What is Black Sludge (rim brake question)?
Re: What is Black Sludge (rim brake question)?
I've always assumed the sludge is a suspension of tiny aluminium oxide, aluminium and pad material particles, that it's their small size (talking just microbes and tens of, I imagine) which helps them stick so well. There has been the odd occasion when sludge hasn't been sufficiently washed away around the pads to affect smooth braking, which seems to need very specific combinations of temperature, braking and amount of water (with my pads and rims at least). Mostly, it's just a bit annoying to know there'll be a couple of minutes needed with a bucket and sponge at the end of the day after descents in wet weather.
Re: What is Black Sludge (rim brake question)?
FWIW most experienced cyclists have found it less easy to maintain rim brakes in recent years, and a lot of newer cyclists assume that high rates of rim wear are inevitable, that rim brakes are 'yesterday's technology', and you should only consider disc brakes.
Well I can't speak for people's state of mind but I honestly believe that the problems come from these main areas
a) Machined rims; the brake surface thickness is usually much thinner than it used to be.
b) Machined rims; the brake surface thickness is usually much less uniform than it used to be.
c) Machined rims; the machining often leaves bits of swarf (invisibly) embedded in the brake track surface.
d) Brake block composition; to 'improve performance' many manufacturers have used compounds which seem more abrasive than they need to be
Regarding a) they are all at it; Mavic have most recently revised all their training rims and now none of them have a decent braking surface thickness. Back in the 1980s you could by rims like the Module E2 (~450g, 1.7mm brake track) or Module 3 (~525g, 2mm brake track thickness). Now the touring/training rims have 1.35mm if you are lucky and the current open pro model measures between 1.1 and 1,0mm thickness. Absolutely pathetic.
Regarding b) if the rim isn't perfectly straight/fixtured when it is machined, then the brake track won't be uniform thickness. Needless to say it wears out first where it is thinnest. I've measured new rims that vary by ~0.25mm in thickness. There are also thickness variations from one side to the other in new rims.
Re c) this is a real killer; swarf comes out of the rim surface and embeds in the (first set of) brake blocks, whereupon it causes extremely rapid wear. The number of people that have said 'my OEM brand X brake blocks were rubbish but these brand Y replacements were lovely' -where you can use almost any makers names as X and Y- is considerable.
Re d) I think this is the smallest element but it is still there. Fortunately you can still buy aftermarket brake blocks which are kind to rims. Possibly they don't give such high friction as some others but I can live with that, small effect as it is.
Machining of brake tracks was meant to make things better. Well it made things better for the manufacturers of bad wheel rims; they now seem to work OK out of the box. But in every other respect it has made things worse.
cheers
Well I can't speak for people's state of mind but I honestly believe that the problems come from these main areas
a) Machined rims; the brake surface thickness is usually much thinner than it used to be.
b) Machined rims; the brake surface thickness is usually much less uniform than it used to be.
c) Machined rims; the machining often leaves bits of swarf (invisibly) embedded in the brake track surface.
d) Brake block composition; to 'improve performance' many manufacturers have used compounds which seem more abrasive than they need to be
Regarding a) they are all at it; Mavic have most recently revised all their training rims and now none of them have a decent braking surface thickness. Back in the 1980s you could by rims like the Module E2 (~450g, 1.7mm brake track) or Module 3 (~525g, 2mm brake track thickness). Now the touring/training rims have 1.35mm if you are lucky and the current open pro model measures between 1.1 and 1,0mm thickness. Absolutely pathetic.
Regarding b) if the rim isn't perfectly straight/fixtured when it is machined, then the brake track won't be uniform thickness. Needless to say it wears out first where it is thinnest. I've measured new rims that vary by ~0.25mm in thickness. There are also thickness variations from one side to the other in new rims.
Re c) this is a real killer; swarf comes out of the rim surface and embeds in the (first set of) brake blocks, whereupon it causes extremely rapid wear. The number of people that have said 'my OEM brand X brake blocks were rubbish but these brand Y replacements were lovely' -where you can use almost any makers names as X and Y- is considerable.
Re d) I think this is the smallest element but it is still there. Fortunately you can still buy aftermarket brake blocks which are kind to rims. Possibly they don't give such high friction as some others but I can live with that, small effect as it is.
Machining of brake tracks was meant to make things better. Well it made things better for the manufacturers of bad wheel rims; they now seem to work OK out of the box. But in every other respect it has made things worse.
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~