them yet.
I get some squealing from time to time, most likely when there's a dampness in the air, but not often when it proper wet. It doesen't happen often enough for me to be too bothered about it.
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I have answered similar questions ...
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I wrote...It may not be the rim, but the brakes. IF XT/R,
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Best,
Dan.
Is that the XTR brakes with the parallelogram arms?
Good luck to anyone who can cure the squeal with those, it was beyond me, I gave up and passed them on. I'm not surprised Shimano dropped them.
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Is that the XTR brakes with the parallelogram arms?
Yes. They seem to develop slop in the links over time and this allows the pads to wobble slightly on braking, producing squeal.
I have three sets of the standard Deore v-brakes and all are silent after extensive use, even on my tandem.
Best,
Dan.
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If I have to replace the whole unit will this one be compatible with my Raven Tour?
SJS Cycles part number : 32678FNT
Best
Matt
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If I have to replace the whole unit will this one be compatible with my Raven Tour?
SJS Cycles part number : 32678FNT
Best
Matt
Yes, any standard size V brake will be compatible.
I prefer the Deore XT, it apparently has better bushings, but my preference is based on the cable clamp being on the top rather than the side.
https://www.sjscycles.co.uk/brakes/shimano-deore-xt-brt780-v-brake-black-front/
I still think before changing the brake you should try going back to harder pads, a change of brakes isn't going to stop the salmon pads wearing like they are and stopping that wear might also stop the squeal.
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I use Salmon pads on my CSS rims, as do two others I ride with, none of us get that pink dust. I suspect Dan is correct and that the rims haven't worn smooth enough for them yet.
I get some squealing from time to time, most likely when there's a dampness in the air, but not often when it proper wet. It doesen't happen often enough for me to be too bothered about it.
Many thanks for your comments.
I'm working on the bike now. While taking a short break I looked at the stats for my Raven and see that I've done 30,000 miles since Feb 2013 on the CSS rims. Maybe they have worn too much?
I can't see a concave on the rim but my eyesight is poor.
Thanks again.
Matt
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While taking a short break I looked at the stats for my Raven and see that I've done 30,000 miles since Feb 2013 on the CSS rims. Maybe they have worn too much?
Matt
That's a good mileage, I can't remember what mine was before I changed to the Salmon pads, I think I'd used two pairs of the specific blue ones before that.
I currently only have one front CSS dynamo wheel in use (I also have a CSS touring wheelset, not in use, which I'm considering selling), the front wheel has been back and forth between bikes so I haven't tracked the mileage, at a guess probably about the same as yours. If I put a steel ruler across it and a light behind I can see there's slight wear, fag paper thick, the surface is polished smooth.
I don't know what the failure mode is? Is the carbide all the way through? I'm assuming it'll wear through the same as an aluminium rim, in which case I/we should still have many years left, I'm expecting mine to see me out.
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I recall once reading an article about some great brakes annoying squeal due to the rubber compounds used to make them brake better than other compounds. It was all about compromise. Better braking power but more noise. Or less noise and less braking power.
Alas, I couldn't find it.
Sheldon Brown's site https://www.sheldonbrown.com/rim-brakes.html#squealing (https://www.sheldonbrown.com/rim-brakes.html#squealing) did have some tips though on sanding the brake pads or on what to causes brake residue to stick to the rim and how to clean it off. The brake residue might have come from oil contamination reacting with the brake rubbers. Leaky hub, chain drips, diesel picked up from road when riding could all be sources even if you have tried to avoid intentionally getting oil on the rims or pads.
Not sure if it helps you out- but makes for a quick read on possible solutions.
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I don't know what the failure mode is? Is the carbide all the way through? I'm assuming it'll wear through the same as an aluminium rim, in which case I/we should still have many years left, I'm expecting mine to see me out.
It is my understanding that there are bits of carbide impregnated in the aluminum and that carbide is what makes it harder wearing. But I believe that the carbide is not all the way through, only part way. I suspect that the rim has less tensile strength where the carbide particles have been impregnated into the aluminum matrix. Thus I assume that most of the rim is pure aluminum alloy without carbide bits.
If that is correct, it should keep going until on some part(s) of the rim the carbide has worn through and then the aluminum can start to wear down faster in that part(s) of the rim.
The way I look at it is that the rims will last longer than my lifespan, but you are a higher mileage rider than I am and maybe you will need to replace a rim on occasion, but likely years from now.
