Brake maintenance for Fulcrum Racing Zero Nite wheels.

Discussion in 'Bicycle Mechanics and Repairs' started by Globalti, 9 Aug 2016.

  1. Globalti

    Globalti Legendary Member

    Worth posting some notes as I've seen quite a few complaints on the web about squealing brakes and wear to the braking surface.

    This is an outstandingly good wheelset, stiff and light and a delight to ride, with excellent braking, the best you'll get on a rim-braked bike. However they do need a little more care and maintenance, but since you've probably got them on your best weekend bike, not your commuter, a few minutes a week of time spent on maintenance won't kill you, will it?

    The rims are coated with aluminium oxide, which makes them very hard and gives a super grippy matt black finish. The brilliance is in the braking surfaces; most people don't realise that the fine grooves machined on the rims are actually a very fine spiral, exactly the same as a vinyl record, meaning that as the wheel rotates the brake pads are constantly being "wiped" downwards to remove debris as the ridges pass the brakes. The aluminium oxide finish requires a blue pad that is softer than the finish so as to prevent wear, meaning that the pads wear fast but the rims remain unworn. I'd rather spend £20 on a set of pads and see my rims remain unworn. The consequence of the faster pad wear is that dark blue dust accumulates on the pads and in the clearance grooves.

    This dust MUST be cleared after every ride by opening the brake and pulling a damp micro-fibre cloth or towel through behind the pads and while you're at it, giving the braking surface of the rim a wipe as well. An accumulation of dust will cause the squealing that bothers careless owners, as well as weaker braking and hence faster wear as you squeeze the brake harder.

    A second point is that these are not wet-weather wheels; the aluminium oxide finish will be ruined very quickly by water and grit. You wouldn't set out to ride your best bike in wet muddy conditions so leave it in the dry and use the winter bike with mudguards and even disc brakes.

    "What? I can't ride these wheels in the wet?" Well if you can afford a set of wheels as good as these you probably have more than one bike and certainly a special bike for commuting.

    Last edited: 9 Aug 2016
  2. Yellow Saddle

    Yellow Saddle Veteran

    Loch side.
    potsy and dave r like this.
  3. outlash

    outlash also available in orange

    ice station zebra
    My posh bike is the one with mudguards so it does get used in wet, muddy conditions. Funnily enough my most expensive wheels are on my crosser so that gets used in wet, muddy conditions too....
  4. Yellow Saddle

    Yellow Saddle Veteran

    Loch side.
    The aluminium oxide on that rim is applied by a process known as anodizing. It is indeed a very, very hard substance. However, that doesn't make it a good braking surface material if you want to stop. It is great for preventing wear but not so good for stopping. Aluminium oxide is an excellent thermal insulator whereas naked aluminium is the opposite, an excellent thermal conductor. When braking, heat is generated when the bike's kinetic energy is converted to heat. That heat is generated in the softer of the two materials in contact at the friction surface and that is of course the rubber. The rubber cannot conduct the heat backwards (it itself is an insulator) and has to pass the heat on. Luckily the heat-greedy aluminium is right there up close and readily accepts the heat where it is distributed and dispersed through radiation and convection.
    Now, if you go and insulate the aluminium, the pads still generate heat but have nowhere to pass it on to. Heat builds up, the pads heat up and melt. This leaves a gooey mess on the rims and the rims complain noisily and your brake performance suffers. To patch (not fix) the problem the rim company now recommends certain pads. These pads don't melt but sublimate i.e. they go directly from solid to smoke. Typical material inside will be wood or cork, neither which melt when heated up. This solves the melting problem but not the heat build-up and subsequent reduction of the co-efficient of friction between the two surfaces as they heat up.

    If the pads can't convert the kinetic energy into heat, they convert it into noise.

    Simply put, brake performance on anodized rims is shockingly poor, especially in the wet.

    The best thing that can happen to those rims is to be ridden in the wet whilst its owner goes for muddy puddles and apply brakes so that the anodizing can be scoured off. Unfortunately it won't come off evenly. This is because at the stress points - where the spokes enter the rim - the rim bulges out slightly and those high spots will go shiny first. Then the rim takes on a mottled appearance which upsets the consumer who perceives it as a defect and bla bla.... To solve that problem, the wheel company invents a story. The narrative involves special pads, avoidance of rain and wet roads, Sunday outings to church only, etc etc.

