The vast majority of modern bikes, whether mountain bikes, road bikes or gravel bikes, come with derailleur gears. The rear derailleur moves your chain up or down a set of sprockets attached to your rear wheel. Those sprockets – or gear wheels, if you prefer – are your cassette.
Cassettes come in a wide range of sizes to suit all disciplines. The size of a cassette is usually expressed by quoting its smallest and largest cogs. As an example, a typical modern road bike cassette may be an 11-32t (teeth) cassette. For a mountain bike cassette, the range may be something like 10-52t.
In this guide, we’ll talk you through what a cassette is and how to tell the ‘speed’ of your cassette, explain the typical range of a cassette for all disciplines, compare the key difference between cheap and expensive cassettes, and much more.
What is a cassette?
Although it might seem straightforward, there’s a lot of engineering that goes into a bike cassette.
Rather than just being a collection of cogs, the sprockets in a cassette are designed to work together as a whole, with the individual sprockets positioned precisely relative to one another to ensure the chain will shift smoothly between cogs.
Individual teeth on the sprockets have shapes that differ from one another and there are usually ramps built into the sides of the sprockets. This helps ensure smooth shifting between gears.
The designs of these ramps have been honed over time.
Shimano, for example, uses a system it calls Hyperglide, which is engineered to provide smooth shifting. Its latest cassettes have a newer system called Hyperglide+, which Shimano says reduces shifting time by up to a third relative to Hyperglide, and improves shifting performance under power, up and down the cassette.
Other cassette suppliers, such as SRAM and Campagnolo, have equivalently honed cassette designs.
Since they’re designed as a whole system, the sprockets in a cassette are sold as a set rather than individually, and usually need to be replaced as a complete group too.
You usually can’t just swap out one sprocket from a set for one with a different number of teeth without compromising shift performance.
We have an explainer on how to change your cassette here.
What ‘speed’ is my cassette?
A cassette might have anything from 7 up to 13 sprockets.
These days, it is increasingly common to see higher-spec road bikes with 12-speed gearing, Shimano having joined SRAM and Campagnolo with 12-speed groupsets in 2021 with the release of its Dura-Ace R9200 groupset.
For mountain bikes, 12-speed cassettes are largely the default for higher-spec groupsets, paired with a single-ring chainset.
The number of sprockets on your cassette must match the number your other components are designed for.
That’s because almost all gear systems are indexed, and shifters are designed to move the derailleur a set distance for each click of their mechanism. This means they won’t work with cassettes that don’t have the same number of sprockets, because sprocket spacing is narrower on cassettes with more sprockets. The chain has to be the right width to match the number of sprockets, too.
In general, lower-spec groupsets offer fewer gear ratios and so have cassettes with fewer sprockets.
There are exceptions though, with SRAM’s X01 DH and GX DH downhill mountain bike groupsets using seven-speed cassettes, which work with 11-speed chains. The lower number of gears is designed to give closer gear ratios and allow shorter cage derailleurs for better ground clearance, on bikes where climbing capability is not required.
Cassette gear ratios
Alongside the number of sprockets, the range of different tooth numbers offered is a key determinant of a cassette’s compatibility with your drivetrain.
In general, cassettes start at 10, 11 or 12 teeth. Again, there are exceptions, with options available with 9-, 13- or 14-tooth smallest sprockets.
You may sometimes see brands refer to their cassettes as having a certain range in the form of a percentage.
For example, SRAM boasts a 520 per cent range with its 10-52t cassettes. How has SRAM arrived at this figure, and how do you work out your gear range percentage?
Well, the smallest cog is a 10-tooth, and the largest cog is 52-tooth, which is 520 per cent larger than the 10-tooth cog, thus giving a 520 per cent range.
It’s important to note that this figure is only indicative of the range of gears you have on your cassette, and is not the same as working out how far you will travel with your chosen gear ratio.
Likewise, it can’t tell you if it is suitable for the type of riding you do. For that, you would calculate gear inches, which is another topic in itself.
Road bike cassettes
Road bike cassettes have mushroomed in size in recent years.
Where an 11-28 would have been considered an ‘easy’ training cassette a few short years ago, the smallest cassette available for a Shimano Dura-Ace R9200 is an 11-28. That might not sound like much but, when you consider pro riders would typically ride on 11-23 or 11-25 cassettes, it’s a sizeable difference.
The reason for this development is firstly due to the increase in cassette speeds.
Now that 12-speed road bike groupsets exist, cassettes can have a larger range and the jumps between each gear can be relatively small.
For example, at the lower end of the cassette, you can have as little as a one-tooth jump between the early cogs, and still have the range at the easier end. If you were running a 7- or 8-speed system, for example, in the same range, the jumps would be bigger.
