Author Topic: CSS rim squealing  (Read 7561 times)

Matt2matt2002

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CSS rim squealing
« on: January 27, 2022, 04:22:46 PM »
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.
« Last Edit: January 27, 2022, 04:28:17 PM by Matt2matt2002 »
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Danneaux

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Re: CSS rim squealing
« Reply #1 on: January 27, 2022, 05:17:13 PM »
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
=====
I wrote...
Quote
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
=====
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.

mickeg

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Re: CSS rim squealing
« Reply #2 on: January 27, 2022, 06:25:25 PM »
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.


Matt2matt2002

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Re: CSS rim squealing
« Reply #3 on: January 27, 2022, 06:28:45 PM »
Many thanks folks.
I now have a weekend project.😉
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PH

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Re: CSS rim squealing
« Reply #4 on: January 27, 2022, 08:42:43 PM »
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.

PH

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Re: CSS rim squealing
« Reply #5 on: January 27, 2022, 08:47:09 PM »
I have answered similar questions ...
=====
I wrote...
Quote
It may not be the rim, but the brakes. IF XT/R,
=====
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.

Danneaux

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Re: CSS rim squealing
« Reply #6 on: January 27, 2022, 09:20:47 PM »
Quote
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.

Matt2matt2002

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Re: CSS rim squealing
« Reply #7 on: January 28, 2022, 08:42:35 AM »
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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PH

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Re: CSS rim squealing
« Reply #8 on: January 28, 2022, 09:35:23 AM »
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.

Matt2matt2002

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Re: CSS rim squealing
« Reply #9 on: January 28, 2022, 10:05:09 AM »
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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PH

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Re: CSS rim squealing
« Reply #10 on: January 28, 2022, 10:21:13 AM »
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. 

steve216c

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Re: CSS rim squealing
« Reply #11 on: January 28, 2022, 11:36:18 AM »
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 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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mickeg

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Re: CSS rim squealing
« Reply #12 on: January 28, 2022, 11:51:03 AM »
...
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.

***

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.

martinf

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Re: CSS rim squealing
« Reply #13 on: January 28, 2022, 12:27:09 PM »
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.

Matt2matt2002

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Re: CSS rim squealing
« Reply #14 on: January 28, 2022, 01:47:07 PM »
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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