I would not be surprised if the CSS rims are more likely to fail from a crack or internal corrosion in the hollow space than they are from brake surface wear.
Decades ago I worked with diamond rock core drilling. There were two kinds of drilling bits, surface set and impregnated. And the description of the CSS rims sounds a lot like impregnated diamond drilling bits as a final product. The manufacturing process was quite different, but the end result was similar. Basically a metal matrix holds bits of a very hard substance in place, and that hard substance is what provides the long wearing life span of the surface.
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On normal aluminum rims, I try to keep my brake pads clean. Any bits of metal I will dig out of the pads. And when my pads get a dark gray coating from the rim, that dark gray is aluminum oxide which is a much harder substance than the aluminum in the rim, thus I have sanded down my brake pads to remove that dark gray coating. I do not know if removing that gray coating has helped improve the lifespan of the rim or not, but I still do it on occasion. But I do not get that dark gray on my brake pads or anything else with CSS rims because they do not wear down like aluminum rims.
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If I have to replace the whole unit will this one be compatible with my Raven Tour?
SJS Cycles part number : 32678FNT
Should be OK, unless you have the mudguards set at maximum height, in which case the "straddle" cable may rub. In that case there are V-brakes with longer arms (about 110 mm), the ones I know about are from Tektro and fairly basic, C310, 855AL and 857AL.
I currently have very similar models to the 32678FNT: Deore XT (2012 model) on one of my Raven Tour frames and Deore LX BR-T670 (more recent) on the other. These all have shorter arms at about 102-103 mm
No major problems so far, I think the brakes on the 2012 bike with CSS rims and blue Swisstop pads squealed a bit at first, but either they have quietened down with time or I have simply stopped noticing.
And I have XTR with the parallel linkage on my Raven Sport Tour, but not had any wear problems yet.
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Thanks Martin, and others.
Just back from a ride having striped down everything and cleaned rims/pads.
Not change to squealing.
I understand the point about the noise coming from the parallelogram set up on the brake.
Not sure if this is significant but the squealing starts at a slow walking pace. Doesn't need to be at speed.
Is this an indication that it's not the parallelogram linkages being slack? They don't appear to wiggle or move 'sideways'.
While putting away my tools I found an unopened set of salmon blocks!
So my next move will be to fit them tomorrow.
If I still have the squealing then it's definitely the brakes. Correct? Not the pads/rims.
Best
Matt
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If I still have the squealing then it's definitely the brakes. Correct? Not the pads/rims.
IMO, not necessarily. But changing the brake mechanism might work.
Before buying a new brake mechanism, if this is possible and not too hard, it might be worth swapping your brakes front to back to see if that changes things.
Or swapping just the brake pads.
I have (or have had) squealing brakes on my bikes lots of times. Often I only bother to try and do anything about when my wife complains, as she really doesn't like the noise.
Sometimes squealing goes away with time. Or wet weather.
Sometimes it comes back after a period of quiet, usually if I haven't used the bike concerned very much.
Sometimes cleaning the rims stops it.
Sometimes "refreshing" the surface of the brake pads by filing, sanding or grinding works.
Sometimes toeing in the front of the pads works (others report getting the pads parallel, or doing the opposite and toeing them out).
Sometimes changing the make or model of brake pad works. Aztec pads squealed on one of my bikes, so I put Koolstop Salmon on and no squeal. And I then used the same Aztec pads on another bike, where for some obscure reason they didn't squeal.
Sometimes changing the brake mechanism works. I noticed this when I replaced some very worn Mafac cantilevers (more than 32,000 kms and I could feel some play at the pivot) with more modern Shimano ones about 20-30 years ago. The Shimano's are now at about 34,500 kms and still not squealing.
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Thanks Martin. Good thoughts.
It appears it's an elimination process.
Working my way through the cheap and quick options.
Since I have new pads to put on, I'll do that tomorrow.
If no cure, I'll pop the rear blue ones on the front.
Stay tuned...
And thanks again to all.
Matt
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While searching the forum for something else, I found this which I wrote in 2007
2007 I've recently put a Rigida Grizzley Carbide rim on the front of my Raven. If it lasts twice as long as a Mavic I would have broken even. If it lasts three or four times as long, as some people are claiming it will, it'll be a great saving. Apart from the price, I'm very happy with it, the wet weather braking is better than with any other rim braking I've had, including Magura HS. The only downside is it squeals, like nothing else.