    Further, anodizing on a cyclically-flexible item like a rim is a very, very bad idea, especially deep, thick anodizing as indicated by the dark colour. Again, the story is not all that straight forward. Hard anodizing is not a layer on top of the aluminium, but a layer that sits hallway on top and halfway inside. It penetrates the aluminium. As the aluminium flexes, the glass-like anodizing develops micro cracks which penetrate the soft aluminium and cause stress fractures, especially around the spoke holes. Again, the narrative will cover that - to be used only for racing, fast but not durable bla bla bla. A good analogy of this mechanism is a scab on your knee. The scab sits sort of on top of your ex-skin but also inside the nervy bit. As you flex your knee and the scab cracks, the crack penetrates and you feel pain. The rim also feels pain and expresses it as a "spoke that pulled through." In fact, the spoke didn't pull through, the rim cracked.

    Even further. The "spiral" in the wheels. That spiral story is pure spin. The reason it is spiral is because the brake surface was finished on a lathe and the nature of a lathe is to cut spirals by default when it is on auto feed. Of course you can minimize the spiral effect when working, but it is always there. The spiral, or just concentric grooves for that matter, do help keeping noise down. Brake pad dust will exit the pad/rim interface no matter what the shape of the grooves. It gets blown off as dust, not as a curly ejection like the swarf from a twist drill. It is all post-rationalized PR speak. The fact that Fulcrum claims that the dust must be cleared after each ride makes me smile. No, it makes me cry. Either the spiral removes the dust or it doesn't. Wheels that require careful attention with a microfiber cloth after a ride are wheels looking for an excuse to exist. Even much further. In the old days we used to wipe stuff with rags - expired Y-fronts and ripped T-shirts. Now we wipe things with "microfiber cloth." What's happening to us? They're assimilating us and our wallets. Lets get real.

    Squealing brakes are par for the course on anodized rims. Poor performance is built into anodized brake surfaces.

    Let's ride without microfiber hankies, enjoy the ride, don't fuss over our wheels and drink beer when it is finished.

    @Globalti Please don't take my rant personally.
    potsy, Ffoeg, Drago and 2 others like this.
  5. winjim

    winjim A youth of interminable age

    That's no ordinary anodizing. That's plasma electrolytic oxidation.
    Ajax Bay likes this.
  6. Tim Hall

    Tim Hall Guest

    Not only that, but I think you'll find the rim has a very fine and compact matrix of alpha and microcrystalline gamma alumina and amorphous alumina embedded on the surface.
    Drago and winjim like this.
  7. dan_bo

    dan_bo How much does it cost to Oldham?

    Werd bra. Well argued.

    Recommend me some tubular rims please.
  8. Ajax Bay

    Ajax Bay Veteran

    East Devon
    Surely you mean 'Verb sap."
    winjim likes this.
  9. dan_bo

    dan_bo How much does it cost to Oldham?

    You've lost me.
  10. OP

    Globalti Legendary Member

    Fascinating post from @Yellow Saddle as always and no personal offence taken! But a few points:

    The braking on these wheels is quite phenomenally good, far better than I have experienced from a standard alloy rim. I'm prepared to concede however that that may be due to the softness of the pads. I once had a second-hand bike with the partially-worn patchy anodising you mention and don't remember the braking being especially bad or good; it was just unsightly.

    They are silent.No squealing or grating, even when very hot after descending the notorious Stocks Lane in Calderdale last Sunday, 200m of descent in 1.7kms.

    On the spiral, I'm not aware of Fulcrum having mentioned this or made any claims in their blurb; I just worked it out when I realised that the braking surfaces of the pads weren't developing wear grooves and tried spinning the wheel with a finger nail in the groove. I reckon it works because the build up of dark blue rubber dust is always on the bottom edge of the pads.

    On the micro-fibre cloth, I do actually use old underpants (good cotton), towels and shirts in my workshop! It's just that somebody sold me a bumper pack of micro-fibre cloths and I have found them to be especally good at cleaning and the fluffy side good for pulling behind the brakes because the fluffy loops clean out the grooves rather well! They are excellent for drying things as they pick up a heck of a lot of water.
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