Attitudes towards gearing have also changed – it’s no longer seen as a badge of pride to needlessly grind away at a lower cadence, and our knees are all the more happy for it.
Both Shimano and Campagnolo have stuck to pre-existing gear ratios in their transformations to 12-speed, and have used the additional cog as a means of bridging the gap between the bigger jumps of the cassette, so that the ratios are closer together. SRAM has gone down a different route (more on that in a moment).
Shimano’s latest R9200 is offered in 11-28, 11-30 and 11-34 options. These ratios also existed in Shimano’s 11-speed configurations, although it’s important to note that Dura-Ace R9100 did not have an 11-34 option.
Campagnolo offers an 11-29 option for all of its 12-speed groupsets, which was the largest range offered in its 11-speed ecosystem.
In addition, there are now 11-32 cassette options across the board. There is also an 11-34 cassette, but that is only available and compatible with Chorus.
SRAM, on the other hand, has shaken up what we have come to understand as conventional gear ratios with its latest 12-speed eTap AXS groupsets.
Its addition of a 12th cog instead acts to increase the range of the cassette. SRAM road cassettes start from a smaller 10t (which requires the use of the XDR freehub body, which we’ll come onto later).
SRAM has also revamped its chainring sizes, that are smaller than convention at 50/37 (Red only), 48/35 and 46/33. This compares to the more conventional gear ratios of 53/39, 52/36 and 50/34.
SRAM cassettes are available in 10-26 (Red only), 10-28 (Force and Red only), 10-30 (Rival only), 10-33 (Force and Red only) and 10-36 (Rival and Force only).
Mountain bike cassettes
Mountain bike cassettes have similarly increased in size. This is largely down to the advent of 1x drivetrains – with no small inner ring for climbing in a 1x setup, cassettes need to offer a wider range in order for riders to be equipped with a suitable climbing gear.
Unlike road bikes, mountain bike cassette options are usually more limited.
Shimano offers just two cassette sizes in its 12-speed line-up – 10-45 (not available for Deore) and 10-51. The 10-51 option can only be used on a 1x setup, but the 10-45 can be used on either 1x or 2x systems.
SRAM also offers just two cassette sizes in its Eagle lineup – 10-50 and 10-52. The 10-52 is the widest-range cassette made by either manufacturer. Although there are currently two options, it’s likely the 10-50 will be phased out in time because it has been superseded by the 10-52.
You need to ensure you’re using a compatible rear derailleur if you’re using the 10-52 option, because the previous-generation Eagle mechanical rear derailleur’s cage is slightly too short.
There are new rear derailleurs on the market that are identifiable as being compatible because they have a ‘520% range’ graphic printed on the derailleur cage. SRAM Eagle AXS rear derailleurs are compatible with the new 10-52 cassettes.
For users of SRAM’s two entry-level Eagle groupsets, SX Eagle and NX Eagle, SRAM offers an 11-50 cassette. This allows the cassette to fit onto a standard Shimano HG freehub (again, more on this later) because the 10t options require the use of an XD freehub.
Gravel bike cassettes
Gravel bikes are best viewed as a crossover between a road and mountain bike. As such, it’s normal to see them specced with either a road or mountain bike cassette.
However, as groupset manufacturers have jumped onto the gravel bandwagon, there are now gravel-specific cassette options available on the market.
SRAM’s eTap AXS XPLR groupsets are designed specifically for gravel riding. SRAM XPLR cassettes have a range of 10-44 and require their own compatible rear derailleur. It is also possible to mix and match drop bar shifters with mountain bike Eagle eTap AXS components if you want an especially wide-range 1x build. SRAM dubs this a ‘mullet’ setup.
Campagnolo is the only mainstream groupset manufacturer to have a 13-speed groupset for gravel. The Campagnolo Ekar 13-speed gravel groupset offers cassettes that start with just nine teeth in their smallest sprocket. Cassettes are offered in 9-36, 9-42 or 10-44 options. Ekar is 1x only.
Shimano GRX users can choose to spec one of their own 11-speed road or mountain bike cassettes. The road cassettes go up to an 11-34 and mountain bike cassettes are offered in 11-40, 11-42 or 11-46. Shimano’s cassette range might sound more limited than its competitors, but it is important to note that you can run GRX either as a 1x or 2x system.
Cassette compatibility explained
Freehub compatibility
A freehub has splines that mesh with notches in your cassette. These ensure that your cassette’s sprockets are positioned correctly relative to one another and are in the right orientation for the whole system to work properly.
Each manufacturer has its own freehub design, meaning that not all cassettes will work with every wheel (or groupset).
A full explainer on freehubs, how they work and their…
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Fuente: www.bikeradar.com
Esta nota fué publicada originalmente el día: 2022-02-18 10:00:42
