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I tend to ride relatively modest gear (Tiagra/Ultegra), but when I'm riding near higher-end bikes, I sometimes notice that the clicking sound that comes from their cassette/free-wheel while coasting seems to be much louder and more distinct than on my bike. Why is this? Intuitively, one would expect that a quieter drive-train would be an indicator of greater efficiency, but that doesn't seem to be the case here. Is it something to do with different construction, or materials? Can you get 'quiet' high-end cassettes, or is being noisy while coasting the price you must pay for being efficient while peddling?

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I don't know of any correlation between the quality of cassettes and the noice they make, but silent ones certainly are available. sheldonbrown.com/gloss_ri-z.html#rollerclutch –  jimirings Apr 16 '13 at 18:58
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I wouldn't call Ultegra particularly modest, the only range better is Dura –  PeteH Apr 16 '13 at 20:12
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It's important to note that the freewheel is part of the hub, and while you might have some or mostly Ultegra parts, many bikes are sold with parts that aren't all from the same groupset. When you say the cassette is loud, what you're actually saying is that the freehub is loud, at least when talking about higher end bikes. Low end bikes typically have a freewheel built into the cassette. –  Kibbee Apr 16 '13 at 20:43
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Loudness in the freehub/freebody is usually due to the very light oil used to lubricate the inner parts. Thicker oil can be used to lessen the noise and even grease in some cases, but it's high viscosity is pointed at for not being so efficient. –  Jahaziel Apr 16 '13 at 20:53
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youtube.com/watch?v=SG0uBDvgXu0 Noisy freehubs are definitely a design thing. I don't get it. –  WTHarper Apr 17 '13 at 0:05

5 Answers 5

up vote 13 down vote accepted

Most of the noise comes from pawls on the freewheel hitting against the splines on the engagment surfaces which makes up the racheting unit.

Some reasons for the noise between freewheels?

  • Tension on pawls could be higher causing more noise as they glide over the engagment surfaces

  • High end freewheels have more pawls and engagement points than lower end freewheels, so there are more ridges in the engagement surface and more pawls hitting the splines on the engagement surface. The reason this is desirable is that more pawls and engagement points means faster engagement when you start pedaling.

  • Different grease (or less grease) could also be used inside higher end freewheels that is less viscous and provides less resistance, allowing the spring action of the pawls to cause more noise as they float over the the splines on the engagement surface since they are less restricted by the grease.

    Of course there are exceptions to these. Some hubs don't use your standard racheting mechanism and use a 'roller clutch' instead. The roller clutches tend to be very quiet, but are more prone to failure.Here's a good description of how those work. http://pardo.net/bike/pic/mobi/d.winners-hub/index.html

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    Great answer. I would like to mention that more points of engagement become particularly using with mountain bikes -- especially when ascending a technical section in a very small gear. I personally don't see the need on the road. –  Paul H Sep 10 '14 at 15:56

    Actually, mtb hubs can be just as loud as road hubs. So it really has nothing to do with riding in a group and being audible for the sake of other riders.

    As for the reason some are loud. Efficiency has a lot to do with it but It has more to do with the grade of punishment components can withstand and still perform well. I say that because if you have small components with less force being applied to them (i.e. Small pawl size and low spring tension holding them in position), the wheel will coast more silently.

    In some higher end components, parts are slightly oversized and/or under more torque or tension. This is to keep the performance of the components tight under stress. Imagine going face first down hill on your favorite double black diamond run trying to use campy components built for road. you will break more than just your campy group. The reason some hubs are loud is because the components are built to perform better than just "okay" and to last.

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    High end road bikes have a louder free hub so that riders in a peloton can have an audible clue that those ahead of them are coasting or braking.

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    Could you give any reference for that. It sounds plausible, however, some reasoning that this is not just a cool idea would be nice. –  Benedikt Bauer Feb 21 at 12:25
        
    No, in a bunch everyone calls what's happening; becsuse if someone collides with you they often take you down with them. In a big bunch there are freewheels clicking on front of you, freewheels clicking beside you, and freewheels clicking behind you. You know what the other riders are doing by sensing it, then hearing their calls, not by clicking. Finally, the premise of the question is flawed: not all high end hubs click loudly, IME it's only medium level Campag. –  andy256 Feb 21 at 13:03

    I had deore xt hubs on my mtn bike, they were silent. I have rebranded Formula on my 2008 Bontrager Race Lites which have a nice clicky sound. Upon servicing I must have put too much grease in and it muted the sound. So perhaps there is a relationship between sound and pawl wear. I have DT Swiss star ratchet on my mtn bike now and they have an excellent sound IMO. Chris king hubs have a legendary sound, describe by customer quote "It rolls good with angry bee sound"

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    I seem to recall reading that Shimano designs their hubs to be quiet. Or perhaps it's that their hub design is inherently quieter. Something like that. –  Paul H Sep 10 '14 at 15:58

    I think loudness is not a good indication of efficiency, since loudness (and pitch as well) can be affected by many more factors at same or similar total energy consumption.

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    Producing noise requires power/energy. If a transmission is very loud it can’t be very efficient. Though a lack of noise doesn’t automatically mean more efficiency. –  Michael 53 mins ago

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