Oh well, that's memory for you, I have no recollection of that, or if I cured it, I blame it on my ageing... :-[
martinf makes a good point about brake arm length, I didn't have that issue on mine with several brakes, though I didn't max out the tyre size. It did remind me that the brake and any fork crown light fitting have to work together, something I did have issues with. Also had the same issue on the Mercury, solved by having a bracket under the straddle wire, which offers loads of clearance, it might possibly have also worked on the Raven if I'd thought to try it.
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Decided to fit new pads to front squealing brakes.
Tough to remove and replace but got there in the end.
However the new pins don't push down completely.
They are in the correct location, since I can see light through the hole.
It's the end part that doesn't push down due to the tip being curved/looped.
Does it show in the attached pictures?
Should I pinch it together?
Old ones removed pushed down further. There was a small ' loop' I could grab with small nosed pliers.
Best
Matt
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However the new pins don't push down completely.
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Old ones removed pushed down further. There was a small ' loop' I could grab with small nosed pliers.
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Not sure what the situation is here. Are you asking if you can use the old pins? Yes you can.
Are you putting new Salmon pads in instead of pads with a harder rubber? I previously suggested trying a harder pad.
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However the new pins don't push down completely.
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Old ones removed pushed down further. There was a small ' loop' I could grab with small nosed pliers.
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Not sure what the situation is here. Are you asking if you can use the old pins? Yes you can.
Are you putting new Salmon pads in instead of pads with a harder rubber? I previously suggested trying a harder pad.
I found a pair of unused Salmon pads as I was putting away my tools yesterday, so I thought I'd pop them in rather than try your kind suggestion of a harder pad.
So this morning to popped them in.
Tough to remove and insert but git there in the end.
The new pins go down ok but as my picture shows, the ends stick out. Unable to push them right down despite seeing right through the hole. It's the end ' hook/ tip that doesn't allow the pin to go as far as the old ones did. I know a little tip should protrude but see above picture.
And now no squealing!
I appreciate your advice to buy a harder pad and I certainly would have, if I hadn't found the spare unused Salome ones.
Best
Matt
Ps, I have kept the old pins.
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The new pins go down ok but as my picture shows, the ends stick out. Unable to push them right down despite seeing right through the hole. It's the end ' hook/ tip that doesn't allow the pin to go as far as the old ones did. I know a little tip should protrude but see above picture.
Ps, I have kept the old pins.
I'd re-use the old pins if they hold the pad securely and are easy to push in/pull out.
I'd have to try again to be certain, but I think that I used pliers to "gently" force down the type of pin shown in your photo, which should lock it in place.
And to remove, I pull fairly hard with pliers. The pin "should" be forced to close and come out easily, but I remember having difficulty removing one pin of that type.
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Thanks again Martin.
I'll take another run at it tomorrow.
Meanwhile, no squealing has given me a new bike!😉
My stats tell me I had 18+ months on the old ones before replacing them today.
6,000+ miles. Still had at least one third of depth left.
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Great that the squealing is gone. Not sure why that would occur if the only change was replacing with new of the same type, but it worked so why question it.
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Great that the squealing is gone. Not sure why that would occur if the only change was replacing with new of the same type, but it worked so why question it.
Yes, one of life's great mysteries.
Maybe the old ones were harder?
I'll be interested to read my stats in a year or so time.
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Glad it's sorted, yes sometimes the cure is a mystery, maybe it just wanted some love and affection ;)
Did you get the pin in properly? They are sometimes awkward, seeing daylight doesn't always mean there's clear passage, I sometimes run a drill through them, also turn them over and push the brake onto the pin, you can see then if it's lined up.
I used to wonder if the pins were needed, then one morning setting off on a club ride from the meeting point I spotted a pair of brake inserts on the floor. I thought someone had dropped them out of their pocket, but no, they'd come out of someones bike, new inserts, fitted by a bike shop, no sign of the pins, but I suspect they either forgot to put them in or hadn't done so properly.
I don't adjust my brakes on the arms, they're set for middle wear and thread locked on. I take the arms off the frame/fork to change pads, I find it easier than fiddling around on the bike. It's also an opportunity to give them a good clean and smear some grease on the bosses.
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I used to wonder if the pins were needed, ...
The old rod brake bikes (yes, I am that old) did not have pins in their brakes. And if you rolled backwards with your brakes on, the inserts could slide out, but often only slid most of the way out instead of completely out because with only part of the pad pressing on the rim, there was often insufficient friction to force it further out.